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Psychology Around Us
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Psychology Around Us Ronald Comer Princeton University
Elizabeth Gould Princeton University
John Wiley & Sons, Inc.
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VICE PRESIDENT AND EXECUTIVE PUBLISHER
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This book was set in Minion by Prepare Inc. and printed and bound by RR Donnelley/Jefferson City. The cover was printed by RR Donnelly/Jefferson City. This book is printed on acid free paper.
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Copyright © 2011 John Wiley & Sons, Inc. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978)750-8400, fax (978)750-4470 or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030-5774, (201)748-6011, fax (201)748-6008, or online at http://www.wiley.com/go/permissions. To order books or for customer service please, call 1-800-CALL WILEY (225-5945). Library of Congress Cataloging in Publication Data: ISBN-13 978- 0-471-38519-6 Printed in the United States of America 10 9 8 7 6 5 4 3 2 1
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About the Authors Ronald Comer
has taught in Princeton University’s Department of Psychology for the past 35 years and has served as Director of Clinical Psychology Studies for most of that time. He has received the President’s Award for Distinguished Teaching at the university. Comer also is the author of the textbooks Abnormal Psychology, now in its seventh edition, and Fundamentals of Abnormal Psychology, now in its sixth edition, and the coauthor of Case Studies in Abnormal Psychology. He is the producer of various educational videos, including The Introduction to Psychology Video Library Series. In addition, he has published journal articles in clinical psychology, personality, social psychology, and family medicine.
Elizabeth Gould has taught in Princeton University’s Department of Psychology for the past 12 years. A leading researcher in the study of adult neurogenesis, she has published numerous journal articles on the production of new neurons in the adult mammalian brain. Gould has been honored for her breakthrough work with a number of awards, including the 2006 NARSAD Distinguished Investigator Award and the 2009 Royal Society of the Arts Benjamin Franklin Medal. She serves on the editorial boards of The Journal of Neuroscience, Neurobiology of Learning and Memory, Biological Psychology, and Cell Stem Cell.
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To our children Lindsey, Sean, and William E.G. Jon and Jami Greg and Emily R.C.
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Brief Contents CHAPTER 1 Psychology: Yesterday and Today. . .2
CHAPTER 2 Psychology As a Science. . . . . .30
CHAPTER 3 Human Development. . . . . . . . . 54
CHAPTER 4 Neuroscience . . . . . . . . . . . 96
CHAPTER 5 Sensation and Perception . . . . 128
CHAPTER 12 Emotion . . . . . . . . . . . . . 384
CHAPTER 13 Personality . . . . . . . . . . . 422
CHAPTER 14 Social Psychology . . . . . . . . 460
CHAPTER 15 Stress, Coping, and Health . . . 500
CHAPTER 16 Psychological Disorders and Their Treatments . . . . . . 536
CHAPTER 6 Consciousness . . . . . . . . . . 164
CHAPTER 7 Learning . . . . . . . . . . . . 202
Glossary . . . . . . . . . . . . G-1 CHAPTER 8 Memory . . . . . . . . . . . . . 238
References . . . . . . . . . . . R-1
CHAPTER 9
Text and Illustration Credits
Language and Thought . . . . . . 276
CHAPTER 10
Photo Credits
. . T–1
. . . . . . . . . P–1
Intelligence . . . . . . . . . . 310
Name Index . . . . . . . . . . NI-1 CHAPTER 11 Motivation . . . . . . . . . . . 350
Subject Index . . . . . . . . . SI-1
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Contents CHAPTER 1
Psychology: Yesterday and Today
Opening Vignette “Trolling” the Internet
2
3
Psychology: Myth vs. Reality 4
What is Psychology? 5 Psychology’s Roots in Philosophy 7 The Early Days of Psychology 9 The Founding of Psychology 9 William Shakespeare (1564–1616), Original Psychologist 10 Structuralism: Looking for the Components of Consciousness 10 Functionalism: Toward the Practical Application of Psychology 11 Gestalt Psychology: More than Putting Together the Building Blocks 12
Twentieth-Century Approaches 14 Psychoanalysis: Psychology of the Unconscious 14 Behaviorism: Psychology of Adaptation 15 Humanistic Psychology: A New Direction 17 Cognitive Psychology: Revitalization of Study of the Mind 18 Psychobiology/Neuroscience: Exploring the Origins of the Mind 18
Psychology Today 21 Branches of Psychology 22 PRACTICALLY SPEAKING: What Can You Do with a Psychology Degree? 22 Shared Values 24 Current Trends in Psychology 24 Pioneering Women Psychologists 26
Summary 28 Key Terms 29
CHAPTER 2
Psychology as a Science
Opening Vignette Ugly Reality?
30
31
What is a Science? 32 Scientific Principles 32 The Scientific Method 33
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Is Psychology a Science? 35 Goals of Psychology 35 Values and the Application of Psychology 36 Misrepresentation of Psychology 37 Making Psychology More Popular 37
How Do Psychologists Conduct Research? 38 State a Hypothesis 38 Choose Participants 39 Pick a Research Method 40
How Do Psychologists Make Sense of Research Results? 43 Correlations: Measures of Relationships 44 Experimental Analyses: Establishing Cause and Effect 46 Using Statistics to Evaluate and Plan Research 47 PRACTICALLY SPEAKING: Tips on Reading a Scientific Journal Article
48
What Ethical Research Guidelines Do Psychologists Follow? 49 Facts and Figures on Animal Research 51
Summary 51 Key Terms 53
CHAPTER 3
Human Development
Opening Vignette Growing Up Super
Understanding How We Develop
54
55
56
What Drives Change? Nature versus Nurture 57 Qualitative versus Quantitative Shifts in Development 57 Do Early Experiences Matter? Critical Periods and Sensitive Periods 58
How Is Developmental Psychology Investigated? 59 Before We are Born How We Develop
61
In the Beginning: Genetics 61 Birth Order Effects: What’s Real? 64 Prenatal Development 64 Prior to Birth When Things Go Wrong 65
Infancy How We Develop
66
Physical Development 66 Cognitive Development 69
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> Social and Emotional Development 72 Parenting Styles How We Differ 73 What Do Fathers Have to Do With Development? A Lot! 74
Childhood How We Develop
75
Physical Development 75 Cognitive Development 76 Social and Emotional Development 80
Adolescence How We Develop
83
Physical Development 83 Cognitive Development 84 Social and Emotional Development 84 PRACTICALLY SPEAKING: The Trials and Tribulations of Becoming an Adult
Adulthood How We Develop
86
87
Physical and Cognitive Development 87 Social and Emotional Development 88
Developmental Psychopathology When Things Go Wrong
89
Bullying: A Continuing Problem 90
Summary 92 Key Terms 93 Cut Across Connection 94 Video Lab Exercise 95
CHAPTER 4
Neuroscience
96
Opening Vignette Your Brain in Jeopardy!
97
How Do Scientists Study the Nervous System? 98 What Cells Make Up the Nervous System? 99 Neurons 99 Glia 100 More Than Just Glue 101
How Do Neurons Work? 101 The Action Potential 101 Communication Across the Synapse 103 Neural Networks 104
Contents
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How is the Nervous System Organized? 105 The Peripheral Nervous System 105 The Central Nervous System 106 Spinal Cord Injuries When Things Go Wrong
107
Structures of the Brain 108 The Brainstem 108 The Pons 109 The Cerebellum 109 The Midbrain 109 The Thalamus 109 The Hypothalamus 110 The Pituitary Gland and the Endocrine System 110 The Amygdala 111 The Hippocampus 111 The Striatum 111 The Nucleus Accumbens 112 The Neocortex 112 The Corpus Callosum 115 Do We Really Use Only 10 Percent of Our Brains? 116 The Integrated Brain 116
Building the Brain How We Develop
117
Brain Development Before We Are Born 117 Brain Development Across the Lifespan 119 Dying Cells in a New Brain? 119
Brain Side and Brain Size How We Differ
120
Differences in Brain Lateralization 120 Gender Differences 121 PRACTICALLY SPEAKING: How Can You Prevent Age-Related Decline in Brain Function?
Neurological Diseases When Things Go Wrong
122
Transplanting Stem Cells to Treat Neurological Disorders 123
Summary 124 Key Terms 125 Cut Across Connection 126 Video Lab Exercise 127
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> CHAPTER 5
Sensation and Perception
Opening Vignette On and Off Sensation
128
129
Common Features of Sensation and Perception 130 The Chemical Senses: Smell and Taste 132 Taste and Smell: How They Work 132 Smell and Taste What Happens in the Brain?
133
What Happens in the Brain When We Eat Pizza 134 Regeneration in the Taste and Smell Systems 136 Smell and Taste How We Develop 137 Smell and Taste How We Differ 137 Smell and Taste When Things Go Wrong 138
The Tactile or Cutaneous Senses: Touch, Pressure, Pain, Vibration 139 Tactile Senses What Happens in the Brain? 140 The Tactile Senses How We Develop 141 Specialized Somatosensory Systems: Whiskers and Star-Shaped Noses 142 Tactile Senses How We Differ 142 Tactile Senses When Things Go Wrong 143 PRACTICALLY SPEAKING: Quick Ways to Reduce Acute Pain
144
The Auditory Sense: Hearing 145 Hearing What Happens in the Brain? 148 Specialized Somatosensory Systems: Synesthesia 149 Hearing How We Develop 149 Hearing How We Differ 150 Hearing When Things Go Wrong 150
The Visual Sense: Sight 151 Seeing the Light 152 Seeing in Color 153 Sight What Happens in the Brain? 155 Sight How We Develop 159 Sight When Things Go Wrong 159
Summary 161 Key Terms 162 Cut Across Connection 163 Video Lab Exercise 163
Contents
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Consciousness
164
Opening Vignette Love and Awareness on an Errand
Going toward the Light: Near-Death Experiences 166
When We Are Awake: Conscious Awareness 167 When We Are Awake What Happens in the Brain? Alert Consciousness How We Develop 170
168
Preconscious and Unconscious States 171 Freud’s Views of the Unconscious 171 Cognitive Views of the Unconscious 172
Hypnosis 173 Hypnotic Procedures and Effects 173 Why Does Hypnosis Work? 174 Hypnosis What Happens in the Brain? 175
Meditation 176 When We are Asleep 177 Why Do We Sleep? 177 Rhythms of Sleep 177 “Owls” and “Larks” How We Differ 178 When We Sleep What Happens in the Brain? 179 Dreams 181 Nightmares, Lucid Dreams, and Daydreams 182 Sleep How We Develop 183 Sleep Deprivation and Sleep Disorders When Things Go Wrong
Psychoactive Drugs 187 PRACTICALLY SPEAKING: Addictions: Living out of control 188 Depressants 189 Binge Drinking and College Students 189 Stimulants 192 Hallucinogens 195 Marijuana as Medicine 196 Psychoactive Drugs What Happens in the Brain? 197
Summary 198 Key Terms 199 Cut Across Connection 200 Video Lab Exercise 201
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> CHAPTER 7
Learning
202
Opening Vignette Name that Tune
203
What is Learning? 204 Nonassociative Learning 204 Associative Learning 207
Classical Conditioning 208 How Does Classical Conditioning Work? 208 Classical Conditioning What Happens in the Brain? Classical Conditioning and Fears 211 Learning to Love Pain? 212 Classical Conditioning and Taste Aversions 213
210
Operant Conditioning 214 How Does Operant Conditioning Work? 215 PRACTICALLY SPEAKING: Using Punishments and Rewards to Teach Children 217 Using Operant Conditioning to Teach New Behaviors 218 Learned Helplessness When Things Go Wrong 219 What Happens in the Brain in Spatial Learning: Taxicab Drivers 220 Learning and Thinking 220
Observational Learning 222 Observational Learning and Violence 222
Factors that Facilitate Learning 223 Timing 223 Awareness and Attention 224
When We Learn What Happens in the Brain?
225
What Happens in the Brain When We Learn to Play a Video Game 228 Prenatal and Postnatal Learning How We Develop Learning and Gender How We Differ
230
231
Gender Differences 231
Learning Disabilities When Things Go Wrong
232
Dyslexia 232 Dyscalculia 233 Attention Deficit Disorders 233
Summary 234 Key Terms 236 Cut Across Connection 236 Video Lab Exercise 237 Contents
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Memory
238
Opening Vignette A Man with No Past
239
What is Memory? 240 How Do We Encode Information into Memory? 242 Even Memory Champions Need to Pay Attention 243 Using Automatic and Effortful Processing to Encode 43 Encoding Information into Working Memory: Transferring from Sensory Memory into Working Memory 244 Encoding Information into Long-Term Memory: Transferring Working Memory into Long-Term Memory 245 In What Form is Information Encoded? 245 PRACTICALLY SPEAKING: Make Your Memories More Meaningful PRACTICALLY SPEAKING: Organizing Your Memories
247
248
How Do We Store Memories? 249 Storage in Working Memory 249 Storage in Long-Term Memory 251
How Do We Retrieve Memories? 253 Priming and Retrieval 254 Context and Retrieval 255 Emotion: A Special Retrieval Cue 255
Why Do We Forget and Misremember? 257 Theories of Forgetting 257 Distorted or Manufactured Memories 260
What Happens in the Brain When We Give Eyewitness Testimony 264 Memory What Happens in the Brain?
266
What is the Anatomy of Memory? 266 What is the Biochemistry of Memory? 267
Disorders of Memory When Things Go Wrong Organic Memory Disorders 269 Dissociative Disorders 271
Summary 273 Key Terms 274 Cut Across Connection 275 Video Lab Exercise 275
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> CHAPTER 9
Language and Thought
276
Opening Vignette “I’d Like to Phone a Friend, Please.”
277
Language 278 Language How we Develop 280 Poverty and Language Development 282 Critical Period for Language Learning? The Case of Genie 284 Language What Happens in the Brain? 285 What the @#?! – Why Curse? 287 Language How We Differ 287
Language and Thought 289 What Happens in the Brain When We Learn A Second Language 290 Thinking without Words: Mental Imagery and Spatial Navigation 292 The Influence of Language on Thought 292
Thought 293 Thinking and Effort: Controlled and Automatic Processing 294 Thinking to Solve Problems 295 Thinking to Make Decisions 298 Metacognition 301 PRACTICALLY SPEAKING: When is it Best to Rely on Emotions for Decision Making? 302 Can Animals Think? 303 Thought When Things Go Wrong 304 Obsessive-Compulsive Disorder 304 Schizophrenia 305
Summary 307 Key Terms 308 Cut Across Connection 308 Video Lab Exercise 309
Contents
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Intelligence
310
Opening Vignette As Smart as They Look?
311
What Do We Mean By Intelligence? 312 Is Intelligence General or Specific? 312 Current Multifactor Theories of Intelligence 314 Where are We Today? 317
Additional Types of Intelligence 317 Emotional Intelligence 317 Social Intelligence 318 Wisdom 318 Creativity 319 Personality Characteristics 320
How Do We Measure Intelligence? 320 Intelligence Test Construction and Interpretation 321 History of Intelligence Testing 322 Galton and “Psychophysical Performance” 322 How Well Do Intelligence Tests Predict Performance? 326 Cultural Bias and Stereotypes in Intelligence Testing 326 The SAT: Soon to Be a Thing of the Past? 327 Is Human Intelligence Increasing? 329
Is Intelligence Governed by Genetic or Environmental Factors? 330 What Are the Social Implications of the Nature/Nurture Debate? 330 The Bell Curve Controversy 331 Genetic Influences on Intelligence 331 Environmental Influences on Intelligence 333 PRACTICALLY SPEAKING: Can Parents Improve Their Children’s Intelligence?
Group Differences in IQ Scores 336 Does Environmental Enrichment Make a Difference? 337 Is There Really a Mozart Effect? 338
Intelligence What Happens in the Brain?
339
Brain Size, Number of Neurons, and Intelligence 339 Brain Speed and Intelligence 340 Brain Activity and Intelligence 340 Cortical Thickness and Intelligence How We Develop 341
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> Extremes in Intelligence How We Differ
343
Mental Retardation 343 Giftedness 345
Summary 346 Key Terms 347 Cut Across Connection 348 Video Lab Exercise 349
CHAPTER 11
Motivation
350
Opening Vignette Hot Dogging: A Different Kind
of Competition
351
Theories of Motivation 352 Instinct Theory 352 Drive Reduction Theory 353 Arousal Theory 354 Incentive Theory 355 Multiple Motivations: Hierarchy of Needs 357
Biological Motivations: Hunger 358 Hunger What Happens in the Brain? 358 Hunger How We Differ 360 Hunger When Things Go Wrong 362 The U.S. Social Stigma Against Obesity 364
Biological Motivations: Sex 365 Sex: Psychological and Social Factors 366 Sex: What Happens in the Body and Brain 367 Sex How We Differ 369 Turnim-Man: When “Girls” Become Men 371 Sex When Things Go Wrong 373
Psychological Motivations: Affiliation and Achievement 377 Affiliation 377 Achievement 378
Contents
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What Happens in the Brain When We’re Motivated to Run a Marathon 380 Summary 382 Key Terms 382 Cut Across Connection 383 Video Lab Exercise 383
CHAPTER 12
Emotion
384
Opening Vignette Emotion in the Driver’s Seat
385
What Is Emotion? 386 Components of Emotion 386 Measurement of Emotions 388 Functions of Emotions 390 Emotional Decision Making 390
Where Do Emotions Come From? 393 James-Lange Theory 393 Cannon-Bard Theory 394 Schachter and Singer’s Two-Factor Theory 395 Cognitive-Mediational Theory 397 Facial-Feedback Theory 397 Evolutionary Theory 399
Emotion How We Develop
401
Lewis’s Cognitive Theory of Emotional Development 401 Izard’s Differential Emotions Theory 402
Emotion What Happens in the Brain?
403
Early Theories 403 Current Research 404 Mixed Emotions 404
What About Positive Emotions? 406 PRACTICALLY SPEAKING: Measuring Your Emotional Well-Being
Emotion How We Differ
409
Patterns of Emotionality 410 Regulation of Emotions 411 Gender Differences in Emotion 412 Cultural and Ethnic Differences in Emotion 413
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> Disorders of Emotion When Things Go Wrong
414
Anxiety Disorders 415 Mood Disorders 417
Summary 418 Key Terms 419 Cut Across Connection 420 Video Lab Exercise 421
CHAPTER 13
Personality
422
Opening Vignette Not So Identical Twins
423
Historic Perspectives on Personality 424 Freud and Psychoanalytic Theory 424 Other Psychodynamic Theories 428 PRACTICALLY SPEAKING: Jung in the Business World
429
Humanistic Theories 430
Understanding Personality Today: Traits versus Situations 432 Trait Theories 432 Situationism and Interactionism 436 Influence of Movies and TV on Personality and Behavior 438
Biological Foundations of Personality 439 How Much Do Genetic Factors Contribute to Personality? How We Develop 439 Personality What Happens in the Brain? 440
Personality How We Differ
443
Gender Differences 443 Differences Among Cultural Groups 445 Differences Among Subcultures 447 Culture, Socioeconomic Environment, and Personality 448
Personality Disorders When Things Go Wrong
449
Narcissistic Personality Disorder 451 Antisocial Personality Disorder 451 School Shootings and Videogames 452 Borderline Personality Disorder 452
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Personality Assessment 454 Personality Inventories 454 PRACTICALLY SPEAKING: Evaluating Personality Quizzes
454
Projective Tests 455
Summary 456 Key Terms 458 Cut Across Connection 458 Video Lab Exercise 459
CHAPTER 14
Social Psychology
460
Opening Vignette Social Psychology in a Storm
Social Cognition: Attitudes 462 Attitudes How We Develop 463 How Do Attitudes Change? 463 Do Attitudes Influence Behavior? 465 Are People Honest About Their Attitudes? 466 Stereotypes and Prejudice 467 Attitudes and the Power of Persuasion 469
Social Cognition: Attributions 471 Dispositional and Situational Attributions 471 The Actor-Observer Effect 472 Exceptions to the Rule 473
Social Forces 474 Norms and Social Roles 475 Gossiping About People We Don’t Even Know 476 Conformity 478 Obedience 479
Social Relations 482 Group Dynamics 483 Helping Behavior 485 Aggression 487 Interpersonal Attraction 488 Falling in Limerence 491
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> Social Functioning What Happens in the Brain?
492
Disorders of Social Functioning When Things Go Wrong
494
Social Phobias and Avoidant Personality Disorder 494 Dependent Personality Disorder 495 Autism 495
Summary 497 Key Terms 498 Cut Across Connection 499 Video Lab Exercise 499
CHAPTER 15
Stress, Coping, and Health
Opening Vignette Just Work Harder
500
501
What Is Stress? 502 Stress and Stressors 502 Ways of Experiencing Stress 503 Sports and Pressure 504 Kinds of Stressors 505
Responding to Stress 510 Physiological Responses to Stress What Happens in the Brain? A Laugh A Day Keeps the Doctor Away? 513 Emotional Responses to Stress 514 Cognitive Responses to Stress 514
510
What Happens in the Brain When Public Speaking Stresses Us Out 516 Individual Responses to Stress How We Differ
518
Coping With Stress 521 Lashing Out 521 Self-Defense 522 Self-Indulgence 522 PRACTICALLY SPEAKING: How Can You Manage Stress?
523
Constructive Strategies 524
Stress and Health 525 Coronary Heart Disease 525 Life Change and Illness 526 Stress and the Immune System 526 The Benefits of Stress 529
Contents
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Posttraumatic Stress Disorder When Things Go Wrong
530
Symptoms of PTSD 530 What Events Cause PTSD? 531 Who Develops PTSD? 531
Summary 533 Key Terms 534 Cut Across Connection 534 Video Lab Exercise 535
CHAPTER 16
Psychological Disorders and Their Treatments
Opening Vignette Depressed and Lost 537
Defining, Classifying, and Diagnosing Psychological Abnormality 539 Classifying Psychological Disorders 540 PRACTICALLY SPEAKING: Can Assessment and Diagnosis Cause Harm? 541
Diagnosing Psychological Disorders 544
Models Of Abnormality 546 The Neuroscience Model What Happens In The Brain?
546
Neuroscience Views of Abnormal Behavior 547 Brain Therapies 548
What Happens in the Brain When a Depressed Person Takes an Antidepressant Drug 550 The Neuroscience Model in Perspective 552
The Psychodynamic Model 552 Psychodynamic Views of Abnormal Behavior 552 Psychodynamic Therapies 554 The Psychodynamic Model in Perspective 555
The Behavioral Model 555 Behavioral Therapies 556 The Behavioral Model in Perspective 558
The Cognitive Model 558 Cognitive Views of Abnormal Behavior 559 Cognitive Therapies 560 The Cognitive Model in Perspective 561
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> The Humanistic-Existential Model 562 Rogers’s Humanistic Theory and Therapy 562 Gestalt Theory and Therapy 563 Existential Theories and Therapy 564 The Humanistic-Existential Model in Perspective 565
Formats of Therapy 565 Group Therapy 565 Family Therapy 567 Couple Therapy 567 Community Treatment 567
Does Therapy Work? 568 PRACTICALLY SPEAKING: How to Choose a Therapist
569
Abnormal Psychology: Social and Cultural Forces 570 Social Change 70 Socioeconomic Class How We Differ 570 Cultural Factors How We Differ 571
Some Final Thoughts About the Field of Psychology 572 Summary 573 Key Terms 574 Cut Across Connection 575 Video Lab Exercise 575
Glossary G-1 References R-1 Text and Illustration Credits T-1 Photo Credits P-1 Name Index NI-1 Subject Index SI-1
Contents
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To the Instructor Psychology is all around us. If ever there was a subject that permeates our everyday lives, it is psychology. Behavior occurs everywhere, and the study of behavior can help shed light on the widest range of events and issues.
This textbook Psychology Around Us helps to open students’ minds to the notion that psychology is indeed around them every day and that its principles are immediately applicable to a whole host of life’s questions. It also features classroom-proven pedagogy to keep students engaged and help them master the material. Between the two of us, we have taught Introductory Psychology, Abnormal Psychology, and Neuroscience for about 50 years. Throughout those years, we have always been struck by how differently students react to various subjects of psychology. For example, most students find Abnormal Psychology fascinating, relevant, and “alive,” while many consider other areas of psychology to be flat and removed from their lives. Thus, while excited by their abnormal psychology text, they are often disappointed by their introductory psychology text. There is something very wrong with this. After all, like abnormal psychology, general psychology deals with people and with behavior; and what can be more interesting than that? Granted, abnormal behaviors are often exotic and puzzling, and people who display them generate empathy, sympathy, and curiosity; but, certainly, normal behavior is every bit as remarkable. This gap between the appeal of abnormal behavior and that of normal behavior occurs throughout psychology. Students are fascinated by instances of “memory gone bad” yet take for granted that people can remember in the first place. They love to follow the activity of serotonin and dopamine when studying mood disorders and schizophrenia, but not when learning about these neurotransmitters in an introductory psychology course. Students are captivated by failures in attention (ADHD), thought (schizophrenia), communication (autism), or coping (posttraumatic stress disorder), yet almost nonchalant about the fact that people usually attend, think, communicate, and cope quite well. They keenly appreciate the importance and effects of psychotherapy, yet almost overlook everyday instances of attitude, behavior, and mood change. Our textbook is dedicated to helping students appreciate that both normal and abnormal behavior are fascinating, and to energizing, exciting, and demonstrating for them the enormous relevance of psychology. It encourages students to examine what they know about human behavior and how they know it, and opens them up to an appreciation of psychology outside of the classroom.
About the Text As instructors and researchers, we (the authors) are both passionate about the study of psychology and genuinely fascinated by behavior, thought, and emotion. When we teach a course, we consider ourselves successful if we have engaged our students in the rigorous study of psychology while simultaneously transferring our passion for the subject. These same criteria of success should be applied to a textbook in psychology: It should broaden the reader's knowledge about the field and, at the same time, move, excite, and motivate the student. To achieve this goal, our textbook includes a range of features—some traditional, others innovative. While implementing the traditional introductory psychology concepts and theories, this textbook also introduces two special pedagogical tools, the Cut Across Connection and What Happens in the Brain When... These features help to demonstrate how psychology’s various topics are relevant to each other and also to everyday life.
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Special Pedagogical Tools Cut Across Connection One of the most important ways that this text will help students “see the big picture” are recurring sections that highlight how the different fields of psychology are connected to each other and how they connect to everyday life. We highlight human development, brain function, abnormal psychology, and individual differences as ideas that literally cut across our discipline. Following a long-standing tradition, for example, most of today’s textbooks offer detailed chapters on developmental psychology early in the book and detailed chapters on psychological disorders late in the textbook. In between are chapters on other subfields of psychology — from sensation, perception, language, and thought, to emotion, personality, and social behavior. These middle chapters focus on the nature, explanations, and applications of each subfield, but they typically do not explore how such areas of psychological functioning develop or what dysfunctions may occur in each area. It is left to the reader to remember developmental material from earlier chapters and see its implications for the material at hand, or to place the current material on hold and tie it weeks later to subsequent chapters on related psychological disorders and treatments. No wonder some students are impatient to “get to the psychology!” They are not set up to appreciate the full range of the field. To achieve our goal of showing students how psychology is indeed all around us, and to bring our textbook in line with the course curricula of most professors, we have structured each of the chapters in our textbook in a very particular way — a cross-sectional presentation. Every chapter on a substantive area of psychology not only offers a thorough presentation of the nature, explanations, and applications of that area, but also includes “Cut-Across” sections on the development, brain function, individual differences, and dysfunctions that occur in that realm of mental life. The Sensation and Perception chapter (Chapter 5), for example, includes the sections “How Does Hearing Develop?”, “What Happens in the Brain When We Hear?”, “Hearing: How We Differ”, and “When Hearing Goes Wrong,” along with comparable sections on smell, taste, touch, and sight. Similarly, the Emotion chapter (Chapter 12) includes the sections “How Do Emotions Develop?”, “What Happens in the Brain When We are Feeling Emotions?”, “Emotions: How We Differ”, and “When Emotions Go Wrong.”
What Happens in the Brain When ... Many introductory psychology students consider the study of neuroscience to be difficult and at times irrelevant to the study of human behavior. In recent years, however, neuroscience has been tied to virtually every subfield of psychology. Remarkable brain imaging studies, in conjunction with animal studies, have helped us to identify the neural mechanisms of everyday experience. Accordingly, Psychology Around Us incorporates neuroscience information into chapters where it has been traditionally absent, such as Social Psychology and Consciousness. In addition, the text offers a key teaching feature that helps bring neuroscience directly into the lives of readers: Exciting and accessible two-page layouts appear throughout the book illustrating what happens in the brain when people are performing such common behaviors as eating pizza, learning a video game, acquiring a second language, giving a speech in public, and running a marathon. These layouts, which include neuroimages and findings from both human studies and relevant animal experiments, draw students into the brain and provide them with up-to-date information about the neural mechanisms at work during their everyday experiences. Regardless of their background in neuroscience, students come away intrigued by material that has traditionally been considered difficult. xxxii To the Instructor
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Additional Features Chapter-Opening Vignettes Every chapter begins with a vignette that shows the power of psychology in understanding a range of human behaviors. This theme is reinforced throughout the chapter, celebrating the extraordinary processes that make the everyday possible.
Guided Learning A Learning Objective for each chapter section identifies the most important material for students to understand while reading that section. These learning objectives also serve as the driving principle in WileyPLUS. Following each section is a Before You Go On feature that helps students check their mastery of the important items covered. • What Do You Know? questions prompt students to stop and review the key concepts just presented. • What Do You Think? questions encourage students to think critically on key questions in the chapter.
Special topics on psychology around us Each chapter highlights interesting news stories, current controversies in psychology, and relevant research findings that demonstrate psychology around us. The Practically Speaking box emphasizes the practical application of everyday psychology.
Helpful study tools… Key Terms are listed at the end of each chapter with page references. Marginal Definitions are defined in the margin next to their discussion in the text. Marginal Notes present interesting facts and quotes throughout the chapter.
Chapter Summary The end-of-chapter Summary reviews the main concepts presented in the chapter with reference to the specific Learning Objectives. It provides students with another opportunity to review what they have learned as well as to see how the key topics within the chapter fit together.
Resources Psychology Around Us is accompanied by a host of resources and ancillary materials designed to facilitate a mastery of psychology.
Powerful Media Resources WileyPLUS is an online teaching and learning environment that integrates the entire digital textbook with the most effective instructor and student resources to fit every learning style. With WileyPLUS, • Students achieve concept mastery in a rich, structured environment that’s available 24/7 and • Instructors can personalize and manage their course more effectively with assessment, assignments, grade tracking, and more. For more information, visit www.wileyplus.com
To the Instructor
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Instructor Resources Instructor Resources can be found within the Psychology Around Us WileyPlus course and on the text’s companion website, www.wiley.com/college/comer.
“Lecture-Launcher” Videos The Psychology Around Us series of “lecture-launcher” videos helps bring lectures to life and, most importantly, captivate students. They help demonstrate the most important theme of an introductory psychology course — that psychology is all around us and that behavior, from everyday normal behavior to abnormal behavior, is truly fascinating. Averaging about five minutes in length, this collection covers a range of relevant topics. Each video is a cream-of-the-crop excerpt from the CBS, BBC, NBC, ABC, Public Broadcasting, or Independent video libraries chosen from a televised news report, documentary, lab study, or the like, and illustrating a particular lecture point, bringing the topic to life in exciting ways. In addition, the package has been produced by Professor Comer and other leading university educators whose extensive teaching, video, and psychology backgrounds enable them to develop video materials that perfectly address the lecture needs and goals of teachers and students. The clips in this 75-piece package focus on topics ranging from the split-brain phenomenon to conformity and obedience, emotions of fear or disgust, sensations of taste and smell, infant facial recognition, gender orientation, and brain development. The videos are accompanied by an extensive Instructor’s Guide. This guide offers a description of each module in the package, its length and source, features of special interest, and relevant textbook/lecture topics. The video program is readily accessible and easily integrated into the Introductory Psychology course through the Psychology Around Us WileyPlus course. Instructors have the option of assigning videos to students for viewing outside of class along with quizzes that test understanding of the video’s content and relevance.
Psychology Around Us Video Lab Activities Psychology Around Us offers a series of 14 active learning projects that students can conduct on their own. Traditionally, such exercises have been presented in book form, with written exercises guiding students through paper-and-pencil tasks. Today students can interact with computerized exercises, become more engaged by video and animated material, and receive immediate feedback about the effects and accuracy of their choices. These lab activities use extensive video material to drive student learning. The combination of video footage and digital interactive technology bring the lab exercises to life for students in ways that were previously impossible, actively engaging the students and helping them to better process the lesson at hand. The kinds of video material included in the Video Lab Activities range from laboratory brain footage to videos of everyday events to psychology documentary excerpts. For example, one video-digital lab exercise on Memory Manufacturing and Eyewitness Testimony unfolds as a cluster of video-digital lab exercises on memory. They guide the student to also explore (1) pre-event and post-event memory interference, (2) childhood memory limits, (3) snapshot memories, and (4) the creation of false memories. Like the “Lecture-Launcher” videos, the Video Labs are accessible through the Psychology Around Us WileyPlus course. Instructors have the option of assigning the Videos Labs to students for completion outside of class; the student’s work is then viewable by the instructor in WileyPlus’s Gradebook section. xxxiv To the Instructor
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Instructor’s Manual Prepared by Elaine Cassel, Lord Fairfax Community College This Instructor’s Manual is designed to help instructors maximize student learning and encourage critical thinking. It presents teaching suggestions for every chapter using the book’s objectives as well as including ideas for lecture classroom discussions, demonstrations, and videos. This manual will also share activity-based applications to everyday life.
Lecture PowerPoint Presentation Prepared by Lisa Hagan, Metropolitan State College of Denver Every chapter contains a Lecture PowerPoint Presentation with a combination of key concepts, figures and tables, and problems and examples from the textbook.
TestBank Prepared by Christopher Mayhorn, North Carolina State University, Matthew Isaak, University of Louisiana at Lafayette, and Susan Weldon of Henry Ford Community College The Test Bank is available in a Word® document format or through Respondus®. The questions are available to instructors to create and print multiple versions of the same test by scrambling the order of all questions found in the Word version of the test bank. This allows users to customize exams by altering or adding new problems.
Prelecture Quizzes Prepared by Brenda Walker-Moore, Kirkwood Community College This resource offers 10-15 questions per chapter that are assignable to students prior to the lecture or for general review purposes.
In-Class Concept Checks Prepared by Brenda Walker-Moore, Kirkwood Community College This resource offers 10-15 questions per chapter that can be used with a variety of person response (or “clicker”) systems.
Student Resources Student Resources can be found within the Psychology Around Us WileyPlus course and on the text’s companion website, www.wiley.com/college/comer.
Online Study Tools Prepared by Brenda Walker-Moore, Kirkwood Community College and Arthur Olguin of Santa Barbara City College Psychology Around Us provides students with a website containing a wealth of support materials to develop their understanding of class material and increase their ability to solve problems in the classroom. On this website students will find Practice Chapter Exams for every chapter that will allow them to assess their understanding of chapter concepts. Students will be able to study using tools available on the webstite that include: Interactive Flash Cards, Chapter Summaries, Learning Objectives, Web Resources, and more! To the Instructor
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Acknowledgments The writing of this text has been a group effort involving the input and support of many individuals. On a personal note, we thank our families, friends, and colleagues for their support and availability, particularly Marlene Comer and Jon Cohen. We greatly appreciate the significant help provided by Linda Chamberlin, Sean Allan, and Emily Graham. We are enormously grateful to those individuals who made important research and writing contributions to early drafts of various elements of the book, including Dina Altshuler, Leslie Carr, Greg Comer, Jon Comer, Lindsay Downs, Jami Furr, Jamie Hambrick, Rob Holaway, and Art Pomponio. And we offer our sincere gratitude and admiration to the terrific team of professionals assembled by John Wiley & Sons who guided the development and production of this book so effectively, particularly those individuals with whom we worked most closely— Chris Johnson, Jay O' Callaghan, Marian Provenzano, Barbara Heaney, Sheralee Connors, Suzanne Thibodeau, Beverly Peavler, Hilary Newman, Jeanine Furino, Elizabeth Morales, and Danielle Torio. Finally, a very special thank you goes out to the hundreds of faculty who have contributed to the development of this first edition text, its art program, its digital resources and its powerful supplemental program. To the reviewers, focus group and workshop participants who gave their time and constructive criticism, we offer our deep appreciation. We are deeply indebted to the following individuals and trust they will recognize their contributions throughout the text.
Reviewers David Alfano, Community College of Rhode Island Evelyn Blanch-Payne, Albany State University Amanda Bozack, University of New Haven Jennifer Breneiser, Valdosta State University Tina Burns, Florida International University Jarrod Calloway, Northwest Mississippi Community College Jill Carlivati, George Washington University Daneen Deptula, Fitchburg State College Dale V. Doty, Monroe Community College Kimberley J. Duff, Cerritos College Jane Dwyer, Rivier College Darlene Earley-Hereford, Southern Union State Community College Julie Evey-Johnson, University of Southern Indiana Linda Fayard, Mississippi Gulf Coast Community College Angela Fellner, University of Cincinnati Christopher M. France, Cleveland State University Adia J. Garrett Butler, University of Maryland-Baltimore County Linda Bolser Gilmore, DeKalb Technical College Marvin Gordon, University of Illinois-Chicago Gladys S. Green, Manatee Community College-Bradenton Laura Gruntmeir, Redlands Community College Alexandria Guzman, University of New Haven Sheryl Hartman, Miami Dade College Myra M. Harville, Holmes Community College Bert Hayslip, Jr., University of North Texas-Denton Tonya Honeycutt, Johnson County Community College Charles Jacob Huffman, James Madison University
xxxvi Acknowledgments
Jessica Jablonski, The Richard Stockton College of New Jersey Cheri L. Kittrell, Manatee Community College-Bradenton Juliana K. Leding, University of North Florida Angela Lipsitz, Northern Kentucky University Missy Madden-Schlegel, Marist College Gregory Manley, University of Texas at San Antonio Christopher B. Mayhorn, North Carolina State University Tamara J. Musumeci-Szabo, Rutgers, The State University of New Jersey Ronnie Naramore, Angelina College Dominic J. Parrott, Georgia State University Terry F. Pettijohn, The Ohio State University-Marion Sean P. Reilley, Morehead State University Karen Rhines, Northampton Community College Margherita Rossi, Broome Community College Maria Shpurik, Florida International University Morgan Slusher, Community College of Baltimore County-Essex Mark Stewart, American River College Inger Thompson, Glendale Community College Suzanne Tomasso, Manatee Community CollegeBradenton Katherine Urquhart, Lake-Sumter Community College Andrew S. Walters, Northern Arizona University C. Edward Watkins, University of North Texas-Denton Mark Watman, South Suburban College Sheree Watson, University of Southern Mississippi Shannon Michelle Welch, University of Idaho Diane Keyser Wentworth, Fairleigh Dickinson University Judith Wightman, Kirkwood Community College
Ann Brandt-Williams, Glendale Community College Manda J. Williamson, University of Nebraska-Lincoln Melissa Wright, Victoria College
Workshop Participants Marion F. Cahill, Our Lady of the Lake College Jarrod Calloway, Northwest Mississippi Community College Mark Covey, Concordia College Dale V. Doty, Monroe Community College Adia J. Garrett Butler, University of Maryland, Baltimore County Esther Hanson, Prince George's Community College Sheila Kennison, Oklahoma State University Cheri Kittrell, State College of Florida, Manatee-Sarasota Ronnie Naramore, Angelina College Marylou Robins, San Jacinto College Maria Shpurik, Florida International University Inger Thompson, Glendale Community College
Focus Group Participants Jake Benfield, Colorado State University Ann Brandt-Williams, Glendale Community College Baine Craft, Seattle Pacific University Linda Bolser Gilmore, DeKalb Technical College Elaine Cassel, Lord Fairfax Community College Shawn Robert Charlton, University of Central Arkansas Laurie Corey, Westchester Community College Angela Fellner, University of Cincinnati Andrew M. Guest, University of Portland
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James E. Hall, Montgomery College Alishia Huntoon, Oregon Institute of Technology Heide D. Island, Seattle Pacific University Dale V. Klopfer, Bowling Green State University Heather LaCost, Waubonsee Community College Fred Leavitt, California State University-Hayward Irv Lichtman, Houston Community College Wade Lueck, Mesa Community College Gregory Manley, University of Texas at San Antonio Timothy D. Matthews, The Citadel Dawn McBride, Illinois State University Eleanor E. Midkiff, Santa Barbara Community College Richard Miller, Western Kentucky University Robin Musselman, Lehigh Carbon Community College Kathryn C. Oleson, Reed College Sean P. Reilley, Morehead State University N. Clayton Silver, University of Nevada-Las Vegas Nancy Wiggins, Lurleen B. Wallace Community College Judith Wightman, Kirkwood Community College Jason Young, Hunter College
Content Consultants Eileen Achorn, University of Texas-San Antonio Bill Altman, Broome Community College Kim Anderson, Brigham Young Universtiy-Idaho Harold E. Arnold, Judson College Eileen Astor-Stetson, Bloomsburg University Kerri Augusto, Becker College Anisah Bagasra, Claflin University Ted Barker, Northwest Florida State College Jacob Benfield, Colorado State University John Billimek, California State University-Long Beach Ann Brandt-Williams, Glendale Community College Laurel Brooke Poerstel, University of North CarolinaWilmington Kimberly Carmitchel, Colorado Mountain College Patrick Carmody, University of Tennessee-Knoxville Juan Casas, University of Nebraska at Omaha Kinho Chan, Hartwick College Shawn Robert Charlton, University of Central Arkansas Kimberly Christopherson, Morningside College Wanda Clark, South Plains College Job Clement, Daytona State College Frank Conner, Grand Rapids Community College Verne Cox, University of Texas at Arlington
Gregory Cutler, Bay de Noc Community College Matthew Dohn, Kutztown University Joan Doolittle, Anne Arundel Community College Darryl L. Douglas, University of Michigan-Flint Vera Dunwoody, Chaffey College Christopher Dyszelski, Madison Area Technical College Melanie Evans, Eastern Connecticut State University Kimberly Fairchild, Manhattan College Sue Frantz, Highline Community College Michael K. Garza, Brookhaven College David Gersh, Houston Community College William Goggin, University of Southern Mississippi Mark Grabe, University of North Dakota Jonathan Grimes, Community College of Baltimore County Gretchen Groth, Metropolitan State College of Denver Nancy Hartshorne, Central Michigan University Jeffrey B. Henriques, University of Wisconsin-Madison Raquel Henry, Lone Star College-Kingwood Rick Herbert, South Plains College James Hess, Black Hills State University James Higley, Brigham Young University Jameson K. Hirsch, East Tennessee State University Farrah Jacquez, University of Cincinnati Richard Kandus, Mt. San Jacinto College-Menifee Campus Dan Klaus, Community College of Beaver County Heather LaCost, Waubonsee Community College Gerard LaMorte, Rutgers, The State University of New Jersey Mark Laumakis, San Diego State College Laura Lauzen-Collins, Moraine Valley Community College Nicolette Lopez, University of Texas at Arlington Tim Maxwell, Hendrix College Barbara McMillan, Alabama Southern University Lisa R. Milford, State University of New York-Buffalo Hal Miller, Brigham Young University Robin Musselman, Lehigh Carbon Community College Ronnie Naramore, Angelina College Jane A. Noll, University of South Florida Christine Offutt, Lock Haven University Andrew Peck, Pennsylvania State University Thomas Peterson, Grand View University Daniel Philip, University of North Florida Ralph Pifer, Sauk Valley Community College William Pithers, Edinboro University Brian Pope, Tusculum College
Diane M. Reddy, University of Wisconsin-Milwaukee Heather Rice, Washington University in St. Louis Marylou Robins, San Jacinto College Richard Rogers, Daytona State College Steve Rouse, Pepperdine University Lisa Routh, Pikes Peak Community College Catherine Sanderson, Amherst College Alan Schlossman, Daytona State College Gloria Shadid, University of Central Oklahoma David Simpson, Carroll University Wayne S. Stein, Brevard Community College Mark Strauss, University of Pittsburgh Marla Sturm, Montgomery County Community College Dr Éva Szeli, Arizona State University Pamela M. Terry, Gordon College Elayne Thompson, Harper College Natasha Trame, Lincoln Land Community College Shaun Vecera, University of Iowa Larry Ventis, College of William and Mary Kurt Wallen, Neumann College Susan Weldon, Henry Ford Community College Jane Whitaker, University of the Cumberlands Nancy Wiggins, Lurleen B. Wallace Community College Robert W. Wildblood, Indiana University-Kokomo Kip Williams, Purdue University Patrick Wise, Monroe Community College Lynn Yankowski, Maui Community College Jennifer Yates, Ohio Wesleyan University Michael Young, Valdosta Technical College Edmond S. Zuromski, Community College of Rhode Island
Cover Consultants Laurie Corey, Westchester Community College Katherine Dowdell, Des Moines Area Community College Kimberley J. Duff, Cerritos College Christopher M. France, Cleveland State University Linda Bolser Gilmore, DeKalb Technical College Andrew M. Guest, University of Portland Charles Jacob Huffman, James Madison University Alishia Huntoon, Oregon Institute of Technology Christopher B. Mayhorn, North Carolina State University Deana Julka, University of Portland Kathryn C. Oleson, Reed College Maria Shpurik, Florida International University Jason Young, Hunter College
Acknowledgments xxxvii
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To the Student How to Use This Book The features in this book promote your reading comprehension, reflection, problem-solving skills, and critical-thinking skills. These skills are key to success in the course and in your life beyond. Let’s walk through the pedagogical features that will help you learn the material in this book.
Chapter-Opening Vignettes
Intelligence
CHAPTER 10
Chapter Outline • What Do We Mean by Intelligence? •
Additional Types of Intelligence
• How Do We Measure Intelligence? •
Is Intelligence Governed by Genetic or Environmental Factors? •
As
Smart
as
They
Intelligence
•
Look?
Extremes in Intelligence
Andre, a son of Romanian diplomats who speaks five languages and delights in scheming people off the show, and
E
ach week on the reality show America’s Most Smartest
Daniel, a Ph.D. candidate in psychology at a major California
Model, producers ask male and female models to com-
university who correctly spells both phosphorescence and
pete in a series of tasks designed to test both their intelligence
Every chapter begins with a vignette that shows the power of psychology in understanding a range of human behaviors. This theme is reinforced throughout the chapter, celebrating the extraordinary processes that make the everyday possible.
Bacchanalian during a spelling bee.
and their modeling skills. An intelligence-testing task, for example, may require rapid-fire responding to trivia questions that will determine how fast a partner has to run on a treadmill or dissecting and correctly identifying the organs from a fetal pig. Winning the intelligence challenge gives a model a decided edge in the modeling challenge. In one episode, for example, the winning team members were assigned a runway show with their dressing room next to the stage, while the losing team had to complete an obstacle course to make it to the runway. Models who fail to compete strongly in both tasks are eliminated from the show. Obviously, much of the show’s humor comes from stereotypes that models are generally not very smart, and certainly the show takes great delight in featuring models who cannot name the vice president of the United States (or, for that matter, do not know a judge’s last name). However, the show is equally derisive of contestants who cannot name an Italian designer under time pressure or do not demonstrate appropriate interpersonal skills during a surprise networking challenge. Further confounding the stereotype of the not-so-smart model, contestants include 310 Chapter 10
Intelligence
Clearly, America’s Most Smartest Model is built on common conceptions of what intelligence is. Like many other aspects of human behavior, however, intelligence is a concept that appears simple at first glance, only to become more and more complicated the closer we look at it. Start with the basic question: How do you define intelligence? Most people use smart or stupid to characterize the other people in their lives all the time, and they generally have a great deal of confidence in their assessments. But answer this: When you describe a friend as a generally smart person, how are you assessing smartness? Are you thinking about how your friend performs in all situations, or are you just impressed by how sophisticated her answers are in English class and ignoring the fact that she’s just scraping by in Chemistry? If you were watching the TV show just described, would you be sympathetic to a contestant’s protest that “street smarts” make him an intelligent person, even if he can’t successfully identify a city in Iraq? And what about that friend of yours who seems to be “book smart” but lacks common sense? Is that person, book smarts and all, the one you want leading you if your plane crashes on a remote island? Okay, then, so what do we mean by intelligence? Does it mean the same thing in every instance? How do we understand it, and how do we measure it? To these basic questions we must add several others: Can we distinguish between intelligence and talent? Are intelligence and wisdom the same thing? Are intelligence and creativity related? And, finally, Intelligence
311
What is Science LEARNING OBJECTIVE 1 Describe the steps in the scientific method.
Before we consider psychology as a science, take a moment to try to an tion, what is a science? You might have answered that question by listin ences, such as chemistry, biology, or physics. You might have envisione coated guy or gal in a lab somewhere, mixing strangely bubbling chemica
Guided Learning Chapter Learning Objectives summarize what you should be able to do once you have studied the chapter. You can use the learning goals in two ways. First, study them before reading the chapter to get an overall picture of how the concepts in the chapter are related to each other and what you will be learning. Then, after reading the chapter, use the learning goals to review what you have learned, either individually or in peer study groups. Advance organizers can improve learning and retention without significantly increasing study time.
Helpful study tools...
Before You Go On What Do You Know? 1. List and provide examples of the four goals of psychology. 2. Define and give an example of pseudopsychology, and contrast
What Do You Think:? What do you think is the appeal of pseudopsychology. Based on what you know about the scientific method, do you think psychology is a science in the same way chemistry, biology, or physics is a science? Whichever side of the debate you fall on, do you think that’s a good thing or a bad
response (believed to be adaptive as it helps animals escape notice and potential preRats and mice respond to the odors of their natural predators like foxes or weasels, with an increase in stress hormones and a characteristic immobilizationresponse (believed to be adaptive as it . response (believed to be adaptive as it helps animals escape notice and potential R d i d h d f h i l d lik f l
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Following each section is a Before You Go On feature that helps you check your mastery of the important items covered. • What Do You Know? questions ask you to stop and review the key concepts just presented. • What Do You Think? questions encourage you to think critically on key questions in the chapter.
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> This text is designed to allow text discus-
and the like. Also intersecting with the
sions to intersect at precise points with
text material at just the right points on
side notes that are placed in the page
each page are elements such as relevant
margins—interesting and relevant psy-
exciting boxes, current controversies in
chology facts, contemporary news stories,
psychology, research surprises, and per-
historical points, material from movies,
fectly selected photos.
to relieve pressure on your skin. The parts of your skin under continuous pressure would develop sores or bruises. Since many everyday experiences would be damaging to our bodies if we were not able to detect discomfort, a lack of ability to detect pain can be very dangerous.
PRACTICALLYSPEAKING
Quick Ways to Reduce Acute Pain
As we discuss in this chapter, medical practitioners are constantly seeking ways to provide relief to patients in chronic, or continuing, pain. But what about acute pain, the short-term pain you feel when you bump your leg on a table, for example? Gate control theory suggests that touch sensations, which frequently travel along fast fibers, can help prevent some pain sensations traveling on the slow pathways from reaching areas of your brain where they are perceived. According to this theory, the brain only processes so much input, so touch can help to set up a “gate” that stops pain. This explains why we have a tendency to rub the skin of areas of our body that have been injured. For example, if you walk into a piece of furniture, you might rub your leg to dampen the pain.
144 Chapter 5
Sensation and Perception
Focusing on your breathing may also help. We often tend to gasp and then hold our breath when we injure ourselves, such as bumping a leg. Formal methods of pain control, such as the Lamaze method for childbirth, work in part by altering this natural tendency, by teaching people to breathe in short, panting gasps (Leventhal et al., 1989). Distraction can also help, whereas anxiously focusing on pain can make it worse (al Absi & Rokke, 1991). Some studies have suggested that simply looking at a pleasant view, e, in Korea, where a meal often consists of many communal side can affect pain tolerance (Ulrich, 1984). Other evidence sugdered proper etiquette to try a little food from each. People in India gests that in order for a distraction to be effective, the expefast, but in Ireland, breakfast is a large meal, often including porrience must be active. Studies have shown that playing an bacon. Food is also strongly associated with social interactions. interesting videogame can dampen pain detection, whereas wn that people eat considerably more when they are in a social setpassive watching of a TV show has little effect. Stress and sexy when it is a relatively large gathering, compared to when eating ual experience also decrease the perception of pain. So, if you & Hillman, 2007). People with schedules that involve business meetbump your leg on the way into a big job interview or on a engagements over meals are likely to eat more than those whose hot date, perhaps you would not notice the pain as much as t include meetings at mealtimes, for example. This may be due to you would under other circ*mstances! als take longer with more participants, as well as the fact that peoattention to restricting their diets when they are engaged in conr et al., 2006). hers have also suggested that we each have an individual body weight chers have long recognized that as adults, our weights tend to stabilize neral level. We may fluctuate in a small range around that weight, but n to the original set point, even after major deviations from it (Pasquet 94). This is particularly evident when people diet. A reduction in body llowed by a rebound back toward the original weight. The Practically discusses why so many dieters fail to achieve lasting weight loss. This se, however. Some people do undergo dramatic weight changes in one her and maintain their new weights for a considerable period of time. ntain a lower body weight typically make permanent changes in their persistently monitor their weight (Dansinger et al., 2005; Warziski et ger et al., 2005). rch suggests, however, that body weight set point is not the only determining how much we eat. The availability of food we like Many individuals in societies such as much of the United States, lentiful, find their weights steadily creeping up over the years ). This can be seen with laboratory rodents, too. Presenting them y of highly palatable foods will cause more eating and weight gain Hagan et al., 2002). This suggests that a firm body weight set point experimental animals or humans. When presented with highly nd a diminishing level of activity, most people have a tendency to s they age.
Key Terms are listed at the end of each chapter with page references.
body weight set point a weight that individuals typically return to even after dieting or overeating.
“
A man seldom thinks with more earnestness of anything than he does of his dinner. –Samuel Johnson, writer
”
Margin Definitions define the key terms discussion in the text. Margin Notes present interesting facts and quotes throughout the chapter.
To the Student
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Seeing the “Big Picture” in Psychology Cut Across Connections Every chapter on a substantive area of psychol-
course will depend on how well you can inte-
ogy not only offers a thorough presentation of
grate this information meaningfully. The more
the nature, explanations, and applications of
often you review you prior knowledge and
that area, but also includes “Cut-Across” sec-
connect it with new knowledge, the more
tions on the development, brain function, indi-
automatic and refined learned knowledge and
vidual differences, and dysfunctions that occur
skills become.
in that realm of mental life. Your success in this
A world of new possibilities After undergoing successful cochlear implant surgery, this four-year-old child practices the violin under the instruction of his music teacher at the Memphis Oral School for the Deaf.
Hearing
Hearing HOW we Differ
There are many conditions that lead to abnormalities in the auditory system. Some cause either partial or total deafness, the loss of hearing. Abnormalities in the auditory system can also add unwanted auditory perceptions.
We differ greatly in our ability to detect specific sounds. People show particular differences in their ability to identify certain notes in a scale. Absolute pitch refers to the ability to recognize an individual note in isolation. This is very difficult for most people. Only about 1 in 10,000 people in Western countries has absolute pitch. This ability seems to originate in childhood, between the ages of three and six years, through musical training, and it is associated with differences in brain anatomy (Zatorre, 2003). Research has shown that portions of the cortex are actually thinner in individuals with absolute pitch (Bermudez et al., 2009). Although it’s not clear whether people with absolute pitch start out with a thinner cortex or whether they develop it through training, it’s possible that synaptic pruning contributes to this structural difference. Studies have shown, however, that people who speak tonal languages, or languages in which differences in tone convey meaning, such as Vietnamese and Mandarin Chinese, are more likely to develop absolute pitch than those speaking Western languages. This again suggests the possibility that early learning of auditory information related to tones can have a permanent effect on the functioning of this sensory system. Just as some people exhibit absolute pitch, others are tone deaf, or unable to discern differences in pitch. Although tone deafness or amusia is sometimes the result of damage to the auditory system, it can be present from birth, and researchers believe it may be related to genetics (Peretz et al., 2007). Tone deafness affects up to 4 percent of the population and mostly results in a diminished appreciation for music. Although music appreciation is an important enriching ability, people with tone deafness are able to enjoy all other aspects of life. This condition only presents serious social problems when it occurs in cultures where the language is tonal.
Deafness Deafness has a variety of causes. It can be genetic or caused by infection, physical trauma or exposure to toxins, including overdose of common medications such as aspirin. Since speech is an important mode of communication for humans, deafness can have dramatic consequences for socialization. This is particularly a concern for children, because young children need auditory stimulation in order to develop normal spoken language skills. For this reason, physicians try to identify auditory deficits at an early life stage. Parents can then make choices among different options to help their children with deafness. Some deaf individuals learn to use sign language and other methods of communication that rely on the senses other than hearing. Research over the past years has made progress in the construction of cochlear implants that help individuals with deafness to hear sounds (Sharma et al., 2009). Although this work is developing at a rapid pace, there remain many deaf people who are not helped by cochlear implants, however. (Battmer et al., 2009). This is one reason that many individuals and families choose to avoid them. Some in the deaf community also believe that hearing is not necessary in order to lead a productive and fulfilling life. For them, the potential benefits of implants may not outweigh the potential risks of surgery required to place them in the cochlea (Hyde & Power, 2006).
Breaking the bad news One of the guilty pleasures for many American Idol fans is that special moment when judge Simon Cowell calls a contestant “tone deaf.”The show includes performers whose musical abilities vary from absolute pitch to tone deafness.
What Happens in the
Hearing B
Hearing How we Develop Our ears are formed and capable of transducing sound waves before we are even born. In fact, human fetuses have been shown to respond to noises long before birth. Research has shown that fetuses respond to loud noises with a startle reflex and that after birth, they are capable of recognizing some sounds they heard while in utero. However, the ability to recognize and respond appropriately to a wide variety of sound stimuli is acquired over many years of postnatal life. Sounds associated with language, for example, become recognizable over postnatal development, as do those associated with music. We describe language development in more detail in Chapter 9. Sensitive periods exist for the development of both language and music learning (Knudson, 2004). As we described in Chapter 3, we acquire certain abilities during sensitive periods of development much more easily that we do after the sensitive period has ended. The tonotopic map in the primary auditory cortex of the brain is organized during such a sensitive period of development (deVillers-Sidani et al., 2007). Studies in experimental animals have shown that exposing animals to pure tones during a certain time in development, leads to a larger representations of those sounds in the auditory cortex. The same exposure after the sensitive period in development is over has no such effect. If a sound is made important to the animal, however, by pairing it either with a reward, such as water, or a punishment, such as an electric shock, the primary auditory cortex can be reorganized so that more of it responds to the relevant tone (Bakin et al., 1996). Such top-down processing of tones indicates that this region of the brain still shows plasticity after the sensitive period is over. It is not as easy, however, to remap the brain after a sensitive period as it is during one. The stimuli needed to produce changes in older animals must be very strong and important, compared to those needed for younger animals (Kuboshima & Sawaguchi,
A bit too early A pregnant woman tries to introduce music to her fetus by positioning headphones on her stomach. Although fetuses do indeed respond to loud noises and can detect certain sounds, the acquisition of musical skills cannot take place until sensitive periods unfold during the pre-school years.
Cut Across Connections shown above are taken from Chapter 5 Sensation and Perception.
xl
They can’t fool the brain (yet) M.I.T. professor Neil G h fi ld d d d k j
RAIN?
After auditory information is transduced from sound waves by the hair cells in the basilar membrane of the cochlea, it travels as signals from nerves in the cochlea to the brainstem, the thalamus, and then the auditory cortex, which is located in the temporal lobe. Part of the primary auditory cortex is organized in a tonotopic map. That is, information transmitted from different parts of the cochlea (sound waves of different frequency and, hence, sounds of different pitch) is projected to specific parts of the auditory cortex, so that our cortex maps the different pitches of sounds we hear. Auditory information from one ear is sent to the auditory cortex areas on both sides of the brain. This enables us to integrate auditory information from both sides of the head and helps us to locate the sources of sounds. From the primary auditory cortex, auditory information moves on to the auditory association areas in the cortex. As we described in Chapter 4, association areas of the brain’s cortex are involved in higher-order mental processes. Association areas help to link the sounds we hear with parts of the brain involved in language comprehension. Association areas also integrate, or coordinate auditory information with signals from other sensory modalities. Have you ever noticed how distracting it is to watch a movie that has an audio slightly out of synchrony with the video image? This is because the brain is set up to integrate information from multiple sensory systems. Over time, we learn to have expectations about the coincidence of certain visual stimuli with specific sounds. When the sounds in a movie do not match the visual images the way they would in real life, our expectations are violated and our attention
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> What Happens in the Brain When ... It’s our hope that you will come to see the
the Brain When . . . . Centering on a com-
fascination of psychology and develop a
mon everyday activity, these lively spreads
passion for this field of study. One example
clarify the remarkable brain events that
of how we demonstrate this to you is a reg-
help give life to the activity and serve as an
ular feature throughout the textbook—a
awe-inspiring reminder that psychology is
two-page spread called What Happens in
everywhere.
SENSING MORE THAN TASTE
What Happens In The Brain When We Eat Pizza
I
s this the best pizza you have ever had or does it fall
smell information to produce flavor. Olfactory receptor
short? When you dig into a slice of pizza, several
neurons transduce pizza odorants and send this
neural circuits are activated to give you the overall
information on to the olfactory bulb and then the
experience. The appearance of your food can play an
olfactory cortex (smell is the only sensory modality that
important role in its enjoyment. Photoreceptors in the
bypasses the thalamus on its way to the cortex).
A large part of somatosensory cortex (shown here with neurons genetically engineered to produce fluorescent dyes) is devoted to processing information about texture, temperature and pain from the tongue. Somatosensory information from the tongue is critical for the enjoyment of food - many people prefer their crust crispy while others like it soft.
eye transmit this information to the brain via the optic nerve which synapses in the brainstem, followed by the
Information about taste, smell, texture, temperature and
thalamus and finally the visual cortex. Taste receptor cells,
appearance is integrated in various association regions of
as well as sensory cells that respond to touch and tem-
the neocortex. These circuits, together with those that
perature, are activated on your tongue. These nerves
store memories related to your previous pizza
carry impulses into the brain where they synapse in the
experiences, work together to produce your perception
brainstem, thalamus and sensory cortex (gustatory
of this particular slice.
cortex and somatosensory cortex). Taste is combined with
Somatosensory Cortex
MAXIMIZING THE EXPERIENCE Visual cortex
Thalamus Gustatory Cortex Brain stem Olfactory bulb
Olfactory cortex
When you eat something delicious and close your eyes, you may be maximizing the experience by turning up the activity in certain parts of cortex. When your eyes are open, activity in parts of cortex serving nonvisual senses is decreased. Closing your eyes increases activity in these areas, including in taste and smell cortex. This fMRI image shows such increased activation in the olfactory cortex (yellow).
Visual pathway Smell pathway
Taste pathway
Somatosensory pathway
BURNING YOUR TONGUE Taste buds contain taste receptor cells (shown here marked with fluorescent dyes) that continually regenerate. The process is hastened when tissue is damaged, such as when you burn your tongue.
134
Chapter 5
Sensation and Perception
The Chemical Senses: Smell and Taste
135
What Happens in the Brain feature shown above taken from Chapter 5 Sensation and Perception.
To the Student
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Review Main Concepts Chapter Summary Each chapter ends with a summary and list of
review what you have learned as well as to
key terms aimed at representing the scope
see how the key topics within the chapter fit
and emphasis of a relatively large amount of
together. You can write your own summary
material in an efficient and concise form. The
first, as a review strategy, and then check
end-of-chapter Summary reviews the main
your work against the text summary to self-
concepts presented in the chapter with refer-
evaluate your understanding of the big pic-
ence to the specific Learning Objectives. It
ture in each chapter.
provides you with another opportunity to
Summary Understanding How We Develop LEARNING OBJECTIVE 1 Understand the key debates underlying research and theory in child development. • Developmental psychology is the study of changes in our behavior and mental processes over time and the various factors that influence the course of those changes. • Key philosophical issues in the study of developmental psychology are what drives change (biological or environmental factors); what’s the nature of the change (qualitative or quantitative); and the role of early experiences in shaping later development.
• Infants make dramatic gains in both physical and psychological capabilities. Our brains grow during this period, preparing us to learn and encode the information that will organize those changes. • One of the most important developmental theorists, Jean Piaget, proposed a theory of cognitive development that suggested that through learning and self-experimentation, we help our thinking to grow progressively more complex. • Piaget believed we passed through multiple stages on the way to formal adult reasoning and that each transition was accompanied by the acquisition of a new cognitive capability. During the sensorimotor stage, in infancy, we become able to hold memories of objects in our minds.
How Is Developmental Psychology Investigated?
• Information-processing researchers have suggested that babies may develop mental capacities at earlier ages than Piaget believed they did.
LEARNING OBJECTIVE 2 Describe and discuss the advantages and disadvantages of cross-sectional and longitudinal designs for researching development.
• Attachment theory suggests that the baby is biologically predisposed to bond and form a relationship with a key caregiver, thus ensuring that his or her needs are met. The security of the attachment relationship will have later implications for how developmental psychology 57 recessive trait 63 secure the person feels in his or her emotional and social maturation 57 codominance 63 capabilities.
• Two major research approaches in developmental psychology are cross-sectional (comparing different age groups to assess change) and longitudinal (studying the same group to see how responses change over time). • The cohort-sequential research design combines elements of the cross-sectional and longitudinal approaches.
Key Terms stage 57
discrete trait 63
• Baumrind found evidence that59 different parenting styles could critical periods polygenic trait 63 also affect the overall well-being of the child, although subsetemperament 63 cross-sectional design 59 quent research suggested that outcomes might vary depending zygote 64 longitudinal design 60 on other environmental and cultural influences. cohort-sequential design 60
placenta 64
prenatal period 60
miscarriage 64
Before We Are Born LEARNING OBJECTIVE 3 Discuss patterns of genetic inheritance and describe stages and potential problems during prenatal development. • Our genetic inheritance comes from both parents, who each contribute half our chromosomes. Genes can combine in various ways to make up our phenotype, or observable traits. • Genetics can influence the manifestation of both physical traits and psychological traits, including temperament, although environment also plays a role. • Prenatal development begins with conception and is divided into three stages: germinal, embryonic, and fetal, each characterized by specific patterns of development. • Individuals are susceptible to multiple influences by biological and environmental forces before they are even born, during the prenatal period.
Infancy LEARNING OBJECTIVE 4 Summarize the major physical, cognitive, and emotional developments that take place during infancy.
92
Chapter 3
Childhood LEARNING OBJECTIVE 5 Summarize the major physical, cognitive, and emotional developments that take place during childhood. • Physical growth continues at a generally slower pace in childhood than in infancy. Myelination and synaptic pruning continue to shape the brain. • Piaget believed that children pass through the stages of preoperational and concrete operations thinking, learning to manipulate their mental schema. Other researchers have suggested children’s thinking may not be as limited during these stages as Piaget thought it was. • Theories of moral development have often focused on moral reasoning (the reasons why a child would do one thing or another) rather than values. Generally, research supports the movement from morality rooted in submitting to authority to morality rooted in more autonomous decisions about right and wrong. • Some researchers suggest that moral reasoning may vary across gender and culture. Other researchers have questioned whether morality theories would be better served by measuring behavior instead of expressed reasoning or attitudes.
Human Development
Summary and Key Terms shown above taken from Chapter 3 Human Development.
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assimilation 69 accommodation 69 equilibrium 69 object permanence 70 information-processing theory 70 habituation 70 attachment 72 reciprocal socialization 74
puberty 82 primary sex characteristics 82 secondary sex characteristics 82 formal operations 84 menopause 87 cellular clock theory 88 wear-and-tear theory 88
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Video Lab Activities
Psychology Around Us Memory Manufacturing and Eyewitness Testimony
Video Lab Exercise
“This is a stick-up!” Memory plays a big role in our lives and in psychology. Generally, most people believe that they can remember things pretty well. Indeed, retrieving past memories, including “buried” memories, is a major part of daily functioning. Similarly, in the criminal justice system, the memories of eyewitnesses are relied upon heavily and lead to many convictions. BUT are our memories as accurate as we like to believe? Should we have great confidence in our recollections of recent everyday events, let alone our adult memories of childhood events, the recollections of eyewitnesses, and the like? As you are working on this online exercise, consider the following questions… • What do you think this lab exercise says about the accuracy of our memories? • What implications might this lab exercise hold for the field of psychology’s assumptions, techniques, and interpretations? • How might this contrived situation differ from a real-life event? Does this contrivance help account for the accuracy or inaccuracy of your memories? Pro or con?
Psychology Around Us
275
These activities use extensive video material to drive student learning. The combination of video footage and digital interactive technology brings the lab exercises to life in ways that were previously impossible. In actively engaging with the material you will better process the concepts. The kinds of video material included in the Video Lab Exercises range from laboratory brain footage to videos of everyday events to psychology documentary excerpts. These activities are accessible via WileyPlus, the optional on-line companion to this textbook
This Video Lab Exercise shown above is taken from Chapter 8 Memory.
CUT/ACROSS CONNECTION What Happens in the
BRAIN? • The main language areas are on the left side of the brain for most people—but not all. • Thinking about images (or smells or tests) activates the same brain areas as if we were actually seeing (or smelling or tasting). Thoughts that involve language activate language areas of the brain. • When we watch other people do things, mirror neurons in our brain can activate just as though we were doing the same things.
HOW we Differ • Girls tend to learn to talk earlier than boys. However, the difference soon disappears. • Babies who learn two languages at home begin talking slightly later than those who learn just one. • The number of words we have in our language for a certain object or concept (such as a color) may influence how we can think about that object or concept.
• Damage near Broca’s area of the brain can cause us to lose our ability to use grammar. • Obsessive-compulsive disorder involves unavoidable thoughts called obsessions and irresistible urges, or compulsions, to perform certain behaviors. • About 1 percent of all people in the United States display schizophrenia, a disorder marked by disorganized thoughts and loss of contact with reality.
How we Develop • Very young infants are able to perceive all the sounds of every language. As time passes, however, we lose the ability to distinguish phonemes of other languages. • Our ability to learn languages is at its best before school age. After we pass age 13, it is much more difficult for us to learn new languages than it was earlier. • We naturally tend to use child-directed speech with babies. It may be an evolutionary adaptation that helps humans learn language. • One of the reasons toddlers don’t play hide-and-seek very well is because their theory of mind abilities are still undeveloped.
This Cut Across Connection feature shown above is taken from Chapter 9 Language and Thought.
Cut/Across Connections Summary This section pulls together fascinating and relevant facts and concepts from the chapter’s Cut Across sections. Used in combination with the Chapter Summary, Cut/Across Connections will help keep you focused on psychology’s “big picture.”
p In some cases, lanmall percentage of o the right hemiroduction is tion
by impairments in • In some cases, related to a social problem, as in t • Because the very large, onl else whe
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nd comprehension n some cases, lanall percentage of right hemisphere. oduction is ciation ologist this
by impairments in o • In some cases, la related to a socia motor problem, a • Because the very large, on else where in
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Hopefully, by understanding the rationale for the pedagogical elements in this text, you will become more motivated to use them while you study. We hope you enjoy using this book as much as we enjoyed writing it for you!
To the Student
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Psychology Around Us
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CHAPTER 1
2
Chapter 1
Psychology: Yesterday and Today
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Psychology: Yesterday and Today chapter outline • •
What is Psychology? •
The Early Days of Psychology • •
“Trolling”
Psychology’s Roots in Philosophy
the
Twentieth Century Approaches
Psychology Today
Internet
so much that YouTube pulled the same prank on its own users one April Fool’s Day, sending everybody who clicked the day’s
T
rolls are no longer villains confined to fairy tales and fan-
featured videos to Rick’s video.
tasy stories. In Internet terminology, troll is a name for
Sometimes, however, trolls dip into much darker territory,
someone who seeks to intentionally disrupt online communi-
such as stealing people’s social security numbers or harass-
ties. Trolls ask distracting questions in comment chains, post
ment. In one infamous case, a troll happened upon a MySpace
wildly inappropriate and disruptive notes on message boards,
memorial to a teen who had committed suicide. That troll pro-
and, like their fictional namesakes, basically seek to sow con-
ceeded to mock, on a well-known troll message board, a typo
fusion and havoc anywhere where there’s a community of
in one of the tributes. The mockery expanded to contempt for
users that appears ripe for pranking.
the victim himself and eventually to a series of cruel events
Troll pranks can involve relatively mild provocations, such
outside the online world. The teen’s bereaved parents were
as stealing another person’s alias on a site and posting under
barraged for a year and a half with anonymous “prank” phone
that name, or taking on wild personas and posting bizarre
calls from people pretending to be the teen or asking for him.
statements that almost force people to respond. Trolls are
Some observers see trolling as evidence of the increasing detachment and moral deterioration of society. Others see it as merely a technology-aided extension of tendencies people have always expressed. How can we understand this bizarre behavior and its implications for society? Is it within the normal range of human experience, or does it exemplify some deviance within our culture or within a select set of individuals? These are the types of questions that the science of psychology is set up to answer. But they’re not the only questions.
credited, for example, with originating “Rick-rolling,” the Internet term for posting a misleading link. Rick-rolling is named after a prank that took unsuspecting users who clicked a link to a videogame site, not to the game they wanted but instead, to a video for the Rick Astley song “Never Gonna Give You Up.” Rick-rolling actually gave the song a huge boost in popularity and entertained mainstream Web programmers
Psychology: Yesterday and Today
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Trolling along. Psychologists study all kinds of mental processes and behaviors, including new ones such as trolling.
While psychology can help us try to understand unusual behavior, like that of trolls, it also helps us understand far more common things that we all do. Why do people even use Facebook or MySpace in the first place, for example? Psychology can provide some insights. As you read this book, you’ll see that all the topics we examine contribute not only to understanding of unusual or problematic behaviors but also to things that happen all around us, every day. We’ll discuss human development, examining how we mature and what shapes us as we age. Maybe trolls experienced some events in childhood that shaped their view of other Internet users. We’ll look at motivation and emotion, getting some ideas about why people do things and how we experience our feelings. What drives people to spend hours every day on the Internet, for example? We’ll look at theories of intelligence, including one that suggests that the kind of intelligence needed to hack into websites and steal social security numbers is different from the kind of intelligence needed to empathize with people such as parents who have lost a child. Along the way, our goal is to help you get insights not only into the attention-grabbing and sometimes bizarre things that can go wrong but also into the often-overlooked but miraculous things that usually go right. We’ve also included several “Practically Speaking” boxes that we hope can help you to use what you learn to make even more things go right in your own life. Every journey begins with a first step, and in this chapter, the first step is to learn what psychology is. After that, we’ll discuss where psychology originated and how it developed. Finally, we’ll learn more about psychology today, including what psychologists do, where they do it, and what’s new and changing in what they do.
Psychology: Myth vs. Reality Go to a party and tell strangers that you’re a psychologist, and they will most likely tell you about their anxieties or phobias. Alternatively, they might smile nervously and comment that you’re probably analyzing their behavior right there. Most people assume that all psychologists are therapists, when, in fact, clinical psychology is but one specialty in a field that includes cognitive, social, developmental, and sports psychology, among many others. Psychology, like most scientific fields, has many myths that
4
Chapter 1
Psychology: Yesterday and Today
lead to inaccurate stereotypes about psychologists and the phenomena that they study. Here are a few others: MYTH #1: The nature versus nurture debate was put to rest years ago. In fact, it is still very much alive in psychology. MYTH #2: Most mental disorders have clear and dominant biological causes. It just seems that way because so many drug treatments are available for people with psychological problems. In fact, we still have much to learn in this realm. MYTH #3: The brain does not produce new neurons after childhood. Actually, current research indicates that new neurons continue to be formed throughout life, even in old age. MYTH #4: As most people age, their neurons die. In fact, in normal non-pathological aging, there is little or no loss of neurons.
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What is Psychology? LEARNING OBJECTIVE 1 Define psychology, and describe the goals and levels of analysis psychologists use.
Curiosity about the inner workings of the mind has probably existed since humans first began to communicate their ideas to others and to recognize that other people have thoughts and emotions that are distinct from their own. Psychology is the study of mental processes and behavior. The term also refers to the application of that knowledge to various realms of human life, including mental dysfunction, education, and business. Mental processes describe the activity of our brains when we are engaged in thinking, observing the environment, and using language. Mental processes include complex experiences, such as joy, love, and even the act of lying. During psychology’s early history, the primary method for exploring internal mental processes was to observe outward behavior, our observable actions, and make inferences, or guesses, about what was happening in the mind. Since psychology became an experimental science in the nineteenth century, however, psychological researchers have sought more direct ways to examine mental processes. In fact, in the past decade, the advent of brain imaging and other forms of technology has enabled scientists to uncover fascinating connections between behavior and mental processes and to move toward a more comprehensive view of how mental processes occur in various individuals and situations. When psychologists study mental processes and behavior, they generally have one of four goals in mind:
“
Man is the only animal for whom his own existence is a problem which he has to solve –Erich Fromm, psychologist and philosopher
”
• Description. Psychologists seek to describe very specifically the things that they observe. As you read this book, you’ll see that psychologists have described phenomena ranging from how babies learn to talk to how we fall in love, how we make decisions, and more. • Explanation. Telling what, where, when, and how are sometimes not enough. A key goal for many psychologists is to answer the question of, “Why?” As we’ll see in Chapter 2, psychologists have developed hypotheses and theories to explain a huge variety of events, from why we get hungry to why we either like or don’t like parties. • Prediction. Psychologists also seek to predict the circ*mstances under which a variety of behaviors and mental process are likely. You’ll learn later in this book, for example, about research that predicts the conditions under which we are most likely to offer help to a stranger in need. • Control. We often encounter situations in which we want to either limit or increase certain behaviors or mental processes—whether our own or those of others. Psychology can give students advice on controlling their own behaviors that ranges from how to limit unhealthy stress or how to increase what we remember from a class. In order to describe, explain, predict, or control mental processes and behaviors, we need to recognize the many various influences on them. All our thoughts and actions, down to the simplest tasks, involve complex activation and coordination of a number of levels—the levels of the brain, the individual, and the group. As you will see throughout this textbook, no psychological process occurs solely at one of these levels. Analyzing how the brain, the individual, and the group influence each other reveals much about how we function—insights that might be overlooked if we were to focus on one of these levels alone (see Table 1-1).
psychology the study of mental processes and behaviors. mental processes activities of our brain when engaged in thinking, observing the environment, and using language. behavior observable activities of an organism, often in response to environmental cues.
What is Psychology? 5
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TABLE 1-1 The Levels of Analysis in Psychology
“
Everything that irritates us about others can lead us to an understanding of ourselves. –Carl Jung, psychiatrist and philosopher
”
culture a set of shared beliefs and practices that are transmitted across generations.
6
Chapter 1
Level
What Is Analyzed
“Trolling”
The brain
How brain structure and brain cell activity differ from person to person and situation to situation
What are the patterns of brain activation in trolls as they seek to upset others?
The person
How the content of the individual’s mental processes form and influence behavior
What values do the trolls hold? Do they have limited capacity for empathy? Are they selfish, narcissistic, or angry persons?
The group
How behavior is shaped by the social and cultural environments
How is troll participation affected by anonymity, sense of affiliation with other troll groups, or decreased connection to the larger society?
At the level of the brain, psychologists consider the brain cell activity that occurs during the transmission and storage of information. They also focus on the design of the brain, including the chemicals and tissues that it is composed of and the genes that guide its formation. As we’ll see later in this chapter, technological advances in the fields of molecular biology and brain imaging have made it possible to study how brain structure and activity differ from person to person and situation to situation. A psychologist studying the brain can now look, for example, at what parts of the brain are activated by the administration of a pharmaceutical or street drug or the brain changes that accompany anxiety and depression (Damsa et al., 2009). At the level of the person, psychologists analyze how the content of mental processes— including emotions, thoughts, and ideas—form and influence behavior. To use a computer analogy, this level relates to the software rather than the mechanical functioning, or hardware, of the brain. The level of the person includes many of the things that people think of first when they discuss psychology—ideas such as consciousness, intelligence, personality, and motivation. Although internal biological structures of the brain allow such person-level processes to occur, we cannot understand the processes unique to each individual, such as personality or motivation, without also studying this content. Psychologists may strive to understand the brain activities and mental processes of an individual, but their understanding remains incomplete without analysis at the level of the group. This perspective acknowledges that humans are shaped by their social environment and that this environment varies over time. Groups can refer to friends, to family members, or to a large population. Often a large group shares a culture, a set of common beliefs, practices, values, and history that are transmitted across generations. The groups to which people belong or perceive themselves to belong, can influence their thoughts and behaviors in fundamental ways (Prinstein & Dodge, 2008). When they conduct research, psychologists may focus on different levels of analysis, but it is important to recognize that activity is happening simultaneously at all three different levels during even our most everyday decisions and tasks. The levels also interact. Brain activity is detectable only with special instruments, like microscopes or neuroimaging machines, but is nevertheless affected by other levels, even by our broad cultural contexts. Similarly, barely noticeable changes in the biology of our brains can cause major changes in our general state of being or how we respond to others.
Psychology: Yesterday and Today
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Let’s go back for a moment to our earlier discussion on Internet trolling. If psychologists set out to understand trolling behavior, they could examine it at various levels. Operating at the level of the brain, they could explore patterns of brain activation in trolls in order to see what brain changes occur when trolls go online or seek to upset or empathize with others. At the level of the person, psychologists could explore questions of intelligence and personality to see whether there are certain characteristics common to most trolls. Finally, at the level of the group, psychologists might examine how anonymity buffers trolls as they disregard general standards of polite behavior or how trolls’ participation on their own message boards strengthens bonds to other trolls and decreases their broader sense of connection to the population at large. As you’ll see throughout this book, the notion of multiple levels of analysis has played an important role in the development of psychological theories (Fodor, 2007, 2006, 1968). Having examined what psychologists study and how they do it, let us next consider how psychology got its start, how historical and societal factors have affected the way psychologists study the mind and behavior, and how psychologists have shifted their energies among the different goals and levels of analysis throughout psychology’s history. We will then consider where the field of psychology is today and where it may be going tomorrow.
Before You Go On What Do You Know? 1. How is behavior different from mental processes? How are they the same? 2. What are the three levels of analysis in psychology?
What Do You Think? What would be the focus of each of the four goals of psychology when studying Internet trolling? How would the questions and actions of a psychologist who seeks to describe trolling differ from those of someone who wants to control trolls, for example?
Psychology’s Roots in Philosophy LEARNING OBJECTIVE 2 Describe the influences of early myths and ancient Greek philosophies on psychology.
Before the development of science as we know it today, humans attempted to explain the natural environment through myths, tales that often gave human qualities to natural events. A volcano might be the result of an angry mountain goddess, for example. In order to control both natural and human behavior, people of past times also developed a number of magical ceremonies and rituals. Some theorists today believe that these methods for influencing and understanding events were the first forms of religious practice and that such practices reflect an innate human need to understand and make sense of people and the natural world. In fact, according to such theorists, the science of today is somewhat similar to primitive myths in that it represents our attempts to describe, explain, predict, and control our reality (Waterfield, 2000). Although they focused on supernatural, life-giving forces, the early rudimentary belief systems contributed to the explosion of intellectual curiosity and information
Mythical explanations. Before the development of science, myths were used to explain natural events. Some have survived. Here a Hawaiian woman places offerings to the Fire Goddess during a ceremony at the crater of Halemaumau Volcano.
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©The New Yorker Collection 1993 Dana Fradon from cartoonbank.com. All Rights Reserved.
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FIGURE 1-1 Hippocrates’ psychological theory This medieval manuscript illustrates the psychological effects of the humours proposed by the Greek physician. The illustration on the left demonstrates the melancholia produced by black bile, while the one on the right depicts the joyous, musical, and passionate personality produced by blood.
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that occurred in the fourth and fifth centuries B.C.E. It was around that time that the great thinkers of ancient Greece began moving beyond supernatural explanations. Instead, they tried to find ways to determine the nature of reality and the limitations of human awareness of reality. To accomplish these difficult goals, they engaged in open, critical discussions of each other’s ideas. Such intellectual dialogue created a flow of ideas, and new ideas of any nature were both respected and challenged. In such open forums, students and nonintellectuals could challenge prevailing doctrines and even their instructors. The history of psychology (and most other sciences) starts with the history of philosophy, as the Greeks’ efforts came to be called. Philosophy is defined as the study of knowledge and reality. The ancient philosophers’ method of introducing problems and then questioning proposed solutions is at the core of today’s modern scientific method, which we will discuss in greater detail in Chapter 2. The freedom of thought found in Greek society emphasized that theories, ideas about the way things work, are never final but rather always capable of improvement. Today’s psychologists still take that view. Hippocrates (ca. 460–377 B.C.E.) actually produced one of the first psychological theories, suggesting that an individual’s physical and psychological health is influenced by humours—four bodily fluids (blood, phlegm, yellow bile, and black bile) that collectively determine a person’s character and well-being and predict the individual’s responses to various situations. He also correctly identified the brain as the organ of mental life. Hippocrates tested his theories with direct observation and at least some dissections. Because of such efforts, academic study became rooted firmly in detailed scientific methods of study (see Figure 1-1). Other Greek philosophers, such as Socrates (ca. 470–399 B.C.E.) and Plato (ca. 427–347 B.C.E.), believed that “truth” lies in the mind and is highly dependent upon our perceived, or subjective, states. Socrates looked for concepts that are the “essence” of human nature and searched for elements that various concepts have in common. He tried, for example, to identify why something – anything – is beautiful and what essential factors an object must possess in order to be beautiful. His student, Plato, believed that certain ideas and concepts are pure and signify an ultimate reality. Plato believed that we could use reasoning to uncover these core ideas deeply imbedded in every human soul. The ideas of these two philosophers represented early studies of mental states and processes. Similarly, Aristotle (ca. 384–322 B.C.E.), the most famous thinker of the Greek period, made key contributions to the foundations of psychology. His writings represent some of the first important theories about many of the topics you will be coming across throughout this book, such as sensations, dreams, sleep, and learning (Hergenhahn, 2005) although, at the same time, he mistakenly believed that the brain was an organ of minor importance. Aristotle was one of the first to promote empirical, or testable, investigations of the natural world. He looked inward at sensory experiences and also scrutinized his environment carefully, searching for the basic purpose of all objects and creatures. In his studies, he formed ideas about how living things are hierarchically categorized, concluding—centuries before Charles Darwin—that humans are closely related to animals.
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Before You Go On What Do You Know? 3. What do the earliest myths have in common with today’s scientific studies? 4. Greek philosophers who believed reasoning would uncover ideals or core ideas were focused on which aspect of psychology? 5. How did the Greek philosopher Hippocrates explain mental processes and behavior? How did his research methods influence today’s study of psychology?
What Do You Think? What advantages do you think a scientific approach has for explaining behavior and mental processes compared to a supernatural approach?
The Early Days of Psychology LEARNING OBJECTIVE 3 Name important early psychologists and describe their major theories and research methods.
Approximately 2,000 years after they lived, the philosophies of the ancient Greeks re-emerged to influence European thinkers during the Renaissance period of the 1400s through the 1600s. In the centuries both during and after the Renaissance, European society underwent a scientific revolution. A spiritual worldview, which had dominated for several centuries, was replaced increasingly by a view of the world based on mathematics and mechanics. By 1800, both the universe and human beings were believed to be machines that were subject to fixed natural laws. The roles of magic and mysticism in science essentially disappeared (Leahey, 2000). Although mysticism declined as a form of explanation for human nature, there remained great confusion and disagreement regarding human motives and origins. In the latter part of the nineteenth century, Charles Darwin proposed the theory of evolution, making the radical suggestion that all life on Earth was related and that human beings were just one outcome of many variations from a common ancestral point. Darwin also suggested natural selection as the mechanism through which some variations survive over the years while others fall out of existence. Natural selection proposes that although all kinds of variations can be passed down from parent to offspring, some variations are adaptive—better suited to an organism’s environment. These adaptive variations help the organism to thrive. On the other hand, less-adaptive variations reduce the ability of an organism to survive. Darwin’s theories about man’s evolution from the ape shifted scientific interest toward an understanding of the origins of humans and our behavior. Social and technological developments during the 1800s also helped set the stage further for the science of psychology. Improvements in transportation, communication, and education allowed information to flow more freely to more levels of society than ever before, leading to a rise of popular interest in science.
The Founding of Psychology In this atmosphere, psychology emerged finally as a distinct scientific field of investigation. As we have observed, prior to the late nineteenth century, psychology was virtually indistinguishable from the study of philosophy. In 1879, however, the physiologist Wilhelm Wundt (1832–1920) opened a laboratory in Leipzig, Germany, dedicated exclusively to the study of psychology. As a natural scientist, Wundt believed that the exper-
Charles Darwin (1809-1882). The theories by the English naturalist about human evolution shifted scientific attention toward human origins and behavior.
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William Shakespeare (1564–1616), Original Psychologist “To be, or not to be,” from Shakespeare’s play Hamlet, is the famous line uttered by the play’s main character to indicate his psychological struggle with suicide as a way to end his mental suffering. Hamlet’s father is murdered by his uncle (his father’s brother), who then marries Hamlet’s mother. After Hamlet learns of his uncle’s brutality from a ghostly vision, he struggles with the ethical and moral contradictions of how to avenge his father’s murder. Hamlet is arguably Shakespeare’s greatest tragedy and through its brilliant prose, both the characters of Hamlet and the audience explore the themes of suicide, revenge, incest, moral corruption, and mental dysfunctioning.
The father of experimental psychology. Wilhelm Wundt works with colleagues in his laboratory at the University of Leipzig, one of the first laboratories devoted exclusively to psychological research.
One aspect of Shakespeare’s genius was his ability to portray the mental lives of his characters in disturbing and realistic detail. Through his keen observations of the human condition, he examined the intricacies of mental disturbances and individuals’ struggles with self-knowledge, themes that did not fully emerge in psychological science until the late nineteenth and early twentieth centuries. Indeed, Shakespeare’s unique understanding of mental dysfunction predated Western psychology by almost 300 years. Through the characters in his plays, he presented many of the classic symptoms associated with contemporary psychological maladies, including sociopathy (Richard III), alcoholism (Henry V), anxiety (Macbeth), depression (King Lear and Hamlet), dementia (Hamlet), epilepsy (Julius Caeser), obsessive compulsive patterns (Macbeth), palsy (Troilus and Cressida), eating disturbances (Henry IV Parts I & II and The Merry Wives of Windsor) and paranoia (Coriolanus, Othello, Hamlet, Macbeth, and Richard, III), to name a few (Cummings, 2003). Altogether, the Bard speculated on the nature and causes of behavior in at least 20 of his 38 plays and many of his sonnets.
imental methods of other sciences were the best way to study the mind and behavior, so he established a program that trained students to perform such experiments in psychology. Psychology’s emphasis on rigorous, scientific experimentation continues to this day, as we’ll see in Chapter 2. Wundt exposed research participants to simple, standardized, repeatable situations and then asked them to make observations, an approach similar to ones used in the study of physiology. One of Wundt’s most famous experiments, for example, involved a clock and pendulum. Wundt found that when determining the exact location of the pendulum at a specific time, his observations were always off by 1/10 of a second. He believed that he had found evidence that humans have a limited attention capacity and that it requires 1/10 of a second to shift focus from one object to another. Wundt studied the content and processes of consciousness, the behaviors and mental processes that we’re aware are happening. In his laboratory, he was particularly interested in studying the idea of will and how it influences what individuals choose to attend to in their environments. He believed that much of behavior is motivated and that attention is focused for an explicit purpose. Wundt called this branch of investigation voluntarism. Later, Wundt also went on to form theories about emotion and the importance of historical and social forces in human behavior. His ideas about cultural psychology are in fact appreciated today for their early recognition that an individual’s social context must also be taken into account in order to fully explain his or her mental processes and behavior (Benjamin, 2007, 1997).
Structuralism: Looking for the Components of Consciousness One of Wundt’s students, Edward Titchener (1867–1927), expanded upon his ideas and formed the school of structuralism in the United States. Titchener’s goal was to uncover the structure, or basic elements, of the conscious mind, much like looking
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at the parts that make up a car engine or bicycle, or the individual bricks in a complicated Lego® sculpture. To study the conscious mind, the structuralists relied heavily on a method originated by Wundt, called introspection, which literally means “looking inward.” This method involved the careful observation of the details of mental processes and how they expand simple thoughts into complex ideas. If shown a house made of Legos, for example, an introspecting structuralist would describe the smooth, shiny texture of each brick, the color of the brick, the tiny gap between it and the adjoining bricks, and so forth. Toward the end of the 1800s, arguments began to emerge against the use of introspection as an experimental technique. Skeptics pointed out that scientists using introspection often arrived at diverse findings, depending on who was using the technique and on what they were trying to find. The school of structuralism also came under attack for its failure to incorporate the study of animals and to examine issues of abnormal behavior. The major concern many psychologists had with structuralism, however, was its emphasis on gathering knowledge for its own sake without any further agendas such as a desire to apply our knowledge of the mind in practical ways. Recall the four goals of psychology discussed earlier. The goal of the structuralists was to use introspection to describe observable mental processes rather than to explain the mechanisms underlying consciousness or to try to control such mechanisms. They believed that speculation about unobservable events had no place in the scientific study of psychology. Ultimately, even Titchener himself acknowledged the need to understand the purpose of human thought and behavior rather than to merely describe it. Although many of structuralism’s principles did not survive, its propositions that psychologists should focus largely on observable events and that scientific study should focus on simple elements as building blocks of complex experience have lived on in certain modern schools of thought.
consciousness personal awareness of ongoing mental processes, behaviors, and environmental events. voluntarism belief that much of behavior is motivated and that attention is focused for an explicit purpose. structuralism belief that mind is a collection of sensory experiences and that study should be focused on mental processes rather than explanation of mechanisms underlying those processes. introspection method of psychological study endorsed by Wundt and his followers, involving careful evaluation of mental processes and how they expand simple thoughts into complex ideas. functionalism belief that mental processes have purpose and focus of study should be on how mind adapts those purposes to changing environments.
Functionalism: Toward the Practical Application of Psychology William James (1842–1910), one of America’s most important psychologists (and philosophers) was instrumental in shifting attention away from the structure of mental content to the purposes and functions of our mental processes. James set up the first psychology laboratory in the United States at Harvard University and wrote one of the first important psychology texts, Principles of Psychology. His view of psychology was that mental events and overt behaviors have functions (Richardson, 2006; Keller, 1973). Thus, James’s approach was called functionalism. To use our earlier analogy, functionalists would be less interested in describing the parts of a car engine or bicycle, and more interested in what the engine or bicycle can do under a variety of conditions. Functionalists viewed the mind as an ever-changing stream of mental events rather than the more or less static set of components that the structuralists were seeking. For this reason, James and his colleagues were also interested in understanding how the mind adapts and functions in a changing environment. Functionalism did not rely primarily on a single research method, such as introspection. It used a variety of methods, and it also highlighted differences among individuals rather than similarities. And unlike structuralism, functionalism emphasized the need for research to include animals, children, and persons with mental disorders
William James. The influential psychologist and philosopher investigated the purposes and functions of our mental processes. His book Principles of Psychology took 12 years to write and was 1200 pages in length.
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Gestalt psychology field of psychology arguing that we have inborn tendencies to structure what we see in particular ways and to structure our perceptions into broad perceptual units.
in order to understand both normal and abnormal psychological functioning (Richardson, 2006; Keller, 1973). The shift from structuralism to functionalism was apparent in an early experiment on how humans locate sound. Participants in the experiment were asked to point to the location of a sound (Angell, 1903). A structuralist would have asked each participant to provide an introspective report of his or her conscious experience of the sound. Functionalists, however, were more concerned with issues, such as how accurately participants could point in the direction in which the sound was physically located. Although it never really became a formal school of psychology, functionalism helped to focus psychologists’ attention on what the mind can and does accomplish. Spurred by the emphasis of functionalists on providing applicable and concrete information, psychology began to tackle socially relevant topics. The researchers William Lowe Bryan and Noble Harter (1897), for example, performed a famous investigation regarding how quickly telegraph operators could learn necessary typing skills. Their findings were used to improve training for railroad telegraphers, and the study is now widely regarded as one of the first to have a significant social and commercial impact. Functionalism also marked the beginning of exploration into socially important issues, such as learning and education, and indeed, educational psychology remains a significant area of research in the field today.
Gestalt Psychology: More than Putting Together the Building Blocks
Facial recognition. Even babies younger than 3-months-old can piece together the component parts of a face and recognize it as a whole object. In particular, they can recognize the familiar face of their mother.
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While opponents of structuralism in the United States were raising concerns that structuralism did not examine the uses of consciousness, other psychologists in Germany were questioning in a more basic way the structuralist idea that consciousness can be reduced to basic mental elements. Gestalt psychology is based on the idea that we have inborn tendencies to impose structure on what we see, and these tendencies cause us to perceive things as broad “perceptual units” rather than as individual sensations. Indeed, the word Gestalt is of German origin, meaning “whole” or “form.” The school subscribed to the idea that “the whole is greater than the sum of its parts.” For example, when you watch TV, you see complete pictures. In fact, each picture is made up of thousands of small dots, called pixels. If you get close enough to the screen, you can see the picture break down, but our brains still favor integrating those dots into a cohesive whole. Similar findings have been gathered regarding our tendency to group eyes, noses, and mouths into recognizable human faces. Children three months of age or younger show a preference for human faces but only when the component parts of faces are arranged correctly in a facial orientation (Gava et al., 2008; Morton & Johnson, 1991). Gestaltists developed over 100 perceptual principles to describe how the brain and sensory systems perceive environmental stimuli. Some of the Gestalt laws are shown in Figure 1-2. Gestaltists also viewed learning as tied to perception. They believed that problem solving occurs when a person develops a sudden and complete insight into a solution—indeed, they believed that problems remain in an unsolved state until such points of insight occur.
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The Gestalt school helped guide psychology away from the study of component parts and toward a more comprehensive view of the human mind and functioning. Many of its concepts and the importance of the study of perception are still present in modern psychology, although Gestalt psychology is no longer a prominent, distinct school. FIGURE 1-2 Gestalt laws Gestalt psychologists
Figure Ground: The tendency to perceive one aspect as the figure and the other as the background. You see a vase or two faces, but not both at the same time.
studied how we perceive stimuli as whole forms or figures rather than individual lines and curves.
Proximity: Objects that are physically close together are grouped together. (In this figure, we see 3 groups of 6 hearts, not 18 separate hearts.) When we see this, Continuity: Objects that continue a pattern are grouped together.
we normally see this
plus this.
Not this.
Closure: The tendency to see a finished unit (triangle, square, or circle) from an incomplete stimulus. Similarity: Similar objects are grouped together (the green colored dots are grouped together and perceived as the number 5).
Before You Go On What Do You Know? 6. What is introspection, and which early school of psychologists relied most heavily upon it? 7. What was the main difference in approach between functionalism and structuralism? 8. What did the Gestalt psychologists study?
What Do You Think? Which early school of psychology most closely resembles the way you view the human mind? Why?
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Twentieth-Century Approaches LEARNING OBJECTIVE 4 Summarize the major principles of the psychoanalytical, behaviorist, humanistic, cognitive, and neuroscience approaches to psychology.
Eye to eye. Sigmund Freud, founder of psychoanalytic theory, examines a sculptured bust of himself at his village home in 1931.
From the late 1800s into the twentieth century, psychology continued to grow as a science. In the years leading up to World War I and through World War II, there was tremendous growth in the field of psychology. The number of psychologists rapidly expanded, and popular interest in psychology grew to unprecedented levels. As more people became interested in the field, more viewpoints on behavior and mental processes continued to emerge. Several twentieth-century schools of thought had major influence on the field, including the psychodynamic approach, the behaviorist approach, the humanistic approach, the cognitive approach, and the sociobiological approach. We’ll explore next the defining features of all of these approaches.
Psychoanalysis: Psychology of the Unconscious
“
Freud: If it’s not one thing, it’s your mother. –Robin Williams, comedian
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Although they held distinctly different views about how the mind is structured and how it should be studied, Wundt, Titchener and the structuralists, James and the functionalists, and the Gestaltists were all alike in one way: They all focused on consciousness, behaviors and mental processes that we are aware are happening. And, as you will see in Chapter 6, their early endeavors into the conscious experience remain an area of considerable study in psychology today. Other theorists, however, eventually came along and focused largely on mental processes of which we are unaware, those that happen in the unconscious mind. Sigmund Freud (1856–1939), a Viennese neurologist, suggested that many of our thoughts and feelings exist beyond the realm of awareness, in the unconscious. Freud did not conduct experimental studies of laboratory participants. He built his theory instead on information from patients he saw in his medical practice. Based on his detailed observations of these people’s cases, Freud came to believe that the mind is a complex interaction of those thoughts and memories that exist at different levels of awareness, some conscious and some unconscious. He saw mental life as a competition among forces that strive to reach the upper levels of awareness. Freud’s theory was developed over decades and is called the psychoanalytic theory. Freud further believed that childhood experiences help set the stage for later psychological functioning by contributing to effective or ineffective interactions among conscious and unconscious forces. According to Freud, certain developmental milestones must be achieved successfully in order for a person to achieve emotional adjustment. He also was interested in how children unconsciously adopt social and moral norms from their parents and, in turn, develop a conscious awareness of what constitutes acceptable and unacceptable expressions of their internal desires. Freud suggested that these conscious standards lead to unavoidable tensions between our unconscious, primal needs and our conscious, social or moral restraints. According to Freud, the backand-forth tension within and between the conscious and unconscious mind is what shapes personality, helps produce abnormal behaviors in some cases, and governs virtually all behavior. In fact, Freud and his followers saw the conscious mind as a thin mask over a deep unconscious mental world, a world that contains impulses and urges that cannot be expressed freely given the constraints of a person’s social environment. Let’s return again to our friends, the Internet trolls. Freud would likely perceive the trolls’ explanations that their behavior is intended to educate the ignorant as tissue-thin justifications for deeper feelings of mistrust or hostility toward the world. He would also be interested
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in why many people become so upset by the deeds of trolls. After all, most of the actions of trolls amount to goofy behavior and anonymous slurs from strangers (trolls) with zero credibility, yet they send many people into a state of near apoplexy. As trolls often state triumphantly, “If you need to write a page-long comment to say that a troll isn’t bothering you, you’ve already lost.” As we shall see later in the textbook, psychoanalytic notions typically have not held up well when subjected to rigorous scientific study. For evidence, Freud relied on anecdotes and case histories of remarkable changes in his patients. Researchers have not been able to find much support for his claims when they test them with larger groups of people (Wallerstein, 2006). The lack of research support, as well as philosophical differences, prevented many of his contemporaries from accepting Freud’s theories. William James, the functionalist, for example, rejected the psychoanalytic notion of the unconscious. To him, conscious ideas were not a product of underlying machinery: what was observed in the conscious mind was the complete experience. Nevertheless, to this day, psychoanalysis remains an influential theory of mental functioning and personality in the field of psychology. Clearly, his theory increased the applications of psychology to many new aspects of everyday life. It stirred interest in motivation, sexuality, child development, dreams, and abnormal behavior—all topics we will discuss later in this book. Freud’s use of discussion as a therapeutic technique helped lead to the creation of psychiatry and clinical psychology as influential therapeutic methods, and these methods continue to thrive. Although many of Freud’s ideas have been challenged, they certainly marked a turning point in the understanding of human nature. Psychoanalytic theory was among the first psychological theories to provide a comprehensive view of human nature, and it helped make psychology relevant to more people than ever before.
unconscious hypothesized repository of thoughts, feelings and sensations outside human awareness, thought in some theories to have a strong bearing on human behavior. psychoanalytic theory psychological theory that human mental processes are influenced by the competition between unconscious forces to come into awareness. behaviorism branch of psychological thought arguing that psychology should study only directly observable behaviors rather than abstract mental processes. stimuli elements of the environment that trigger changes in our internal or external states. response ways we react to stimuli.
Behaviorism: Psychology of Adaptation In addition to theories about the conscious mind and the unconscious mind, a third area of psychology, called behaviorism, emerged in the early part of the twentieth century. This school of thought was founded on the belief that psychology should study only behaviors that are directly observable rather than abstract mental processes. Early behaviorists tended to focus on the relationships between stimuli—things that trigger changes in our internal or external states—and responses—the ways we react to stimuli. As you’ll read in Chapter 7 on Learning, these behaviorists developed a number of influential ideas about how responses produce consequences and how those consequences in turn affect an organism’s future responses to stimuli. Behaviorism originated in America and Russia. In the United States, animal research was growing in popularity, while in Russia, Ivan Pavlov’s (1849–1936) discovery of a phenomenon that came to be called conditioning linked various animal behaviors to events in the animals’ environments (Bitterman, 2006; Bauer, 1952). Such successful studies of nonhuman behavior called into question the methods being used to investigate human behavior. Even though animals could not introspect, scientists seemed to be learning a great deal by observing their behavior. Edward Thorndike (1874–1949), who was technically a functionalist, helped transition the field of psychology toward behaviorism by proposing that animal findings could help explain human behavior. As behaviorism proved increasingly fruitful and popular, tensions grew between investigators who used introspection and those who relied on observation. John Watson (1878–1958) is generally credited with pioneering the school of behaviorism. He agreed with Thorndike that animals could be useful in guiding our understanding of human psychology, and he sharply disagreed with psychoanalysis and with
The box! B.F. Skinner developed the so-called “Skinner box” to help him investigate how consequences reinforce behavior. Here he uses the box to train a rat to press a lever for a food reward.
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reinforcement learning process in which the consequence resulting from a behavior will increase or decrease the likelihood that the behavior will occur again. humanistic psychology theory of psychology that sought to give greater prominence to special and unique features of human functioning. client-centered therapy approach to therapy founded by Carl Rogers, based on the notion that the client is an equal and positive gains are made by mirroring clients’ thoughts and feelings in an atmosphere of unconditional positive regard.
The real teachers. Behaviorists use principles of conditioning, reinforcement, and modeling to teach animals various behaviors in laboratory settings. However, like this young Bonobo chimpanzee, animals (and humans) usually learn behaviors in their natural environments where their parents and other important figures inadvertently apply learning principles.
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the notion of unobservable mental processes. As we’ll discuss in Chapter 7, he was able to extend Pavlov’s animal work to young children, and he essentially launched modern psychological theory by demonstrating that children could be conditioned by researchers to fear various objects and situations. B.F. Skinner (1904–1990), who emerged as the leading behaviorist after World War II, helped expand behaviorism’s perspective by acknowledging that internal, mental processes may indeed be at work in some situations, such as when an animal runs to get food. But even here, Skinner argued, empirical—observable—information should be gathered first, and then theories about causation could be formulated from that. That is, even when behaviorists acknowledged that internal mental processes were probably at work, they held that their primary job was to describe empirical phenomena not to explain them. For example, when observing the behavior of a monkey who is attempting to obtain food, a behaviorist might describe how the animal distinguishes a particular food from other stimuli, how it approaches the food, and what steps it takes to obtain it – observations meant to reveal how particular responses come to be associated with the food stimulus. An idea central to behaviorism is that the consequence resulting from a particular behavior serves to either increase or decrease the likelihood that an individual will perform that same behavior again in the future. If the consequence of a given behavior is rewarding, it is regarded as reinforcing, and the individual will be more likely to repeat the behavior down the road. A behavior is positively reinforcing when it brings about a desired outcome (such as food or a prize), and negatively reinforcing when it helps an organism avoid undesirable outcomes. For example, procrastination may be negatively reinforcing to the extent that it helps people avoid the pain of actually sitting down to do their homework. Remember, if a behavior is either positively or negatively reinforcing, we are more likely to do it again later. The term negative reinforcement is sometimes confused with punishment, but the latter is really a very different factor in behavior. Unlike negative reinforcements, punishments render behaviors less likely to be repeated. Back to our Internet trolling behavior, some comment board moderators have tried to control trolling by “disemvoweling,” removing all the vowels from the offending comments of trolls. This punishing practice makes troll comments easier to detect and harder to read, and therefore, less likely to generate the kind of outraged response a troll finds rewarding. Disemvoweling punishes the troll and effectively has decreased the numbers of offensive comments and hijacked comment threads on many message boards. The principles of behaviorism became widely used in advertising and in helping businesses address personnel problems. As behaviorism grew in popularity, its principles were applied to numerous industries as well as to courts, schools, and even the military. During this period, researchers also placed great emphasis on the development of controlled scientific methods that might establish psychology once and for all as a true science. Given the appeal of its objective and controlled methods of investigation, behaviorism reached considerable prominence in the academic field, and it continues to have a strong influence on psychology today. Indeed, most of today’s experimental studies continue to adhere to rigorous research standards similar to those laid down by behaviorists. Behaviorism was not embraced by all, however. Some psychologists criticized John Watson and other prominent behaviorists for popularizing and, in their view, cheapening psychology. In 1929, for example, psychologist Joseph Jastrow wrote that behaviorism’s portrayal in popular magazines and newspapers undermined psychology’s role as a valid science (Jastrow, 1929). Similarly, other psychologists raised questions about the merits of this area of psychology.
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In addition, over time, the behaviorists themselves began to disagree with each other and to divide into competing schools of thought. In the 1960s, for example, the psychologist Albert Bandura (1925– ) demonstrated that children often seem to learn not by conditioning or clear rewards and punishments but by social observation, or modeling. Bandura and other psychologists also showed that people could learn without any apparent change in their overt behavior, a phenomenon that suggested individual changes might reflect some kind of internal representations and mental processes. With these and related developments, pure behaviorism (that is, behaviorism with no attention to mental processes, such as beliefs or thoughts) began to lose some of its influence.
Humanistic Psychology: A New Direction By the 1950s and 1960s, psychoanalytic and behaviorist theories were at opposite ends of the psychology spectrum, one focusing exclusively on mental processes and the other exclusively on behavior. The 1960s were a particularly troubled time socially and economically in the United States and also a time when heated debates took place regarding the relationship between people and authority figures and when questions Humanistic pioneer. Carl Rogers was the founder of were raised about essential human rights. In this atmosphere, humanistic psycholclient-centered therapy, which promotes an equal ogy emerged as an alternative theory that sought to give greater prominence to the relationship between therapists and clients and helps special and unique features of human functioning than to the mechanistic principles clients to achieve their full potential. that characterized psychoanalysis and behaviorism. Founding humanistic theorists Carl Rogers (1902–1987) and Abraham Maslow (1908–1970) rejected the approach of behaviorists. They felt that behaviorists looked at humans just as they looked at animals, largely regarding people as machines that could be predicted and controlled but giving little or no weight to consciousness and other distinctly human characteristics. Humanism, in contrast, focused on the potential of individuals and highlighted each person’s subjectivity, consciousness, free will, and other special human qualities. According to humanistic psychologists, all people have the potential for creativity, positive outlook, and the pursuit of higher values. They claimed that if we can fulfill our full potential, we will inevitably lead a positive life of psychological growth. Maslow, in fact, proposed that each of us has a basic, broad motive to fulfill our special potential as human beings, which he called the drive for self-actualization. He suggested that anyone who achieved this broad motive would indeed lead a positive and fulfilling life. Maslow’s hierarchy of human needs summarized his theory and is shown in Figure 1-3. FIGURE 1-3 Maslow’s hierarchy Carl Rogers developed a humanistic alternative to the psychoanalytic approach of needs Maslow prioritized our numerous needs and believed to psychotherapy, which he called client-centered therapy. According to Rogers, that we must satisfy basic phystherapists should respect their clients as equals. The therapist establishes a trustiological and safety needs ing and warm relationship with the client by “mirroring” feelings and conveyfirst. Only then can we progress up the hierarchy ing unconditional support and positive regard for the client. This very and achieve self-actualSelf-actualization human approach to therapy played an important role in the estabization. needs: lishment of the fields of clinical and counseling psychology after to find self-fulfillment and World War II. realize one’s potential In certain respects, the humanists were not actually seekEsteem needs: to achieve, be ing to prove behaviorists and psychoanalysts wrong but rather competent, gain approval, and excel to complete their ideas. They believed that behaviorism Belonging and love needs: to affiliate with others, be accepted, and give and receive attention was too limited to the objective realm and that psychoanalysis failed to acknowledge the free will and autonomy Safety needs: to feel secure and safe, to seek pleasure and avoid pain of individuals. The goal of humanists, in contrast, was to Physiological needs: hunger, thirst, and maintenance jolt people from a psychological rut and to help them realof internal state of the body ize their innate and grand potential. Although humanism did Twentieth-Century Approaches 17
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cognitive psychology field of psychology studying mental processes as forms of information processing, or the ways in which information is stored and operated in our minds.
not ultimately have as great an impact on psychology as the schools of behaviorism and psychoanalysis, it sparked a greater appreciation of human consciousness and helped to establish a balance between the prevailing views of psychology. Perhaps most importantly, the movement triggered an increased interest in mental processes.
information processing means by which information is stored and operated internally. cultural psychology the study of how cognitive processing varies across different populations. neuroscience study of psychological functions by looking at biological foundations of those functions. Previously known as psychobiology. behavioral genetics subfield of psychology looking at the influence of genes on human behavior. sociobiologists theorists who believe humans have a genetically innate concept of how social behavior should be organized. evolutionary psychology field of study believing that the body and brain are products of evolution and that genetic inheritance plays an important role in shaping the complete range of thoughts and behaviors.
Cognitive Psychology: Revitalization of Study of the Mind In the years after World War II, a new school of psychology emerged whose goal was to measure mental processes effectively. The famous psychologist George A. Miller has recalled that period as a time when “cognition [mental process] was a dirty word because cognitive psychologists were seen as fuzzy, hand-waving, imprecise people who really never did anything that was testable” (Baars, 1986, p. 254). While serving as president of the American Psychological Association in 1960, the Canadian psychologist Donald Hebb (1904–1985) urged the psychological community to apply the rigorous experimental standards seen in behavioral studies—that is controlled and objective methods—to the study of human thought. In 1967, Ulric Neisser, a student of Miller’s, published the influential text Cognitive Psychology in which he described cognition as “all the processes by which....sensory input is transformed, reduced, elaborated, stored, recovered, and used” (Neisser, 1967, pg. 4). Neisser went on to define cognitive psychology as the study of information processing, the means by which information is stored and operates internally. Cognitive psychologists compared the human mind to a computer, likening mental processes to the mind’s software and the human nervous system to the system’s hardware. Early cognitive psychologists reasoned that if modifying software can control the “behavior” of computers, identifying and modifying mental processes can control human behavior. Cognitive psychology soon became the dominant model of the mind. Under this engineering model, cognitive psychologists focused their attention on the functioning of cognitive mechanisms rather than on their content. Cognitive researchers were able to observe the “inputs” and “outputs” of the mental system through carefully controlled experimentation and then to theorize about the internal mechanisms that must underlie such mental functioning. Cognitive psychology continues to influence contemporary theory and research into memory, perception, and consciousness, among other areas that we will discuss in this text. The rigorous experimental standards established by cognitive scientists continue to define current methods for studying how information is stored and manipulated by the brain across different situations. Moreover, at the core of a relatively new field called cultural psychology is an interest in how cognitive processing may vary across different populations. Cross-cultural research uses cognitive experimental methods to help distinguish mental processes that are universal to all humans from those that are shaped by particular variables in the social and physical environment (Byrne et al, 2009; Cole, 1996).
Psychobiology/Neuroscience: Exploring the Origins of the Mind Interest in the biological basis of psychological phenomena can be traced through the work of Hippocrates, Aristotle, Pavlov, and even Freud. Thus it is not surprising that eventually a distinct area of psychology, called psychobiology, emerged. Psychobiology attempted to explain psychological functions by looking primarily at their biological foundations (Gariepy & Blair, 2008; Hergenhahn, 2005). In particular, psychobiology explored brain structure and brain activity and the ways they might be related to individual behaviors and 18
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group dynamics. The term psychobiology has fallen into disuse, although this subfield of psychology has continued to grow. It is now referred to as neuroscience. Early psychobiology gained momentum with the advancement of scientific and medical techniques. Karl Lashley (1890–1958), one of the most influential psychobiologists, based his work on the study of animal neurological functioning. He used surgical techniques to destroy certain areas in the brains of animals and then observed the effects of such destruction on memory, learning, and other cognitive processes. Lashley found that the tissues within certain areas of the brain were often linked to particular cognitive functions. His ultimate goal was to pinpoint all areas of the brain responsible for memory, learning, and other higher functions. He was never able to accomplish this goal fully, and it continues to be a major interest in contemporary research. Roger Sperry (1913–1994), a researcher who was influenced greatly by Lashley, pioneered split-brain research on animals. Sperry and his colleagues severed the connections responsible for relaying information between the left and right hemispheres, or halves, of the brain. They found that even after the brain is split surgically, the two hemispheres of animals can often function and learn independently. Later investigators found similar results when they studied human beings who had undergone a similar split-brain surgery to treat severe seizures (Colvin & Gazzaniga, 2007). Split-brain research on both animals and humans made it possible to study the separate functioning of the brain’s hemispheres, which, as we’ll see in Chapter 4, remains a popular topic in contemporary psychology. A number of psychological subfields have been influenced by the field of neuroscience, as well as by Darwin’s early work on evolution. Behavioral genetics, for example, studies the influence of genes on cognition and behavior. This is not a completely new field. Early in the twentieth century, and even during the rise of behaviorism, a number of animal researchers used evolutionary principles to help explain human behavior. Similarly, sociobiologists, as they were initially called, theorized that humans have an innate concept of how social behavior should be organized. In 1975 Harvard biologist Edward O. Wilson, a specialist on ants, brought great attention to this view with his book Sociobiology: The New Synthesis. He and other sociobiologists suggested that humans are genetically more predisposed than other organisms to learn language, create culture, protect territory, and acquire specific societal rules and regulations. Sociobiologists did not claim that genetic influences are necessarily more important than environmental factors, such as parenting or the mass media. Rather, they proposed that our social behavior is the result of biological and cultural influences. One sociobiologist, David Barash (1979, p. 45), commented, “For too long social science and biological science have pursued ‘nothing but’ approaches. Sociobiology may just help redress that imbalance.” The subfield of sociobiology is now part of a still broader subfield called evolutionary psychology. Evolutionary psychologists continue to hold that the body and brain are largely products of evolution and that inheritance plays an important role in shaping thought and behavior (see Table 1-2). The laws of evolutionary psychology are thought to apply to all organisms and to all kinds of mental functions and behaviors (not only social ones), just as the laws of physics apply to all bodies in space. Evolutionary psychology has become one of the most popular topics in contemporary psychology (Buss, 2009, 2005, 1999). Evolutionary psychologists suggest that some behaviors and mental processes are more effective than others at solving problems of living – namely, those that help people to survive and reproduce. These successful strategies are passed on to people’s children, as well as taught to others, and they eventually become important parts of each individual’s inborn makeup.
Studying the human brain Neuroscientists examine brain structure and brain activity to determine how they are related to behavior. Here a researcher dissects the brain of a former patient with dementia as part of a study to learn more about memory and memory disorders.
©The New Yorker Collection 1986 J.B. Handelsman from cartoonbank.com. All Rights Reserved.
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That certain look. Facial expressions of sadness (left two photos) and happiness (right two photos) are universal across all cultures. Are these commonalities related to our evolutionary history?
One goal of evolutionary psychologists is to identify cultural universality, human behaviors and practices that occur across all cultures. Just as behaviorists study animal behavior to identify simple actions that form the basis of more complex human behaviors, evolutionary psychologists believe that uncovering universal human behaviors will help identify inborn functions common to all humans. Theoretically, such knowledge will answer important questions about the relative impact of biological factors and life experiences on our development. Throughout this book, we’ll be observing a number of common practices displayed by people across cultures, such as using specific facial expressions to express emotions, displaying a fear of snakes, telling stories, and giving gifts (Chomsky, 2005; Brown, 1991). But are such commonalities the direct result of evolutionary forces? Have these behaviors and reactions been passed on from generation to generation largely because they remain highly adaptive? In fact, two evolutionary biologists, Stephen Jay Gould and Richard Lewontin (1979), did not think so. They argued that some of the TABLE 1-2 The Major Perspectives in Psychology Today traits and behaviors seen across cultures are no longer evolutionarily advantageous and instead Perspectives Major emphases may be byproducts of behaviors that served adaptive functions a long time ago. Initially, for examPsychoanalytic Interactions between the conscious and ple, the human smile may have represented a unconscious mind govern virtually all submissive baring of teeth often seen in animals, behavior; childhood experiences set the designed to ward off attacks by enemies. Over stage for later psychological functioning many, many years, however, it has come to be used in human social environments to signal the presBehaviorist Only observable behavior can be studied scientifically. ence of a friend, or to signal humor. Perspective focuses on stimulus-response relationships and the consequences for behavior Although it can be difficult and at times misleading to identify evolutionary roots for today’s behaviors, Humanist People can be helped to realize their full and grand potential, the study of genetics and inheritance continues to play which will inevitably lead to their positive psychological an important role in psychology. Indeed, many invesgrowth tigations conducted over the past two decades have established the importance of genetic influences on Cognitive Mental processes are studied using an information processing human development. We’ll see later in this book, for model (inputs/outputs) example, that studies of twins who were separated at birth and reared in different families often find that the Neuroscience/ Psychological functions are explained primarily in twins continue to share many characteristics Psychobiological terms of their biological foundations (Bouchard, 1984). The verdict on evolutionary psychology may still be out, but few of today’s psycholoEvolutionary Behavior and mental processes are explained in terms of evogists question the contribution of genetic factors to lution, inheritance, and adaptation. mental functioning and behavior.
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Before You Go On What Do You Know? 9. Which theorist is most closely associated with psychoanalytic theory—the theory that unconscious conflicts, rooted in childhood, affect much of our behavior? 10. According to behaviorist theorists, what are the various reinforcement principles, and what impact does each have on behavior? 11. What did humanist theorist Abraham Maslow suggest is the ultimate goal of human beings? 12. What are cognitions? 13. What is the main contention of evolutionary psychology?
What Do You Think? Which of the theories presented here depend largely on biological principles? Which of the theories seem to be based more on environmental explanations? And which appear to rely on an interaction of factors?
Psychology Today LEARNING OBJECTIVE 5 Describe the three major branches of psychology and summarize key trends in psychology.
In the contemporary field of psychology, we can recognize the influence of various schools of thought that date back to the days of Greek philosophers. The psychological orientations we have discussed in this chapter, such as functionalism, behaviorism, and cognitive science, have not disappeared but rather continue to develop and interact with one another. Indeed, today there is broad recognition that psychology must be as diverse as the humans whose behavior it attempts to explain 2% 1% (Sternberg & Grigorenko, 2001). 7% Educational 5% General Social and Other More detailed information is available now than ever before about 4% personality Cognitive how the brain functions, and this information has in fact served to empha6% size the importance of analyzing human thought and behavior at a vari- Developmental ety of levels. Brain imaging studies have, for example, been used to test 6% behavioral principles, identifying which areas of the brain are activated School 47% when a behavior is performed or when an outcome is better (or worse) 4% Clinical than expected (Cumming, 2009). Similarly, cognitive psychologists and Industrial organizational biologists have examined psychoanalytic notions, such as the proposal that 8% our unconscious minds hold memories that might be too anxiety-proCounseling 9% voking for our conscious minds. Recent investigations have, for example, Neuroscience/ linked real memories to one pattern of brain activity and false memories Experimental to another (Garoff-Eaton, Slotnick, & Schacter, 2006). FIGURE 1-4 Percentage of recent doctorates As the diversity of the field has increased, so too has the need for there to be awarded in each subfield of psychology communication among its various voices. Indeed, today’s psychologists are reprePsychologists today have a wide variety of areas to pursue (APA, 2008). sented in various professional organizations including the American Psychological Association (150,000 members), the Association for Psychological Science (20,000 members), and the Society for Neuroscience (38,000 members), which collectivity address the interests and needs of more than 50 different specialities in psycholcultural universality behaviors and practices that occur across all cultures. ogy. Figure 1-4 shows the variety of fields of study in psychology today.
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Branches of Psychology
28% Universities and colleges
4% Medical schools 8% Schools and other educational settings
14% Hospitals
12% Self-employed 12% Government or business
11% Other
11% Human service agencies
FIGURE 1-5 Where do new psychologists work? The primary work settings for recent PhDs in psychology are colleges, hospitals, the government, businesses, and human service agencies (APA, 2009).
PRACTICALLYSPEAKING
There are currently three key branches of psychology –academic psychology, applied psychology, and clinical and counseling psychology. Psychologists from all three branches share an interest in mental processes and behavior. They differ in the amount of emphasis they each place on the psychology of individuals, the discovery of general principles of psychology, and the application of psychological knowledge to groups of people. Figure 1-5 summarizes the range of settings in which academic, applied, and clinical and counseling psychologists work.
Academic Psychology When Wilhelm Wundt founded psychology as a discipline distinct from philosophy in 1879, his goal was to examine human nature. He did not focus on questions of how psychology could be applied or used outside the laboratory. Today, the branch of psychology known as academic psychology carries on Wundt’s mission. Academic psychology involves research and instruction on a wide variety of psychological topics. Academic psychologists typically work at colleges and universities, where they often divide their time between teaching and conducting research in their particular fields of interest. A developmental psychologist, for example, may teach courses on child devel-
What Can You Do with a Psychology Degree?
Psychology is the study of behavior and mental life. Students who major in psychology gain a broad understanding of what makes people “tick” from a wide range of perspectives, including developmental, social, clinical, and biological. They also Psychology’s wide influence. Psychologist acquire a body of Daniel Kahneman (left) is awarded the 2002 knowledge and set of Nobel Prize in Economics. skills that help qualify them for a broad range of career choices. If people want to become psychologists, they will find that an undergraduate degree in psychology prepares them to pursue graduate degrees in any number of psychology subfields, including clinical, health, cognitive, social, neuroscience, organizational, educational, and sports psychology. Alternatively, being an undergraduate major in psychology can help open the door to graduate study in many other fields, such as law, business management, economics, and medicine.
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Even if graduate study is not for you, an undergraduate degree in psychology can lead to interesting jobs and careers. Psychology majors are typically viewed by prospective employers as well qualified to work in fields that require people skills, as well as, analytical, research, and writing abilities. “But,” you might say, “just about every job deals with people.” Yes, that’s the point. An undergraduate degree in psychology particularly qualifies individuals for entry-level jobs in people-oriented careers such as communications, marketing, human resources, sales, and business. Beyond people skills, the analytic, research and writing skills of psychology majors enhance their eligibility for human-service, legal, and law-enforcement jobs, including positions as paralegals and corrections officers. Furthermore, the same skills may make individuals good candidates for careers in general business, marketing research, management consulting, computer game design, and investment banking. In short, psychology is related to so much in our world that a degree in this discipline can lead to work and careers in more areas and fields than you might imagine. Keep in mind, for example, that the psychologists Daniel Kahneman (2002) and Herbert Simon (1978) are Nobel Laureates in economics, while the neuroscientists Eric Kandel (2000), Rita Levi-Montalcini (1986), and Roger Sperry (1981) won their Nobel Prizes in medicine and physiology.
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opment while also researching how children think and behave. The efforts of academic researchers have resulted in a large body of psychological knowledge, and, for the most part, the chapters throughout this textbook reflect their considerable work and findings. Applied Psychology Although Wilhelm Wundt intended for psychology to pursue “pure” scientific knowledge, many of his students went on to apply their knowledge to a variety of disciplines (Hergenhahn, 2005). Functionalism, founded by William James, marked the first formal branch of applied psychology. As you’ll recall, this orientation was influenced by evolutionary theory and focused on applying psychological principles to social issues. Today, the branch of psychology called applied psychology involves the application of psychological principles to help solve practical problems in education, marketing, and other fields (Steg et al., 2008). Lawyers may consult with psychologists to help determine whom to select for a jury. Advertisers may consult with psychologists to conduct research to determine how best to market products to teenagers. Throughout this book, we shall examine a wide range of research developments, both those that have immediate practical applications and those that simply further our insights about the human mind and behavior. Applied psychologists have earned either a master’s degree, which requires two years of graduate study, or a Ph.D. (doctorate of philosophy). Many applied psychologists specialize in a broad traditional academic field, such as developmental or social psychology, and use their expertise further to help guide decisions and work outside of academic settings. There are also a number of specialized programs of study within applied psychology. Sports psychologists, for example, may provide guidance to athletes or teams, helping them overcome feelings of anxiety or frustration or teaching them to focus their energy more effectively.
academic psychology branch of psychology focusing on research and instruction in the various areas or fields of study in psychology. applied psychology branch of psychology applying psychological principles to practical problems in other fields, such as education, marketing, or industry. clinical and counseling psychology the study of abnormal psychological behavior and interventions designed to change that behavior.
Clinical and Counseling Psychology Clinical and counseling psychology help individuals to cope more effectively or to overcome abnormal functioning. Actually, there are several different types of mental-health practitioners. • Clinical psychologists generally provide psychotherapy, which involves helping people to modify thoughts, feelings, and behaviors that are causing them distress or inhibiting their functioning. They also may administer and interpret psychological tests to provide further information relevant to treatment. Many clinical psychologists earn a Ph.D. degree awarded by a university graduate program, which typically requires training in therapeutic practices and in the conduct and interpretation of research. Some clinical psychologists earn a Psy.D. (doctorate of psychology) degree. This degree is awarded by graduate programs that place less emphasis on research and greater emphasis on psychotherapy and psychological testing. • Counseling psychologists and psychiatric social workers also provide psychotherapy for people with psychological problems. These professionals may also help individuals and families deal with issues tied to relationships, careers, child-rearing, and other important areas of functioning. In addition, some social workers provide aid to families through social service systems that are available in a community. Counseling psychologists earn a Ph.D. or Psy.D. in their field, while social workers earn either an M.S.W. (masters of social work) or D.S.W. (doctorate of social work) degree from a school of social work. • Psychiatrists, who may also provide guidance and therapy to individuals, are professionals who attend medical school and earn an M.D. (doctorate of medicine). Psychiatrists generally have less training in psychological research and
The couch! Sigmund Freud’s signature therapy procedure was to have patients lie on a couch and say whatever came to mind, while he took notes behind them. This wax recreation of the neurologist and his office is on display at a museum in Berlin, Germany.
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New Mexico and Louisiana currently are the only states that grant prescription privileges to psychologists who receive special pharmacological training. The U.S. territory of Guam also grants such privileges to psychologists.
testing than clinical psychologists, but they have medical knowledge and the ability to prescribe medications for abnormal emotional states or behavior problems, a professional privilege that most states do not grant to clinical or counseling psychologists or social workers.
Shared Values Although the three branches of psychology—academic, applied, and clinical and counseling—have different goals and ways of meeting those goals, they do share important values that guide their work. Many of those values will shape our discussions throughout this textbook, so let’s take a look at them here.
collectivist culture whose members focus more on the needs of the group and less on individual desires. individualistic culture that places the wants or desires of the person over the needs of the group. cognitive neuroscience study of mental processes and how they relate to the biological functions of the brain. social neuroscience study of social functioning and how it is tied to brain activity.
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• Psychology is theory-driven. If you’re going to explain human behavior, you have to have a theory. We will describe the elements of a good theory in Chapter 2. Psychologists have developed theories, or potential answers, for many key questions: Do mental processes exist? What are the relative roles of biological inheritance and environmental influence in shaping human psychology? How do we explain deviant behavior, such as Internet trolling? Each school of psychology provides ideas to help answer such questions. And every branch of psychology uses its potential answers to guide research or improve psychological interventions. • Psychology is empirical. From its very start, what separated psychology from other human disciplines, such as philosophy was its emphasis on controlled observations and experimentation. Psychology finds more use and value in ideas that receive strong empirical, or research, support, than in ideas, even seemingly compelling ones, that cannot be supported with evidence from systematic testing. • Psychology is multilevel. As we discussed at the beginning of this chapter, to understand the complete picture of human mental processes and behavior, psychologists must account for what is happening at the levels of the brain, the person, and the group. Although certain theories place more emphasis on one level than another, all of the levels are indeed operating to influence whatever mental process or behavior we may be observing. Thus, in chapters throughout this textbook, we will be presenting evidence about what happens at each of these three levels. • Psychology is contextual. As recently as 20 years ago, the thought of Internet trolls—actually, even the thought of the Internet—was unimaginable to most people. As the history of psychology shows, however, technological advances have had a strong influence on the development, rise, and fall of particular theories. Without the computer, for example, the field of cognitive psychology would have been described very differently. In fact, technological and other societal changes force us to look at human behavior from new perspectives that broaden our awareness. All of this means that some of the theories you’re studying today may eventually go the way of structuralism—influential but dramatically changed in nature. This is the way that science progresses.
Current Trends in Psychology The values of psychology, as theory-driven, empirical, multilevel, and contextual, work together to drive constant progress and change in the field. Today, those values, as well as larger social developments, are shaping several trends in psychology. In particular, the field is growing more diverse, continuing to profit from technological advances, and continuing to give birth to new schools of thought.
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Mary Whilton Calkins, who worked with William James and was the first female president of the American Psychological Association, completed all her coursework at Harvard but was denied a Ph.D. because she was a woman.
1974
2005
70
Cognitive N/A
Experimental
60
Advances in Technology As we observed earlier, technological shifts also 50 contribute to shifts in psychological theory. The development of computers 40 in the 1950s and 1960s contributed to the cognitive psychology revolution. 30 Technology has continued to change the face of science and psychology in 20 more recent years. Innovations such as brain imaging and effective pharma10 cological, or drug, treatments for mental disorders have revealed a great deal 0 about human mental processes and behavior. As you’ll see in Chapter 4, for example, the development of brain-imaging technology has made it possible for researchers to observe activity in the brain directly. In fact, in recent years a new area of psychological study and theory has emerged: Cognitive neuroscience focuses not only on mental processes but also on how mental processes interact with the biological functions of the brain. That is, what happens in the brain when we are remembering something, making a decision, or paying attention to something? One goal of cognitive neuroscientists is to link specific mental processes to particular brain activities. Similarly, a field called social neuroscience has
Industrial organizational
Percent of PhDs who are female
Growing Diversity Early in the history of psychology, few women or members of racial minority groups were able to obtain the advanced education and professional status necessary to contribute to the field. As psychology itself has grown more diverse, however, so have psychologists (see Figure 1-6). Psychology now has more women earning graduate degrees than does any other science. Indeed, 71 percent of newly earned Ph.D.s in psychology are awarded to women (APA, 2009). In addition, 16 percent of newly earned Ph.D.s are awarded to minority group members, compared to 7 percent thirty years ago (APA, 2009). Growing diversity among psychologists has overlapped with an increased interest in the diversity of the people they study, treat, and influence. Cultural psychology has, for example, become an important area of investigation. As we observed earlier, this field of study seeks to uncover mental processes that exist across all cultures, as well as important cultural differences. Cultural psychologists often focus on differences between collectivist cultures and individualistic cultures. Members of collectivist cultures emphasize the needs of the group and subsume individual desires to those of the family or peer group. In contrast, individualistic cultures stress the needs of persons over those of the group. One study of differences between these two types of cultures examined positive emotions, such as happiness. Individuals from Eastern cultures, which tend to be more collectivist, and Western cultures, which tend to be more individualistic, appear to hold different beliefs about the sources of happiness. When asked to talk about events that make them feel happy, Chinese research participants focused on interpersonal interactions and evaluations from others, while Western participants pointed to personal achievement and selfevaluation (Lu & Shih, 1997). Research has also indicated that even within a broad culture, subcultures may differ with regard to happiness. Studies have shown, for example, that positive emotions, such as strong self-acceptance are, on average, a bit lower among individuals from southern parts of the United States than among those from the West or Midwest. Some researchers have hypothesized that these lower levels of well-being and self-acceptance may reflect a subculture that is relatively more concerned with showing hospitality and respecting tradition than with fostering positive self-concepts and promoting personal growth (Markus et al., 2004). Given psychology’s growing interest in these and related differences among people and between groups, we have included throughout the textbook sections 100 called “How We Differ.” These sections examine how memory, emotions, social 90 values, and the like differ from situation to situation, person to person, and 80 group to group.
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FIGURE 1-6 Growth of women Ph.D.s in psychology Over a 30-year period, the increase in the percentage of women earning Ph.D.s has been dramatic, especially in the clinical, developmental, and counseling fields (Cynkar, 2007).
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Pioneering Women Psychologists Since the beginnings of psychology as a science, women have made important discoveries and contributions to psychology. Here are but a few of the field’s female pioneers. The work of Mary Whiton Calkins (1863–1930) was noteworthy for her emphasis on the self, consciousness, emotions, and dreams, which stood in stark contrast to John Watson’s behaviorist movement at the time. Calkins was the first woman president of the American Psychological Association (APA). Margaret Floy Washburn (1871–1939), was the first woman to receive a Ph.D. in psychology (1894) and the first woman elected to the National Academy of Sciences (1932). She was one of the earliest experimental psychologists to insist that mental phenomena were as important for scientific study as observable behaviors. Karen Horney (1885-1952), was one of the most influential early psychoanalytic theorists, a pioneer in the discipline of “feminine psychiatry,” and a leader in the Neo-Freudian movement that challenged traditional Freudian views. She was especially critical of Freud’s theory of sexuality, challenging many of his notions in this area of functioning. Leta Hollingsworth (1886-1939), was best known for her studies of “mentally deficient” and “mentally gifted” individuals and for her views on gender differences in mental functioning. She was one of the first theorists of her time to challenge the notion that relatively fewer female achievements reflected biologically inferiority, arguing instead that women were victims of a male-dominated social order.
Nancy Bayley (1899–1994) was best known for her work in the measurement of infant intelligence and human development, which remain the standard today. Bayley was the first woman to receive the Distinguished Scientific Contribution Award from the APA. Mamie Phipps Clark (1917–1983) and her psychologist husband Kenneth Clark were two of the first well-known AfricanAmerican psychologists. She and her husband were best known for their work on the effects of segregation on the self-images of minority children. Brenda Milner (1918-) has been a pioneer in the study of memory and other cognitive functions in humans. She was the first to investigate how damage to the brain’s hippocampus affects memory through her study of a famous amnesia patient known as H.M. in the research literature. Carol Gilligan (1936– ) is best known for her pioneering work on gender differences, which has forever changed society’s understanding of the human experience. Gilligan was named one of the 25 most influential Americans in 1996 by Time Magazine and received the fourth annual Heinz Award in the Human Condition in 1998. Anne Treisman (1935- ) has been a leading researcher of visual attention, object perception, and memory. She was the first psychologist to propose that different kinds of attention enable people to combine the observed separate features of an object into a consciously experienced whole.
emerged, which seeks to link social functioning to particular brain activities. Recent studies have, for example, found that there is a network of nerve cells in the brain that is activated when we show empathy, our ability to understand the intentions of others. Cognitive and social neuroscience are currently among psychology’s more active areas of theory and research. Given the enormous growth and impact of such areas, we have also included throughout the book a section called “What Happens in the Brain?” In these sections, you’ll learn about the neuroscience of memory, emotions, social behavior, and the like. You’ll discover, for example, what happens in the brain when you are learning new material before an important test and then again when you get together with friends to celebrate the completion of that test. The development of imaging tools, computer technology, and a number of biological techniques has also helped enhance our understanding and treatment of mental dysfunctioning in recent years. These tools have enabled researchers to look directly at the brains of disturbed persons while they are feeling sad or anxious, hearing voices, or recalling repressed memories. Such studies have helped reveal that depression, for example, is related not only to traumatic childhood experiences, significant losses in life, and feelings of helplessness but also to abnormal activity of key chemicals in the brain. Given such wide-ranging insights, we also have included in most chapters a section called “When Things Go Wrong.” We discuss in these sections what happens when normal psychological processes, such as memory, emotional coping, social engagement, and the like, go astray. 26
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At first glance, psychology’s intensified focus on the brain may make it appear that technology and biology are dominating contemporary psychology. However, it is unlikely that psychology will ever be overtaken by biology. Indeed, recent findings in cognitive neuroscience and other areas suggest that our insights about mental functions (and dysfunctions) and about behavior are most complete when the different branches of the field intersect and cooperate. In clinical psychology, for example, it is now clear that many mental disorders are best understood and treated when explanations and techniques from different schools of thought are combined. One important area of psychology that has intersected with other areas of the field for many years is developmental psychology, the study of how we change over the course of our lives. Developmental psychology has both incorporated and contributed to research in areas, such as our use of language, our emotions, our personalities, and the structure of our brains. We emphasize the cross-fertilization of development and other areas by including in most chapters a section called “How We Develop.” New Schools of Thought As we saw earlier, historical schools of thought in psychology sow the seeds for related but new ideas. We can see, for example, influences of the functionalists, who were interested in applying psychological research, and the humanists, who were interested in helping people achieve their highest potential, when we look at a relatively new movement in the field called positive psychology. Positive psychology gives special focus to more upbeat features of human functioning, including happiness, meaning in life, and character strengths, as well as increased attention to how those features of positive living might be developed more readily (Baumgardner & Crothers, 2009; Seligman & Csikszentmihalyi, 2000). Happiness seems to have become a buzz word of the twenty-first century. It has been embraced particularly by the popular media, fueling a self-help industry that claims to give people tools for achieving emotional well-being. This heightened interest in positive functioning has been used to help market nutritional advice, as seen, for example, in the book The Good Mood Diet: Feel Great While You Lose Weight (Kleiner & Condor, 2007), and has appeared even in fields not associated primarily with psychology, as in the book The Architecture of Happiness (Botton, 2006). The field of positive psychology has tried to devote scholarly discussion and scientific study to happiness and its positive counterparts. In fact, an estimated 150 psychology departments in the United States now offer courses in positive psychology (Senior, 2006). A growing body of research does indeed suggest that positive emotions can have a profound impact on development and behavior. As you’ll see in Chapter 15, for example, when we discuss stress, coping, and health, a number of studies have found that having a positive outlook promotes resilience, the ability to bounce back in the face of adversity (Bonanno, 2008, 2005, 2004). Similarly, studies indicate that positive emotions may boost the functioning of our immune systems. Research even suggests that our emotions help influence how well we resist common colds (Cohen et al., 2008, 2003)! In Chapter 12 on emotions, we’ll also come upon a line of research that suggests that each of us has a particular “set-point” on our happiness thermometer, a relatively stable level of well-being that we may carry with us to each situation in our lives. We may depart from that set-point for short periods of time, but many of us return to our particular level of happiness within weeks or months of a destabilizing event (Headey, 2008). In Chapter 16, we’ll see that some psychologists have even developed a new form of therapy, called positive psychotherapy, that does not target specific symptoms of mental dysfunction but rather focuses on increasing the positive emotions and sense of engagement and meaning experienced by clients (Seligman et al., 2006). According to
Accentuating the positive. Residents of a small Spanish village cry out in joy as they are drenched with 30 tons of water during a water festival. Positive psychologists study the impact that happiness and positive emotions have on human functioning.
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Socrates’ approach to teaching involved leading students through their assumptions and logic by asking them specific, precise questions. This approach, called the Socratic method, remains an important part of a clinical psychologist’s therapeutic practice to this day.
proponents of positive psychology, certain techniques and behaviors can be of particular help to people in their efforts to achieve happiness or return to happiness after unpleasant events. What Changes and What Remains Constant? Since the early years of Greek philosophy, theorists have attempted to determine how the human mind operates and whether there are universal laws that govern mental processes and behaviors. Those questions remain at the forefront of contemporary psychology as today’s neuroscientists, cultural theorists, and other psychologists try to determine how the mind and body are related, whether there are knowable universal truths about mental processes and human behaviors, and whether such truths are best understood through the perspective of the brain, the individual, or the group, or a particular combination of the three. It is not likely that psychology can ever provide complete answers to these complex questions, but striving to uncover even partial answers has already uncovered a wealth of information about how human beings function and has produced a range of compelling theories and research findings. As you read about these theories and findings throughout this textbook, you will do well to keep asking yourself a question raised by Carl Jung (1875–1961), one of the field’s most famous clinical theorists, “How much truth [is] captured by this [particular] viewpoint?” Ideas move in and out of vogue, and what is accepted today as a useful or accurate outlook might not be seen the same way tomorrow. Both historical and social forces determine the focus of scientific energy. Psychology, perhaps more than any other field, struggles constantly to achieve a proper balance between popular trends and interests, societal influences, and scientific objectivity (Leahey, 2000, p. 544). Although fads and fashions will likely continue to exert some influence on the development of psychology in the coming years, it is important to recognize that such fads hardly comprise the substance of the field. Moreover, we must always keep in mind the limitations of psychology (or of any discipline) in answering the basic questions of human existence. As we noted at the beginning of this chapter, scientific knowledge serves as a means for exploring such questions rather than an end.
Before You Go On What Do You Know? 14. What are the three major branches of psychology? 15. What is cultural universality, and which psychologists are interested in it? 16. What is the focus of positive psychology?
What Do You Think? Which branch of psychology most appeals to you as a potential profession? Why? What kinds of things do you think would be important for positive psychologists to study?
Summary What is Psychology? LEARNING OBJECTIVE 1 Define psychology, and describe the goals and levels of analysis psychologists use. • Psychology is the study of mental processes and behavior.
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• The goals of psychology are to describe, explain, predict, and control behavior and mental processes. Psychologists vary in the degree to which they focus on some of these goals more than others. • The study of psychology must occur at multiple levels, including the level of the brain (the biological activity associated with mental processes and behavior), the level of the person (the content of mental processes), and the level of the group (social influences on behavior).
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Psychology’s Roots in Philosophy LEARNING OBJECTIVE 2 Describe the influences of early myths and ancient Greek philosophies on psychology. • Early explanations of human behavior were rooted in superstition and magic. • Later, philosophers, beginning with the ancient Greeks, tried to develop more objective theories of human consciousness and reality. • The work of such early philosophers as Hippocrates, Socrates, Plato, and Aristotle contributed to the later formation of psychology as a natural science.
The Early Days of Psychology LEARNING OBJECTIVE 3 Name important early psychologists and describe their major theories and research methods. • The development of psychology has been strongly influenced by shifts in the social environment and development of new technology. • The first psychology laboratory was founded in Leipzig, Germany by physiologist Wilhelm Wundt. Wundt was interested in human consciousness and will, which he studied through small, structured activities that could be easily watched and replicated. • Structuralism, a school of thought developed by one of Wundt’s students, relied upon the use of introspection, the careful observation of human perception. The goal of the structuralists was to find the smallest building blocks of consciousness. • William James established the first psychology laboratory in the United States at Harvard and helped shift the field’s focus to the functions of the mental events and behaviors, forming a school of thought known as functionalism. • Gestalt psychologists, rather than divide consciousness into its smallest parts, studied human tendencies to perceive pattern, putting together the “parts,” or individual sensations, to create a “whole” or perception that went beyond the sum of the parts.
Twentieth-Century Approaches
• Over the years, different fields of psychology emerged, with different ideas about what was the appropriate area of study for human psychology. Some of the most influential fields were the psychoanalytic, behaviorist, humanistic, cognitive, and neuroscience schools of thought. • Sigmund Freud’s psychoanalytical theory focused on the importance of unconscious mental processes. • Behaviorists believed strongly that psychology should restrict its focus to the careful study of observable behaviors. • Humanistic psychologists reacted against the mechanical portrayals of people by the behaviorists, and emphasized individuals’ potential for growth and self-actualization. • Cognitive psychologists reignited interest in the study of mental processes, comparing the workings of the mind to the workings of computers. • Biological science, including interest in the workings of the brain and in our genetic inheritance, is the major influence on neuroscience approaches.
Psychology Today LEARNING OBJECTIVE 5 Describe the three major branches of psychology and summarize key trends in psychology. • The theoretical and cultural diversity of the field of psychology has increased dramatically over recent years. • There are three key branches of psychology: academic, applied, and clinical/counseling. • Across the three branches and many specialty areas in psychology, psychologists are united by their shared values. Psychologists generally agree that psychology is theory-driven, empirical, multilevel, and contextual. • Currently, psychology appears to be developing as a science in response to a growing diversity throughout the field, advances in technology (such as brain scanning), and the development of new schools such as positive psychology.
LEARNING OBJECTIVE 4 Summarize the major principles of the psychoanalytical, behaviorist, humanistic, cognitive, and neuroscience approaches to psychology.
Key Terms psychology 5
gestalt psychology 12
cognitive psychology 18
applied psychology 23
mental processes 5
unconscious 15
information processing 18
behavior 5
psychoanalytic theory 15
cultural psychology 18
clinical and counseling psychology 23
culture 6
behaviorism 15
neuroscience 18
collectivist 24
consciousness 11
stimuli 15
behavioral genetics 18
individualistic 24
voluntarism 11
response 15
sociobiologists 18
cognitive neuroscience 24
structuralism 11
reinforcement 16
evolutionary psychology 18
social neuroscience 24
introspection 11
humanistic psychology 16
cultural universality 21
functionalism 11
client-centered therapy 16
academic psychology 23
Key Terms
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CHAPTER 2
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Psychology as a Science chapter outline •
What is a Science? • •
• •
Ugly
Is Psychology a Science?
How Do Psychologists Conduct Research?
How Do Psychologists Make Sense of Research Results? What Ethical Research Guidelines Do Psychologists Follow?
Reality?
perately needs” improvements in their house. Then the
Extreme Makeover team—designers, workers, even neigh-
R
eality television has become an increasingly present and
bors—spend a week renovating the chosen family’s entire
controversial part of the world media over the past
house and property. The moments in which a family first learns
decade. Shows, such as American Idol, Survivor, Dancing with
that it has been selected for a makeover and those in which
the Stars, and The Amazing Race currently dominate network
the family later sees their renovated home are the emotional
television. And their cousins—Flavor of Love, Jackass, and
highlights of each show.
Real Housewives of Atlanta—receive huge ratings on cable
Many criticisms have been leveled at reality TV (Hirschorn,
television. Actually, there are various kinds of reality shows—
2007). It’s crass, say its detractors. It’s exploitative. It lowers the
for example, the competition realities, in which people vie for
level of cultural discussion and encourages audiences to take
a job, recognition, or a dream mate; the real-life realities,
pleasure in the humiliation of other human beings.
which have people conduct their lives as usual, for all the
Defenders of reality TV counter that such criticisms are
world to see; and the advice realities, in which professionals
“snobbery.” They point out that participants on reality TV
tell individuals how to improve their behaviors.
include individuals from a variety of racial and socioeconomic
Among the most popular reality shows are the give-
backgrounds who rarely receive much exposure on scripted
away/makeover programs: shows in which people who are
television shows. At their best, defenders argue, reality shows,
poor, down on their luck, or appearance-challenged are cho-
particularly the giveaway/makeover ones, bring out admirable
sen to receive special gifts, makeovers, or opportunities that
qualities in viewers, tapping into positive feelings such as altru-
will improve their lives markedly. Today’s giveaway/makeover
ism, empathy, and concern for others, and, in turn, offering a
shows have roots dating back to 1956 when Queen for a Day
window into social instincts, behaviors, and interactions.
hit the TV airways. In this popular show, several women would each tell their hard-luck life story to a studio audience who would then decide, by way of applause, which woman should receive a refrigerator and other life-changing prizes. Similarly, one of today’s most popular giveaway/makeover shows, Extreme Makeover: Home Edition, invites people from across the world to nominate a “deserving family that des-
Is reality TV a barbaric force? Is it a force for good, giving a voice to the voiceless and providing natural demonstrations of human behavior? Or is it, after all, just television? Viewers may base their answers to these questions on their personal experiences. Journalists and media critics may use comparisons to other televisions shows or look at trends over time. Sociologists and anthropologists might look for large-scale cultural shifts in moral or other standards. Psychologists try to Psychology as a Science
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Reality mania Supporters of reality television contestant Susan Boyle gather to watch her compete on the final episode of “Britain’s Got Talent” in 2009. Viewers often seem to be enormously affected by the people and events on display in today’s reality TV shows.
answer questions like these by using scientific research methods to look for relationships between reality TV and systematic changes in individual people’s mental processes and behavior. In this chapter, you’ll find out exactly what the scientific research methods of psychologists are and how psychologists use them. We’ll begin the chapter by defining what science is. Then we’ll consider just how well psychology fits with the definition of a science, particularly in comparison to other fields. Next we’ll examine in some detail the methods that psychologists use to conduct research, including, by way of example, research into the nature and impact of television viewing habits. Finally, we’ll look at the statistics that help researchers interpret their results and the ethical rules that guide them when working with humans or animals.
What is a Science? LEARNING OBJECTIVE 1 List two core beliefs of science, and describe the steps in the scientific method.
Before we look at psychology in particular, take a moment to try to answer the general question, what is a science? You might answer by listing types of sciences, such as chemistry, biology, or physics. You might envision a white-coated person in a lab somewhere, mixing strangely bubbling chemicals or lecturing students about where to start an incision on the frog in the tray in front of them. Such things are only sometimes associated with science. Two characteristics that all sciences share, however, are similar principles, or beliefs, about how best to understand the world and reliance on the scientific method as a way to discovering knowledge.
Scientific Principles Science is built on a foundation of core beliefs about the world. Two essential beliefs are that: • The universe operates according to certain natural laws. Scientists believe that things happen in and around us in some kind of orderly fashion that can be described using rules or laws. The natural law of cause and effect, for example, 32
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suggests that when something is set in motion, it has an effect on other things. Psychologists look for the laws that describe mental processes and behavior. • Such laws are discoverable and testable. By carefully observing what happens in the natural world, we can figure out the laws governing those events. In turn, we can use these laws to make predictions about what might happen, and we can then experiment to see whether those predictions come true. As a natural science, psychology operates according to these two core beliefs. Psychology also shares with other sciences a similar logical approach to discovering and testing laws about how things happen: the scientific method.
The Scientific Method The scientific method relies upon a process of logical reasoning derived from philosophy. Early perspectives on human knowledge were governed by deductive reasoning, a process that starts with broad basic principles and applies them in specific situations to prove hundreds and thousands of other, smaller truths. If you ever applied the Pythagorean theorem to calculate the length of a side of a right triangle, you were using deductive reasoning; you were applying a broad principle to a specific case. Sir Francis Bacon, a British philosopher and statesman in the early 1600s, was one of the first to question the deductive reasoning approach. Bacon felt deductive reasoning was too susceptible to the thinker’s biases—personal beliefs or conventional wisdom that a particular thinker mistakenly accepts as broad, basic truths. We’ll see throughout this book that psychological research has shown many times that widely accepted conventional wisdom can be biased. For example, people typically consider themselves to be free and independent thinkers who will always stand up for what they believe to be right. As we’ll discuss in Chapter 14, however, scientists have been able to demonstrate that, when confronted by an authority figure or even just a small group of people with opposite views, many people go along with the higher authority or the crowd rather than follow their own beliefs. Bacon argued that, to avoid bias, science and philosophy should proceed in an opposite direction of deductive reasoning, using a process called inductive reasoning instead. Here, thinkers use controlled direct observations to generate broad conclusions, and over time such conclusions are combined to achieve nonbiased truths about the laws of the universe. Psychologists using inductive reasoning would begin the search for natural laws by making empirical, or objectively testable, observations of mental processes and behaviors. Their observations would in turn lead them to develop theories, ideas about the laws that govern those processes and behavior. Inductive reasoning is still a key idea in much scientific research. There are so many factors governing human behavior, however, that if psychologists were to rely entirely on induction, or observation, they could never discover and specify all of the potential factors affecting human behavior—the factors needed to generate accurate broad theories. Thus, to build on the best of both deductive and inductive reasoning approaches, psychologists today typically employ a blended model known as the hypotheticodeductive approach (Locke, 2007). They begin with a deductive process: they identify a hypothesis. According to the famous philosopher Karl Popper (1902–1942), a sound scientific theory must establish, in advance, the observations that would refute it (Popper, 1963, 1959). In other words, a sound theory runs the risk of being proven false. To test the soundness of their theories, researchers create hypotheses, specific statements that are objectively falsifiable (that is, they can be disproved). A physicist, for example, might generate a hypothesis based on the theory of cause and effect, which states that hitting
Law seeking This meteorologist relies on physical laws to describe and predict the force and path of hurricanes. Similarly, psychologists seek out laws to describe and predict mental processes and behavior.
deductive reasoning reasoning proceeding from broad basic principles applied to specific situations. biases distorted beliefs based on a person’s subjective sense of reality. inductive reasoning reasoning process proceeding from small specific situations to more general truths. empirical able to be tested in objective ways. theories ideas about laws that govern phenomena. hypothetico-deductive reasoning process of modern science where scientists begin with an educated guess about how the world works, and then set about designing small controlled observations to support or invalidate that hypothesis. hypothesis a general statement about the way variables relate that is objectively falsifiable.
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a baseball with a bat causes the ball to move in a new direction. If researchers were then to discover that baseballs keep going straight into the catcher’s mitt, even after being hit, the hypothesis would be disObservation/ Theory Hypothesis proved and scientists would have to reconsider their theory of the law experiment of cause and effect. Similarly, in the hypothetico-deductive approach, psychologists set out to create controlled observations that will prove or disprove Observation/ Predictions Predictions experiment their hypotheses. In many cases, research results do indeed disprove their hypotheses. Psychologists may then reject or modify their theories and generate new hypotheses for further testing. Through repHypothesis supported etition of this process, theories evolve over time to become more and Observation/ Theory or not supported: experiment more accurate explanations of human thought and behavior. This theory built approach is outlined in Figure 2-1. FIGURE 2-1 Reasoning and the scientific method As we discussed at the beginning of the chapter, many people have Several different kinds of reasoning may be used as ideas about whether reality TV has good or bad effects or indeed any effects at all on scientists carry out their work. Most psychological viewers. To produce a scientific theory about the effects of reality TV, a person would researchers use the hypothetico-deductive approach. need to step outside his or her personal beliefs in order to avoid bias. A scientific approach would involve the steps described below: HYPOTHETICODEDUCTIVE REASONING INDUCTIVE REASONING DEDUCTIVE REASONING
• Make observation. We might first examine what viewers do after watching a reality TV show. Do, for example, they exhibit moral behavior after watching an episode of Extreme Makeover: Home Edition. That is, do they engage in behaviors that suggest increased empathy and awareness of others’ beliefs and needs? • Develop hypotheses. After making such observations, we would generate hypotheses about what led to the behavior we observed. If viewers acted more morally, for example, did positive behavior on the show cause viewers to think of their fellow human beings in a more positive light? Or were the viewers simply modeling themselves after the television cast? Whatever our explanation, we would generate a falsifiable hypothesis to test. One hypothesis, for example, might be that viewers change their behavior to be more like the people they see on reality TV shows. • Test hypotheses. As we’ll see in this chapter, there are several kinds of research studies we could conduct to see if this hypothesis can be disproved. • Build a theory. If the hypothesis is, indeed, disproved, we might modify or even throw it out and develop and test a new hypothesis. If our hypothesis that people who watch reality TV change their behavior to be more like the cast of the show is not disproved, we might test it further. We might, for example, decide to study the viewers of a variety of reality shows. If the results continue to support our hypothesis, the hypothesis can become a theory. A theory, in turn, can become a framework to generate additional hypotheses.
Before You Go On What Do You Know? 1. What are the two core beliefs of a science? 2. What is the difference between inductive and deductive reasoning? 3. What is the difference between a hypothesis and a theory? 4. What is the hypothetico-deductive method?
What Do You Think? Based on what you know about the scientific method, do you think psychology is a science in the same way chemistry, biology, and physics are sciences?
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Is Psychology a Science? LEARNING OBJECTIVE 2 Compare and contrast psychology with other natural sciences, such as biology, chemistry, and physics, and with pseudosciences, such as astrology.
As we saw in Chapter 1, prior to the nineteenth century, psychology was a field based largely on philosophy, religion, and even mysticism. With a rise in the popularity of animal research in the nineteenth century, however, scientists began to develop an increased interest in physiology and how human actions are tied to innate biological functions. Charles Darwin’s theories on evolution, along with advances in the field of biology, raised questions about the interactions between humans and our environments. Given such roots, many credit the influence of biological science for shifting psychology from a philosophy toward becoming a science (Hergenhahn, 2005). Although psychology is now defined as a natural science that uses experimental methods to study mental processes and behavior, it does differ from the physical sciences, such as biology, in key ways, including how it pursues scientific goals and its role in influencing personal and social values.
Francis Bacon was so committed to the scientific method that it may have killed him. In 1626, he hypothesized that snow might be a good way to preserve meat. He went out, bought a goose, and stuffed it with snow, but in the process he contracted pneumonia and died.
Goals of Psychology As we saw in Chapter 1, all sciences share the goals of describing, explaining, predicting, and controlling the phenomena they study. However, the emphasis each field places on these goals may vary. One key difference between psychology and the physical sciences, for example, is in the area of description. A core goal of many physical sciences is to isolate and describe the smallest elements that contribute to a larger whole. Biologists look at how a cell contributes to the overall functioning of an organism, for example. Chemists and physicists examine how atoms and subatomic particles make up the structure of, well, everything. Although psychology also attempts to isolate fundamental elements of behavior and mental processes, psychologists face an additional task because behavior is determined by many such factors simultaneously. These factors can be temporary or permanent fixtures in a person’s life. The atomic structure of gold, for example, is the same in all gold all over the world, but a complex behavior, such as reading this textbook cannot be broken down into a standard set of elements that work the same for every person. The reading behavior of a student might be influenced by a temporary factor, such as anticipation of an upcoming exam, that does not affect the reading behavior of nonstudents. The idea behind psychological research is both to isolate the relative contribution of such factors and to think about how these factors come together to influence human behavior. Psychologists face an additional challenge because much of what they study does not have a clear and observable physical reality like the basic units of study in other scientific fields. With the help of special tools, scientists in those fields can observe even the tiniest bits of matter, including atoms and DNA. Of course, this is also true of psychology to some degree. Behaviors, sensations, or physiological responses, for example, can be directly observed, measured, and explained. In his review of science, the great German philosopher Immanuel Kant suggested that when studying phenomena such as these, psychology is indeed empirical and very close to a “real” science (Kant, 2003). Other psychologists, such as the behaviorist B. F. Skinner, also advocated this view of psychology, and in fact, as we saw in Chapter 1, many behaviorists have stated that, as scientists, psychologists should study only what is directly observable.
Multiple influences Behavior is complex and is determined by many factors operating simultaneously. What factors—temporary, permanent, or both—might be influencing this man to take a dip in the ocean on a cold day?
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Thoughts versus behaviors Thoughts cannot be observed directly, but behaviors can. Thus psychologists can be more certain about the romantic feelings of the woman on the right than those of the woman on the left.
On the other hand, as Kant himself observed, many of the processes that form the basis of psychology cannot be observed or described directly. We have no microscopes or tests that will allow us to see a thought or an emotion, for example, with the same clarity as a cell. Granted, good scientific work and sound experimental study have enabled us to look at many of the ways thoughts and feelings can influence behaviors, and psychologists are always seeking out new ways of objectively defining these and other elusive features of mental functioning. But direct observation continues to be a difficult task in the field of psychology.
Values and the Application of Psychology
Happy Birthday! Yangyang, a female goat cloned by Chinese scientists in 2000, wears a wreath at her 6th birthday party. Advances in genetic research and genetic engineering hold much promise but the ethical implications are important to consider.
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Psychology is also distinct from other scientific fields inasmuch as it deals in major ways with issues associated with values, morality, and personal preference—issues that historically were addressed exclusively by spiritual and political leaders. Like all scientists, psychologists try to provide society with useful information that has practical applications. But people are particularly inclined to use psychological information to decide issues that overlap with philosophy, religion, the law, and other such realms of life. For example, the American Psychological Association recently gave testimony to the Supreme Court about adolescent brain function and risk-taking behavior. The Association reported findings that many adolescents’ brains are not yet developed enough to allow them to understand fully the consequences of their behaviors. Based on this testimony, the Court ruled on an important moral, ethical, and legal question—deciding that adolescents who commit murder should not be faced with the possibility of the death penalty. Of course, other sciences also influence the values and ethics of human beings to various degrees. The field of genetic research, for example, was pioneered by biological scientists who were looking for better farming practices, but some early geneticists soon came to believe that selective breeding could be applied to humans to increase the likelihood of desired offspring. Their research contributed to a field eventually known as eugenics, which influenced not only many people’s personal childbearing decisions, but also contributed to policies of governments and social agencies in some locations that required forced sterilization surgery for people deemed unfit to reproduce (Whitaker, 2002). Indeed, eugenics often was associated with racism and hom*ophobia. Today the field of genetic research sparks
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concerns and debate about food practices, stem cell research, human cloning, and other such issues. Every scientific field must wrestle with questions of how to ethically apply the knowledge it discovers about the world, but few more so than the field of psychology. In addition, few sciences are as plagued as psychology is with popular imitations and misrepresentations of their work.
Misrepresentation of Psychology It is natural for people to seek guidance periodically on how to live their lives. And psychologists certainly do not shy away from helping people with their problems, as evidenced by the thriving areas of clinical and counseling psychology and other applied disciplines described in Chapter 1. Ultimately, however, science—even psychology—cannot answer fundamental and subjective questions about human nature. People who claim to do so are misrepresenting the science of psychology with pseudopsychology. Pseudopsychology, or pop psychology, has no basis in the scientific method, yet it takes on the trappings of science, often with the goal of promoting certain moral or religious values (Hergenhan, 2005). A fundamental difference between pseudopsychology and psychology is that psychology does not claim to address all human issues, whereas pseudoscientists argue that psychological principles can provide the answers to all of life’s major questions (Leahey, 2005). Astrology is a good example of pseudopsychology. It uses Zodiac “signs” to predict one’s future and give advice about one’s relationships and decisions. Astrology’s guiding principle is that all human beings have particular personality traits that are based upon the alignment of planets on the dates of their births and those traits determine
“
Do you believe in UFOs, astral projections, mental telepathy, ESP, [and] clairvoyance…? Uh, if there’s a steady paycheck in it, I’ll believe anything you say. –Dialogue from the 1984 movie Ghostbusters
”
Making Psychology More Popular Within many scientific disciplines, there are charismatic researchers and practitioners who are able to describe their complex topics so that almost anyone can understand the concepts. These individuals present facts about science in ways that engage the public’s imagination. As a result, some of them become well known figures in the popular media, such as in massmarket books, magazines, television, and radio. Psychology too has its share of such individuals. Antonio Damasio, MD, Ph.D., for example, is an award-winning, internationally recognized neuroscientist. He is director of the University of Southern California’s Brain and Creativity Institute. Damasio is also the author of best-selling books that explain the underlying neurobiological systems for emotion, memory, language, consciousness, and ethics (Damasio, 2003, 1999, 1994). His books have made neuroscience accessible to a wide audience. Another popular researcher is psychologist Steven Pinker, Ph.D. who teaches at Harvard University. His specialties include
visual cognition and language development. He is the author of award-winning and best-selling books that explore the idea that language is instinctual for human beings (Pinker, 2007, 2002, 1999, 1997, 1994). Pinker was named one of Time Magazine’s 100 most influential people in the world in 2004 and received the Humanist of the Year award in 2006. And then, of course, there are the celebrity practitioners—professionals who are very well known to the public as talk show hosts on radio and television. Some such practitioners are well trained and have appropriate professional credentials. Celebrity talk-show host, Drew Pinsky, M.D., for example, is a board certified internist, addiction medicine specialist with psychological training, and licensed private practitioner. Since 1995, Pinsky has hosted a national radio advice show called Loveline, and he also hosts television programs on VH1 and MTV. He is known to listeners as “Dr. Drew” and provides them with medical, sexual, relationship, and drug-addiction advice. But a word to the wise. For each Pinsky, who is well qualified, there are many more celebrity practitioners who do not have proper training or appropriate credentials in their supposed areas of expertise, including some of the media’s most popular TV and radio advisors. Before listening too closely, it is always best to check the qualifications of a psychologist or other professional who is dispensing advice on radio, television, or the Web.
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how people will react to events and interact with others. Although they have no scientific foundation, the methods and tests used in astrology resemble psychological personality tests. Astrologers often adopt the terminology and topics of psychology, and so confuse many individuals—including many astrologers themselves—into believing that their field is scientifically based. Clearly, psychologists must maintain a difficult balance. On the one hand, it is important to encourage the human drive to seek guidance and derive meaning about how to live effectively. On the other hand, psychology must distance itself from pseudoscience to maintain its status as a natural, empirically-based science. As one researcher wrote, “Mainstream psychologists have a problem differentiating themselves from what they regard as a pseudoscience without seeming dogmatically intolerant” (Hergenhahn, 2005, p. 532).
Before You Go On What Do You Know? 5. What are the four goals of psychology? 6. What is the main difference between psychology and pseudopsychology?
What Do You Think? Why do you think that pseudopsychology appeals to so many people even though it is not based on science and does not reflect the truth?
How Do Psychologists Conduct Research? LEARNING OBJECTIVE 3 List steps in the research process and key characteristics of descriptive and experimental psychological research methods.
©The New Yorker Collection 1994 Sam Gross from cartoonbook.com. All Rights Reserved.
Let’s go back to the controversy over reality TV. Suppose that you frequently watch Extreme Makeover: Home Edition, the giveaway/makeover show in which workers and friends renovate the homes of deserving and needy families. Let’s say that after viewing the show, you notice that you’re more charitable toward your friends.You wonder whether all people who watch this particular show become morally superior to those people who do not. How would you, as a psychological researcher, study this question? As we described earlier, the scientific method begins with observation. So, after noting your own reaction, you may decide to observe other viewers. Maybe you get together with some friends or sit in a common area when the reality show is on, and you watch how everyone interacts with each other during and after the show.
State a Hypothesis After you’ve made such observations, you need to generate a prediction; this is your research hypothesis (see Figure 2-2). As we have noted, a hypothesis defines what you think will happen and states your prediction in a way that can be tested and found to be either true or false. Your hypothesis might be: Watching Extreme Makeover: Home Edition typically increases viewers’ charitable behavior. 38
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Notice in your hypothesis that you are saying that one thing results in Step 1 another thing. The two things are called variables. A variable is a conIdentify Questions dition or event or situation—it can really be many things. A conof Interest and dition or event that is thought to be a factor in changing Review the Literature another condition or event is known as an independent variable. In this study, watching or not watching the giveaway/makeover show is an independent Step 2 variable. A researcher could change this variable to Step 6 Develop a Testable Build a Theory Hypothesis (must be see how it affects charitable behavior. Charitable operationally defined) behavior would be a dependent variable, the condition or event you expect to change as a result of varying the independent variable. In addition to defining these variables, you also have to operationalize the variables—develop very Step 3 Step 5 Select a Research precise definitions of the independent and depenSeek Scientific Method, Choose Review, Publish and dent variables that allow you to measure and test Participants and Replicate Collect the Data them. In this case, you might define the independent variable as the length of time viewers watch the show. As a researcher, you may require the participants in your study to watch part of an episode, a whole episode, or even a Step 4 Analyze the Data series of episodes. and Accept or While it may be relatively easy to create an operational definition Reject the Hypothesis of watching, it is harder to operationalize the dependent variable in this study, charitable behavior. You might have participants fill out a questionnaire asking FIGURE 2-2 How do psychologists conduct research? Psychologists follow certain steps and conabout their charitable feelings and their intentions to volunteer their time, give money front a number of choice points as they study questo good causes, or help out friends. If you did this, however, you would not know for tions about mental processes and behaviors. sure that the attitudes and intentions stated on the questionnaire reflect actual charitable behavior. Many people think a lot about volunteering or helping others without actually doing so. Thus, you might prefer to have participants in your study demonstrate some kind of actual charitable behavior. You could, for example, set up a situation in which each participant has to make a donation to other participants in the study or to a charity, and then see who gives larger contributions. Even here, however, you would not be sure that your operational definition of charitable behavior is on target. You might not be measuring “true-life” moral behavior; the participants might be altering their research behavior because they know they are being watched. There are yet other ways researchers could operationally define charitable behavior. Each definition would have advantages and disadvantages and each would have implications for the conclusions the researchers can draw.
Choose Participants Once you’ve identified your variables, you need to select the people who will participate in your study. It generally isn’t feasible for researchers to go out into the world and study the entire population of people whose behavior interests them. Indeed, a population of interest could sometimes include everybody in the whole world. Even when psychologists are not interested in the entire human population, their populations of interest may be very large groups, such as all Americans, adults, teenagers, men, or women. In your reality show study, the population of interest includes everyone who watches Extreme Makeover: Home Edition and everyone who doesn’t. Because they cannot usually study an entire population, researchers must obtain a subset, or sample, from their population of interest, to stand in for the population as a whole. Population sampling of this kind is used very frequently. Political pollsters, for
variable condition, event, or situation that is studied in an experiment. independent variable condition or event that is thought to be a factor in changing another condition or event. dependent variable condition or event that you expect to change as a result of variations in the independent variable. operationalize to develop a working definition of a variable that allows you to test it. sample the group of people studied in an experiment, used to stand in for an entire group of people.
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Proper sampling Which of the people in this photo should be included in a study? All of them, if a researcher wants to draw conclusions about the entire population. Only some of them, if the researcher seeks to understand just children, just adults, just women, or other subgroups.
example, interview samples of the voting population in order to predict which candidate will win a national or statewide election. Ideally, researchers choose their samples through random selection. Random selection is simply a fancy term for choosing your participants in such a way that everybody in the population of interest has an equal chance of becoming part of the sample. That way, you can minimize sampling biases—that is, you will not inadvertently select a group that is especially likely to confirm your hypothesis. If you include only your pro-reality show friends in your sample, the study probably will yield very different results than if you include only elite television critics. Indeed, neither sample would be fully representative of the population at large. Truly random selection can be elusive. The part of your population who do not watch Extreme Makeover: Home Edition includes, for example, 4-year-olds, who probably are not interested in this adult-oriented program and who probably are not capable of making the same kinds of choices about charitable behavior that 25- or 45-year-old persons might make. Thus, you may decide to narrow your sample to include adults only. Of course, such a choice would mean that your findings will be relevant to adults only, rather than to the entire human population. Researchers in psychology often try to choose samples that make their results relevant to the broadest possible segments of their populations of interest.
Pick a Research Method Researchers have several options when designing studies to test their hypotheses. Research methods differ in their goals, samples, and the ability of researchers to generalize their results to a population. Most of the methods we describe next, including case studies, naturalistic observation, and surveys, are known as descriptive research methods. They allow researchers to pursue the goal of description: to determine the existence (and sometimes the strength) of a relationship between the variables of interest. In addition to such descriptive methods, we will also describe experiments, which allow researchers to explain the causes of behavior (see Figure 2-3). Case Studies A case study focuses on a single person. Medical and psychological practitioners who treat people with problems often conduct case studies to help deter-
FIGURE 2-3 Descriptive versus experimental research Because descriptive methods and experimental methods each serve particular purposes and have different advantages and disadvantages, psychological research includes both kinds of approaches.
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Descriptive Research: Case studies, naturalistic observation, surveys
Experimental Research: Manipulation and control of variables
Purpose: Observe, collect, and record data (Meets the descriptive goal of psychology)
Purpose: Identify cause and effect (Meets the explanation goal of psychology)
Advantages: Good for developing early ideas, more reflective of actual behavior than other methods, easier to collect data
Disadvantages: Little or no control over variables, researcher and participant biases, cannot explain cause and effect
Advantages: Allows researchers precise control over variables and to identify cause and effect
Disadvantages: Ethical concerns, practical limits, artificiality of lab conditions, confounding variables, researcher and participant biases
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mine whether therapeutic interventions affect their client’s symptoms (Martin & Hull, 2007). A case study can be a good resource for developing early ideas about phenomena. One disadvantage of a case study, however, is that it can be affected greatly by researcher bias, which occurs when researchers see only what they expect to see in their studies. Some clinician/researchers may, for example, note only the healthy behaviors of persons after they have provided treatment to those individuals. Another disadvantage of case studies is that researchers cannot confidently generalize to other situations from the study of a single person. Suppose, for example, that in order to test your hypothesis that watching a giveaway/makeover reality show increases charitable behavior, you conduct a case study: you closely observe one man who watches such a show, and you find that he later reports himself to be generous and charitable, giving hours of service to a homeless shelter every weekend. Your case study observation might indicate that your hypothesis is worthy of further research, but without comparison participants, it is impossible to say much about other viewers of the show. You would not know whether this person’s behavior after watching the show is the norm or an exception.
A first-hand look Unlike case studies or surveys, naturalistic observations enable researchers to directly observe people in their natural settings. Here, for example, a psychologist observes a preschool classroom through a one-way mirror.
Naturalistic Observation In naturalistic observations, researchers watch as unobtrusively as possible while people behave as they normally do. Researchers often make naturalistic observations of children in schools or day-care centers. Perhaps as a researcher you could go into participants’ homes over multiple weeks and see whether they watch a particular giveaway/makeover show. You could then observe whether those people who watch the show engage in more moral behavior and whether those who don’t watch behave less morally. Naturalistic observations have the advantage of being more reflective of actual human behavior than most other research designs. A disadvantage of this type of research, however, is that naturalistic observations can be subject once again to researcher bias—observers may notice only what they expect to see (Connor-Greene, 2007). Another potential problem is that the mere presence of a researcher or even a video camera in an otherwise natural environment can change the behavior of the participants. Many people become nicer or more considerate when they are aware that they are being watched, for example. Surveys A third descriptive approach, frequently used in psychological research, is the survey. In a survey, researchers ask people a series of questions. Researchers can conduct surveys using in-person, telephone, or e-mail interviews, or they may ask the questions via a written questionnaire. To test your reality show hypothesis, for example, you might design a questionnaire that asks people about their Extreme Makeover: Home Edition watching habits and about their charitable attitudes, and use their answers to determine whether or not a relationship exists between the two variables. The advantage of a survey approach is that surveys allow researchers to obtain information that they might not be able to gather using case studies or naturalistic observations. It might be hard, for example, to tell whether a person in a case study is engaging in moral behavior because he or she wishes to do the right thing, or whether the individual is behaving morally in order to get some kind of reward. A survey can help pin down such issues. Another reason surveys are sometimes favored by psychologists is that they can also provide data that enables researchers to measure how strong the relationship is between two variables of interest. Surveys do suffer some disadvantages, however. Their data can be unreliable because people frequently answer in ways that are socially acceptable rather than in ways that are
random selection identifying a sample in such a way that everyone in the population of interest has an equal chance of being involved in the study. descriptive research methods studies that allow researchers to demonstrate a relationship between the variables of interest, without specifying a causal relationship. case study study focusing on a single person. naturalistic observation study in which researchers directly observe people in a study behaving as they normally do. survey study in which researchers give participants a questionnaire or interview them.
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experiment controlled observation, in which researchers manipulate the presence or amount of the independent variable to see what effect it has on the dependent variable. experimental group group that is exposed to the independent variable. control group group that has not been or will not be exposed to the independent variable. double-blind procedure study in which neither the participant nor the researcher knows what treatment or procedure the participant is receiving.
reflective of their true attitudes, a problem known as subject bias. Thus, people in your giveaway/makeover show study may describe themselves on a survey as more charitable than they actually are because they know that being charitable is considered a more socially appropriate trait than being selfish or stingy. Similarly, participants in a survey study may have inflated views of just how charitable they are. Although subject bias obviously is a common concern for survey researchers, it can also occur in experiments and other types of research as well, as we shall soon see. Another problem is that survey data cannot tell us the direction of the relationship between variables. Do people who watch a particular reality show a lot become more charitable, or are highly charitable people drawn to watch that show a lot? A survey cannot help you answer this question.
Experiments If you want to know what causes what, you have to design an experiment. An experiment is a controlled observation in which researchers manipulate levels of one variable—the independent variable—and then observe any changes in another variable—the dependent variable—that result from their manipulation. One way of experimentally testing your reality show hypothesis in this kind of study would be to divide your sample into two groups: an experimental group and a control group. An experimental group is the one exposed to the independent variable. In our example, the experimental group would consist of people who are instructed to watch Extreme Makeover: Home Edition. A control group, in contrast, consists of people who are similar to those in the experimental group but who are not exposed to the independent variable—for example, people not instructed to view that show. By comparing the charitable behavior of the two groups after one group watches the show and the other does not, you might conclude with some degree of confidence that differences in charitable behavior are caused by exposure to Extreme Makeover: Home Edition. You could also create a more complex experiment, in which multiple experimental groups watch varying amounts of this reality show, and compare them with the nonwatching control FIGURE 2-4 The experimental design Key features group participants in order to determine how much viewing of the show it takes to proof experimental designs are independent and duce changes in charitable behavior. dependent variables and random assignment of The composition of experimental and control groups needs careful attention. In our experimental and control groups. example, no one in the control group has ever seen Extreme Makeover: Home Edition (see Figure 2-4) and none will be instructed to do so for the study. But what about the Representative experimental group? Should you include people who’ve watched the show previously, sample is divided into two groups or should you begin with a group of participants who—like the control group—have based on random never, ever watched the show, and then expose the experimental group to a marathon assignment of this reality show’s episodes. Either approach is acceptable, but the two approaches may lead to different conclusions. Other kinds of differences—past or present—between the experimental and Experimental Control control groups may also influence the results of an experiment. Even when group group they use random assignment to make sure that everyone in their sample has an equal chance of being in either the control or experimental group, researchers still run the risk that the groups will differ in some important ways. Not exposed to Exposed to Suppose that you randomly assign your reality TV participants to each of your independent independent groups, but nevertheless wind up with wealthy individuals in one group and variable (for variable (for example, do not example, poor individuals in the other group. Such an unintended group difference may watch reality TV) watch reality TV) affect the participants’ subsequent charitable behaviors and so may lead you to draw incorrect conclusions. Some researchers pre-interview or give questionnaires to participants in both the experimental and control groups to Measure change in Measure change in make sure that the groups are comparable to one another. Their goal is to help dependent variable dependent variable guarantee that whatever effects emerge in the study are caused by the exper(for example, (for example, charitable charitable imental manipulation of the independent variable and are not attributable to behavior) behavior) other, pre-existing variables, such as income level. 42
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In addition, experimenters must be careful when deciding what tasks will be performed by participants in the control group. Researchers often have the participants in a control group engage in an activity of some kind, just to make sure that the changes seen in the experimental participants are indeed due to the impact of the independent variable and not the result of the experimental participants being particularly active during the study. You might, for example, have your control group participants view another—nonreality—TV show that is just as engaging as Extreme Makeover: Home Edition. You could, for example, show the animated cartoon series Pokemon to the control group. If the experimental participants still demonstrate more charitable behavior than the control participants afterwards, you can be more certain that the reality show is in fact responsible. Finally, experimenters must be careful to avoid bias in their studies. Once again, they must avoid subject bias and researcher bias—sources of bias that we discussed earlier. In addition, they must set up their studies so that they do not unintentionally convey to participants the outcome that they (the experimenters) expect to see, an undesired effect known as a demand characteristic. If a researcher were to tell participants in the experimental group of the reality TV study that their answers to a charitability questionnaire will indicate how much reality TV contributes to positive real-life behavior, the researcher might be creating a demand characteristic that is encouraging those participants to overstate their charitable inclinations. For this reason, many studies, particularly pharmaceutical ones, are designed so that the persons who administer the study or who evaluate the behavior of participants are unaware of the hypotheses of the study. Indeed, a number of studies use a specialized method known as a double-blind procedure, in which neither the participant nor the researcher knows which group—experimental or control—the participant is in. Doubleblind studies help keep researchers from observing or creating what they want to observe and participants from intentionally acting in ways that confirm a researcher’s hypothesis.
Experimental answer Do complex visual images stimulate babies? To answer this causal question, experimenters have shown swirling designs to one group of babies (experimental group) and bland designs to another group (control group). Babies in the experimental group typically attend to their designs longer than do those in the control group, suggesting that complex images do indeed attract the attention of babies.
Before You Go On What Do You Know? 7. Which variable is controlled or manipulated by an experimenter? 8. What are three descriptive research methods used in psychology? 9. Which research method allows research to say that one variable causes another?
What Do You Think? What would you conclude if people’s charitable behavior increased after a single exposure to Extreme Makeover: Home Edition? How would that conclusion be different if charitable behavior only increased after a marathon viewing of the show?
How Do Psychologists Make Sense of Research Results? LEARNING OBJECTIVE 4 Tell what information is conveyed by statistics, including correlation coefficients, means, and standard deviations, and explain how psychologists draw conclusions about cause and effect.
Once researchers obtain results from an experiment or descriptive study, what do they do with them? Can they simply eyeball their findings and say that there’s a relationship between this and that variable, or that the two groups under study are different? No. Scientists cannot depend just on impressions or logic. If they tried, they would have no way of knowing whether a relationship found between variables or a difference between groups actually matters. How Do Psychologists Make Sense of Research Results? 43
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correlation predictable relationship between two or more variables. correlation coefficient statistic expressing the strength and nature of a relationship between two variables. positive correlation relationship in which scores on two variables increase together. negative correlation relationship in which scores on one variable increase as scores on another variable decrease. perfect correlation one in which two variables are exactly related, such that low, medium, and high scores on both variables are always exactly related.
Psychologists use statistics to describe and measure relationships between variables. There are many statistical analyses that scientists use to look at the differences and similarities between groups. We won’t go into a lot of depth about statistics here. We will, however, give you a few tips to help you understand the research findings you’ll be reading about in this book and elsewhere. We’ll discuss correlations, which describe the relationships between variables, and then go on to discuss the statistical tests researchers use to determine how likely it is that their results might be occurring simply by chance. Then, we will examine how researchers use the statistical results to decide whether or not their hypothesis has been supported and to guide the next steps in the research process.
Correlations: Measures of Relationships A predictable relationship between two or more variables is called a correlation. To describe correlations, especially in descriptive studies, psychologists use a statistic called a correlation coefficient. A correlation coefficient can range from ⫺1.00 to ⫹1.00. The number itself and the positive or negative sign in the correlation coefficient each convey different information. The positive or negative signs tell you the direction of the relationship. When scores on both variables get bigger together, the relationship is known as a positive correlation. In our example of a reality show study, we predicted a positive correlation between Extreme Makeover: Home Edition watching and charitable behavior: As watching increases, so will charitable behavior. If we had suggested that charitable behavior does not increase, but actually drops, as people watch more and more reality TV, then we would be predicting a negative correlation. When the variables are negatively correlated, higher scores on one variable are related to lower scores on another variable. Figure 2-5 shows various such relationships.
Study 1
Study 2
High
High
Variable A
Variable A
Low
Low Low
Variable B Perfect positive correlation
High
Low
Study 3
FIGURE 2-5 Graphing correlations If we were to plot each participant’s score on Variable A and Variable B on a graph, we would see that the variables display a perfect positive correlation in Study 1, strong positive correlation in Study 2, strong negative correlation in Study 3, and near zero correlation in Study 4.
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Variable B
High
Strong positive correlation
Study 4
High
High
Variable A
Variable A
Low
Low Low
Variable B Strong negative correlation
High
Low
Variable B Near zero correlation
High
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In addition to looking at the positive or negative sign, we must consider the value of the number in the correlation coefficient. The number tells the size, or strength, of the relationship between variables—that is, how well can we predict one variable if we know the other. The larger the number, the stronger the relationship. Thus, a correlation coefficient of 0.00 means that there is no relationship between the two variables. Knowing a person’s score on one variable tells you nothing about the person’s score on the other. The farther a correlation coefficient gets from 0 in either the positive or negative direction, the stronger the relationship between the two variables. A high positive correlation coefficient means that scores on the two variables under examination typically rise and fall together, and a high negative correlation coefficient means that a rise in one of the variables usually is accompanied by a fall in the other. A correlation of ⫺1.00 or ⫹1.00 is known as a perfect correlation, one in which the variables’ scores are always perfectly related. Again, it is important to keep in mind that in correlation coefficients, the positive and negative sign and the number itself provide two different pieces of information. A correlation with a negative coefficient is not weaker than one with a positive coefficient. In fact, the relationship may be stronger if, for example, the negative correlation is ⫺0.7 and the positive correlation is ⫹0.2. A negative correlation of ⫺0.7 would mean that the two variables are quite strongly related in such a way that low scores on one variable very often are associated with high scores on the other (see Figure 2-6). In psychology, really exciting relationships are often reflected by a correlation coefficient of 0.3 and above. This is far from a perfect correlation, largely because relationships between behaviors, thoughts, and emotions can be so complex and because so many other variables may also be at work in such relationships. Nevertheless, 0.3 or above typically means that the two variables in question do indeed have some kind of predictable relationship. Correlations offer lots of useful information, particularly when we are interested in the scientific goal of prediction. The correlation coefficient tells us just how well we can use one piece of information about someone, such as how much the person watches a giveaway/makeover reality show, to predict his or her behavior in another realm, in this case charitable behavior. One key piece of information correlations do not tell us, however, is causality, whether or not a change in one variable actually causes the change in the other (see Figure 2-7). As we mentioned earlier, only experimental studies and experimental analyses can tell us whether causality is at work.
Stress
+1.00
Perfect positive relationship
+.88
Very strong positive relationship
+.62
Strong positive relationship
+.38
Moderate positive relationship
+.12
Weak positive relationship
0.00
No relationship
–.12
Weak negative relationship
–.38
Moderate negative relationship
–.62
Strong negative relationship
–.88
Very strong negative relationship
–1.00
Perfect negative relationship
FIGURE 2-6 How to read a correlation coefficient The sign of the coefficient tells us the direction and the number tells us the magnitude, or strength, of the relationship between two variables.
Depression or
Depression
Stress or
Stress
A third factor (for example, poverty)
Depression
FIGURE 2-7 Correlation versus causation Research has found a strong correlation between stress and clinical depression. However, this correlation does not tell us whether stress causes depression, depression causes stressful events, or other factors, such as poverty, produce both stress and depression.
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Correlation versus causality The repeated co-occurrence of two events (correlation) does not necessarily mean that one is causing the other. Children who eat ice cream, for example, tend to have bike accidents. It may be that eating ice cream while riding causes young bikers to have more accidents. Or, it may be that parents typically treat their children to ice cream whenever they have accidents. Or, perhaps hot summer days lead to increases in both ice cream eating and bike riding.
Experimental Analyses: Establishing Cause and Effect If you want to examine differences between groups and establish causality, you have to do a different set of statistical analyses. Collectively, these are called experimental analyses because they are associated with experiments. Researchers sometimes divide experimental analyses into two categories: descriptive statistics, which describe or summarize the data gathered from a study, and inferential statistics, which tell researchers what they can conclude, or infer, more broadly from their results. In order to describe differences between the scores of experimental group and control groups, researchers calculate the mean and standard deviation of Charitable donations each group. The mean is the arithmetic average of the scores of all participants in a group. This is the same average you’ve been calculating since fourth grade Pokemon Extreme Makeover: Home Edition math class. Big differences between the mean—the average score—of an exper1 4 imental group and the mean of a control group may indeed suggest big dif2 5 ferences between the participants in the groups. 12 4 11 6 To be certain of this, however, researchers also look at the standard devi5 5 ation, an index of how much the participants’ scores vary from one another 9 4 within each group. Suppose, for example, you have ten control-group partic4 4 1 7 ipants who watch Pokemon and then make donations to charity of 4, 5, 4, 6, 3 5 5, 4, 4, 7, 5, and 6 dollars in a charitability task, and ten experimental-group 2 6 participants who watch Extreme Makeover: Home Edition, then make dona5 5 Mean tions of 1, 2, 12, 11, 5, 9, 4, 1, 3, and 2 dollars. Each group would have a mean Standard deviation 4.20 1.05 donation of 5 dollars. Unless you also examine the standard deviations for both groups (1.05 for the control group and 4.20 for the experimental group), you might not realize that there are more extreme reactions in the reality show FIGURE 2-8 Variability and the standard deviation group than in the other group (see Figure 2-8). Although these two sets of data have the same mean, or average, score of charitability in our fictiAfter determining the mean and standard deviation of each group, researchers can tious study, viewers of Extreme Makeover: Home compare the two groups. Psychologists typically compare means using statistical proEdition are much more varied in their charitable cedures known as t-tests (for two groups) or analyses of variance (for two or more behaviors (high standard deviation) than are viewers groups). These procedures look both at the mean differences and at the variance within of Pokemon (low standard deviation). 46
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© The New Yorker Collection 2006 P.C. Vey from cartoonbank.com. All Rights Reserved.
the groups, as well as at the size of the groups. The statistical procedures are known as significance tests because they measure whether the differences found between groups are statistically significant. In statistics, the word significant has a slightly different meaning from most people’s everyday use of the same word. A test of statistical significance tells us how likely it is that the differences found between groups are due to experimental manipulations rather than due to chance. Such tests indicate this likelihood by calculating a probability statistic. If a test of statistical significance yields a probability statistic of p ⬍ .05, it means that if researchers were to conduct the same study 100 times, they would, by chance alone, get the same result found in the current study less than 5 percent of the time. In other words, there’s an extremely low probability that the result found in the current study occurred simply as a random act of chance. Most likely, it occurred because of a real difference between the two groups of subjects in the study. By convention, when a test of statistical analysis yields a probability of less than .05 (p ⬍ .05), psychological researchers conclude that the difference they have found between groups in their study is statistically significant—i.e., likely to be a real difference that is due to the manipulations carried out in the study. Keep in mind that the numerical difference between group means and the probability statistic says nothing about how big an effect you’re seeing in your study. Let’s say that participants who watch Extreme Makeover: Home Edition later display a higher mean charity score than do those who watch Pokemon, and that the probability statistic is less than 0.01 (p ⬍ .01). This does not necessarily mean that the reality show viewers have become much more charitable than the nonviewers. It just means that there’s less than 1 chance in 100 that you obtained that result by chance. If you want to know how big the effect of watching reality TV is, you need to calculate yet another statistic, known as effect size, which describes the strength of the relationship between two variables. If you were to find a large effect size in your study, it would suggest that watching the reality show strongly increases charitable behavior.
Using Statistics to Evaluate and Plan Research If you get a result like this—a difference between groups that is very unlikely to have occurred by chance—does it mean you have fully supported your hypothesis and should sit back and toast your success? Well, not yet. Scientists need to be sure. They need to go back and test their hypotheses some more. It is only through replication, taking the data from one observation and expanding on it to see if it holds up under multiple conditions and in multiple samples, that we can determine whether what we hypothesize is correct. Over time, replication enables hypotheses to become theories and theories to become laws. Another important feature of science is to use different research methods to explore the same research question. If researchers use several approaches, including surveys, experimentation, and independent observations, and obtain the same results, they can be more certain that their hypotheses are accurate and have confidence about incorporating those hypotheses into theories. As we described earlier, in our discussion of the scientific method, a theory is also a framework to generate additional hypotheses. If your hypothesis about Extreme Makeover: Home Edition proves correct, and people on average report themselves to be more charitable and exhibit more charitable behaviors on experimental tasks, you have reason to continue your line of research. You can conduct the same experiment with
mean arithmetic average of a set of scores. standard deviation statistical index of how much scores vary within a group. replication repeated testing of a hypothesis to insure that the results you achieve in one experiment are not due to chance.
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other reality shows, such as Survivor or American Idol and see whether the hypothesis continues to hold up for all kinds of reality shows. You may also decide to look at other forms of moral behavior besides charity, such as empathy or sense of fair play. If you continue to replicate these results with other shows and other moral behaviors, you are effectively supporting the theory that watching reality TV in fact contributes to increased moral behavior within a culture. A Nobel Prize is inevitable.
PRACTICALLYSPEAKING
Tips on Reading a Scientific Journal Article
As a psychology student, particularly if you major in psychology, you will most likely read journal articles for some of your required classes. Initially, this task may seem overwhelming. The authors of journal articles tend to use unfamiliar language, condense complex concepts into a small space, and make assumptions about the reader’s knowledge of their topic. However, you can turn this task into something interesting and worthwhile by following a few simple steps. When you read a research paper, try to understand the scientific contributions the authors are making. You should read the paper critically and not assume that the authors are always correct. You do not need to read the paper sequentially to get the gist of it. First, you might read the abstract, the introduction,
and the conclusions. Next look through the references to determine whose work is at the root of the current research. After this first read through, try to summarize the article in one or two sentences. Then, go back and read the entire paper from beginning to end. Study the figures, re-read parts that are difficult to understand, and look up unfamiliar words. Make notes in the margins or on separate sheets of paper. And answer the following questions as you work: • Title: What does this tell you about the problem? • Abstract: What does this general overview tell you about the current paper? • Introduction: What are the authors’ assumptions, important ideas, and hypotheses? • Methods: Do the methods seem to effectively test the authors’ hypotheses? • Related work: How does the current work relate to past work? What is new or different about the current study? • Conclusions: What were the study’s results, and do they make sense? What were the study’s limitations? What do the authors propose for future research? How does the study contribute to a better understanding of the problem? You also may choose to outline, summarize, or keep more detailed notes, especially if you are using the article for a term paper.
Before You Go On What Do You Know? 10. What two pieces of information does a correlation coefficient give about the relationship between variables? 11. What do the mean and standard deviation tell you about scores of a group? 12. What do t-tests tell experimenters?
What Do You Think? What are some examples of positive and negative correlations you’ve observed in everyday life?
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What Ethical Research Guidelines Do Psychologists Follow? LEARNING OBJECTIVE 5 Tell what ethical steps psychologists take to protect the rights of human research participants.
For 40 years between 1932 and 1972, the American government committed a grave breach of ethics in the now-infamous Tuskegee Syphilis Study, an extensive clinical investigation concerning the course and treatment of syphilis in AfricanAmerican men. Many of the men in the study who tested positive for syphilis were not treated, or were treated only minimally for the disease, to ensure that they would not benefit from treatment because researchers wanted to study the course of the disease when left untreated. In a later interview, John Heller, one of the medical directors of the project stated, “The men’s status did not warrant ethical debate. They were subjects, not patients; clinical material, not sick people” (Jones, 1981, p. 179). Horrors, such as the Tuskegee experiment alarmed the public and heightened awareness and concern about the ethical practices of scientists, including psychologists, who conduct research with human and animal participants (Katz et al., 2008; McGaha & Korn, 1995). Today, psychological research must be designed with the goal of protecting the participants involved with the study. Psychology researchers are bound by the same broad ethical principles that govern doctors and other clinicians. The Code of Ethics of the American Psychological Association states it clearly: “Psychologists . . . take care to do no harm” (APA Code of Ethics, 2002). To ensure that researchers follow proper ethical practices, institutional review boards (IRBs) provide oversight in academic and other research settings across the world. Any institution (university, private corporation, government agency, or medical school) conducting research involving human participants is expected to appoint an IRB, which often consists of a mixture of researchers from inside and outside the field and of individuals from the community. IRBs examine research proposals and rule on the potential risks and benefits of each study’s procedures. If the risk or discomfort associated with a proposed study is deemed to outweigh the potential scientific benefit from the study, then the undertaking is rejected. IRBs generally require that psychologists studying human participants take the following steps to protect human participants:
A nation apologizes In a 1997 White House ceremony, President Bill Clinton offers an official apology to 94-year-old Herman Shaw and other African American men whose syphilis went untreated by government doctors and researchers in the infamous Tuskegee Syphilis Study.
• Obtain informed consent. Informed consent from participants requires that researchers give as much information as possible about the purpose, procedures, risks, and benefits of a study, so participants can make informed decisions about whether they want to be involved in the study. If participants include children, researchers must obtain informed consent from both the parents or caregivers and the child. • Protect participants from harm and discomfort. In addition to medical or physical risks, such as those faced by the men in the Tuskegee studies, researchers must avoid putting participants in situations that could cause them undue emotional stress, for example. • Protect confidentiality. Researchers must have in place, and explain to participants, careful plans to protect information about the identities of participants and the confidentiality of their research responses.
institutional review board (IRB) research oversight group that evaluates research to protect the rights of participants in the study. informed consent requirement that researchers give as much information as possible about the purpose, procedures, risks, and benefits of the study so that a participant can make an informed decision about whether or not to participate.
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Consent has its limits To protect children who participate in studies, researchers must also obtain informed consent from their parents or caregivers.
“
The purpose of psychology is to give us a completely different idea of the things we know best. –Paul Valery, French poet and essayist
”
debriefing supplying full information to participants at the end of their participation in a research study.
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• Provide complete debriefing. In some cases, if participants were to have full knowledge about the purposes and goals of a study before it began, their responses during the study might be influenced by that knowledge. Researchers often try to balance giving participants enough information before a study to protect their rights, yet withholding information that may affect participants’ responses. Thus, at the end of a study, researchers are required to offer a debriefing to participants—an information session during which they reveal any information that was withheld earlier. In addition to ruling on the costs and benefits of the study, review boards also assess other issues. They look, for example, at the compensation individuals receive for their participation (to make sure that participants are not tempted to participate in potentially dangerous studies by high levels of compensation), and they determine whether particular groups (such as men, women, or members of minority ethnic groups) are singled out unnecessarily. In a related development, the ethics of psychological research involving animals has come under scrutiny. Animal rights advocates point out that animals are especially vulnerable research participants, since they cannot give their consent to be part of a study. They also argue that animals may be exposed to more extreme risks than humans, for sometimes unclear benefits. Although animal rights activists are certainly correct in pointing to such problems as consent and enhanced risk for animals, they are not correct when some of them suggest that the study of human psychology has derived little benefit from the study of animals. Much of our knowledge about learning and motivation began with studies of animals, such as Pavlov’s famous dogs (which we will talk more about in Chapter 7). We also have gained substantial knowledge about the nervous system from work on animals, using research procedures that could never be conducted on human beings. And animal research has played a major role in the development of medications, including medications for psychological and neurological disorders. The American Psychological Association, the Society for Neuroscience, and the National Institutes for Health have issued specific ethical guidelines regarding research with animals. These guidelines mandate that the research must advance both human and animal welfare, should only be used when it advances our knowledge of behavior or neuropsycho-
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Facts and Figures on Animal Research As you have seen in this chapter, research involving animals has been the focus of scrutiny and debate in recent years. Thus let’s clarify some important facts and figures about animal research (APA, 2009; ILAR, 2009; MORI, 2005, 1999). 1. The welfare of animal subjects is of great interest and concern not only to animals activists but also to animal researchers, government agencies, scientific organizations, and the public. 2. Around 8 percent of psychological research involves the use of animals; 90 percent of the animals used are rodents and
birds (mostly rats and mice); only 5 percent are monkeys and other primates. 3. Every regulated institution that conducts animal research is required by law to have an Institutional Animal Care and Use Committee (IACUC), which carefully reviews and oversees all such studies at their institution. The IACUC ensures that each study follows all ethical, legal, and humane guidelines, and the commitee pays close attention to such issues as the prevention or alleviation of animal pain, alternatives to the use of animals, and the clinical and scientific importance of the study. 4. In surveys, 75 percent of the public say that they can accept animal research as long as it is for scientific purposes. And most respondents even approve of experiments that bring some pain to animals when those investigations are seeking a cure for childhood leukemia, AIDS, or other significant problems.
logical functioning, and must first consider alternatives to the use of animals (such as computer modeling or the use of different procedures with human participants) (ILAR, 2009; APA Code of Ethics, 2002). All such guidelines—for both animal and human research undertakings—help ensure not only more ethical procedures but better science as well.
Before You Go On What Do You Know? 13. What does an institutional review board do? 14. What is informed consent and how does it relate to debriefing?
What Do You Think? Are ethical standards different for psychology than those for other sciences? Should they be?
Summary What is a Science? LEARNING OBJECTIVE 1 List two core beliefs of science, and describe the steps in the scientific method. • Science is an approach to knowing the world built on the core principles that (1) the universe operates according to certain natural laws and (2) these laws are discoverable and testable.
• Science is founded upon the scientific method, a process that moves from making controlled, direct observations to generating progressively broader conclusions and tests and attempting to disprove hypotheses.
Summary
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Is Psychology Really a Science? LEARNING OBJECTIVE 2 Compare and contrast psychology with other natural sciences, such as biology, chemistry, and physics, and with pseudopsychologies, such as astrology. • Psychology shares with every science the primary goals of describing, explaining, predicting, and controlling the objects of study. The goals of psychology differ from those of other sciences because the search for elements of mental processes and behavior is complicated by constantly shifting human factors. • Psychology also shares more similarity with the fields of religion and philosophy than many sciences do because psychological findings are more often associated with values, morality, and personal preference. • Psychology is different from pseudopsychology. Although the latter also attempts to answer fundamental questions about human nature and behavior, it has no basis in the scientific method.
How Do Psychologists Conduct Research? LEARNING OBJECTIVE 3 List steps in the research process and key characteristics of descriptive and experimental psychological research methods. • Psychological research is rooted in first generating a hypothesis, or prediction, about the relationship between two or more variables based on observations. • Psychologists conduct research with a sample, a small group meant to represent the larger population of interest. The best means of selecting a sample is random selection, a procedure in which everyone in the population has an equal chance of being selected to be in the sample. • Descriptive research methods include case studies, naturalistic observations, and surveys. • Case studies are in-depth observations of a single individual. • Naturalistic observation involves observing people in settings outside of laboratories where their behavior occurs naturally. • Surveys may be conducted in interviews or with questionnaires. • Only experiments allow researchers to draw conclusions about cause-and-effect relationships. • All research methods have advantages for particular uses and all are subject to various drawbacks. Researchers must plan carefully to avoid subject bias, researcher bias, and demand characteristics.
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How Do Psychologists Make Sense of Research Results? LEARNING OBJECTIVE 4 Tell what information is conveyed by statistics, including correlation coefficients, means, and standard deviations, and explain how psychologists draw conclusions about cause and effect. • Correlations allow us to describe and measure relationships between two or more variables. A correlation coefficient tells the direction and size of a correlation. • Researchers use the mean and standard deviation to describe and summarize their results. • Researchers use p values to determine the statistical significance of results. Effect size tells how strong the relationship is between variables. • Replication of experiments and repeated study of the same predictions using different methods help hypotheses become theories.
What Ethical Research Guidelines Do Psychologists Follow? LEARNING OBJECTIVE 5 Tell what ethical steps psychologists take to protect the rights of human research participants. • As egregious ethical practices came to light in the United States in the 1960s and 1970s, people took action to protect the rights of research participants. • Today, oversight boards called institutional review boards (IRBs) help to protect human rights. • Psychological researchers must obtain informed consent from human participants, protect them from harm and discomfort, protect their confidentiality, and completely debrief them at the end of their participation. • The use of animal participants in research has also raised ethical concerns. Oversight boards called Institutional Animal Care and Use Committees (IACUC) help to protect animals needs and comfort in experiments.
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Key Terms deductive reasoning 33
independent variable 39
experiment 42
mean 47
biases 33
dependent variable 39
experimental group 42
standard deviation 47
inductive reasoning 33
operationalize 39
control group 42
replication 47
empirical 33
sample 39
double-blind procedure 42
theories 33
random selection 41
correlation 44
institutional review board (IRB) 49
hypothetico-deductive reasoning 33
descriptive research methods 41
correlation coefficient 44
informed consent 49
case study 41
positive correlation 44
debriefing 50
hypothesis 33
naturalistic observation 41
negative correlation 44
variable 39
survey 41
perfect correlation 44
Key Terms
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CHAPTER 3
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Human Development chapter outline •
Understanding How We Develop •
Growing
D
Before We Are Born
Up
•
How Is Developmental Psychology Investigated?
•
Infancy •
•
Developmental Psychopathology
Super
id you ever think about what it takes to become a superhero? Many seem to be shaped by early tragedy.
Superman is the last survivor of a doomed alien race, adopted and raised by a human couple in Kansas. Batman’s will to fight evil was forged after a thug killed his parents in front of him when he was 12 years old. Perhaps the most complicated and tragic is Peter Parker, your friendly neighborhood Spider-Man. Like Bruce Wayne and Clark Kent, Peter is an orphan. Raised by his elderly aunt and uncle, Peter is a good student, but shy and constantly worried. When he is bitten by a radioactive spider, and acquires super strength and agility, Peter’s first thought is not heroism, but freedom. His newfound superpowers lead to a short but exciting career in wrestling, earning him money and stardom and the chance to be that outgoing, wisecracking, popular person he always wanted to be. All that comes to an end when, in a moment of selfishness, he allows a thief to run past him, and the same thief later kills his Uncle Ben. Peter’s crime fighting career as Spider-Man is sparked by this tragedy as he reflects on his uncle’s greatest lesson: “With great power comes great responsibility.”
If you were charting the development of a superhero, what would you focus on? Unlike other fields in psychology, which often focus on what a person is like at a particular moment in his or her life, developmental psychology is interested in changes in our behavior and mental processes over time and
Childhood •
Adolescence
•
Adulthood
how various factors influence the course of those changes. Developmental psychologists might wonder whether the fact that Batman, Superman, and Spider-Man are all orphans helps explain their heroism. They might notice that, even though Bruce Wayne, Clark Kent, and Peter Parker were orphaned, they each had caregivers who helped to buffer the loss of their parents. Bruce Wayne’s family butler, Alfred, stepped in as his father figure, Clark had the kindly Kents, and Peter had his aunt and uncle. In addition to noticing similarities between groups of people, developmental psychologists are interested in differences between individuals. Clark Kent’s trauma happened before he was born, and he was raised by parents with strong values about right and wrong; perhaps as a result, he appears to be the least conflicted about his role in the world. Bruce Wayne saw his parents murdered right in front of him. His outlook on life appears to be much darker and more cynical than Superman’s, although he is equally single-minded in his pursuit of justice. Peter Parker feels burdened consistently by the role of Spider-Man and often tries to give it up, only to remember his guilt over his uncle’s murder and resume his crime fighting. Pondering the development of superheroes is interesting, but most of us are even more interested in our own origins. What happened to make us into the women and men we are? Was it genes, or parents, or friends, or other, more individualized factors that led to you being where you are right at this moment? Do changes occur because of biological factors or because of our experiences? Are we all doomed to turn into our mothers or fathers? Unfortunately, development is too complex and depends on too many influences that steer the course of our lives in one direction or another for developmental psychologists to state with precision what causes us to be the way we are. Instead, they try to identify several general factors that work together to influence how we grow and change across our lifespan.
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We worry about what a child will become tomorrow, yet we forget that he is someone today. –Stacia Tauscher, author
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It’s worth noting that the terms developmental psychology and child psychology have often been treated interchangeably. If you take a developmental psychology course, you’ll probably wind up spending most of your time on child psychology; you’ll be lucky if you make it to adolescence (we mean in the course, not in life). And this chapter will in some ways be more of the same. We’re going to spend a lot of time talking about childhood, simply because that’s what most of the pioneering theorists in developmental psychology spent their time thinking about and studying. However, a revolution has started over the last few years. Developmental psychologists now acknowledge that developmental changes do not stop when we leave childhood (see Table 3-1). As we’ll see later in the chapter, a trend toward longer human lifespans has also given rise to fields of study, such as gerontology and the psychology of aging. We’ll also need to talk about how things go wrong, an area in which another revolution has been brewing. A new field of study called developmental psychopathology has provided a new way to help us think closely about the factors over the course of a lifetime that contribute to one person becoming a superhero and another becoming a supervillain.
TABLE 3-1 Developmental Stages Over the Lifespan Stage
Approximate Age
Prenatal
Conception to birth
Infancy
Birth to 2 years
Early childhood
2–6 years
Middle childhood
6–12 years
Adolescence
12–20 years
Young adulthood
20–45 years
Middle adulthood
45–60 years
Later adulthood
60 years to death
Understanding How We Develop LEARNING OBJECTIVE 1 Understand the key debates underlying research and theory in child development.
Before we discuss what happens in development, it’s useful to consider some of the key issues that concern developmental psychologists. These issues are often foundations for theory, research, and clinical work, but they are not always directly tested. As you read through the rest of the chapter, you may want to think about how the theories we will discuss later fit with these big ideas about human development. 56
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What Drives Change? Nature versus Nurture The key debate in human development is: how much of our growth, personality, and behavior is influenced by nature, our genetic inheritance, and how much is influenced by nurture, a term that encompasses the environment around us as well as our experiences as we grow. Scientists who take a strong view of the influence of genetics or biology on development are said to view development endogenously. They look at development as biologically programmed to happen sequentially, a process known as maturation. Other scientists believe that our experiences have a greater influence on how we develop, a perspective known as an exogenous view of development. Going back to our superhero examples, Superman’s superpowers are the product of endogenous developmental factors. His alien nature makes him stronger than a locomotive and able to leap tall buildings in a single bound. Batman’s development is more exogenous. The early experience of losing his parents led him to commit himself to a study and workout regimen designed to bring him to the point of human perfection. It is not as easy, however, to attribute the characteristics of people outside the superhero world exclusively to either nature or nurture. In the real world, our traits and behaviors are almost always influenced by an interaction between such factors. Still, researchers continue to have robust debates about whether endogenous or exogenous factors are more important. You will see that the so-called nature-nurture issue applies not only to questions about development but also to ideas about intelligence (discussed in Chapter 10), social behavior (Chapter 14), and pretty much all of the psychological disorders that we discuss at the end of each chapter.
developmental psychology the study of changes in behavior and mental processes over time and the factors that influence the course of those changes. maturation the unfolding of development in a particular sequence and time frame. stage developmental point at which organisms achieve certain levels of functioning.
Qualitative versus Quantitative Shifts in Development Throughout this chapter, whether we are referring to physical development, social development, or cognitive development, you will notice that we talk a lot about stages. A stage is a developmental point at which we achieve certain levels of functioning, such as saying a first word, taking a first step, or getting a driver’s license. Developmental researchers have significant arguments about whether or not these stages represent qualitative shifts in the growth of persons, meaning that individuals make developmental jumps that result in them becoming different than they were before (see Figure 3-1). Qualitative theorists would argue that once we acquire language, for example, we think of the world in a different way because we are able to give things
Infancy (a) Qualitative development
Adulthood
Infancy
Adulthood
(b) Quantitative development
FIGURE 3-1 Do stages represent qualitative or quantitative shifts in development? (a) Some theorists believe that individuals make qualitative jumps in development as they move from stage to stage. (b) Others think that development is a steady continuous process.
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© The New Yorker Collection 2002 David Sipress from cartoonbank.com. All Rights Reserved.
names and even to think about things that don’t have a concrete reality. Without the word “love,” they argue, it would be hard to conceive of the various things that love means, because one cannot point to love or sense it in a direct way (at least not the same way you do a ball or a favorite toy). Stage theories are largely endogenous; they hold that major qualitative shifts are biologically programmed to happen in a certain sequence and at a certain time, leading people to progress through development in the same general way and hit milestones at around the same time. For example, the majority of humans begin to walk sometime close to the age of 1 year. Even though human development is sequential in many ways, the timing of developmental milestones does often vary. Some children take their first steps weeks or even months earlier than others. Many theorists believe the individual variations in timing indicate that development often represents more of a quantitative shift. According to these theorists, development is the result of an ongoing acquisition of new information and new experiences, and what seem like big, sudden developmental changes actually are the result of a gradual accumulation of many small changes, often so small that they are hard to notice. Theorists and researchers in the quantitative camp believe that walking comes as a result of a series of small developmental changes, including the steady growth of our muscles until they can hold our body weight and the development of our brains until they can control physical coordination. Quantitative theorists have an easier time accounting for individual differences in the timing of milestones but a harder time explaining why most people go through similar sequences of development during similar times of life, despite considerable variations in their experiences.
Do Early Experiences Matter? Critical Periods and Sensitive Periods The followers By exposing these baby geese to him alone during their first day of life, ethology pioneer Konrad Lorenz manipulated them into viewing him as their mother. For geese, the first 36 hours after birth is a critical learning period during which they become imprinted to their mother—or a mother substitute.
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Related to the question of stage theories versus continuous theories of development is the question of whether there are critical periods in development. A critical period is a point in development when the organism is extremely sensitive to a particular kind of environmental input, making it easier for the organism to acquire certain brain functions. If the environmental input does not occur at that point, development will be thrown off track (hence, the term critical). For example, the pioneering critical period theorist, Konrad Lorenz, found that goslings will forever connect with whatever moving stimuli they see most often during the first 36 hours of their lives. In Lorenz’s work, he was able to get certain goslings to think of him (or more specifically, his boots) as their mother. He used the term imprinting to describe the development of this attachment. Take a look at the accompanying photo, especially if you are having trouble believing this. Psychologists have long been curious about whether people also have critical periods. Of course, it would be unethical for researchers to deprive human beings of their usual early experiences in order to see what would happen, but cases of human deprivation— extreme poverty or death of one’s parents, for exam-
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ple—do sometimes occur naturally. By studying the histories of children in these unfortunate situations, researchers have learned that serious psychological disabilities may result from early deprivations (Michel & Tyler, 2005). At the same time, however, other studies have found that subsequent changes in environmental input (for example, removing deprived children from their early negative environments and placing them in more positive ones) can help the children recover partially or, in some cases, completely. Because individuals can recover at least partially even after deprivation during key time periods in their lives, most of today’s psychologists and biologists believe that critical periods are better defined as sensitive periods, times when we are especially receptive to environmental input, but not rigidly so (Michel & Tyler, 2005). Theorists today are less inclined to believe that input is essential during a critical period, like a countdown that is running out on your opportunity to develop particular traits or functions. Instead, they view sensitive periods as largely experience-driven, flexible enough to extend past typical time frames for development (Armstrong et al., 2006).
All is not lost Early deprivation, such as that experienced by these young children at a Vietnamese orphanage, can result in severe psychological disabilities. Moving the children to more positive and stimulating settings, however, can help many of them to recover at least partially.
Before You Go On What Do You Know? 1. How do quantitative theories of development differ from qualitative theories of development? 2. What is the difference between a critical period and a sensitive period?
What Do You Think? Do you see biological or environmental factors as playing a more major role in your development?
How is Developmental Psychology Investigated? LEARNING OBJECTIVE 2 Describe and discuss the advantages and disadvantages of cross-sectional and longitudinal designs for researching development.
As we’ve noted, developmental psychologists are interested in learning about changes that happen as we age. How do they go about measuring those changes? One approach is the cross-sectional design. In this approach, researchers compare groups of different-aged people to one another. For example, they might compare a group of 60-year-olds to a group of 30-year-olds on a memory task to see how memory changes over time. The benefit of the cross-sectional approach is that it’s easy and straightforward, as well as convenient, for both researchers and participants. The big problem with the cross-sectional approach is that it assumes that any changes found in a study are the result of age. Researchers must remember to also consider other factors that might influence their results. Let’s say that the task used to measure memory differences between the two age groups mentioned above is computer-based. If the 30-year-olds perform better on the memory task, the researchers might conclude that the results are due to age-related changes in memory. But the findings could be related more to the fact that 30-year-olds are more familiar with and less intimidated by computer technology than 60-year-olds are.
critical periods points in development when an organism is extremely sensitive to environmental input, making it easier for the organism to acquire certain brain functions and behaviors. cross-sectional design research comparisons of groups of different-aged people to one another.
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FIGURE 3-2 Cross-sectional versus longitudinal research design Cross-sectional research uses participants of various ages to examine age-related differences. Longitudinal research studies the same participants over time to determine age-related changes.
CROSS-SECTIONAL DESIGN
Different participants of various ages are compared at one point in time to determine age-related differences
Group One 30-year-old participants Group Two 60-year-old participants
Research done in 2011
Group Three 90-year-old participants
LONGITUDINAL DESIGN
Study One Participants are 30 years old The same participants are studied at various ages to determine age-related changes
longitudinal design research following the same people over a period of time by administering the same tasks or questionnaires and seeing how their responses change. cohort-sequential design blended cross-sectional and longitudinal research, designed to look at both how individuals from different age groups compare to one another and also follow them over time. prenatal period period of development stretching from conception to birth. genes basic building blocks of our biological inheritance.
allele variation of a gene. hom*ozygous both parents contribute the same genetic material for a particular trait.
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Research done in 2071
TABLE 3-2 Cross-sectional and Longitudinal Research Designs Compared Cross-sectional design
Longitudinal design
Advantages
• Easy and straightforward • Convenient for both researchers and participants
• Gives reasonably reliable information about age changes
Disadvantages
• Cohort effects are difficult to separate • Does not explain how or when changes may have occurred
• Requires considerable time and money • Many participants drop out over the course of study
genotype a person’s genetic inheritance. phenotype the observable manifestation of a person’s genetic inheritance.
Study Three Same participants are now 90 years old
Research done in 2041
Another drawback of cross-sectional research is that it does not provide much explanation of how or when age-related changes may have occurred. If older participants actually have memory declines, for example, did those declines occur suddenly, in their early 50s, or accumulate gradually over the past 30 years? For these reasons, many developmental researchers prefer a longitudinal design (see Figure 3-2). This research follows the same group of people over a period of time, administering the same tasks or questionnaires to them at different points in their lives to see how their responses change. We’ll discuss one of the most famous of these longitudinal studies in Chapter 10 when we talk about a long-term longitudinal study of extremely intelligent people (Feldhusen, 2003). The main benefit of longitudinal research is that researchers can be reasonably confident that the observed changes are a function of time and developmental experiences. Unfortunately, longitudinal studies require considerable time and money. The study you’ll read about in Chapter 10 went on for 85 years! Moreover, many participants in longitudinal studies drop out of the studies over the course of their lives because they move away, lose interest, become ill, or even die (see Table 3-2).
deoxyribonucleic acid (DNA) molecules in which genetic information is enclosed. chromosomes strands of DNA; each human being has 46 chromosomes, distributed in pairs.
Study Two Same participants are now 60 years old
Research done in 2011
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Seeking to obtain the advantages and avoid the drawbacks of cross-sectional and longitudinal designs, some developmental researchers design studies that combine the two. A cohort-sequential design looks at both how age groups compare to one another at various points in the research but also takes a longitudinal approach to see how those differences vary over time.
Before You Go On What Do You Know? 3. What is the main advantage of using a longitudinal design instead of a cross-sectional design?
What Do You Think? If a researcher today finds differences between a group of 20-year-olds and a group of 60-year-olds, what historical, social, and cultural factors might have contributed to those differences?
Before We are Born How we Develop LEARNING OBJECTIVE 3 Discuss patterns of genetic inheritance and describe stages and potential problems during prenatal development.
An enormous amount goes into shaping human development during the prenatal period, the nine months or so stretching from conception to birth. Growth during this period happens incredibly quickly. Our biological parents are the starting point for our development by contributing parts of their own genetic inheritance. We’ll see that the contributions from a mother and a father can form a variety of combinations—some matching exactly, some differing completely.
In the Beginning: Genetics Genes are the most basic building blocks of our biological inheritance. Each gene is composed of a specific sequence of deoxyribonucleic acid, or DNA, molecules. DNA and genes are arranged in strands called chromosomes, found in each cell of our bodies. Each of us has 23 pairs, or 46 total, chromosomes. Twenty-three chromosomes are contributed by each of our biological parents, and the resulting combination is called our genotype, which broadly refers to a person’s genetic inheritance. A person’s phenotype is the observable manifestation of that genotype, the physical and psychological characteristics that are on display in each individual. It is difficult to determine a person’s genotype solely on the basis of his or her phenotype—appearance or behavior. Consider the ability to roll your tongue. Tongue rolling is genetically determined; either you are born with the ability or you will never have it (Fry, 1988). If you can roll your tongue, you display a tongue-rolling phenotype. Without further information, however, we cannot say exactly what your genotype is. As we have noted, each parent contributes half of a child’s chromosomal makeup; half of the offspring’s genes come from the biological mother and half from the father. Variations of the same gene, such as the gene for tongue rolling, are called alleles. If both parents contribute the same allele, then the person is hom*ozygous for the trait—
Magical pairs A person’s entire genetic inheritance is contained in 23 pairs of chromosomes, with each parent contributing one chromosome to each pair. Here we see an individual’s chromosomes stained with dyes and photographed under a microscope.
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that is, he or she has two matching alleles of the same gene. If you can roll your tongue, you may be hom*ozygous for the tongue-rolling gene. It turns out, however, that people can still roll their tongues if they inherit a tonguerolling allele from one of their parents and a nonrolling allele from the other. In such instances, the individuals have the observable phenotype of tongue rolling, but their genotype is heterozygous, a combination of two different alleles. Thus, if you can roll your tongue, you are displaying a tongue-rolling phenotype, and this phenotype may reflect either a hom*ozygous or a heterozygous genotype (see Figure 3-3). Depending on the trait in question, any of three different phenotypes can result when a person has a heterozygous combination of different alleles (Adapted from Truett et al., 1994):
To roll or not to roll In this family, the father can roll his tongue (a dominant trait), while the mother cannot (a recessive trait). As a result, their daughter displays a tongue-rolling phenotype, which is rooted in a heterozygous tongue-rolling genotype.
• One possibility is that the trait either will be expressed in its entirety or will not be expressed at all. This is the case with heterozygous tongue rolling. If you have one “rolling” allele and one “nonrolling” allele, you will be able to roll your tongue. Tongue rolling is a dominant trait, a trait that is expressed in your phenotype regardless of whether your genotype is hom*ozygous or heterozygous for the trait. A recessive trait, on the other hand, is one that is expressed in your phenotype only when you are hom*ozygous for that trait. The inability to roll your tongue is recessive. You must have two matching “nonrolling” alleles in order to be prevented from rolling your tongue. • For some traits, a person with a heterozygous pair of alleles may show a mixture of genetic coding. For example, children of couples who have different racial backgrounds can have features associated with the backgrounds of both parents, such as blended skin color or eye shape. • For yet other traits, persons with a heterozygous pair of alleles may express both of the parents’ genes in their phenotype. This outcome is called codominance. An example of codominance is found in blood type. If one parent has blood Type A and the other parent has Type B, the child can express both in the form blood Type AB. The thing that makes the study of genetics particularly challenging is that only a few of our traits are discrete traits, the product of a single gene pair. Instead, most human traits are polygenic traits, ones that involve the combined impact of multiple genes. It is especially likely that traits affecting our behavior are polygenetic. As we noted in Chapter 1, many psychological researchers are interested in trying to determine how much of the way we think and act is influenced by our genetic inheritance, a field of study called behavioral genetics. Developmental psychologists are often in a position to examine the influence of genetics. One of the key areas of focus of both
Genotype :
FIGURE 3-3 Genotype versus phenotype Individuals who are able to roll their tongues may have either a hom*ozygous or a heterozygous genotype for tongue rolling. In contrast, people who cannot roll their tongues must have a hom*ozygous genotype for non-tongue rolling.
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Parent Contributions :
Phenotype :
hom*ozygous
Heterozygous
hom*ozygous
Mother: Father: Mother: Father: Mother: Father: tongue tongue tongue nonnonnonrolling rolling rolling tongue tongue tongue allele allele allele rolling rolling rolling allele allele allele Tongue rolling trait will be expressed
Tongue rolling trait will be expressed
Tongue rolling trait will not be expressed
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behavioral genetics and developmental psychology, for example, has been temperament, often defined as a biologically-based tendency to respond to certain situations in similar ways throughout our lifetimes (Henderson & Wachs, 2007; Bates, 1989). In a longitudinal study that began in the 1950s, researchers Stella Chess and Alexander Thomas (1996) suggested that, as infants, people tend to fall into one of three temperament categories:
“
The first half of our lives is ruined by our parents, and the second half by our children. –Clarence Darrow, attorney
”
• Easy. Babies with easy temperaments were described as playful, regular in bodily functions, such as eating and sleeping, and open to novelty. • Difficult.—Babies with difficult temperaments tend to be irritable and likely to have intensely negative reactions to changes or new situations. • Slow-to-warm-up. Babies in this category are less active and less responsive than babies in the other two categories. In general, they tend to withdraw in the face of change, but their withdrawal is not as sharply negative as those with difficult temperaments. Following Chess and Thomas’s studies, many researchers have examined how our temperament relates to our later personality characteristics. In a famous line of work, biologist and psychologist Jerome Kagan (2008, 2001) conducted a longitudinal study examining the relationship between babies’ levels of behavioral inhibition, the tendency to withdraw from new or different situations, and levels of shyness later in life. He found that children who were highly inhibited at 21 months of age were more likely than uninhibited toddlers to be shy when they were 12 to 14 years old. Kagan’s research seems to illustrate two key aspects of temperament: 1. Temperament is inborn. For an attribute to be temperamentally based, it must appear early (for example, shortly after birth). Considering that Kagan tested babies at such a young age, it is doubtful that they had much of an opportunity to learn to be fearful of new situations. Thus, many researchers believe that inhibited temperaments are biologically inherited. 2. Temperament is stable across situations and time. The participants in Kagan’s study who were most shy temperamentally were the ones who were most inhibited at different times and in different situations. Researchers have also established that other aspects of a person’s temperament are stable over time and place (Henderson & Wachs, 2007). This is not to say, however, that there is no variability at all from time to time and situation to situation. Indeed, investigators have found greater stability of temperament when measuring behavior across similar situations, such as in various family situations, than when comparing temperamental influences on children’s behavior across different situations, such as school versus home. Despite the biological factors implied above, it is important to recognize that our environments also play important roles in how we behave. Kagan’s studies revealed, for example, that not all of the babies who were inhibited at birth later developed into shy teenagers. Similarly, being highly extroverted around new toys as a newborn did not always lead his infant participants to become life-of-the-party teenagers. In fact, if genetics were destiny, we’d all have a much easier time predicting how people will turn out, and this would be a much shorter chapter. As we’ll see, however, our environment plays a very strong role in determining our development, beginning before we are even born.
heterozygous parents contribute two different alleles to offspring. dominant trait trait that is expressed in a phenotype, no matter whether the genotype is hom*ozygous or heterozygous for the trait. recessive trait trait that is only expressed if a person carries the same two genetic alleles (e.g., is hom*ozygous for the trait). codominance in a heterozygous combination of alleles, both traits are expressed in the offspring. discrete trait trait that results as the product of a single gene pairing. polygenic trait trait that manifests as the result of the contributions of multiple genes. temperament biologically-based tendencies to respond to certain situations in similar ways throughout our lifetimes.
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Birth Order Effects: What’s Real? Have you ever explained yourself by referring to your birth order? “Oh, I’m the middle child, so I just don’t feel like I belong.” Or perhaps, “I’m spoiled and act out because I’m an only child.” In reality, the effect of birth order on personality is hotly debated by psychologists, and most of the “effects” of birth order may be more anecdotal than they are actual. In 1996, scientist and scholar Frank Sulloway published the book Born to Rebel in which he argued that first-borns tend to be more responsible while later-borns tend to be more rebellious. He further hypothesized that later-borns tend to be more open to experience and more agreeable than first-borns, and, at the same time, less neurotic, less extraverted, and less conscientious (Jefferson, Herbst, & McCrae, 1998). Although Sulloway’s book was widely praised at first, many psychologists eventually questioned his methodology and noted inconsistencies in his data. Most notably, in 2000, the journal Politics and the Life Sciences attempted to publish a roundtable issue devoted to a discussion of Sulloway’s book. The issue was to include articles and commentaries from a number of scholars who rejected or questioned Sulloway’s work (Townsend, 2000, p. 135). The
debate became so heated that, according to the journal’s editor, Sulloway threatened legal action and the publication of the issue was delayed for four years, eventually appearing in 2004. Scientists typically subject research to peer review, in which an article is read by fellow scientists and intensely scrutinized and revised before it is published. Books, however, do not have to go through this process, which was one of the criticisms leveled against Sulloway’s research (Townsend, 2000). In contrast to Sulloway’s findings, a peer-reviewed article that examined over 1000 birth order studies has concluded that birth order does not influence personality in a clear and consistent way (Jefferson et al., 1998). Perhaps that is why birth order research seems to be shifting away from the area of personality and toward other areas, such as intelligence and physical features. It has been found, for example, that first-borns tend to score about three points higher on IQ tests compared to second-borns. Similarly, children born earlier in a family are, on average, taller and weigh more than those born later (Kluger, 2007). Despite the fact that birth order studies have not yet yielded clear or compelling findings, the topic remains very popular in the public domain. Indeed, in recent years, Time and other newsmagazines have presented several cover stories on the relationship between birth order and psychological and social functioning, an indicator that even as many psychologists believe birth order to be a subject unworthy of research, the public’s fascination with the topic continues to grow (Kluger, 2007).
Prenatal Development
zygote single cell resulting from successful fertilization of the egg by sperm. placenta nutrient-rich structure that serves to feed the developing fetus. miscarriage discharge of the fetus from the uterus before it is able to function on its own.
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Prenatal development begins with conception, when a sperm fertilizes an egg, resulting in the creation of a single cell, called a zygote. The first 2 weeks after conception is known as the germinal stage. During the first 36 hours of this stage, the single cell zygote divides and becomes two cells. Then these two cells divide to become four, those four divide and become eight, and so on. As its cells keep multiplying, the zygote moves up through the mother’s fallopian tube (where it was first fertilized) to her uterus. About a week after fertilization, the zygote attaches itself inside the uterus. The other major transition that occurs during the germinal stage is the formation of a nutrientrich structure called the placenta that will allow the swiftly developing individual to begin performing the basic functions of life, such as breathing, feeding, and waste excretion. The second stage of the prenatal period is the embryonic stage (2 to 8 weeks). Most of the major systems of the body, such as the nervous and circulatory systems, as well as the basic structure of the body, begin to take shape during this stage. It is during this stage that the new organism is most vulnerable to miscarriage, discharge from the uterus before it is able to function on its own, or to the development of defects. Given
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Fallopian tube
(b)
(2)
(1) (3) Ovary
(a)
Interior of uterus
(c)
Cervix
FIGURE 3-4 Prenatal development (a) Germinal period: From ovulation to implantation: After the egg leaves the ovary (1), it travels to the opening of the fallopian tube (2) where it is fertilized and becomes a zygote. About a week later, the zygote reaches the uterus, implants itself in the wall of the uterus (3), and triggers the formation of the nutrient-rich placenta. (b) Embryonic stage: Once the zygote is implanted it grows rapidly. By 8 weeks, many external body structures and internal organs have been formed. Notice that the head grows faster than the rest of the body. At this stage, the embryo is vulnerable to miscarriage. (c) Fetal stage: From 8 weeks to birth, the fetus continues to enlarge rapidly and the basic structures undergo substantial change.
such possibilities, new parents often wait until the pregnancy has lasted well into the last stage, or fetal stage, before announcing it (see Figure 3-4). The fetal stage lasts from the end of the embryonic stage until the birth of the baby. The fetus has several characteristics, including a developing muscular and skeletal system, that lead to a sudden ability to move. Especially during the last three months, the fetus’ brain begins to grow at a remarkable pace. Organs that began to emerge in the embryonic stage now start to function independently, and the fetus begins to hiccup, see, hear, and sleep. All of these functions contribute to the fetus’ eventual ability to function independently of the mother.
Prior to Birth The fetus is vulnerable to any number of problems soon after it moves beyond being a twinkle in someone’s eye. As you will see throughout the book, many disorders are inherited from the parents. Some of these disorders, such as sickle-cell anemia, cystic fibrosis, or phenylketonuria (PKU) are linked to recessive genes. Still other disorders are linked to chromosomal problems. In Chapter 10, for example, when we talk about intelligence, we’ll also talk about Down Syndrome, a pattern caused by the presence of an extra chromosome in the twenty-first chromosome pair.
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In addition to genetic and chromosomal problems, a number of environmental risks, called teratogens, can influence the fetus’ development during the prenatal period. Pregnant women should avoid risks, such as smoking or ingesting alcohol and other substances, legal and illegal, all of which have been linked to birth defects. Even soft cheeses and deli meats can pose certain risks because of the possibility of contracting listeria, a bacterium that can put the fetus at significant risk (Guevara, 2008; Stehlin, 1996).
Before You Go On What Do You Know? 4. What are the possible phenotypic outcomes from a heterozygous genotype? 5. How did Chess and Thomas categorize the temperaments of babies in their studies, and what were the major attributes of each temperament category? 6. What are the key things that identify a behavior as temperamentally-based? 7. What are the three stages of prenatal development, and what happens at each stage?
What Do You Think? How do you think environment might influence a genetically-influenced trait, such as behavioral inhibition? For example, what might parents or teachers of an inhibited toddler do that would either contribute to or tend to decrease later shyness?
Infancy How we Develop LEARNING OBJECTIVE 4 Summarize the major physical, cognitive, and emotional developments that take place during infancy.
Families of newborns often think of their infants as factories for eating, drooling, and excreting. It’s true, a baby’s capabilities are limited at this point in some ways, but in other important ways they are ready to go.
Physical Development Compared to some other species, human infants are still relatively “unfinished” at birth. Our key senses develop fully during our first months and we learn to walk after about a year or so, but our brains—although they also show amazing development during infancy—are not fully developed until we are teenagers or young adults.
teratogens environmental risks to a fetus’s development during gestation.
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What Happens in the Body During Infancy? The senses of taste, smell, and touch are all highly developed at birth. A baby can distinguish the scent of his or her mother’s milk from another woman’s milk and can make fine distinctions between various tastes after only a few days out of the womb. Other senses are less developed. Hearing is still immature and affected by fluid from the mother’s womb that continues to take up space in the newborn’s ears. If you’ve ever spent a day swimming, you’ve probably had a sense of what it’s like to hear like a baby. Things sound a little muddled, with greater sensitivity to high and low pitched sounds. These limitations change quickly, however. Within a few days the baby can distinguish familiar speech from new sounds and words that they have not heard before.
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TABLE 3-3 Common Newborn Reflexes Reflex
Stimulation
Response
Function
Rooting
Touch the corner of the infant’s mouth
Infant turns toward the stimulation and begins to suck
Helps infant begin feeding
Grasping
Press finger against infant’s palm
Infant grasps finger and holds on
Allows infant to hold on to caregiver for safety
Moro
Let infant’s head lose support
Infant flings arms outward and then inward in a hugging motion
May have helped infant to hold on to caregiver when support is lost
Babinski
Stroke sole of infant’s foot
Toes spread apart
Unknown
Vision is a baby’s least developed sense (Kellman & Arterberry, 1998; Maurer & Salapatek, 1976). Newborns cannot clearly see objects much more than 7 or 10 inches away. Similarly, their ability to scan objects is limited. If they look at a triangle, they will focus only on one of its corners. If they look at a face, they will focus largely on the chin or hairline. And they do not develop good color vision until they are 3 months of age. At first, these visual limitations are not a big deal; after all, babies do not travel very far, and they can see far enough to make eye contact with their mothers while nursing. Interestingly, their vision improves steadily, and by the time babies start moving around, about 7 to 8 months of age, their vision has approached adult levels. In addition to our senses, we are also born with certain reflexes, programmed reactions to certain cues that do not require any conscious thought to perform. For example, babies pucker their lips and begin to suck whenever something brushes their cheeks or is put in their mouths, a response called the rooting reflex. Other common reflexes are listed in Table 3-3. What Happens in the
Infancy B R A I N ? Perhaps you have heard popular claims that most of our brain development happens before age 3. Are they right? As with many questions in psychology, the answer here is yes and no. Infancy is, indeed, a time of remarkable changes in our brains. Although a newborn’s head is only about one-fourth the size of an adult’s, there is a lot going on in there! As you’ll see throughout this book, however, the brain continues to At birth 1 month change and develop throughout our whole lives. Two key processes are responsible for the amazing growth of the brain in the earliest years of life. The first is a sheer increase in connections among neurons, the brain’s nerve cells. As we will describe in detail in Chapter 4, information is passed from neuron to neuron at transmission points called synapses. Born with 100 billion neurons, the child acquires synaptic connections at a staggering rate during its first few years, expanding from 2500 such connections per neuron at birth to around 15,000 per neuron by age 2 or 3 years (Bock, 2005; Di Pietro, 2000). Many of these connections develop as a function of normal maturation, regardless of the baby’s experiences and, in fact, serve as a way of helping the baby process new experiences. As babies, we actually develop far greater numbers of synapses than we will eventually need. As we grow older, two-thirds of our early synaptic connections fall away (Bock, 2005; Di Pietro, 2000). Our experiences help to stimulate and strengthen some of the connections, while
Brain growth in the first two years This illustration shows the increases in the complexity of neurons that occur over the course of infancy.
3 months
15 months
24 months
reflexes programmed physical reactions to certain cues that do not require any conscious thought to perform. synapses transmission points between neurons.
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synaptic pruning developmental reduction of neuronal connections, allowing stronger connections to flourish. myelination development of fatty deposits on neurons that allow electric impulses to pass through neurons more efficiently. proximodistal growth from more central areas of the body to parts at the outer edges. motor skills ability to control our bodily movements.
synapses that are not used weaken and dissipate. This process is called synaptic pruning because of its similarity to pruning, or cutting away, the dead branches of a tree or bush in order to help the healthy, live branches flourish (Edin et al., 2007). The other process that accounts for increased brain growth is myelination. Myelin is a fatty white deposit that forms around and insulates portions of many neurons, helping electric impulses pass through a neuron more efficiently. During infancy, much of myelination occurs in the spinal cord and in areas of the brain primarily associated with movement, reflexes, sensory responses, and certain low-level learning processes. For the most part, brain and body development follow a proximodistal pattern, in which parts closer to the center (that is, the spine) develop sooner than parts at the outer edges (the extremities). In this way, our most vital organs and body parts form first. How Do We Learn to Control Our Movements? By the end of their first year, most babies are up and moving. Motor skills, the ability to control one’s bodily movements, include achievements such as grasping objects, crawling, and eventually walking. Table 3-4 shows the typical ages at which children in the United States reach particular motor-development milestones. As we noted earlier in the chapter, most babies acquire motor skills in roughly the same order, which suggests that there may be a maturational explanation for the way in which they unfold. At the same time, and as Table 3-4 also shows, there is considerable variability regarding when a child hits a particular milestone. The timing of motor development can be influenced by a number of environmental factors. Negative influences, such as abuse, neglect, or poor nutrition, can slow a child’s motor development. Cultural practices that either encourage or discourage early motor development can also influence the timetable. For example, the Kipsigis people in Kenya begin working with babies shortly after birth to help them sit up, stand, and walk (Super, 1976). In turn, Kipsigis children achieve these milestones about a month before children raised in the United States. On the other hand, the Ache parents in Paraguay worry about their children moving more than a few feet away, and they actively discourage independent motor development in their children. As a result, Ache children do not walk until an average of one year later than children in the United States (Kaplan & Dove, 1987).
TABLE 3-4 Milestones in Motor Development Motor Milestone
Average Age Achieved
Age Range
When prone, lifts chin up
2 months
3 weeks–4 months
Rolls over
2 months
3 weeks–5 months
Sits alone
7 months
5–9 months
Crawls
7 months
5–11 months
Stands holding furniture
8 months
5–12 months
Stands alone
11 months
9–16 months
Walks alone
11 months, 3 weeks
9–17 months
Walks up steps
17 months
12–23 months
Based on Laura E. Berk, Infants, Children, and Adolescents, 6e (Boston: Allyn & Bacon, 2008) Table 5.2, p. 188.
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© The New Yorker Collection 1989 Lee Lorenz from Cartoonbank.com. All Rights Reserved.
As we noted at the beginning of this chapter, the timetable for learning to walk provides an excellent example of the interaction of nature and nurture in our development. Although achieving a developmental milestone three months early or one year late is significant (particularly to a worried or proud parent), it is equally significant that the process keeps moving forward—that most everyone eventually hits this particular milestone.
Cognitive Development Amazingly, in just two short years, people proceed from wordless, vague (but cute) babies who are completely dependent on others to little yappers who can get into just about everything and figure out how to get a glass of juice that catches their eye. What happens during this period of time that triggers such a dramatic shift? We will talk about how we learn our languages in Chapter 9. Here, we discuss the important changes in thinking ability that happen during those first two years. Piaget’s Theory One of the world’s most influential developmental psychologists, Jean Piaget, focused on cognitive development, how thinking changes (Piaget, 2003, 2000, 1985). Piaget’s theory began with naturalistic observations of children, including his own, in real life situations (Mayer, 2005). On the basis of his observations, Piaget hypothesized that young children’s thinking processes might differ from that of adults. He then proceeded to test his hypotheses by making small changes in the children’s situations and watching to see how they responded to those changes (Phillips, 1975). Based on the results of these tests, Piaget developed a theory of how we acquire knowledge and the abilities to use it. According to Piaget, all of us have mental frameworks or structures for understanding and thinking about the world. He called these frameworks schemata, and he believed that people acquire and continuously build their schemata through their experiences in the world. For example, you may have acquired a schema about Chinese restaurants, based on your experiences. When you go to a Chinese restaurant in your community, you can predict some of the dishes that are going to be on the menu, and you know not to look for pizza or a hamburger. Piaget believed that when children gain new knowledge, their schemata change. This can happen in two ways. The first, assimilation, was defined by Piaget as the inclusion of new information or experiences into pre-existing schemata. During your first few visits to Chinese restaurants, for example, you may have ordered only General Tso’s chicken. In later visits, however, you may have expanded, but not drastically altered, your schema with new information by trying other chicken dishes. Sometimes, we come across new information so different from what we already know that we cannot simply add it to our old schemata. We must alter a pre-existing schema significantly to fit in new information or experiences, an adjustment Piaget called accommodation. Let’s say that you traveled for the first time to New York’s Chinatown neighborhood. There you learned not only that there are several different styles of Chinese cooking but also that your favorite dish, General Tso’s chicken, is not even really Chinese. It is a dish created in New York to interest Americans in Chinese cuisine. Based on this experience, you would have to radically revise your mental framework for Chinese restaurants. According to Piaget, engaging in assimilation and accommodation helps us to reach a mental balance, or equilibrium. As a result of your experiences in Chinese restaurants at home and in New York, you may now feel comfortable in a variety of Chinese restaurants. Piaget’s theory is a stage theory. He suggested that we travel through several stages of cognitive development in life, progressing from being, as babies, unable to even form schemata to being able, as teenagers and adults, to perform complicated mental feats
cognitive development changes in thinking that occur over the course of time. schemata Piaget’s proposed mental structures or frameworks for understanding or thinking about the world. assimilation one of two ways of acquiring knowledge, defined by Piaget as the inclusion of new information or experiences into preexisting schemata. accommodation one of two ways of acquiring knowledge, defined by Piaget as the alteration of pre-existing mental frameworks to take in new information. equilibrium balance in a mental framework.
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TABLE 3-5 Piaget’s Four Stages of Cognitive Development
object permanence an infant’s realization that objects continue to exist even when they are outside one’s immediate sensory awareness. information-processing theory developmental theory focusing on how children take in and use information from their environment. habituation process in which individuals pay less attention to a stimulus after it is presented to them over and over again.
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Stage
Age
Description
Sensorimotor
Birth to age 2
“Thinks” by using senses and motor skills; no thought beyond immediate experience
Preoperational
Age 2–7
Able to hold ideas of objects in imagination; unable to consider another’s point of view or distinguish between cause and effect
Concrete operational
Age 7–11
Can think about complex relationships (cause and effect, categorization); understands conservation; unable to think abstractly or hypothetically
Formal operational
Age 11 on
Able to think abstractly and hypothetically
of logic using schemata. Piaget believed strongly that, as we move from stage to stage, qualitative shifts occur in our thinking. Children in one stage not only know more but actually become different sorts of thinkers than they were at earlier stages. Table 3-5 shows the four developmental stages proposed by Piaget. He proposed that, during infancy, we are in the earliest, or sensorimotor, stage. Piaget named this first stage sensorimotor because he thought that, early on, babies can think only about the world in terms of what they can sense directly or encounter through simple motor actions—that is, a ball, a favorite toy, or a parent is present only insofar as the baby can sense it directly or lay hold on it in some way. Once that pacifier is under the couch, it’s gone. Out of sight, out of mind. Piaget believed that much of our early learning happens as a result of our reflexes. He observed that even though they are “hardwired” into us, reflexes are susceptible to change. As the baby engages in reflex behaviors, he or she gets feedback about how those responses affect him or her and the surrounding world. The rooting reflex often brings food to a hungry infant, for example. In this way, babies are acquiring knowledge that contributes to the formation of schemata. The baby may come to develop a schema relating rooting behavior to feeding. A major cognitive milestone of the sensorimotor stage is the development of object permanence at around 8 months of age, the realization that objects continue to exist even when they are out of a baby’s immediate sensory awareness. A child may cry when a toy rolls under the couch, for example. When children eventually begin to demonstrate awareness of things out of their sensory awareness, it suggests that they are beginning to hold concepts in mind. They have developed mental schemata of those objects. Eventually, babies become able not only to hold objects in their minds, but also to manipulate and make predictions about those objects and how they interact with other objects. A baby may try to lift a cloth to look under it for a hidden toy, for example. By the end of the sensorimotor stage, Piaget believed that the young child’s schemata have changed from needing a direct experience of the world to one in which ideas and concepts stand in for those objects. Information Processing Views of Cognitive Development Piaget often looked at what children could not do and then used their mistakes to determine their cognitive abilities. Today, however, psychologists who adhere to the information-processing theory— who study how children take in information—look to see what children can do, as opposed to what they cannot. Such theorists have found that Piaget probably underestimated children’s competencies at various developmental stages (Lourenç & Machado, 1996).
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Out of sight, out of mind Prior to 8 months of age, babies have no recognition of object permanence. For example, here a young infant plays happily with a stuffed dog (left), but displays no awareness that the animal continues to exist after an experimenter removes it from sight (middle). In contrast, the 10-month-old on the right immediately seeks out and finds a favorite toy that has been hidden from him under a cloth.
To see when a baby developed object permanence, for example, Piaget would hide the object and see whether the baby looked for it. Searching suggests that the baby still had the object in his or her mind. As we have noted, however, it takes some time for babies to master control over their bodies enough to move purposefully and conduct a search. If you cannot grab a cloth that is hiding a toy, you cannot lift it and look under it. Thus, other researchers have suggested that a better indicator of object permanence is whether or not babies react with surprise when hidden objects are revealed again (Baillargeon, 1987). After all, to be surprised, you have to have an expectation that is challenged in some way. Such surprise implies that you have a mental representation of the situation. Studies focusing on the surprise reaction suggest that babies as young as 3 months may display some form of object permanence. Researchers also have found evidence that babies can learn and remember right after birth. Throughout life, individuals often learn to perform and repeat certain behaviors by experiencing positive consequences after they first manifest the behaviors, a process called operant conditioning that we’ll talk about much more in Chapter 7 (Lipsitt et al., 1966). It turns out that even very young babies learn to perform certain behaviors when they are systematically rewarded by researchers. If babies can shift their strategies to bring about positive outcomes or avoid negative ones, they must have some concepts (and, by extension, memories) of the relationships between behaviors and outcomes. Babies also display habituation—that is, they stop responding over time to the same stimulus if it is presented again and again. If babies had no memory or no idea of external objects, they would not be able to become bored by repeated presentations. Habituation has also become a crucial research tool for measuring infant perceptions of colors, sounds, faces, and other such things. Believe it or not, researchers also have been able to demonstrate that babies may be able to do math! As you can see in Figure 3-5, psychologist Karen Wynn conducted a series of studies in which she showed 5-month-old babies a sequence of events where one doll is put in a case behind a screen followed by another doll (McCrink & Wynn, 2004, 2002; Wynn 2002, 1992). She found that when the screen was dropped, the babies expressed surprise and looked longer if only one doll was in the case than if both dolls were present. The babies seemed to know that the case should hold two dolls. This result has been replicated with even larger numbers (five to ten dolls) in 9-month-old children! By adjusting their approaches to focus more on the child’s capacities, informationprocessing researchers have found that cognitive development may involve fewer qualitative shifts and more quantitative growth than Piaget believed. Nevertheless, Piaget remains very influential. His stages still provide a general guideline for the cognitive development of children, and for that reason, we will continue to look at his later stages in this chapter. In addition, his theory remains influential in generating research that
1. Object placed 2. Screen comes up in case
3. Second object added
4. Hand leaves empty
5. Screen drops ...revealing 1 object
FIGURE 3-5 Baby math To see whether 5-monthold infants have an appreciation of addition and subtraction, Wynn showed them the sequence of events illustrated above. If the infants express surprise when the screen drops and they see only one object, it suggests that they understand that 1 ⫹ 1 ⫽ 2. (Adapted from Wynn, 1992)
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. . . [A]ssessing the impact of Piaget on developmental psychology is like assessing the impact of Shakespeare on English literature or Aristotle on philosophy—impossible. The impact is too monumental to embrace and at the same time too omnipresent to detect –Harry Beilin, psychologist
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seeks both to support the theory and to rebut it. If nothing else, the controversy ignited by Piaget’s ideas has helped us think about how to best study children’s thought processes. Perhaps most importantly, Piaget encouraged psychologists to stop thinking of children as organisms programmed by biology or by early experiences but rather as active interpreters of their world. Piaget considered children to be little scientists constantly drawing conclusions about the world on the basis of their own personal research, conducted through their experiences in the world.
Social and Emotional Development Parents are at the center of an infant’s social world, and many psychologists have focused on the importance of the early experiences children have with their parents. Attachment theory has made the best empirical case for how crucial this relationship is (Nelson & Bennett, 2008). In this section, we’ll talk about the principles of this theory and how parent-child relationships may influence a child’s social and emotional development.
attachment a close emotional bond to another person, such as a baby to a caregiver.
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Attachment Theory Theorist John Bowlby believed that human beings are born with a drive to form an attachment, to become emotionally close to one particular caregiver, usually their mother. He suggested that early positive experiences with that caregiver are critical to health and well-being and that they shape how well the individual will function emotionally, socially, and even cognitively later in life. Bowlby also argued that all the behaviors of infants are targeted at bringing them closer to their mothers. He believed, for example, that reflexes such as rooting or reaching out help babies build relationships with their mothers (Bowlby 1958). To Bowlby, the presence of these reflexes provided evidence that attachment processes are inborn and crucial to the survival and well-being of babies. Bowlby also thought that children with strong attachments to their parents will actually feel safer than children who are more independent and less attached to their parents. Indeed, he suggested that steady, consistent responsiveness to a baby’s needs is actually the best way for a mother to eventually bring about a truly independent and well-functioning child. Initially, the scientific community reacted to this assertion negatively. The psychological wisdom of Bowlby’s day had held that parents who respond to children’s needs by drawing the children in will succeed only in fostering neediness and dependence. Mary Ainsworth, a student of Bowlby’s who had conducted naturalistic observations in Uganda, supported Bowlby’s ideas that mother-child attachment occurs around the world (Ainsworth, 1993, 1985, 1967). Ainsworth further noticed that some mothers, whom she labeled “highly sensitive,” seemed to form attachments that were more successful in fostering their children’s independence. Ainsworth developed a way to test the attachment between babies and their mothers in a laboratory setting. Using her procedure, called the Strange Situation (see Figure 3-6), Ainsworth observed systematically how various babies and mothers work together to cope with new and moderately stressful situations. Based on her experimental findings, Ainsworth, like Bowlby, argued that babies attach to their mothers because that is how their needs get met (Bretherton, 1992). Ainsworth identified three basic attachment styles: secure, anxious/avoidant, and anxious/ambivalent (see Figure 3-7). Later, psychologist Mary Main noted that some children fail to show any reliable way of coping with separations and reunions, exhibiting features of all three of the other styles, without any pattern or consistency. She added a fourth category to describe this pattern: disorganized/disoriented (Main & Solomon, 1990). Based on Ainsworth’s work, Bowlby (1969) later suggested that early attachment experiences help people create an internal working model of the world and themselves. If children come to think of other people as supportive and helpful, as a result of having sensitive mothers, Bowlby suggested that this positive model will influence their later
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(b)
(c)
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relationships in a healthy way. In contrast, children who develop a working model that the world is insensitive or does not care may be at risk for poor adjustment or difficult relationships with other people later in their lives. The vast majority of attachment research has focused on mothers, and indeed, cultural practice bears out the importance of the mother-child relationship; in almost every society, mothers do the majority of child care (Parke, 1995). Evidence also indicates, however, that fathers are indeed capable of responding in highly sensitive ways (as defined by Ainsworth) and that if a father is highly sensitive, a baby generally turns out to be securely attached (Howes, 1999).
(e)
FIGURE 3-6 The Strange Situation procedure (a) The baby plays while the mother is nearby. (b) A stranger enters the room, speaks to the mother, and approaches the child. (c) The mother leaves and the stranger stays in the room with an unhappy baby. (d) The mother returns and the stranger leaves. (e) The baby is reunited with the mother.
Parenting Styles HOW we Differ Once attachment theory gave psychologists a way of operationalizing (or defining in a measurable way) the relationship between parents and children, other researchers began applying those insights to understanding how parent behaviors might contribute to development. For example, Diana Baumrind, a psychologist at University of California-Berkley, conducted interviews and observations of primarily white, middleclass preschool children and their parents and found that two characteristics of parental behavior seem particularly important: how many demands the parent puts on the child and how responsive the parent is to the child (Baumrind, 1991). Combining those two
FIGURE 3-7 Styles of attachment Ainsworth and Main identified four styles of attachment. Secure attachment (60 percent): The infant uses the mother as a secure
60% Secure attachment
15% Disorganized/ disoriented attachment
10% Anxious/ ambivalent attachment 15% Anxious/ avoidant attachment
base from which to explore and as a support in time of trouble. When the mother leaves the room, the infant is moderately distressed and happy when she returns. Anxious/avoidant attachment (15 percent): The infant is unresponsive with the mother and is usually indifferent when she leaves the room and when she returns. Anxious/ambivalent attachment (10 percent): The infant reacts strongly when the mother leaves the room. When she returns, the infant shows mixed emotions, seeking close contact and then squirming away angrily. Disorganized/disoriented attachment (15 percent): The infant displays confused and contradictory behavior when the mother returns; for example, ignoring the mother while being held, appearing flat and depressed, looking dazed, crying out, and/or showing a rigid posture.
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reciprocal socialization the transactional relationship between parent and child.
dimensions, Baumrind has identified four parenting styles and the child outcomes associated with them, as depicted in Table 3-6. A key question about Baumrind’s theory has been how well it applies outside white, individualistic cultures. As we discussed in Chapter 1, individualistic cultures are those in which people are expected to be self-reliant and self-achieving, while collectivist cultures expect people to be focused primarily on the needs of the group. Cross-cultural research has found that parents in a variety of cultures can be classified into the same four styles. It is not clear, however, that the outcomes of the four parenting styles are the same across different cultures. Research has suggested, for example, that in Asian cultures, the highdemand, low-responsiveness authoritarian parenting style does not necessarily lead to negative child outcomes as it often does in the United States. In fact, the authoritarian style can benefit children’s academic performances during adolescence (Chao, 2001). Research also suggests that outcomes of parenting styles vary among cultural groups in the United States. An authoritarian parenting style seems to be more harmful to middle-class boys than to middle-class girls, to white American preschool girls than to African-American preschool girls, and to white American boys than to Hispanic-American boys (Baumrind, 1991). Another important question researchers have examined is how children’s behaviors affect parenting styles, a transaction known as reciprocal socialization. Highly rambunctious children are, for example, more likely to evoke authoritarian control behaviors in their parents (Caspi, 1998). Most of today’s research on reciprocal socialization emphasizes the transaction between the parent and the child and holds that the fit between a parent and child’s behavioral styles is more important than some objectively right or wrong style.
What Do Fathers Have to Do With Development? A Lot! It takes both a sperm and an egg to create a child. Yet if you looked at child development research conducted prior to the mid-70s, you would have thought that researchers were unaware of this fact! Case in point: upon reviewing the existing literature in 1975, psychologist Michael Lamb declared that fathers were “forgotten contributors to child development” (Lewis & Lamb, 2003). Why were fathers so long ignored, and what do we now know about their impact on children? Fathers were left out of developmental research for decades for both pragmatic and stereotype-based reasons. Mothers were more likely to be the primary caregivers of children, leading researchers to believe that their impact was more important to study. In addition, fathers were more difficult to recruit for research because they tended to work outside of the home during regular business hours. Early childhood educators also tended to have more frequent contact with mothers than fathers, leading mothers to be most salient when those educators conducted studies of “parenting” effects (Gadsden & Ray, 2003). There were also implicit biases driving the oversight, such as the widelyheld belief that fathers lacked the sensitivity toward children that could only come from “maternal instinct” (Solantaus & Salo, 2005).
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In recent years, however, it has been found that parenting styles are largely equivalent between the sexes. Research on families with same-sex parents has helped clarify this point. Moreover, while mothers in more conventional family structures do tend to be slightly more sensitive caregivers than fathers, particularly after the child reaches 1 year of age, the amount of parenting experience seems to underlie much of this effect. That is, if a father spends more time taking care of the child, his sensitivity tends to be higher. For a variety of cultural reasons, American fathers tend to be more involved in play with their children than in caretaking. In fact, given the choice, infants prefer to play with their fathers than with their mothers. Such differences in interaction styles, however, are not large (Lewis & Lamb, 2003). Research suggests that, on average, children from families in which two parents are present and active have many advantages over those raised in mother-only families (NFI, 2009; Cuff et al., 2005; Harpet et al., 2004; Hoffman, 2002). They have, for example, fewer accidents as toddlers, are less likely to be depressed as children and adults, and display lower rates of juvenile delinquency, teenage pregnancy, drug use, and incarceration. Although developmental research still focuses more heavily on mothers than on fathers, the field has come a long way over the past 30 years. Moreover, the number of articles and books devoted to fathers seems to be on the increase (e.g., Lamb & Day, 2004; TamisLeMonda & Cabrera, 2002).
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TABLE 3-6 Parenting Styles Parental style
Parental behavior
Associated outcome in children
Authoritative
Warm, sensitive to child’s needs, nurturing; makes reasonable demands and encourages appropriate autonomy
High self esteem, cooperativeness, self control, social maturity
Authoritarian
Cold, rejecting; makes coercive demands; frequently critical of child
Low self esteem, anxious, unhappy, often angry and aggressive
Permissive
Warm, accepting but overindulgent and inattentive
Impulsive, disobedient, overly dependent on adults, low initiative
Uninvolved
Emotionally detached and depressed; little time or energy for child rearing
Anxious, poor communication skills, antisocial behavior
Before You Go On What Do You Know? 8. What is the role of myelination in the development of the brain? 9. What is the Strange Situation? 10. What are the major parenting styles, and what are the major child outcomes associated with each style?
What Do You Think? How do you think the various attachment styles correlate with Baumrind’s parenting styles? Do you think there is one optimal form of parenting?
Childhood How we Develop LEARNING OBJECTIVE 5 Summarize the major physical, cognitive, and emotional developments that take place during childhood.
Although physical growth slows somewhat during childhood, our inner and outer lives become increasingly complex. We develop the cognitive capacity to think and talk about the world in new ways that do not involve the concrete reality right in front of us. Our social and emotional lives also become more complex and expand to include peers and teachers. In this section, we’ll focus on how the world gets a lot bigger during childhood and how children manage to keep up.
Physical Development Growth during early childhood, which lasts from about the ages of 2 to 6 years, and middle childhood, which lasts from about age 6 until 12, is not as dramatic as it was during infancy. Although progress is more gradual, children’s brains and bodies still experience major changes. Both become much more efficient, as we’ll see. Childhood How We Develop
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How Does the Body Grow During Childhood? The dramatic physical growth that occurs from conception through our second year slows down during early childhood, such that we grow only about 21/2 to 3 inches a year. We master a good deal of motor and physical control during this period. Children develop basic control over their urination and bowel movements, and they solidify a preference for their right or left hand for most tasks. Of course, during early childhood many aspects of development remain works-in-progress. Although our coordination improves and we can work the buttons, zippers, and shoelaces necessary to dress ourselves, that doesn’t necessarily mean that we can coordinate clothes effectively. Remember those embarrassing family pictures? As children move from early into middle childhood, around age 6, things begin to rev-up again. Children’s motor abilities improve dramatically as they gain coordination, agility, and strength. At the same time, the first major distinctions between boys and girls begin to appear. Girls experience a growth spurt in height and weight during their tenth or eleventh year, while boys have to wait a couple of years more for their spurt. On the other hand, boys develop somewhat more muscle mass, meaning they can throw and jump a little farther and run a little faster. Girls tend to be a bit more agile on average. As we’ll see later in the chapter, these average differences become much more pronounced as children move into adolescence. What Happens in the
Childhood B R A I N ? Throughout early and middle childhood, the brain becomes more efficient through a continued combination of the myelination and synaptic pruning that began in infancy. During childhood, myelination is concentrated in the brain areas known as the association regions. These are the areas of the brain that coordinate the activity and operation of other regions of the brain (Paus et al., 1999). The increased efficiency of the association regions as they become myelinated leads to more sophisticated planning and problem-solving abilities. Most 4-year-olds cannot play chess very effectively, for example, but many elementary school children have the strategic skills to be good chess players. As we discussed earlier, synaptic pruning helps solidify the neural connections that are most beneficial to the child. As childhood draws to a close, pruning slows some. The numbers of synaptic connections between particular neurons and the overall electric activity in the brain both begin to stabilize.
Association regions of the brain The association regions (all areas of the cortex not colored blue in this illustration) undergo extensive development during childhood, leading to further growth of the cognitive processes.
Cognitive Development One of the major activities of childhood is going to school, and in most countries, formal education begins around the age of 6 or 7. We’ll see in this section that school entry coincides with the development of the cognitive skills that Piaget called operations, the ability to hold an idea in mind and manipulate it mentally. Piaget suggested that between the ages of about 2 and 12 children go through two stages of cognitive development: the preoperational stage, which lasts from age 2 through 7, followed by the concrete operational stage, lasting from age 7 through 12. Schools also provide rich social environments, a factor that another cognitive development theorist, Lev Vygotsky, believed is crucial to learning. Piaget’s Preoperational Stage According to Piaget, as children move into the preoperational stage, they become able to hold memories, or representations, of objects in their imaginations and to work with them as ideas. This represents a dramatic shift from the earlier sensorimotor stage in which they were able to manipulate actual objects only. The thinking of children at this stage still shows some limitations, compared to adult thinking, however.
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One major limitation is what Piaget called irreversibility. Although they can work with symbols and concepts that stand in for real-world objects, children at the preoperational stage still think in rather simplistic ways about the relationships between those concepts and objects. For them, changes in relationships happen in one direction only. One researcher offers the following example of a 4-year-old who was asked about his family: “Do you have a brother?” “Yes.” “What’s his name?” “Jim.” “Does Jim have a brother?” “No.” (Phillips, 1975)
operations Piagetian description of a child’s ability to hold an idea in his or her mind and mentally manipulate it. preoperational stage according to Piaget, a developmental stage during which the child begins to develop ideas of objects in the external world and the ability to work with them in his or her mind. egocentrism flaws in a child’s reasoning based on his or her inability to take other perspectives. conservation the understanding that certain properties of an object (such as volume and number) remain the same despite changes in the object’s outward appearance.
The boy is able to hold the idea of his brother Jim in his head, even though Jim is not there, indicating he has developed object permanence. At the same time, he has adopted this concept in one direction only: Jim is my brother. The boy is unable to think about the reverse relationship—that he is Jim’s brother also. The reason this child cannot think of himself as Jim’s brother, according to Piaget, is because he cannot take Jim’s point of view, an inability Piaget referred to as egocentrism. Piaget did not use the term egocentrism to mean the boy is arrogant. His use of the term refers strictly to children’s flaws in logical reasoning. This boy cannot yet realize that other people also have brothers. Piaget believed that perspective-taking, the ability to take another person’s point of view, is not mastered until a later stage. Irreversibility is also related to a lack of conservation, the ability to understand that something can stay the same even though its appearance changes. Piaget used a nowfamous task to demonstrate young children’s problems with conservation. He gave a child two identical beakers with equal amounts of water in each and asked which of the beakers held more water. Children over 2 years old were usually able to say that both beakers held the same amount. Piaget would then ask the child to pour the water into two new beakers that were shaped differently, one shallow and wide and the other tall and narrow. After the children poured the water, Piaget again asked which held more water. Children between the ages of 2 and 7—even after they themselves had poured the water into the new beakers—were more likely to say the tall, narrow beaker held more water. Piaget believed this indicated that the children could not mentally reverse
Shapes can be misleading In the classic test for conservation, a child is shown two identical short thick glasses, each filled with liquid. The child then watches as the liquid from one glass is poured into a tall thin glass and is asked to indicate which glass now has more liquid. Most children between 2 and 7 years incorrectly pick the tall thin glass.
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A child of five would understand this. Send someone to fetch a child of five. –Groucho Marx, comedian
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the pouring of the water to imagine that the two amounts of water would once again match if both were returned to their original containers. Children’s lack of conservation also may be related to difficulty in making distinctions between appearance and reality. In one classic example of this confusion, researcher Rheta DeVries (1969) allowed children to play with her cat, Maynard. After a while, DeVries and her assistants would hide Maynard’s front half from view while they strapped a dog mask onto the cat’s face. (We have no idea how she got a cat to agree to wear a dog mask.) DeVries then asked the toddlers what kind of animal Maynard was. Even though Maynard was never completely out of view, the majority of the 3-year-old participants, and a good number of 4- and 5-year-olds thought the cat had magically become a dog. By the age of 6, when they were nearing the concrete operational stage, none of the children made this mistake. Piaget’s Concrete Operational Stage During the stage of concrete operations, children demonstrate the ability to think about ideas. They start to talk authoritatively about complex relationships, such as cause and effect and categorization. They can take others’ perspectives and reverse operations. By now, they consider the notion that a cat can mysteriously become a dog ridiculous. They know dogs and cats fit into certain hard and fast categories, and they can now extend those categories to other organisms that share the same features. Children at this stage show a mastery of real-world relationships. This mastery is limited, however, to ideas that have real-world counterparts, such as brothers and sisters and other family members, categories of plants or animals, or causes of weather conditions. That’s why Piaget refers to the stage as concrete operations. Children in this stage have difficulty with abstract relationships between objects that do not exist in the real world, such as abstract mathematical relationships. They also find it difficult to think about hypothetical, alternate possibilities and have trouble speculating on questions, such as “What ways can this situation play out?” A mastery of those kinds of relationships is left for the next stage of development.
concrete operations Piagetian stage during which children are able to talk about complex relationships, such as categorization and cause and effect, but are still limited to understanding ideas in terms of real-world relationships. theory of mind a recognition that other people base their behaviors on their own perspectives, not on information that is unavailable to them. scaffolding developmental adjustments that adults make to give children the help that they need, but not so much that they fail to move forward. zone of proximal development the gap between what a child could accomplish alone and what the child can accomplish with help from others.
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Criticisms of the Preoperational and Concrete Operations Stages Many critics have challenged Piaget’s belief that children in the preoperational and concrete operations stages have problems taking others’ point of view. In fact, some researchers have become very interested in young children’s beliefs about how their own minds and the minds of others work, a field of research called theory of mind. Theory of mind was first studied in an experiment with children between the ages of 3 and 9. Each child participant was told a story about a boy named Maxi who tries to sneak some chocolate from his mom (Wimmer & Perner, 1983). According to the story, Maxi’s mother brings home some chocolate to make a cake, and while Maxi is watching, she puts the chocolate in a blue cupboard (see Figure 3-8). Maxi then goes out to play. While he is outside, his mother makes the cake and puts the remaining chocolate in a green cupboard. Next, Maxi comes back in, wanting some chocolate. The researchers then asked the children in the study where Maxi would look for the chocolate. This deceptively simple task actually requires a high level of thought. Children have to not only remember where the chocolate has traveled, but also take the viewpoint of Maxi and realize that Maxi has no way of knowing that his mom moved the chocolate. Three- and four-year-olds regularly fail such tests, suggesting this task is too complicated for them, while six-year-olds regularly succeed. Experiments such as these support Piaget’s notion that young children are highly egocentric, but also suggest that many such children are able to take other people’s thoughts and feelings into account much sooner than Piaget had predicted.
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FIGURE 3-8 Theory of mind Young research participants are told a story in which a child first sees his mother place chocolate in a upper cupboard, then he leaves while she makes a chocolate cake. In his absence, the mother places the leftover chocolate in a lower cupboard, and the child then returns looking for leftover chocolate. Participants with a theory of mind recognize that the child in the story will look for the leftover chocolate in the original upper cupboard, because the child is not aware of the mother’s switch of locations.
In part, Piaget’s approach may have been limited by a failure to listen to his own theory. Piaget believed that thought preceded language, that our thinking develops faster than our ability to use words. Yet, his tests of his theories rested on observations of children’s performances on language-based tasks, such as the question about Jim’s brother. Other researchers, by focusing on nonverbal responses or by making their questions more age-appropriate or child-friendly, have found evidence that children develop certain cognitive competencies sooner: for example, pictures accompanied the story of Maxi. Still other critics have charged that Piaget’s theory fails to account fully for social factors, the influences that other people may have on a child’s cognitive development. Piaget’s theory, instead, focuses on how children guide their own development through experimentation and reflection. Later in his life, Piaget himself also wondered whether his theory said enough about the role of social experiences in development (Inhelder & Piaget, 1979; Piaget, 1972). As we’ll see next, a contemporary of Piaget’s had more to say about social influences on cognitive development.
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Parents can only give good advice or put them on the right path, but the final forming of a person’s character lies in their own hands. —Anne Frank, diarist and Holocaust victim
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Vygotsky and the Role of Cultural Factors While Piaget was focusing on how children’s private experiments and reflections shape their thinking, a Russian psychologist named Lev Vygotsky was becoming increasingly interested in how social interactions with parents might drive the development of children. Unlike Piaget, who viewed a child’s development as a process of individual achievement, Vygotsky (2004, 1991, 1978) believed that constructive interactions with parents, older children, teachers, and siblings help the child develop ways of thinking about and functioning in the world. In Vygotsky’s view, an older “mentor,” such as a parent, helps the child by initially taking responsibility for the basic skills and capabilities the child is developing. Over time, the “mentor” takes less and less responsibility. Vygotsky referred to the mentor’s step-by-step assistance as scaffolding. Vygotsky labeled the gap between what children can accomplish by themselves and what they can accomplish with the help of others as the zone of proximal development. Because of his death at the young age of 37 and the chilly political climate between the former Soviet Union and the West, Vygotsky’s ideas have come to light only in recent years. Developmental psychologists have found numerous ways to apply Vygotsky’s Childhood How We Develop
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Every function in the child’s cultural development appears twice: first, between people (interpsychological) and then inside the child (intrapsychological). This applies equally to voluntary attention, to logical memory, and to the formation of ideas. All the higher functions originate as actual relationships between individuals. –Lev Vygotsky, Russian psychologist
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ideas, however. He has become one of today’s most influential developmental theorists (Feldman, 2003). Indeed, ideas of scaffolding and zones of proximal development are now an important part of educational systems throughout the United States. When helping children learn to read, for example, many teachers begin by reading books to them, then gradually turn over responsibility for various reading skills. The children may first follow along with the pictures as the teacher reads the words, then point to letters. Eventually, they learn to read single words, then sentences, and finally entire books on their own, as the teacher provides less and less scaffolding and the children’s zone of proximal development becomes smaller. Whereas Piaget believed that thinking preceded language, Vygotsky believed that language is crucial to cognitive development because a great deal of mentoring relies on talking and listening. Both theorists noticed that preschool-aged children seem to talk to themselves a lot. Piaget regarded this incessant chatter as largely unimportant, egocentric babble. Vygotsky, however, called that chatter private speech. He believed that children use private speech to regulate their behavior and internal experiences, to plan, and to solve problems, often repeating or imitating the words of their mentors. Vygotsky believed that, eventually, these private chats turn into silent, internal dialogues, perhaps similar to the conversations adults have in their heads each morning about whether to hit the snooze button on their alarm clocks one more time and risk being late for that first appointment. Because Vygotsky believed that other individuals are critical to helping children develop, he also believed that there is a great deal more variability in how children develop. He believed that each culture has its own specific challenges, and that those challenges change over the course of life, meaning that development has to meet those challenges.
Social and Emotional Development We will focus on many features of a child’s social and emotional development in Chapters 12 and 14. Here, our main focus will be on moral development, how children acquire an understanding of right and wrong and how to function in a complex society. Heinz and the Drug Kohlberg’s Theory of Moral Development In Europe, a woman was near death from a special kind of cancer. There was one drug Lawrence Kohlberg was a student of Jean Piaget who that the doctors thought might save her. It was a form of radium that a druggist in the was interested in Piaget’s ideas on moral developsame town had recently discovered. The drug was expensive to make, but the druggist was charging ten times what the drug cost him to make. He paid $400 for the radium and ment. Piaget believed that, as with general logical charged $4,000 for a small dose of the drug. The sick woman's husband, Heinz, went to reasoning, children learn how to reason morally by everyone he knew to borrow the money and tried every legal means, but he could only get translating their behaviors and experiences into together about $2,000, which is half of what it cost. He told the druggist that his wife was dying, and asked him to sell it cheaper or let him pay later. But the druggist said, "No, I general moral principles that they can apply across discovered the drug and I'm going to make money from it." So, having tried every legal different situations. He proposed that children’s means, Heinz gets desperate and considers breaking into the man's store to steal the drug. morality is based initially on obeying adults. As they Question: Should Heinz steal the drug? Why or why not? get older, the basis of their moral reasoning shifts toward cooperation with peers (Piaget, 1965). Kohlberg expanded upon Piaget’s ideas and develFIGURE 3-9 Kohlberg’s moral dilemma story oped a method to evaluate the moral reasoning processes of children. He presented them (Paragraph excerpted from Scot Lilienfeld, Steven with stories about moral dilemmas, such as the story of Heinz in Figure 3-9, and asked Lynn, Laura Namy, and Nancy Wolf, Psychology: them to say what the main characters in the stories should do and why. From Inquiry to Understanding (Boston: Pearson: Allyn & Bacon.) On the basis of his studies, Kohlberg developed a stage theory of moral development, depicted in Table 3-7 (Kohlberg, 2008, 1994, 1963). The focus of this theory is moral reasoning, how children come to their decisions about what is right and wrong rather than on the particular decisions that they make. Like Piaget, Kohlberg believed that young children make moral choices that seem likely to ensure the least amount of 80
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TABLE 3-7 Kohlberg’s Stage Theory of Moral Development Stage
Reason to steal drug
Reason not to steal drug
Preconventional: Morality centers on what you can get away with
He can get away with it.
He will be caught and go to jail
Conventional: Morality centers on avoiding others’ disapproval and obeying society’s rules
If he doesn’t steal the drug people will think he is a terrible person.
If he steals people will think he is a criminal; it’s against the law.
Postconventional: Morality is determined by abstract ethical principles
Sometimes the law is unjust and it is right to break it.
He will not have lived up to his own standards of honesty and will lose his self-respect.
trouble with authority figures. However, Kohlberg also looked beyond childhood to adolescence and described how older children and adults become more independent in their moral reasoning. Although Kohlberg believed that moral reasoning often is correlated with other areas of development, such as cognition or intelligence, he held that it develops along its own track. As the ability of children to take another person’s point of view grows, their moral reasoning also becomes more complex. To reach the highest stages of moral reasoning, Kohlberg believed, individuals must be exposed to complex social situations, such as working at jobs that involve lots of people or going to college. Like Piaget’s theory of general cognitive development, Kohlberg’s theory suggests that each stage of moral development is not just a shift in complexity but instead represents a new framework for making moral decisions. Each such stage forms a foundation for the next stage, and children must travel through the stages of moral development in sequence. A child may be delayed, or perhaps even fail to reach some of the higher stages, but he or she must go through each earlier stage to reach the next one. Finally, Kohlberg believed that the process of moral development is universal and happens the same way in every culture. Kohlberg’s original research included boys only, but he later studied girls and conducted moral dilemma interviews in villages in Mexico, Taiwan, and Turkey. Gilligan’s Theory of Moral Development One of Kohlberg’s collaborators, Carol Gilligan, eventually questioned some of his findings and ideas, partly because his studies initially focused on boys alone and also because his later studies that did include girls seemed to suggest that girls are morally less developed than boys. Kohlberg believed that girls do not have as many complex social opportunities as boys and, as a result, are excessively concerned with the standards of others and often fail to achieve higher stages of moral reasoning. Gilligan interpreted the boy-girl findings differently. She argued that the moral reasoning used by girls is indeed different from that of boys but not inferior. She noticed that boys tend to base their decisions about moral dilemmas on abstract moral values, such as justice and fairness. Many girls look at the situations differently. Instead of the abstract values involved, they focus more on the value relationships between the principal players. A boy’s answer to the Heinz dilemma might center on the importance of property value for the druggist, for example, while a girl’s answer might stress that Heinz will not be able to help his wife if he is jailed for stealing the drug (Gilligan, 1993). Gilligan argued that the reasoning of boys and girls is equally sophisticated, but their goals and the aspects of the dilemma that they notice differ. Gilligan went on to conduct her own interviews with men and women and found further support for her theory that women are inclined to make moral judgments based more on caring and managing relationships than on Kohlberg’s notions of justice and fairness.
private speech a child’s self-talk, which Vygotsky believed the child uses to regulate behavior and internal experiences.
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puberty development of full sexual maturity during adolescence. primary sex characteristics changes in body structure that occur during puberty that have to do specifically with the reproductive system, including the growth of the testes and the ovaries. secondary sex characteristics changes that occur during puberty and that differ according to gender, but aren’t directly related to sex.
Other studies have not always supported Gilligan’s theory that women and men differ in their moral orientation. Nor, however, have they always supported Kohlberg’s notions of moral superiority among males (Walker, 2006). Some recent studies, for example, suggest that differences in the education levels of their research participants may have accounted for the apparent moral differences between males and females observed by these two investigators; when education level is controlled for, females and males often earn similar moral stage scores (Dawson, 2002). Gilligan’s ideas have had a broad influence on psychology, anthropology, and other social sciences. In a classic book, In A Different Voice, Gilligan (1993) noted that over the years many psychological theorists have embraced male development patterns as the norm and viewed differences from that norm as inferior. Similarly, she argued that women have been underrepresented in many of psychology’s most influential studies and theories. As a result of her arguments, many researchers now include more females in their studies. In addition, most of today’s researchers think of differences among participants as individual variations rather than positive or negative characteristics. Current Directions in Moral Development Much research in moral development over the last 50 years has been influenced by Kohlberg’s and Gilligan’s theories. Many researchers have focused on Kohlberg’s notion that the stages of moral development are the same for everyone, and indeed a review of 45 studies conducted across a wide range of cultures has found that Kohlberg’s claims of universality hold up pretty well for the early stages of moral development (Snarey, 1985). Such research also has suggested that people from different cultures rarely skip stages or revert to previous ones. Cross-cultural researchers have also noted cultural differences that support Gilligan’s ideas. Some researchers have found, for example, that respondents from collectivist cultures tend to score lower on the Kohlberg scales than do those from individualistic cultures (Gibbs et al., 2007). Close examinations indicate, however, that these score differences reflect differences in the kinds of moral problems faced by people in each of these cultures, not moral superiority or inferiority. As described in Chapter 1, collectivistic cultures put greater emphasis on society and relationships than individualistic cultures, which tend to emphasize individual justice and fairness. Finally, a number of moral development researchers have wondered how much the expressed moral attitudes of people reflect their actual decision-making (Krebs & Denton, 2006). As we will see in our discussion of attitudes in Chapter 14, people do not always actually do what they say they will do (an experience you’ve probably had once or twice in your own life). Because the vast majority of research into moral reasoning has relied on Kohlberg’s moral dilemma interviews, many researchers argue that we may be able to say a fair amount about people’s moral philosophies but little about their behavior.
Before You Go On What Do You Know? 11. In what areas of the brain is myelination concentrated during childhood, and how does myelination of these areas affect the child’s cognitive functioning? 12. What are the crucial differences between Piaget’s view of cognitive development and Vygotsky’s view of cognitive development? 13. How are the ideas of scaffolding and zone of proximal development reflected in contemporary American educational practices? 14. How do contemporary theories of moral reasoning differ from Piaget, Kohlberg, and Gilligan?
What Do You Think? Do you think that men and women reason differently about morality? If the outcome is the same in our moral choices, does the reasoning we used to achieve that outcome matter?
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Adolescence How we Develop LEARNING OBJECTIVE 6 Summarize the major physical, cognitive, and emotional changes that take place during adolescence.
With the possible exception of the first couple years of life, the amount of change that occurs during adolescence rivals that of any other developmental passage. Most crucially, puberty begins. In the cognitive sphere, adolescents display features of both children and adults, and they begin to learn how to function independently. In this section, we will describe the key biological, cognitive, and social transitions that characterize this dramatic period.
Physical Development Puberty refers to the physical development of primary and secondary sex characteristics. Primary sex characteristics are the body structures that have to do specifically with the reproductive system, including growth of the testes and the ovaries. Secondary sex characteristics refer to nonreproductive body events that differ according to gender, such as the deepening of the male voice or the increase in female breast size (see Figure 3-10). The onset and course of puberty is influenced largely by the pituitary gland, which coordinates the activities of the rest of the endocrine system. As you’ll see in Chapter 4, the endocrine system includes the adrenal glands, testes, and ovaries. During adolescence, events throughout this system stimulate the growth of body hair and muscle tissue and trigger the onset of the female menstrual cycle, among other changes. One of the most important changes is a growth spurt triggered by the thyroid gland that, as we observed earlier, actually begins for girls in middle childhood and for boys during early adolescence (see Figure 3-11). The growth spurt happens about two years before the primary sex characteristics kick in and is not only a harbinger of those later changes, but also helps prepare the body for them (Rekers, 1992). Facial and underarm hair growth
Larynx enlargement Underarm hair growth Breast development Enlargement of uterus Beginning of menstruation Pubic hair growth
Adrenal glands
Ovaries Testes
Pubic hair growth Growth of penis and testes Beginning of ejacul*tion
FIGURE 3-10 Primary and secondary sex characteristics The complex changes in puberty primarily result when hormones are released from the pituitary gland, adrenal gland, and ovaries and testes.
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Height gain (cm/year)
10
8
Males
Females
6
4
The changes of puberty stabilize after a couple years. In the meantime, however, many of those changes can be very disruptive to adolescents. Of course, we’re all familiar with the big ones: hair (or the lack of hair) in embarrassing places, acne, cracking voices. For both boys and girls, variations from age norms for puberty can be upsetting; girls who mature early and boys who mature late report more problems making the transitions through adolescence than those who hit puberty “on time” (Hayatbakhsh et al., 2009). The brain also goes through significant changes during adolescence. Myelination continues to increase and synaptic connections continue to decrease as a result of synaptic pruning. As with middle childhood, many of these changes appear to be localized; they now focus on the prefrontal cortex, the brain area that helps coordinate brain functions and is instrumental in making sound judgments. Many psychologists point to the pruning that occurs in the prefrontal cortex as the reason teenagers often display poor judgment in their daily functioning for a while (Compas, 2004).
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Cognitive Development 0
6
12
18
Age (years)
FIGURE 3-11 Adolescent growth spurt The growth spurt of girls occurs, on average, two years before that of boys. Thus, between the ages of 10 and 14 years, the average girl is taller than most boys.
As we mentioned above, adolescent thinking has features of both child cognition and adult cognition. Teenagers show increased capacity for reasoning about abstract things but also have deficits in their abilities to see outside of the moment or to take others’ points of view. These strengths and limitations both come into play in their social and emotional growth as adolescents attempt to define themselves as persons. Piaget’s Formal Operations Stage Piaget suggested that at around the age of 12, we cross over into mature adult thinking processes, a final stage known as formal operations. Piaget believed that the hallmark achievement of this stage is the ability to think about ideas conceptually without needing concrete referents from the real world. The successful transition to formal operations means that teens are no longer bound by the concrete realities of their world. For example, in math class they have moved beyond using real-life representations of numbers, such as counters, and now can use rules to solve problems, even algebra problems involving variables. They can conceive of other worlds and other possible realities, even ones that do not exist outside their own imaginations. Although formal operations represent the apex of cognitive development, teenagers continue to experience some egocentric thought. They may, for example, display the so-called personal fable: over the course of searching for a sense of identity and spending time in deep focus on their own thoughts and feelings, teens may become convinced that they are special—the first persons in history to have those particular thoughts and feelings. Another form of egocentric thought that marks adolescence is the imaginary audience. The imaginary audience describes the teenager’s feeling that everyone is scrutinizing him or her, a notion that leads to strong feelings of inhibition and self-consciousness.
Social and Emotional Development
formal operations Piaget’s final stage of cognitive development; the child achieves formal adult reasoning and the ability to think about things that don’t have a concrete reality.
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German psychologist Erik Erikson is one of the few major developmental theorists to look at development across the entire lifespan (Erikson, 1985, 1984, 1959). Erikson divided the span from birth to old age into eight stages. Each of Erikson’s stages is associated with a “main task,” a challenge the person must meet and reconcile. An individual’s achievement at each stage has a direct impact on how he or she meets the challenges of the next stage. Erikson believed that culture and relationships play strong roles in personality formation, and so he referred to his work as a stage theory of psychosocial development.
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TABLE 3-8 Erikson’s Stages of Psychosocial Development
Stage 1 Trust versus mistrust (birth –age 1) Infants develop a basic trust in others. If their needs are not met by their caregivers, mistrust develops. Stage 2 Autonomy versus shame and doubt (ages 1–3) Children exercise their new motor and mental skills. If caregivers are encouraging, children develop a sense of autonomy versus shame and doubt. Stage 3 Initiative versus guilt (ages 3–6) Children enjoy initiating activities and mastering new tasks. Supportive caregivers promote feelings of power and self-confidence versus guilt. Stage 4 Industry versus inferiority (ages 6–12) Children learn productive skills and develop the capacity to work with others; if not, they feel inferior. Stage 5 Identity versus role confusion (ages 12–20) Adolescents seek to develop a satisfying identity and a sense of their role in society. Failure may lead to a lack of stable identity and confusion about their adult roles. Stage 6 Intimacy versus isolation (ages 20–30) Young adults work to establish intimate relationships with others; if they cannot, they face isolation. Stage 7 Generativity versus self-absorption (ages 30–65) Middle aged-adults seek ways to influence the welfare of the next generation. If they fail, they may become self-absorbed. Stage 8 Integrity versus despair (ages 65+) Older people reflect on the lives they have lived. If they do not feel a sense of accomplishment and satisfaction with their lives, they live in fear of death.
As Table 3-8 shows, Erikson believed that each stage of development is associated with a potentially positive outcome versus a potentially negative outcome. For example, the conflicts and challenges associated with infancy determine whether a baby will develop a basic trust of the world (positive outcome) or mistrust (negative outcome). Babies whose parents respond attentively when they cry with hunger, learn that the world is a good place and that other people can be trusted. The key developmental task faced by adolescents is to resolve the conflict between identity and role confusion. During adolescence, teenagers start making decisions that affect their future roles, such as where they want to go to college or what they want to do with their lives, as well as decisions about abstract aspects of their identities, such as political or religious beliefs. According to Erikson, if we do not reach a successful resolution of the conflict confronted at a particular stage, we may find it harder to meet the challenges of subsequent stages. Teenagers who did not effectively resolve the conflicts of their earlier psychosocial stages may enter adolescence with heightened feelings of mistrust and shame. These lingering feelings may render the teens particularly confused about which roles and beliefs truly reflect their own values and which ones reflect excessive peer and family influences. Peer relationships are extremely important to all teenagers, and Erikson believed that vulnerable teens are particularly likely to be confused about where their own beliefs start and the wishes of others end. A number of other theorists and researchers have also highlighted the critical role that identity formation plays while teens are seeking to negotiate their way through adolescence successfully. James Marcia (2007, 1994), for example, expanded Erikson’s theory, suggesting that a combination of identity “crises” (and identity explorations) and personal decisions to make commitments in life help to define a teen’s identity.
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The best way to keep children home is to make the home atmosphere pleasant— and let the air out of the tires. —Dorothy Parker, author
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The Trials and Tribulations of Becoming an Adult
You are in college now and your parents inform you that you are a responsible grown-up. Such a pronouncement can create an internal conflict for you because you do not feel all that grown up, yet. But don’t despair. If you are feeling confused and uncertain about yourself, your abilities, your relationships, and your future, you actually are in the majority. College-aged, young adults are still maturing both physically and psychologically. From the ages of 18–23, significant changes occur in your brain (Bennett & Baird 2006). Along with profound changes in mental and cognitive capacities, emerging adults experience psychological transformations as they become more self-aware, develop a sense of purpose, find their moral compass and value system, and make decisions about long-term goals—career, intimate partnerships, and family (Perry, 1970). In the face of such changes, you will most likely experiment with different roles and experiences to help you find what is “right” for you. In fact, this period of your life has been called a
“psychosocial moratorium” (Erikson, 1968). Welcome to one of your most significant periods of developmental change! Fortunately, there are some things that might help you cope with the developmental roller-coaster ride that takes you into adulthood. First of all, accept that you are changing. Your physical and psychological development occur over a very long period of time, and some of these changes creep up on you when you least expect them. This developmental period is very different from the stages and changes that characterized your childhood; in particular, you have a much greater mental capacity to examine what is happening to you and to determine how best to cope. One useful coping strategy during this period is to share your concerns with a trusted friend or close family member. If you do not want to share with someone you know, try talking to a school counselor. One of the least productive things you can do is isolate yourself by either withdrawing or pushing people away—whether by inappropriate behavior, constant partying, or offensive remarks. Sometimes, just letting off steam is enough to let go of what is bothering you. If you find yourself talking about the same problems repeatedly, however, it may be time to work on a proactive solution and implement it. Bounce around ideas, search for solutions, and then try them out. And, while you are evolving, you might try to keep a version of the golden rule in mind; treat others as you would like to be treated. Try to show kindness and respect both for yourself and those around you.
Before You Go On What Do You Know? 15. If a child arrives at puberty significantly earlier or later than his/her peer group, how might that affect his/her adjustment? 16. Define formal operations. 17. Describe what Erikson believed was the major dilemma and risk for adolescence.
What Do You Think? How might Erikson explain Bruce Wayne’s or Peter Parker’s difficulties with adjustment during these developmental stages?
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Adulthood How we Develop LEARNING OBJECTIVE 7 Describe key physical, social, and emotional changes that take place throughout adulthood.
Traditionally, developmental psychology viewed adulthood as an outcome rather than a period of time worthy of study. As we’ll see, however, adulthood is in fact a time of continuing change—and by change, we do not necessarily mean decline. Let’s look at some of the developmental changes that happen during adulthood.
Physical and Cognitive Development With the end of adolescence comes full maturity. Nevertheless, the body continues to go through changes during adulthood. And, as we’ll see, so does the brain. What Happens in the Body During Adulthood? Generally, physical attributes, such as strength, reaction time, and overall body function are at their peak during our 20s. As we move into our 30s, the body begins to decline slowly. Our metabolism slows, for example, so it takes a bit more work to keep some roundness from appearing around the waist. During our 30s and 40s, we begin to show the first significant signs of aging. Skin begins to lose some of its tautness and grey hairs begin to sprout. Although we’re significantly past our sensory peak, only in their 40s do most people begin to notice decline in that area of functioning (Fozard et al., 1977). We become more farsighted, finding it hard to read or see small objects close to us, and we have difficulty seeing in the dark or recovering from sudden glares of light. We also become less sensitive to high-frequency noises. Women in their 50s typically go through a major change called menopause (Nelson, 2008). Menopause involves a series of changes in hormonal function that eventually lead to the end of the menstrual cycle and reproductive capabilities. The early phase of menopause is often associated with a variety of physical experiences, such as hot flashes, headaches, and sudden shifts in mood. As we move into late adulthood, during our 60s and 70s, we may become a bit shorter and thinner due to changes in our skeletal structure and metabolism (Bord-Hoffman & Donius, 2005). Our immune systems also begin to decline in function, leaving us at higher risk for illness. Our vision and hearing continue to decline, joined by our sense of taste. Our pupils shrink, so that less light reaches the retina, making it harder for us to see in low light. The story is not as simple as a long, slow, inevitable decline, however. Exogenous factors, such as exercise, stress, diet, and life experience, can have a dramatic influence on the course and impact of these changes (Larson et al., 2006; Brach et al., 2003). Although declines are common, many of the changes can be subtle and have minimal impact on how well we function in the world. What Happens in the
Adulthood B R A I N ? Until recently, neuroscientists believed that our brains begin to shrink during adulthood, both in terms of volume and weight, and that much of this loss is attributable to the shrinkage and loss of active brain cells (Miller & O’Callaghan, 2005). Research over the past decade, however, has revealed that no significant loss of neurons occurs in adulthood, except in cases of brain pathology (Miller & O’Callaghan, 2005); that new neurons keep being formed in certain parts of the brain
menopause series of changes in hormonal function occurring in women during their 50s, which lead to the end of the menstrual cycle and reproductive capabilities.
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Downward slide In this computer illustration, the green-glowing proteins at the end of the chromosomes are telomeres, tiny structures that help cells to reproduce. The structures appear to grow shorter and shorter with repeated use, leading eventually to reduced cell reproduction and poor self-repair by the body.
cellular clock theory theory suggesting that we age because our cells have built-in limits on their ability to reproduce. wear-and-tear theory theory suggesting we age because use of our body wears it out. free-radical theory theory suggesting we age because special negatively charged oxygen molecules become more prevalent in our body as we get older, destabilizing cellular structures and causing the effects of aging. developmental psychopathology the study of how problematic behaviors evolve as a function of a person’s genetics and early experiences and how those early problematic issues affect the person at later life stages. risk factors biological and environmental factors that contribute to problematic outcomes. conduct disorder clinical disorder in children and adolescence associated with emotional and behavioral problems, such as rule-breaking, trouble with limit-setting from authority figures, bullying and fighting with other people, and cruelty.
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throughout life, including during adulthood (Gould, 2007); and that such neurons may be the result of new learning, play a role in further learning, or both (Leuner, Gould, & Shors, 2006). Given the stability and even addition of neurons during adulthood, it is not surprising that most of our broad intellectual capabilities remain intact throughout our lives. We’re able to solve problems and process information in our adult years about as quickly as we could in our 20s (Park & Gutchess, 2006; Park et al., 2002). As we move into our 40s and 50s, however, we do begin to see some intellectual shifts. Recovering information from long-term memory starts to take a little longer, and it takes a bit longer to learn new material. During our 60s and 70s, our memories decline, as does our confidence in our ability to remember and to solve problems (Freedman et al., 2001). Overall, as we’ll discuss in Chapter 8, such declines tend to have a more significant impact on our ability to recall information than on our skill at solving problems or dealing with new situations. Why Do We Age? Scientists have offered many theories about why we age; no single explanation is widely accepted (Pierpaoli, 2005). One important theory of aging, the cellular clock theory, suggests that aging is built into our cells. Tiny structures on the ends of DNA strands, called telomeres, aid in cell reproduction but grow shorter each time they are used. Eventually they become too short, and cells can no longer reproduce themselves. As a result, the body is less able to repair itself. The various changes of aging—saggy skin and decreases in vision and memory, for example—are the direct result of those events. Two other theories of aging are more rooted in our experiences and the impact that life events can have on us. The wear-and-tear and free-radical theories suggest that years of use help wear out our bodies. The wear-and-tear theory boils down to: the more mileage we put on our bodies through living (augmented by factors, such as stress, poor diet, and exposure to environmental teratogens), the sooner we wear out (Hawkley et al., 2005). The free-radical theory provides a chemistry-oriented explanation (Boldyrev & Johnson, 2007). Free radicals are oxygen molecules that are negatively charged. A negative charge on a molecule can attract small particles of matter called electrons from other molecules. According to the free-radical theory of aging, free radicals become more prevalent in our system as we get older, increasingly destabilizing cell structures and doing progressively more damage to our bodies—resulting in the aging effects described above.
Social and Emotional Development Although the social and emotional changes that occur in adulthood are more gradual than those that characterize childhood, adults experience multiple transitions in these areas (Roberts et al., 2002, 2006; Palkovitz et al., 2001). As you saw in Table 3-8, Erikson proposed that adults travel through three major life stages—stages marked by the need to resolve conflicts between intimacy and isolation (our ability to form sustaining relationships with others), generativity and self-absorption (our ability to give back to the world and provide for the future), and integrity and despair (our ability to face our mortality with a sense of a life well lived). The journeys through each of these stages correspond to many of the rites of passage associated with adulthood, including marriage, parenting, retirement, and death—events that we’ll be discussing further throughout the book. It is worth noting that, in many societies, the timing and form of such milestones of adulthood are now more variable than they were in earlier days. In the past, for example, the length of time a couple would spend married before having their first child was relatively short. That time has extended greatly in recent decades; moreover, the number of couples who choose to remain childless has doubled since 1960 (Demo et al., 2000). It has also become more acceptable in some societies for people who are not married to raise children (Weinraub et al., 2002).
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Similarly, the average human lifespan continues to increase, lengthening the time that older adults remain part of the workforce, as well as part of the retired population, before dying (Volz, 2000). Such cultural shifts have opened new areas of study for psychologists, who are seeking to understand how these shifts may affect adult development.
Before You Go On What Do You Know? 18. What is the difference between the wear-and-tear theory of aging and the free-radical theory of aging? 19. Describe and define Erikson’s major crises of adult development.
What Do You Think? Do you think that life experiences may actually increase adults’ cognitive, or mental, abilities? Why might this be so?
Developmental Psychopathology LEARNING OBJECTIVE 8 Understand how the developmental psychopathology approach uses a developmental perspective to look at problematic behaviors.
Throughout the textbook, we will consider the ways that different psychological attributes and faculties develop and how those attributes and faculties may go wrong. We’ll examine in depth, for example, memory disorders in Chapter 8 and autism in Chapter 16. For now, however, we’ll offer just a broad understanding of how things can go wrong during development. Psychologists in the field of developmental psychopathology are interested in how problematic behavior patterns evolve, based on both genetics and early childhood experiences, and in how those early problematic patterns affect functioning as individuals move through later life stages (Hinshaw, 2008; Hudziak, 2008). Developmental psychopathologists also compare and contrast problematic behavior patterns with more normal behavior patterns, seeking to identify risk factors—biological and environmental factors that contribute to problematic outcomes. In addition, they seek to identify other factors that can help children avoid or recover from such negative outcomes. One disorder of special interest is called conduct disorder, a diagnosis applied strictly to children and adolescents. Conduct disorder (and its less severe cousin, oppositional defiant disorder) is characterized by a number of emotional and behavioral problems, including frequent rule-breaking, trouble following the limits imposed by authority figures, bullying and fighting, and cruelty. Looking at how developmental psychopathologists approach this disorder can help us understand how they approach all psychological disorders. Developmental psychopathologists focus first on the various behaviors shown by children with conduct disorders (Hinshaw, 2002) to distinguish the conduct disorder from other disorders and see whether it has any relationships to milder problems, such as impulsiveness and distractibility. The negative behaviors of conduct disorder, such as defying authority, breaking rules, and fighting, are categorized as externalizing behaviors (as opposed to internalizing behaviors, such as fearful responses, crying, or withdrawal).
Violating, hurting, and disregarding others Many children with conduct disorder wind up in trouble with the law. Here a teenager and two ten-year-olds are led from a courtroom after being accused of attacking a homeless day laborer.
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Bullying: A Continuing Problem A report examining the many school shootings that have occurred across the United States over the past decade found that bullying was a factor in most of them (Crisp, 2001). Sometimes, the shooters had been bullies; more often, they had been the victims of bullying. One survey asked children aged 8 to 15 what issues in school troubled them most, and the children pointed to teasing and bullying as “big problems” that ranked even higher than racial discrimination, AIDS, and sex or alcohol peer pressures (Cukan, 2001). Overall, over one-quarter of students report being bullied frequently and more than 70 percent report having been victimized at least once, leading in many cases to feelings of humiliation or anxiety (Jacobs, 2008; Nishina et al., 2005). In addition, our online world has broadened the ways in which children and adolescents can be bullied, and today cyberbullying—
equifinality the idea that different individuals can start out from different places and wind up at the same outcome. multifinality the idea that children can start from the same spot and wind up in any numbers of other outcomes. resilience the ability to recover from or avoid the serious effects of negative circ*mstances.
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bullying by e-mail, text-messaging, or the like—is increasing (Jacobs, 2008). In response to these alarming trends, many schools—elementary through high school—have started programs that teach students how to deal more effectively with bullies, work to change the thinking of bullies, train teachers, conduct parent discussion groups, and applied classroom prevention measures (Jacobs, 2008; Frey et al., 2005; Twemlow, 2003). Furthermore, public health campaigns have tried to educate the public about antibullying programs, including the U.S. Government’s “Stop Bullying Now” campaign. Although recognizing the negative—and potentially tragic— impact of bullying, some experts worry that the sheer prevalence of bullying may make it a very difficult problem to overcome. It is hard, for example, for educators and clinicians to identify which bullies or bullied children will turn violent given that a full 70 percent of children have experienced bullying. Can we really rid our schools and communities of a problem as common as this? One observer has even argued, “Short of raising kids in isolation chambers...bullying behaviors can never be eliminated entirely from the sustained hazing ritual known as growing up” (Angier, 2001).
Like other developmental psychologists, developmental psychopathologists look for patterns and changes over time. Some studies have suggested, for example, that when externalizing behaviors begin in early childhood, they are more likely to be due to biological factors, such as genetic inheritance (Taylor, Iacono, & McGue, 2000), placing children with early-onset conduct disorders at greater risk for problems later in life than those whose conduct problems begin in adolescence. Still other studies indicate that, although externalizing behaviors tend to be moderately stable over time, the specific forms of the behaviors do shift with age. For example, explicitly aggressive acts, such as picking fights, typically decrease over time, while less overt acts of aggression tend to increase during early adolescence (Hinshaw, 2002). It seems that many children with conduct disorder learn as a result of the negative consequences for their bad behavior, but they do not really change internally. They learn primarily to hide their aggressive behavior so that they do not get into as much trouble. Again, like other kinds of developmental psychologists, those interested in developmental psychopathology hold that behavior can be analyzed in a variety of ways. According to this view, a full accounting of how children get off-track (or stay on-track) requires looking at how genetics, environmental influences, and the children’s own psychological processes all collaborate to bring about their current pattern of behavior and functioning. Two concepts that developmental psychopathologists have provided to the field of psychology are equifinality and multifinality (Mitchell et al., 2004; Cicchetti & Rogosch, 1996). The concept of equifinality holds that individuals can start out from all sorts of different places and yet, through their life experiences, wind up functioning (or dysfunctioning) in similar ways. Multifinality follows the opposite principle. It suggests
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that children can start from the same point and TABLE 3-9 Risk Factors that Link Conduct Disorders to the Commission wind up in any number of different psychologiof Violent Crimes During Adolescence or Adulthood cal places. Applying these two concepts to conduct disorders, it appears that various roads may Family violence Multiple clinical disorders lead to the development of a conduct disorder during adolescence. A child with conduct disorFamily dysfunction/conflict Risky behavior der may have been born with a difficult temperament, experienced poor parenting, or Family distress Gun availability/risk developed poor social skills. Table 3-9 lists risk factors that link conduct disorders to the likeliChildhood exposure to violence Antisocial parent hood of committing serious and violent crimes Childhood maltreatment Gang membership during adolescence or adulthood. As suggested by the notion of equifinality, regardless of which set Childhood neglect Peer violence of risk factors is at play, the outcome is often similar. Childhood adversity Personality disorder At the same time, multifinality assures us that not every difficult baby and not every baby Substance abuse Academic failure with ineffective parents will wind up with a conHyperactivity Social incompetence duct disorder. Indeed, the vast majority will wind up with no pathology at all. Developmental psySource: FAS, 2008; Weaver et al, 2008; Gonzales et al., 2007; Lahey & Waldman, 2007; Mueser et chopathologists are very interested in the bio- al., 2006; Panko, 2005. logical, psychological, or environmental factors that help buffer against or negate the impact of risk factors—factors that help produce resilience, an ability to recover from or avoid the serious effects of negative circ*mstances (Greene, 2008; Hudziak & Bartels, 2008). In short, according to this viewpoint, it is just as critical to understand what goes right as it is to understand what goes wrong. Let’s return one more time to one of the superheroes at the start of this chapter. A developmental psychopathologist might hypothesize that Bruce Wayne faced several major risk factors for conduct disorder, including the loss of his parents when he was 8 years old, witnessing the trauma unfold, and living in social isolation afterward. The psychologist would be equally interested in identifying those factors that may have helped contribute to Bruce Wayne’s resilience, including his high socioeconomic status (he’s impossibly wealthy), his surrogate father-son relationship with his butler Alfred, his later positive parent-like relationship with his ward Dick Grayson (a.k.a. Robin), and his peer relationship with Commissioner Gordon.
Before You Go On What Do You Know? 20. How do externalizing behaviors differ from internalizing behaviors? 21. Why is resilience important to developmental psychopathology? 22. What is the difference between equifinality and multifinality?
What Do You Think? Consider problems such as anxiety and depression. Do you see any advantages to looking at emotional or mental problems from a developmental perspective, as the product of a lifetime of biological and environmental experiences, rather than just examining the symptoms displayed by people with these problems? Do you see any disadvantages to this approach?
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Summary Understanding How We Develop LEARNING OBJECTIVE 1 Understand the key debates underlying research and theory in child development. • Developmental psychology is the study of changes in our behavior and mental processes over time and the various factors that influence the course of those changes. • Key philosophical issues in the study of developmental psychology are what drives change (biological or environmental factors); what’s the nature of the change (qualitative or quantitative); and the role of early experiences in shaping later development.
• Infants make dramatic gains in both physical and psychological capabilities. Our brains grow during this period, preparing us to learn and encode the information that will organize those changes. • One of the most important developmental theorists, Jean Piaget, proposed a theory of cognitive development that suggested that through learning and self-experimentation, we help our thinking to grow progressively more complex. • Piaget believed we passed through multiple stages on the way to formal adult reasoning and that each transition was accompanied by the acquisition of a new cognitive capability. During the sensorimotor stage, in infancy, we become able to hold memories of objects in our minds.
How Is Developmental Psychology Investigated?
• Information-processing researchers have suggested that babies may develop mental capacities at earlier ages than Piaget believed they did.
LEARNING OBJECTIVE 2 Describe and discuss the advantages and disadvantages of cross-sectional and longitudinal designs for researching development.
• Attachment theory suggests that the baby is biologically predisposed to bond and form a relationship with a key caregiver, thus ensuring that his or her needs are met. The security of the attachment relationship will have later implications for how secure the person feels in his or her emotional and social capabilities.
• Two major research approaches in developmental psychology are cross-sectional (comparing different age groups to assess change) and longitudinal (studying the same group to see how responses change over time). • The cohort-sequential research design combines elements of the cross-sectional and longitudinal approaches.
• Baumrind found evidence that different parenting styles could also affect the overall well-being of the child, although subsequent research suggested that outcomes might vary depending on other environmental and cultural influences.
Before We Are Born LEARNING OBJECTIVE 3 Discuss patterns of genetic inheritance and describe stages and potential problems during prenatal development. • Our genetic inheritance comes from both parents, who each contribute half our chromosomes. Genes can combine in various ways to make up our phenotype, or observable traits. • Genetics can influence the manifestation of both physical traits and psychological traits, including temperament, although environment also plays a role. • Prenatal development begins with conception and is divided into three stages: germinal, embryonic, and fetal, each characterized by specific patterns of development. • Individuals are susceptible to multiple influences by biological and environmental forces before they are even born, during the prenatal period.
Infancy LEARNING OBJECTIVE 4 Summarize the major physical, cognitive, and emotional developments that take place during infancy.
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Childhood LEARNING OBJECTIVE 5 Summarize the major physical, cognitive, and emotional developments that take place during childhood. • Physical growth continues at a generally slower pace in childhood than in infancy. Myelination and synaptic pruning continue to shape the brain. • Piaget believed that children pass through the stages of preoperational and concrete operations thinking, learning to manipulate their mental schema. Other researchers have suggested children’s thinking may not be as limited during these stages as Piaget thought it was. • Theories of moral development have often focused on moral reasoning (the reasons why a child would do one thing or another) rather than values. Generally, research supports the movement from morality rooted in submitting to authority to morality rooted in more autonomous decisions about right and wrong. • Some researchers suggest that moral reasoning may vary across gender and culture. Other researchers have questioned whether morality theories would be better served by measuring behavior instead of expressed reasoning or attitudes.
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Adolescence
Developmental Psychopathology
LEARNING OBJECTIVE 6 Summarize the major physical, cognitive, and emotional changes that take place during adolescence.
LEARNING OBJECTIVE 8 Understand how the developmental psychopathology approach uses a developmental perspective to look at problematic behaviors.
• Adolescence is generally associated with many substantial changes, including the onset of full sexual and physical maturity, as well as reasoning capabilities that approach adult levels. However, the teenager has certain limitations that influence his or her ability to make sound judgments and avoid risky situations. • Erikson proposed a theory of development that stretched across the lifespan and incorporated various dilemmas that needed to be successfully reconciled in order for development to stay on track.
Adulthood How We Develop LEARNING OBJECTIVE 7 Describe key physical, social, and emotional changes that take place throughout adulthood.
• The developmental psychopathology approach studies how early problematic behaviors evolve as a function of a person’s genetics and early experiences and how those behaviors affect the person in later life. • Developmental psychopathologists are particularly interested in identifying the risk factors that contribute to problematic outcomes. • The concept of equifinality holds that although children may start out at different places, through their life experiences they wind up functioning (or dysfunctioning) in similar ways. The concept of multifinality holds that children can start out at the same place but may wind up in a number of different psychological places. • Developmental psychopathologists are also interested in the factors that contribute to resilience, the ability to recover from or avoid the serious effects of negative circ*mstances.
• Adult physical and psychological development is often characterized by some degree of decline. However, most basic faculties remain intact across the lifespan. • The ages at which adults are expected to reach major social and emotional milestones, such as marriage and parenting, are more flexible now in many societies than they were in the past.
Key Terms developmental psychology 57
recessive trait 63
maturation 57
codominance 63
stage 57
discrete trait 63
critical periods 59
polygenic trait 63
cross-sectional design 59
temperament 63
longitudinal design 60
zygote 64
cohort-sequential design 60
placenta 64
prenatal period 60
miscarriage 64
genes 60
teratogens 66
deoxyribonucleic acid (DNA) 60
reflexes 67
chromosomes 60
synapses 67
genotype 60
synaptic pruning 68
phenotype 60
myelination 68
allele 62
proximodistal 68
hom*ozygous 62
motor skills 68
heterozygous 63
cognitive development 69
dominant trait 63
schemata 69
assimilation 69 accommodation 69 equilibrium 69 object permanence 70 information-processing theory 70 habituation 70 attachment 72 reciprocal socialization 74 operations 77 preoperational stage 77 egocentrism 77 conservation 77 concrete operations 78 theory of mind 78 scaffolding 78 zone of proximal development 78 private speech 81
puberty 82 primary sex characteristics 82 secondary sex characteristics 82 formal operations 84 menopause 87 cellular clock theory 88 wear-and-tear theory 88 free-radical theory 88 developmental psychopathology 88 risk factors 88 conduct disorder 88 equifinality 90 multifinality 90 resilience 90
Key Terms
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CUT/ACROSS CONNECTION What Happens in the
BRAIN? • At birth we have aproximately 100 billion neurons. A newborn has around 2500 synaptic connections per neuron while a 3-year-old has six times that many connections! But a 20-yearold has only around one-third the synaptic connections per neuron of a 3-year-old, a huge reduction due to synaptic pruning. • Myelination, the formation of fatty white coverings around neurons, helps neurons transmit information more efficiently. During infancy, much of myelination occurs in brain areas tied to movement, reflexes, and sensory responses. During childhood, myelination is concentrated in brain areas that help coordinate activity, planning, and problem solving. • Despite past beliefs, no significant loss of neurons occurs in adulthood, except in cases of brain pathology. • New neurons keep being formed in certain parts of the brain throughout life, including during adulthood.
• Environmental risks, called teratogens, can influence prenatal development adversely. Thus, pregnant women should avoid risks, such as smoking or ingesting alcohol, each of which has been linked to birth defects. • Developmental psychopathologists seek to identify biological, psychological, and environmental risk factors that contribute to the development of behavioral problems and psychological disorders. • Risk factors for the development of conduct disorders in children and adults include family violence or dysfunction, childhood maltreatment, substance abuse, peer violence, and personality disorders. • Despite the appearance of such risk factors, many children do not develop conduct disorders—a phenomenon attributed to their resilience. Like risk factors, the biological, psychological, and environmental factors that help produce resilience are of enormous interest to developmental psychopathologists.
How we Develop
HOW we Differ • Only a few human traits are the product of a single gene pair. Most traits, particularly behavioral ones, are polygenic, helping to produce many variations in how traits are expressed from person to person. • Babies tend to display either an easy, difficult, or slow-towarm-up temperament, and their particular infant temperament often helps predict their reactions to situations throughout the lifespan. • On average, Kipsigis in Kenya walk a month before babies in the United States, and Ache babies in Paraguay begin walking a year later than U.S. children—variations due to cultural differences in parenting. • Babies may display either a secure, anxious/avoidant, anxious/resistant, or disorganized attachment style—a style that helps predict later relationship needs. • On average, girls experience a growth spurt during their tenth or eleventh year, a couple of years prior to boys. • Primary sex characteristics during puberty include growth of the testes for boys and growth of the ovaries for girls. Secondary sex characteristics include a deepening of the voice for boys and increase in breast size for girls. • According to some research, the higher stages of moral development of males tend to focus on justice, fairness, and other abstract moral values, whereas those of females factor in relationship needs and responsibilities.
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• •
•
•
• •
• At birth, the senses of taste, smell, and touch are highly developed, hearing is somewhat immature, and vision is extremely limited. Babies may have some sense of mathematics as early as 5 months of age. Most children do not develop a theory of mind, the ability to recognize that other persons have a perspective different from their own, prior to 3 years of age. Young children tend to make moral decisions that help ensure they will not get into trouble with parents or adults. In contrast, the moral decisions of adolescents and young adults tend to be more complex and guided by broader principles of right and wrong. Although less egocentric than younger children, many teenagers often display personal fables in which they are convinced that they are special—the first persons to have various thoughts and feelings—and perceive an imaginary audience in which they believe everyone is scrutinizing them. It is not entirely clear why we age and grow old. The human lifespan has continued to increase with each generation.
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Psychology Around Us School Days, “Cool” Days
Video Lab Exercise
Young children spending recess in their elementary schoolyard—breaking into different groups, playing various games, having all kinds of interactions. Each doing their own thing? Not really. The schoolyard conversations, physical activities, and mental processes generally follow the principles, milestones, and even rules cited in developmental stage theories. While the children recess away, your job is to identify and explain the stages of physical, cognitive, and social-emotional development reflected by their recess activities. Fast forward to adolescence and to a teenage party. Individuals finally doing their own thing? Once again, the answer is no. And once again, your job is to detect the developmental stages and principles that their “cool” behaviors, talk, and posturing reflect. As you are working on this online exercise, consider the following questions: • What does this lab exercise say about the nature-versus-nurture debate in developmental psychology? • Do the behaviors and interactions on display in the lab exercise indicate that stage differences are qualitative or quantitative? • What events and steps have helped transform the enthusiastic (but awkward) elementary school kids of one video into the “cool” (though still awkward) high school kids of the second video? • Stages or no stages, the children and teenagers in the lab exercise also show many individual differences. How did that happen?
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CHAPTER 4
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Neuroscience chapter outline •
How Do Scientists Study the Nervous System? • •
How Do Neurons Work? • •
Your
F
Brain
in
•
What Cells Make Up the Nervous System?
How Is the Nervous System Organized?
Structures of the Brain
•
Brain Side and Brain Size •
Jeopardy!
or decades, one of the most popular game shows on television has been Jeopardy! Maybe you’ve watched it
yourself, or even tried to play along at home. If so, you know that Jeopardy! is all about demonstrating brain power. It is
a quiz show where contestants compete to be the first to correctly supply “questions” in response to answer clues in a number of categories. Winning contestants must be strategic and fast, as well as having a lot of facts memorized. Even as they listen to the host preview the categories, contestants must quickly plan their strategies, deciding for example whether they know more about “British Playwrights” or “American Poets.” Then, they need speed and physical coordination; the only way to be allowed to answer a question is to be the first to press a buzzer. And of course, throughout the show, contestants must control their emotions. Jeopardy! contestants are never shown bursting into anxious tears or having angry confrontations with one another or the host. Like the Jeopardy! contestants, we all rely on our brains and our nervous systems all day long. We remember things we have learned, and we learn new things. Without a nervous system, we wouldn’t be able to register changes in the environment, nor would we be able to react to those changes.
Building the Brain Neurological Diseases
Whenever we see, hear, and speak, whether about Jeopardy! clues or what’s for dinner, we’re using our nervous system. We use it as we experience a variety of emotions over the course of the day. Like the Jeopardy! contestants, we rely on it to form plans and strategies. Sometimes, we even need it to enable us to take quick physical actions, such as pressing a buzzer. Neuroscience is the study of the nervous system. In this chapter—and in What Happens in the Brain sections of other chapters of the book—we’ll examine many of the discoveries of this fascinating field. The complexity of the adult human brain is so staggering that its study has been referred to as the “final frontier.” We’ll see in this chapter that, although considerable progress has been made in understanding the organization and function of the brain, there remain large gaps in our knowledge about how the actions of the billions of microscopic cells in the brain produce complex behaviors, such as thought. No less perplexing and impressive is the consideration of how the brain developed in the first place. Before we are even born, many millions of brain cells are arranged in an orderly fashion. Each one of them must hook up with other appropriate brain cells in order to transmit the messages that will let us breathe, eat, see, hear and think. Just as with the adult brain, we are still far from understanding exactly how the cellular events that occur during brain development are appropriately orchestrated, but progress has been made on many fronts. Amazingly, this highly complicated process works right almost all the time. Sometimes things go wrong in the nervous system, as we’ll see later in this chapter, but the overwhelming majority of people have normally functioning brains.
Neuroscience
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neuroscience the study of the nervous system. neuroimaging techniques that allow for studying brain activity by obtaining visual images in awake humans. neuron a nerve cell. dendrites the parts of neurons that collect input from other neurons. axon the part of the neuron that carries information away from the cell body toward other neurons. axon terminal the end of a neuron’s axon, from which neurotransmitters are released.
How Do Scientists Study the Nervous System? LEARNING OBJECTIVE 1 Understand the key methods that scientists use to learn about brain anatomy and functioning.
In the past, researchers on psychological issues in humans often avoided analyzing the brain, mainly for technical reasons. Until recently, it was difficult, if not impossible, to study what goes on in the human brain without causing damage to brain tissue. As a result, human neuroscience relied on one of the following methods: • Examining autopsy tissue. This method allows neuroscientists to see what our brains look like, but has the obvious drawback of telling them little about how these systems worked while the person was alive and using them. • Testing the behavior of patients with damage to certain parts of the brain. Scientists called neuropsychologists have learned a lot about the brain from studying patients with brain damage. Patients with localized brain damage often have loss of some function. The loss of function then suggests what the brain region does when it is undamaged. The obvious drawback of this approach is that it involves inferring information about the normally functioning brain from the damaged brain. Even patients with localized brain damage may have smaller undetectable abnormalities in other areas of the brain. Also, the damaged brain may undergo reorganization over time so abnormalities in behavior may not reflect what goes on in the intact brain. • Recording brain activity, or brain waves, from the surface of the scalp. Scientists have used electroencephalograms, or EEGs, to learn about the activity of our brains during certain states (awake and asleep) as well as during certain behavioral tasks. The drawback of this type of analysis is that surface recordings only provide a summary of activity over a large expanse of tissue—pinpointing the location of activity using this method can only be done in a general sense.
The brain at work This 3D computer generated image of a human brain shows areas of brain activation (colored areas) in individuals undergoing a moral decision-making task. This study employed fMRI technology which uses changes in blood flow as a measure of changes in neural activity.
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These findings have been combined with those from animal studies where specific brain regions are examined microscopically, recorded from electrically or targeted for destruction, a process called lesioning. Taken together, these approaches have provided us with a great deal of information about the brain and the nervous system in general, but they all share drawbacks. They can tell us little about activity in specific regions of healthy, living, human brains. Over the past few decades, however, several new techniques, collectively referred to as neuroimaging, have been developed to study brain activity in awake, healthy humans. These techniques enable researchers to identify brain regions that become active under certain conditions. Among the most useful neuroimaging methods are positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). PET scans enable the detection of uptake of certain molecules so that brain areas of increased activity can be identifìed. fMRI allows for the detection of changes in blood flow, a presumed indicator of changes in the activity of neurons. The availability of these neuroimaging technologies has produced an explosion of research that has infused neuroscience into virtually every area of psychological investigation. The results have confirmed many previously held claims about brain function and raised additional new questions. As the technology is rapidly developing, and neuroimaging methods become more and more sensitive, there is no doubt we will gain a better understanding of the organ that serves most human behavior: the brain.
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Before You Go On What Do You Know? 1. Describe how studies of people with brain damage and EEGs have contributed to our knowledge of the brain and nervous system. 2. What are the main advantages of neuroimaging methods over earlier neuroscience research methods?
What Do You Think? Do you think it will be possible to use neuroimaging techniques to determine what a person is thinking? What are the ethical implications of using this technology?
What Cells Make Up the Nervous System? LEARNING OBJECTIVE 2 Name the two major types of cells in the nervous system and describe the primary functions of each.
We know that the neuron, or nerve cell, is the fundamental unit of the nervous system (Jones, 2007) and that communication among neurons is necessary for normal functioning of the brain and spinal cord. The peripheral nervous system that runs throughout the rest of our bodies, outside the brain and spinal cord, is also made up of neurons. The structure and function of individual neurons, as well as how these cells work individually and in groups, called networks, has been the subject of considerable scientific inquiry for over a century (Jones, 2007). Neuroscientists have discovered that neurons have specialized structures that enable them to communicate with other neurons using both electrical and chemical signals. But neurons are not the only cells in the nervous system. As we’ll see, neuroscientists have increased their attention to glia, the other type of cell found in our nervous systems.
Neurons The human brain contains about 100 billion neurons. The basic structure of a neuron is shown in Figure 4-1. Like most of our other cells, neurons have a cell body filled with cytoplasm that contains a nucleus (the residence of chromosomes that contain the genetic material). In addition, neurons contain organelles that enable the cell to make proteins and other molecules, produce energy, as well as permit the breakdown and elimination of toxic substances. However, as Figure 4-1 shows, neurons are different from other cells, in that they have specialized structures called dendrites and axons that are important for communication with other neurons. Dendrites extend like branches from the cell body to collect inputs from other neurons. Neurons can have many dendrites and, indeed, some have very extensive dendritic “trees” that allow a single neuron to receive more than 200,000 inputs from other neurons. Axons also extend from the cell body. Unlike dendrites, however, axons typically function to carry information away from the cell body, toward other neurons. Axons have a specialized region at the end, called the axon terminal. Unlike the case with dendrites, neurons usually have only one axon. The axon can be very long. One of your axons, for example, runs from your spinal cord all the way to the end of your big toe. In addition, axons can be highly branched. These branches, or collaterals, greatly increase the number of neurons that the axon contacts.
Neurons have a cell body (shown here in this fluorescent image in blue), as well as axons and dendrites (shown in green) for communicating with other neurons.
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FIGURE 4-1 The neuron The major structures of the neuron include the cell body, the axon, and the dendrites. Dendrites typically receive information from other neurons, while axons send information away from the cell body to communicate with other neurons. Arrows indicate the direction of information flow.
Dendrites
Cell body
Axon
Axon terminal
Various shapes These drawings by the early neuroanatomist Santiago Ramon y Cajal are just two examples of the vast diversity in the shape of neurons in the brain.
There are many different kinds of neurons. Some are large, while others are relatively small. Some have very elaborate dendritic trees, while others possess a single unbranched dendrite. Although these cells all look quite different from one another, they have two features in common. All neurons are covered by a membrane that surrounds the entire neuron, including its axon and dendrites, and all have the capability of communicating with other cells by producing and sending electrical signals.
Glia In addition to neurons, the nervous system contains a large number of nonneuronal cells called glia. In fact, in some parts of the human brain, glia outnumber neurons by a factor of about 10. Their vast numbers make it surprising that glia have received relatively little attention by neuroscientists. In the past, glia were considered to be support cells, which implies a passive structural function. Discoveries over the past two decades, however, have confirmed that these cells are diverse and actively serve many purposes, that are critical for normal functioning of neurons. Although most of the rest of this chapter focuses on neurons and systems made up of neurons, glia are actively involved in nervous system function. We will return to glial cells periodically throughout the rest of this chapter.
Before You Go On What Do You Know? 3. What are the two types of cells in the nervous system? 4. What are the three major types of glia and the functions of each type?
What Do You Think? Why do you think the function of glia was overlooked by researchers for so long?
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More Than Just Glue
When glial cells were first discovered, they were given a Greek name that means “glue” because scientists believed their chief function was to hold the brain together. Now more than 100 years later, we know that glia play many roles in the brain that are crit-
ical for normal function. There are three major categories of glia, astroglia, oligodendroglia, and microglia. Astroglia are so-named because most are shaped like stars (see photo on left) – this glial type is important for creating the blood-brain barrier, a system that monitors the passage of molecules from the blood to the brain, and for regulating the flow of blood into regions with changes in neuronal activity (Iadecola and Nedergaard, 2007). Astroglia also function to take in chemicals released by neighboring neurons and to provide important growth-promoting molecules to neurons. Astrocytes will migrate to the site of brain injury, enlarge, and multiply to form a glial scar (Fitch and Silver, 2008). Astroglia also serve to communicate with neurons, influencing their electrical activity (Haydon et al., 2009). Another type of astroglia serves as a stem cell in the adult brain (Doetsch, 2003). These cells are capable of dividing and producing new cells, including new neurons. The oligodendroglia are important for providing a protective fatty sheath, or coating, called myelin that wraps around the axons of neurons. Myelin serves to insulate axons from nearby neurons. This is particularly important in the brain and spinal cord, where neurons are very closely packed and axons are often organized into bundles. Myelin also enables more efficient transfer of electrical signals down the axon. Finally, microglia, so-named because they are very small, are important for cleaning up the debris of dead cells so that brain regions can continue with their normal functioning. Microglia are an important brain defense against infection and illness.
How Do Neurons Work? LEARNING OBJECTIVE 3 Describe what happens when a neuron “fires” and how neurons send messages to one another.
Neurons send messages to one another via electrochemical events. A sudden change in the electrical charge of a neuron’s axon causes it to release a chemical that can be received by other neurons.
Your brain uses 20% of your body’s energy, but it makes up only 2% of your body’s weight.
The Action Potential As we have discussed, neurons are covered by a membrane. On both sides of this membrane, inside and outside the neuron, are fluids. Like other bodily fluids, the extracellular fluid that surrounds the outside of nerve cells contains charged particles called ions. Ions can be either positive or negative in charge. Ions are also found in the cytoplasm that fills the neuron. This gives neurons an electrical charge, even when they are resting. (When a neuron is not sending a message,
glia the cells that, in addition to neurons, make up the nervous system.
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resting potential the electrical charge of a neuron when it is at rest.
it is said to be resting) This charge, called the resting potential, is negative; the fluid inside the neuron is more negatively charged than the fluid outside the cell. If you put a very small recording electrode into an axon, it will read a negative charge, typically ion channels pores in the cell membrane that open and close to allow certain ions into and around –70 millivolts, relative to outside of the cell. out of the cell. The neuron’s membrane exhibits selective permeability to ions. Embedded in the action potential a sudden positive change in the membrane are specialized ion channels, or pores, that only allow the passage of cerelectrical charge of a neuron’s axon. Also known tain ions into and out of the cell. These ion channels can open or close depending on as a spike, or firing, action potentials rapidly information the cell receives from other neurons. Some of the key ions that are transmit an excitatory charge down the axon. involved in determining the resting potential are the positively charged ions sodium (Na⫹) and potassium (K⫹) and the negatively charged chloride (Cl⫺) ion. When the neuron is at rest, positive sodium ions are higher in concentration outside of the cell. This concentration gradient changes dramatically when the cell is activated by other neurons. When information received from other neurons is positively charged, or excitatory, and reaches a certain threshold, an event begins at the axon, known as an action potential. The action potential is shown in Figure 4-2. During an action potential (also known as a spike), ion channels that allow the passage of sodium (Na⫹) through the membrane open rapidly. This enables Na⫹, which is present in higher concentrations outside of the axon, to rush through the Na⫹ channels into the axon. The sudden influx of positive ions shifts the electrical charge of the axon, from negative to positive. At the peak of the action potential, the membrane charge is about ⫹50 mV. As Figure 4-2 shows, the action potential travels down the axon, away from the cell body toward the terminal. As each portion of the axon spikes, or fires, the Na⫹ channels on the next patch of membrane open, letting the spike continue its progress toward the axon terminal. After the action potential has passed a particular segment of the axon, the membrane works to restore the resting potential by using specialized proteins to pump K⫹ ions out of the cell. Action potentials are not graded— there cannot be weaker or stronger action potentials. They follow an all-or-none principle. If the stimulation reaching the neuron exceeds a certain threshold, it fires; otherwise, it does not. To facilitate the transfer of the action potential down the axon, the axons of many neurons are insulated by (a) This figure shows an action potential occurring along a segment of the axon membrane. During an action potential, Na+ channels in the axon membrane myelin, produced by specialized glial cells. open and Na+ enters the cell, giving the membrane a more positive charge. Wrapped areas of the axon are broken up at regular intervals by regions that expose the neuronal membrane to the extracellular fluid. These regions are called nodes of Ranvier. As shown in Figure 4-3, action potentials travel very quickly down myelinated axons by jumping from node to node.
(b) As the action potential moves past a certain patch of membrane, the membrane works to restore the resting potential by closing the Na+ channels so no more Na+ enters the cell. K+ channels are opened and K+, which is more concentrated inside the cell, exits through the channels. Thus, the resting potential is restored.
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FIGURE 4-2 The action potential
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Nodes of Ranvier
Myelin sheath
Axon
–– ++ ++ ––
Action potential
FIGURE 4-3 Nodes of Ranvier The nodes of Ranvier are the regions of bare axon that are between areas wrapped in myelin. Action potentials travel down the axon by jumping from node to node.
–– ++ ++ ––
Axon
Node of Ranvier
After it fires, the neuron cannot fire again for a short time, known as a refractory period. Immediately following an action potential, the axon is completely unable to fire no matter how strong the stimulus to the neuron. This time is called the absolute refractory period. During the relative refractory period, which begins a little later, the cell can fire if it is given a strong enough stimulus, but the threshold for spiking is higher than usual. Since action potentials are all-or-none, they don’t convey a lot of specific information. However, the pattern of action potentials, whether they occur in rapid succession or at a slow pace, whether they are regular or more sporadic, can provide a neural code that is specific.
Communication Across the Synapse Once the positive charge of an action potential reaches the axon terminal, it stimulates special events that enable the passage of information to other neurons. Neurons are not physically connected to one another; they are separated by small gaps. These gaps, called synapses, are tiny spaces (about 20 nm or 0.00002 mm wide) usually between the axon terminal of one cell and the dendrite of another cell by which neurons communicate. Communication across these spaces involves specialized chemicals called neurotransmitters. Neurotransmitter molecules are usually contained within small synaptic vesicles in the axon terminal, also known as the presynaptic terminal, of the neuron sending information. When the spike reaches the presynaptic axon terminal, it causes the release of neurotransmitter molecules into the synapse. As Figure 4-4 shows, the neurotransmitter then diffuses across the synapse and binds to neurotransmitter receptors on the dendrite of the receiving, or postsynaptic, neuron. Neurotransmitter receptors are proteins in the cell membrane that recognize specific molecules. They operate in a lock and key fashion, so that receptors can only receive the specific neurotransmitter that “fits” them. When a neurotransmitter binds to a receptor, the combination stimulates an electrical event in the postsynaptic membrane. These electrical events, called postsynaptic potentials, can be excitatory or inhibitory. The electrical response of the postsynaptic cell is determined by the receptor. If the receptor has an excitatory action, then the postsynaptic cell will be depolarized; the membrane potential will become less negative. Depolarizations that arise from inputs of a single neuron may not be
myelin a fatty, white substance, formed from glial cells, that insulates the axons of many neurons. absolute refractory period a short time after an action potential, during which a neuron is completely unable to fire again. relative refractory period just after the absolute refractory period during which a neuron can only fire if it receives a stimulus stronger than its usual threshold level. synapses tiny spaces between the axon terminal of one neuron and the next neuron through which communication occurs. neurotransmitters specialized chemicals that travel across synapses to allow communication between neurons. synaptic vesicles membrane-bound spheres in the axon terminals of neurons where neurotransmitters are stored before their release. neurotransmitter receptors proteins in the membranes of neurons that bind to neurotransmitters. postsynaptic potentials electrical events in postsynaptic neurons, that occur when a neurotransmitter binds to one of its receptors.
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Action potential 1
Presynaptic terminal Synaptic vesicle Synapse
2
3
Membrane of postsynaptic neuron
Neurotransmitter receptors
Neurotransmitter receptors
Neurotransmitter
Ion channels open
FIGURE 4-4 Communication across the synapse (1) A positive charge reaches the end of the axon; (2) the positive charge stimulates release of neurotransmitters contained in membrane-bound vesicles into the synapse; (3) neurotransmitters bind to receptors on the postsynaptic neuron; ion channels open and electrical charge in postsynaptic neuron changes.
great enough to trigger an action potential in the postsynaptic neuron, but when summed with other excitatory inputs to the same neuron, the threshold will be reached and the neuron will fire. This will then send the information on to the next neuron in the chain. Alternatively, if the neurotransmitter has an inhibitory action, then the postsynaptic cell will be hyperpolarized: its membrane potential will become more negative. Hyperpolarization makes it less likely that the postsynaptic neuron will fire an action potential. Compared to the action potential, which is an all-or-none depolarization, postsynaptic electrical events are much more varied. As described above, they can be depolarizing or hyperpolarizing and graded in strength. In addition, postsynaptic events at individual synapses can change with experience. Repeated release of neurotransmitter into the synapse can result in long-lasting changes in neurotransmitter receptors located on the postsynaptic membrane (CostaMattioli et al., 2009). Glial cells also release chemicals, called gliotransmitters, that can cause long-term changes in postsynaptic membranes (Angulo et al., 2008). These receptor changes may make the postsynaptic response stronger or weaker, depending on the characteristics of the input. Change in the nervous system is generally referred to as plasticity. Plasticity at the synapse, such as the changes that occur from repeated release of neurotransmitters, is called synaptic plasticity. Neuroscientists have studied synaptic plasticity extensively because evidence suggests that it may explain some types of learning as we will describe further in Chapter 7.
Neural Networks
Neural network Neurons form circuits or networks that expand the communications among different brain regions. This image shows axons and dendrites (red) extending from the neuronal cell bodies (shown in blue).
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In the brain, the number of neurons involved in a neural circuit is typically much greater than two. Collections of neurons that communicate with one another are referred to as neural circuits or neural networks. Given that the human brain contains about 100 billion neurons, each of which receives numerous synaptic inputs from a multitude of other neurons, the computational power of this organ is vast. Some clusters of neurons in specific brain regions communicate more heavily with those of other specific regions—these combinations participate in certain functions. Neuroscientists have focused attention on individual neural systems in order to better grasp the functioning of neural circuits related to specific behaviors.
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Before You Go On What Do You Know? 5. 6. 7. 8.
How do neurons work? What happens in the axon of a neuron during an action potential? neural circuits or neural networks collections When an action potential reaches the axon terminal, what happens? of neurons that communicate with one another. How does a postsynaptic neuron receive and respond to messages from other neurons?
What Do You Think? Long axons are vulnerable to damage – what do you think some advantages might be of having a neuron with a very long axon (for example, one with a cell body in the spinal cord and axon terminal in the toe or finger)?
How is the Nervous System Organized? LEARNING OBJECTIVE 4 Name and describe the functions and subdivisions of the two major parts of the nervous system.
plasticity change in the nervous system. somatic nervous system all the peripheral nerves that transmit information about the senses and movement to and from the central nervous system.
As shown in Figure 4-5, the human nervous system can be divided into two main components: the central nervous system and the peripheral nervous system. The central nervous system consists of the brain and spinal cord. The peripheral nervous system consists of the nerves that extend throughout our bodies to provide a means for sending information back and forth between the periphery (for example, your arm) and the central nervous system.
The Peripheral Nervous System The peripheral nervous system consists of the somatic nervous system and the autonomic nervous system. The somatic nervous system consists of all of the nerves that gather sensory information (typically about touch and pain) from all over the body, neck, and head, and deliver it to the spinal cord and brain, as well as the nerves that send information about movement from the central nervous system to the muscles of Nervous System
Central Nervous System
Spinal Cord
Peripheral Nervous System
Brain
Central Nervous System
Somatic Nervous System
FIGURE 4-5 Organization of the nervous system The nervous system is divided into the central nervous system (consisting of the brain and spinal cord) and the peripheral nervous system (consisting of the somatic nervous system and the autonomic nervous system). The autonomic nervous system is further subdivided into the sympathetic and parasympathetic nervous systems.
Autonomic Nervous System
Sympathetic Nervous System
Parasympathetic Nervous System
Somatic Nervous System Autonomic Nervous System
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The social kind of threat The sympathetic nervous system doesn’t distinguish between threats of physical harm or situations of social stress. It arouses the body to respond to both, with physiological reactions such as dry mouth, lack of appetite, or pounding heart.
the body, neck, and head. As we will see shortly, the somatic nervous system doesn’t serve any function without the integrating capacity of the central nervous system. Even very simple reflexes require the central nervous system. By contrast, parts of the autonomic nervous system operate, in large part, without help from the central nervous system. The autonomic nervous system can be subdivided into two parts: the sympathetic nervous system and parasympathetic nervous system. Both components of the autonomic nervous system consist of collections of nerve cells and their axons distributed throughout the body. However, they serve opposing functions. The sympathetic nervous system is activated under conditions of stress, whereas the parasympathetic nervous system is inhibited during those times, but active during more restful times. The sympathetic nervous system is responsible for the “fight-or-flight” reaction, the physiological response that enables us to respond to potentially life-threatening situations. The parasympathetic nervous system, on the other hand, is important for controlling basic functions that occur when the individual is not at immediate risk. For instance, digestion is a function under the control of the parasympathetic nervous system. Not surprisingly, when stressful situations occur and the sympathetic nervous system is activated, digestion stops. This makes good adaptive sense. Energy spent digesting food could be diverted to serve other functions (such as increasing blood flow to the leg muscles) so that the individual can escape the threatening situation. Sometimes the sympathetic nervous system is activated when humans are not necessarily at risk of bodily harm, but under social situations where the major fear is one of embarrassment and humiliation, such as competing on Jeopardy! You don’t have to be on television to experience a sympathetic nervous system response, however. Have you ever given a speech in front of a group of people? Many people experience a strong stress response to such situations. They develop a rapid heart rate and a dry mouth, signs that the sympathetic nervous system has kicked in. Although this reaction can be particularly disturbing, given that it often lessens the quality of your speech, it is a clear example of stress activating a physiological system. Mentally reframing such experiences as exciting opportunities can lessen the negative effects of stress. Some aspects of the autonomic nervous system, such as the components that regulate digestion, are active without input from the central nervous system, often abbreviated as CNS, but activation of the sympathetic nervous system definitely requires input from the brain, since recognizing and responding to an experience as stressful requires the CNS. We talk more about the role of the brain in stress in Chapter 15.
autonomic nervous system portion of the peripheral nervous system that includes the sympathetic and parasympathetic nervous systems.
The Central Nervous System
sympathetic nervous system the division of the autonomic nervous system activated under conditions of stress.
The Spinal Cord The spinal cord extends from the base of the brain down the back. The spinal cord is very important for gathering information from the body and sending it to the brain as well as for enabling the brain to control movement of the body. As described earlier, the somatic nervous system operates in concert with the CNS to integrate sensory information with motor output. In most cases, this integration involves the brain (voluntary movement, for example, requires brain involvement). However, some very basic functions, including reflexes, involve just the somatic nervous system and the spinal cord. Have you ever stepped on something sharp, possibly a tack, and pulled your foot back before you even get a chance to yell “ouch”? This rapid reaction is the result of activity in the pain reflex circuit of your spinal cord, as shown in Figure 4-6. Simple circuits consisting of three neurons—a sensory neuron whose cell body is located out in the periphery but whose axon travels into the spinal cord; a connecting neuron, called an interneuron;
parasympathetic nervous system the division of the autonomic nervous system active during restful times. spinal cord portion of the central nervous system that extends from the base of the brain and mediates sensory and motor information. interneuron neuron that typically has a short axon and serves as a relay between different classes of neurons. In the spinal cord, interneurons communicate with both sensory and motor neurons.
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As we’ve noted, the CNS consists of the spinal cord and the brain.
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1 In a simple reflex circuit, the axon of a sensory neuron (for example, in your foot) sends pain information to the spinal cord
Spinal cord (cross section)
Signal to brain
Sensory neuron
Motor neuron
3 The pain information also travels to the brain but takes more time because it must cross more synapses Interneuron
2 The sensory neuron synapses with an interneuron which in turn connects with a motor neuron; the motor neuron initiates a muscle response Reflex
Muscle responds by contracting
FIGURE 4-6 The reflex circuit of the spinal cord Sensory information travels into the spinal cord where it synapses on interneurons. Interneurons send information to the motor neurons, which then send impulses back out to the periphery to induce movement.
and a motor neuron whose cell body is located in the spinal cord and whose axon travels out to the body—can control pain reflexes without any communication with the brain. Pain information also travels up to the brain and enables you to vocalize about the pain and carry out other movements, such as hobbling to a chair, sitting down, and pulling the tack out, but these reactions are slower than the reflex because the information must travel greater distances and more importantly, it must travel across many more synapses (information flows more slowly across synapses because synaptic communication involves the flow of chemicals as well as receptor events, both of which take more time than it takes for action potentials to travel down the axon).
Spinal Cord Injuries In addition to controlling simple reflexes, the spinal cord is very important for carrying sensory information up to the brain and motor information back out to the body. When the spinal cord is damaged such that the flow of information to and from the brain is disrupted, individuals become paralyzed, as well as incapable of noticing touch or pain sensations on the body. The higher up the spinal cord the damage occurs (the closer it occurs to the brain), the larger the proportion of the body that is afflicted. Thus, when individuals break their necks and permanently damage the spinal cord close to the brain, they lose touch and pain sensation everywhere but their heads and faces, and they become quadriplegic, paralyzed everywhere but the head and neck. If the damage occurs farther down the back, then they may retain sensation and usage of the upper limbs and torso but not of the lower limbs. Since spinal cord damage is so devastating and afflicts such a large number of young people (about 11,000 new cases in the U.S. each year, the majority of which are between the ages of 18 and 30), scientists have directed attention to finding ways to enhance regeneration of severed axons in the spinal cord, as well as the potential replenishment of motor neurons destroyed by injury (Barnabé-Heider et al., 2008). Although some progress has been made in the treatment of spinal cord injury, there is much work to be done. In most cases, spinal cord injury results in permanent loss of function. How is the Nervous System Organized? 107
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Before You Go On What Do You Know? 9. What are the two parts of the central nervous system? 10. What happens when the sympathetic nervous system is operating? How does that compare to the operation of the parasympathetic nervous system? 11. How do the brain and spinal cord work together? 12. What neuron types are important for simple reflexes? 13. What determines how much disability will result from a spinal cord injury?
What Do You Think? Describe an occasion when you’ve experienced the workings of the sympathetic nervous system. Have you ever been able to control your sympathetic or parasympathetic reactions? If so, how?
Structures of the Brain brainstem or medulla the part of the brain closest to the spinal cord that serves basic functions. reticular formation a brain structure important for sleep and wakefulness. serotonin neurotransmitter involved in activity levels and mood regulation.
LEARNING OBJECTIVE 5 List key structures of the brain and describe their relationships to our behavior.
Like the spinal cord, different parts of which integrate information from and about different parts of the body, the brain is also divided into regions, which serve varying functions. Figure 4-7 shows the major structures of the brain.
The Brainstem The part of the brain closest to the spinal cord is called the brainstem or medulla. The brainstem is important for basic bodily functions, including respiration and heart rate regulation. Although most of the actions of the brainstem occur without our conscious knowledge or involvement, this part of the brain is critical for survival and normal functioning. Damage to the brainstem, as a result of stroke or trauma, is often fatal.
Thalamus Neocortex
Hypothalamus Substantia nigra Pituitary gland Reticular formation
Cerebellum Amygdala
Brainstem Hippocampus
FIGURE 4-7 Major structures of the brain The brain is subdivided into several major structures, each with specific functions.
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The brainstem is also important for integrating information about pain and touch from the head and neck with motor output. Neurons from the face, mouth, and tongue related to touch, pain, pressure, and vibration send inputs into the CNS that connect first in the brainstem. Parts of the brainstem are important for controlling eye movement, tongue movement, and facial expressions. Several neuron groups, or nuclei, in the brainstem work together to form an area known as the reticular formation, which is important for sleep and wakefulness. Groups of neurons in the reticular formation are the major brain source of the neurotransmitter serotonin. These serotonin neurons send axons throughout the brain. Brain serotonin has been implicated in a number of important functions, such as activity levels and mood regulation (Lowry et al., 2008). Several popular drugs for depression and anxiety are those that increase the action of serotonin.
pons part of the brain anterior to the brainstem that includes the locus coeruleus. norepinephrine neurotransmitter important for arousal and attention. cerebellum part of the brain, near the back of the head, important for motor coordination. substantia nigra brain region important in fluidity of movement and inhibiting movements. dopamine neurotransmitter plentiful in brain areas involving movement and rewards. thalamus an area of the brain that serves as a relay station for incoming sensory information.
The Pons Above the brainstem is a region called the pons. This part of the brain also contains cell groups, such as the locus coeruleus, that belong to the reticular formation. Neurons of the locus coeruleus have long axons projecting throughout the brain and spinal cord. These neurons use the neurotransmitter norepinephrine and are important for arousal and attention (Viggiano et al., 2004).
The Cerebellum Sitting at the back of the brain, connected to the brainstem by the pons, is the highly convoluted cerebellum. This part of the brain is important for motor coordination. People with cerebellar damage often have an awkward gait and have difficulty reaching for objects without trembling. In addition to its role in motor coordination, the cerebellum is important for certain types of learning involving movement. For example, when you learn to tie your shoelaces or to play the piano, your cerebellum is at work. Other parts of the brain participate as well, particularly in cases where the task involves paying attention to a complicated series of instructions. The cerebellum then stores the learned motor information to be recalled automatically once it’s completely learned.
The Midbrain Above the pons sits a collection of brain regions collectively called the midbrain. The midbrain contains a number of different nuclei, including an area called the substantia nigra. Like the cerebellum, the substantia nigra is important for movement, but this area serves different functions from those of the cerebellum. Neurons in the substantia nigra that produce a neurotransmitter called dopamine communicate with other brain regions located in the forebrain. These pathways are critical for fluidity of movement as well as inhibition of movement. This brain region is the major structure damaged in a neurological disorder called Parkinson’s disease (Cenci, 2007) that we discuss in more detail later in this chapter.
A convoluted brain region The cerebellum has many folds on its surface, shown here in this fluorescent image of a slice through this part of the brain.
The Thalamus The thalamus is a large collection of nuclei located anterior to, or in front of, the substantia nigra. Many of the thalamic nuclei serve as relay stations for incoming sensory information. In fact, all of our sensory systems, with the exception of the sense of smell, have a major pathway that synapses in the thalamus. Two major components of the thalamus are the lateral geniculate nucleus (LGN) and the medial geniculate nucleus (MGN). The LGN is important for relaying information about visual stimuli and the MGN is important for relaying information about auditory stimuli. Structures of the Brain
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The Hypothalamus
“
Adopting the right attitude can convert a negative stress into a positive one. —Hans Selye, Canadian physiologist and founder of field of stress research
”
The hypothalamus is aptly named because this collection of nuclei sits beneath the thalamus (the prefix hypo- comes from ancient Greek for below or under). Regions of the hypothalamus are important for a number of motivational processes, including eating, drinking, sex, and maternal behavior. Damage to discrete parts of the hypothalamus can alter these basic behaviors dramatically. The hypothalamus is also critical for the control of the endocrine, or hormonal, system.
The Pituitary Gland and the Endocrine System The hypothalamus is connected to a structure called the pituitary gland. The pituitary works with the hypothalamus to control a particular class of chemical messengers in the body—hormones—that are important for growth, reproduction, metabolism, and stress. There are two parts of the pituitary gland, the anterior pituitary and the posterior pituitary. The anterior pituitary is connected to the hypothalamus via blood vessels that allow it to receive signaling molecules from specific neuron groups of the hypothalamus. These parts of the hypothalamus communicate with the anterior pituitary to release various peptides, chemicals that can act as hormones themselves (such as growth hormone) or that can work to stimulate the release of hormones from endocrine glands in the periphery. There are a number of key endocrine glands. The anterior pituitary produces releasing factors that control endocrine glands, such as the ovaries, the testes, the thyroid, and the adrenal glands. The ovaries and testes are sex glands, or gonads. They produce our reproductive hormones: estrogen and progesterone for the Hypothalamus ovaries, testosterone for the testes. The thyroid gland produces thyroid hormones that are important for metabolism. The adrenal glands produce hormones that are critical for (–) responding to stressful situations. As shown in Figure 4-8, the hypo(+) thalamus, pituitary, and adrenals work together in a system called the Anterior hypothalamic-pituitary-adrenal (HPA) axis, which is an important pituitary component of the stress response. The HPA axis works in concert with activation of the sympathetic nervous system to maximize our chances of survival under adverse conditions. Negative(–) Our hormones not only affect organs and muscles throughfeedback out the body, they also provide feedback and interact with the brain. Hormones of the ovaries, testes, thyroid, and adrenals are small molecules that readily cross the blood-brain barrier. In the brain, one of their major actions is to provide a negative feedback sig(+) nal. For example, when high enough levels of adrenal stress hormones Adrenal (+) gland (called glucocorticoids or cortisol in humans) reach the hypothalamus, they provide a feedback signal to stop further stimulation to the HPA axis. In addition to their actions in negative feedback, hormones of the ovaries, testes, thyroid, and adrenals have been shown to influence the functioning of our neurons as well as biochemistry and growth, both during develCortisol opment and in adulthood. Thus, the appropriate control of the pituitary releasing factors by the anterior pituitary is critical for numerous functions. FIGURE 4-8 The hypothalamic-pituitary-adrenal Like the anterior pituitary, the posterior pituitary is also connected to the hypo(HPA) axis In response to stress, the HPA axis is activated. The hypothalamus produces a hormone that stimthalamus, this time by a bundle of axons. The parts of the hypothalamus that comulates the anterior pituitary to release another hormone municate with the posterior pituitary do so by sending nerve impulses to the posterior into the blood stream. The adrenal gland then releases pituitary. The posterior pituitary also plays a role in the endocrine system. Activation the stress hormone cortisol. Cortisol travels to the brain and shuts off the HPA axis via negative feedback. of the posterior pituitary leads to the release of hormones called neuropeptides into
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the blood stream. These hormones are oxytocin, important for nursing, and vasopression, important in regulating blood pressure. Oxytocin and vasopressin are also produced by neurons within the rest of the brain, where they act as neuromodulators, chemicals that work at the synapse to modify the actions of neurotransmitters. Brain oxytocin and vasopressin have been implicated in social behavior, including pair bonding and parental care, as well as in stress responses (Donaldson & Young, 2008).
The Amygdala The amygdala is located deep within the brain, in a region referred to as the temporal lobe. Like the thalamus and hypothalamus, the amygdala is not a hom*ogeneous structure. Instead, it is a collection of nuclei that serve different functions. The amygdala is involved in recognizing, learning about, and responding to stimuli that induce fear (LeDoux, 2007). This brain region has been the focus of considerable attention by neuroscientists because it may be involved in the development of phobias, or abnormal fears. In addition, the amygdala has been implicated in processing information about more positive emotions.
The Hippocampus The amygdala communicates with the hippocampus, a brain region important for certain types of learning and memory. Neuroscientists have extensively studied individuals with damage to the hippocampus and found that they are incapable of forming new episodic memories, or memories about events (described in more detail in Chapter 8). Destruction of the hippocampus in adulthood doesn’t wipe out all memories of early life or one’s identity, merely those that occurred relatively close to the time of brain damage. This suggests that the hippocampus only temporarily stores information about events (Squire et al., 2004). In addition to its role in the formation and transient storage of episodic memories, the hippocampus is important for learning about one’s spatial environment. Learning how to navigate around a new campus, for instance, requires the hippocampus. Animal research shows that the hippocampus has neurons called “place cells” that show changes in activity only when the animal is located in a specific location in space (Moser et al., 2008). Unlike the situation for the temporary role of the hippocampus in episodic memory, the hippocampus seems to retain its critical role in the storage of spatial navigation information for a long time, perhaps an entire lifetime. The hippocampus doesn’t consist of well-delineated collections of neurons or nuclei. Instead, it is organized in regions and layers. Because of the layered structure of the hippocampus, neuroscientists have been able to both record from and stimulate individual parts of the hippocampus, so that much of the function and connectivity of this brain region has been studied. The hippocampus is a major site of plasticity, or the ability of neurons to change, as we described earlier. Neurons in the hippocampus show both synaptic and structural plasticity. In fact, it is a region known to produce entirely new neurons in adulthood (Gould, 2007, Cameron & McKay, 2001). The function of these new neurons remains unknown, but their presence suggests that the adult brain is capable of regenerative processes, and furthermore, that the process of neuron birth, or neurogenesis (which we discuss in more detail later in this chapter), may be harnessed for purposes of brain repair. We will return to the hippocampus at length when we discuss learning and memory in Chapters 7 and 8.
The Striatum Located more toward the midline of the brain are the striatum and its related structures. This brain region works with the substantia nigra to produce fluid movements, such as those needed to hit the buzzer as a Jeopardy! contestant. Damage to either of these brain
The amygdala in action The amygdala processes the stimuli that elicit fear, such as when one is out alone on a dark night.
hypothalamus brain structure important for motivation and control of the endocrine system. endocrine system the system that controls levels of hormones throughout the body. pituitary gland brain structure that plays a central role in controlling the endocrine system. amygdala brain area involved in processing information about emotions, particularly fear. hippocampus brain region important for certain types of learning and memory. striatum a brain area that works with the substantia nigra to enable fluid movements.
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regions produces a collection of debilitating motor symptoms, such as uncontrollable shaking. In addition to its role in movement, the striatum is important for certain types of learning and memory (Grahn et al., 2008), namely those that do not require conscious awareness. As we will see in the later chapters on learning and memory, we learn some information unintentionally and often are unaware that learning has occurred. Under some circ*mstances, this ability involves the striatum. Occipital lobe
Frontal lobe
Parietal lobe
The Nucleus Accumbens Temporal lobe
FIGURE 4-9 The lobes of the neocortex The neocortex can be subdivided into four lobes—frontal, parietal, occipital, and temporal.
Anterior to the striatum is a brain region called the nucleus accumbens, an area important for motivation and reward learning (Goto & Grace, 2008). It receives important projections from neurons in the midbrain that use dopamine as a neurotransmitter. Dopamine release in the nucleus accumbens has been associated with reward learning and has been implicated in drug abuse (Nestler, 2004). All of the above-mentioned brain regions are collectively referred to as subcortical because they are located beneath the largest and most complex part of the human brain: the neocortex.
The Neocortex The human neocortex is huge, much too large to fit in the skull if it were stretched out. This is the reason why the human brain is all folded on the surface. The neocortex has many convolutions or folds that enable it to cram a large number of neurons into a head small enough to be supported by the human neck. The neocortex is highly developed in humans and is responsible for many of our most complex behaviors, including language and thought. Although some of the functions of neocortical regions are not well understood, there is consensus among neuroscientists that within the neocortex, there is localization of function. This means that certain parts of the neocortex are important for specific behaviors or abilities. At the most macroscopic level, the neocortex can be subdivided into four different parts or lobes, as shown in Figure 4-9: occipital, temporal, parietal and frontal. Within each of these regions, there are two major classifications:
Parallel processing Air traffic controllers must react to an array of sensory stimuli and make quick decisions. Communication among the association cortex within and between the lobes of the brain allows us to perform such complex functions simultaneously.
1. Primary sensory and/or motor areas. These areas are responsible for processing basic information about the senses as well as for producing signals that lead to voluntary movement. As we will see, many of the primary sensory and motor parts of the neocortex process information related to the opposite, or contralateral, side of the body. 2. Association cortex. Association cortex in each region is responsible for many complex functions, including higher-order sensory processing, integrating information from different senses (how you know that an object that looks like a violin is producing the music), thinking, planning, and other complex functions. The Occipital Cortex The occipital cortex, the cortical area at the back of the skull, contains primary sensory regions important for processing very basic information about visual stimuli, such as orientation and lines. As shown in Figure 4-10, visual information arrives in the occipital cortex via partially crossed connections. The visual information from each eye that is closest to the midline between the two eyes is actually projected to the opposite side of the brain. As a result, the representation of your left visual field is on your right primary visual cortex, and vice versa. Association areas in the occipital cortex integrate information about color, complex patterns, and motion. Since vision is such an important sense for primates, the occipital
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FIGURE 4-10 The visual system is a partially crossed pathway Visual cues from the temporal (toward the side) part of the visual field are sent to the opposite side of the brain, while those of the medial (toward the nose) part of the visual field are transmitted to the same side of the brain.
Left visual field
Visual area of left hemisphere
Right visual field
Visual area of right hemisphere
cortex is very well developed in humans. Although the occipital cortex is often referred to as the visual cortex, it’s important to realize that visual information is also processed in other parts of the neocortex. In fact, some estimates suggest that 50 percent of the human neocortex is devoted to some sort of visual task! Connections to other parts of the neocortex enable us to hook up visual information with information from other sensory modalities as well as with our memory stores (for example, connecting the sight of a potato chip with its smell, taste, sound when crunched, feel, and memories of having that type of food in your past). This serves as an important reminder that no brain region operates entirely on its own. Each receives input from other areas and communicates with many other regions to produce integrated responses. The Temporal Cortex The temporal cortex is located on the sides of the head within the temporal lobe. It wraps around the hippocampus and amygdala. The temporal cortex includes areas important for processing information about auditory stimuli, or sounds. Abnormal electrical activity in the temporal cortex, such as what occurs with seizures or epilepsy, has been shown to result in auditory hallucinations. People who have epileptic seizures centered in this region sometimes “hear” in their minds very loud music during seizures. Neurosurgery to remove a region causing seizures is particularly dangerous in this part of the brain since there are so many critical functions that may be disrupted.
nucleus accumbens a brain area important for motivation and reward. neocortex the largest portion of the brain, responsible for complex behaviors including language and thought. association cortex areas of the neocortex responsible for complex functions, including higher-order sensory processing, thinking, and planning. occipital cortex lobe of the neocortex at the back of the skull, important for processing very visual information. temporal cortex part of the neocortex important in processing sounds, in speech comprehension, and in recognizing complex visual stimuli, such as faces.
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FIGURE 4-11 Major brain regions important for speech production and language comprehension Broca’s area, located in the frontal lobe, is critical for speaking and Wernicke’s area, located in the temporal lobe, is critical for understanding language.
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Cross-section through primary motor strip (in frontal lobe)
Frontal lobe Primary motor strip Somatosensory strip Parietal lobe
FIGURE 4-12 Motor and sensory cortices are organized according to body parts Areas of motor cortex that control the movement of specific body parts and those of somatosensory cortex that receive tactile information are grouped according to body parts. Some regions are overrepresented, including the mouth and hands.
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The Parietal Cortex The parietal cortex is localized on the top middle of the brain. The primary sensory parts of this cortical region are critical for processing information about touch or s somatosensory stimuli: our senses of touch, pressure, er ng Fi vibration, and pain. The parietal cortex contains a b um Th region known as the somatosensory strip, a band of e Ey cortex that processes tactile information about se No different body parts. As Figure 4-12 shows, this Genitals e Fac area of the brain forms a systematic body map, Lips but one in which some parts of the body are Teeth represented more than others. For instance, Gums somatosensory information about the lips Jaw (which are particularly sensitive) occupies Tongu e Ph a greater amount of cortex than does ary Int raa nx bd somatosensory information about the elbow. om ina l In addition, the parietal cortex plays an Cross-section through somatosensory strip important role in the higher-order processing (in parietal lobe) of visual stimuli. As we will see in Chapter 5 on sensation and perception, processing visual stimuli involves localizing visual cues in space. The parietal cortex contains a system known as the “where pathway” that enables us to see and respond to visual information in a spatially appropriate way. People with damage to the “where pathway” can find it impossible to pour water from a pitcher into a glass. This deficiency is not due to a motor disturbance, but rather to an inability to properly determine where the glass is located relative to the pitcher. Trunk
Broca's area
For instance, the temporal cortex also contains regions important for language comprehension (Damasio et al., 2004). Shown in Figure 4-11, this area, called Wernicke’s area, is located on the left side of the brain in the vast majority of humans (over 90 percent). (This is a good example of a phenomenon called lateralization of function, which means Wernicke's that the particular ability is localized to one side of the brain. We will return to this area general issue later in the chapter.) Wernicke’s area communicates with other areas, including a region located in another cortical area important for the recognition of appropriate syntax (language rules) and the production of speech. In addition to the temporal cortex involvement in hearing and language comprehension, this lobe plays important roles in learning and memory as well as in recognition of objects via visual cues. Regions of the temporal cortex respond to complex visual stimuli, such as faces (Gross, 2005). Neuroimaging studies have shown that parts of this brain region are activated when people view photos of faces, particularly those of familiar faces. These findings are strengthened by the fact that recording electrodes placed into these same brain regions show changes in neuronal activity, or firing rate, when the same complex visual stimuli are presented (Seeck et al., 1993). At first consideration, the presence of neurons that respond to faces in the temporal cortex might suggest that direct projections from the eye activate a set of cells in the temporal lobe that are programmed to respond to complex visual stimuli. This is not the case though. The “face cells” in the temporal cortex respond to faces because they receive inputs from visual areas in the occipital cortex as well as memory centers in the brain, allowing for the recognition of faces previously seen. Ne ck He ad Arm Elb ow Fo re ar Ha m nd
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The Frontal Cortex Located at the front of the brain (behind the forehead) is the frontal cortex. The frontal cortex is a relatively large cortical region and is proportionately larger in humans compared to less complex animals. Like the other cortical regions, however, the frontal cortex is not just one area, but a large collection of regions that serve numerous functions. The frontal cortex is important for planning and movement.Voluntary movements begin in the frontal cortex, in a part referred to as the primary motor strip, also
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shown in Figure 4-12. For a long time it has been known that stimulation of different parts of the primary motor strip invokes movement in specific groups of muscles. However, recent research suggests that parts of motor cortex are not just involved in contracting specific muscles but in coordinating the use of these muscles in complex movements (Graziano, 2006). In addition to its role in controlling movement, the frontal cortex contains a region called Broca’s area, which is critical for speech production. Individuals with damage to this region, or to the connections between Wernicke’s and Broca’s area, find it impossible to generate speech, despite normal language comprehension. The part of the frontal cortex closest to the front of the head is referred to as the prefrontal cortex and it is important for a large number of functions. Among them is short-term memory or working memory (Soto et al., 2008). When you call information for a phone number and hold that number in your mind while you dial, you are using your prefrontal cortex. In addition, when you execute complex plans, such as planning and hosting a party or creating a Jeopardy! strategy, you are using your prefrontal cortex. Moral reasoning (discussed in Chapter 3) has also been localized, at least in part, to a component of the prefrontal cortex. Children with damage to the prefrontal cortex can have difficulty understanding ethical principles despite normal IQ (Anderson et al., 1999). The prefrontal cortex has also been implicated in some aspects of mood regulation. Studies have shown that individuals with a positive outlook on life tend to have more activity on one side of their prefrontal cortex (Urry et al., 2004). One of the earliest examples of localization of function involved an individual with damage to the prefrontal cortex. In the mid-1800s, a railroad worker named Phineas Gage experienced severe brain damage when a metal railroad spike penetrated his frontal lobes during an explosion (Figure 4-13). Gage miraculously recovered physically, but those who knew him previously reported that his personality was never the same again. Once a mild-mannered individual, Gage became hot-tempered and prone to outbursts of anger. Stories such as this, as well as some experimental data, led to the suggestion that the prefrontal cortex is important for personality. Such claims, which do have some basis but were perhaps overstated, led to the development of a once popular procedure called a prefrontal lobotomy that was used to treat individuals with problems ranging from severe mental illness to nonconformity and rebellion (Heller et al., 2006). Due to the lack of scientific basis and the side effects of its application, this surgery has (appropriately) fallen out of fashion. However, more limited destruction of the prefrontal cortex is still used for a small number of patients suffering from severe depression or other forms of mental illness who do not respond to drug therapy (Abosch & Cosgrove, 2008). The four general regions of the neocortex can be further subdivided into many areas, which serve different functions and have different neural connections. However, all parts of the neocortex share some neuroanatomical features. The neocortex consists of six layers, whether occipital, temporal, parietal, or frontal. Although some variations exist in the composition of the layers across regions, in general, the output neurons (those that project to subcortical structures) are located in the deepest layers.
The Corpus Callosum Communication from one side of the neocortex to the other occurs via a bundle of axons that make up a large structure called the corpus callosum, shown in Figure 4-14. The corpus callosum appears to connect two relatively equal halves of the brain, called hemispheres, but the brain is actually not completely symmetrical, nor do the hemispheres work quite the way you might expect. For instance, you might expect the right hemisphere to control things that happen on the right half of the body, and
FIGURE 4-13 After the accident Phineas Gage holds the railroad spike that impaled his brain (left). A reconstruction shows how the spike likely entered Gage’s head, damaging the frontal cortex (right). After the accident, Gage’s personality drastically changed.
Wernicke’s area an area of the temporal cortex important in helping us understand language. parietal cortex lobe of the neocortex involved in processing information related to touch and complex visual information, particularly about locations. somatosensory strip an area of the parietal cortex that processes tactile information coming from our body parts. frontal cortex lobe of the neocortex involved in many functions including movement and speech production. Broca’s area brain region located in the frontal lobe that’s important for speech production. prefrontal cortex portion of the frontal cortex involved in higher-order thinking, such as memory, moral reasoning, and planning. corpus callosum bundle of axons that allows communication from one side of neocortex to the other. hemispheres halves of the brain.
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Do We Really Use Only 10 Percent of Our Brains? A popular claim about brain function is that we only use a small fraction of our brains while the rest lies dormant. Many claim that we could transcend what we commonly consider human limitations if we could only tap into the potential of this large, “unused” percentage of the brain. The idea that we only use 10 percent of our brain is false and has no support at all in the scientific literature of today. In fact, scientists have shown that large parts of our brains are activated at all times, both during wakefulness and sleep. The myth that we use very little of our brains was probably based, in part, on neuroscience studies done by the psychologist
Corpus Callosum
Karl Lashley in the early part of the 20th century (Lashley, 1929). Lashley showed that rats could learn some mazes even after very large parts of their brains had been removed. Those who supported this myth also pointed out that in some instances, large parts of the brain can be damaged in humans with little functional deficit; people with major brain damage often seem “as good as new.” It’s important to consider that although a brain region may not be critical for solving a maze or carrying out another task, it may be active nonetheless. Neuroimaging studies have shown that even when humans engage in relatively simple tasks, such as pressing an elevator button, visual, motor, memory, and attention areas are activated. Thus, people without brain damage actually are using large areas of the brain in these tasks (Bédard & Sanes, 2009), even though we could get along without some of those regions if we had to. Some of us may seem at times to be using only 10 percent of the abilities but how well we are putting our brains to use is a whole other question. The research is clear about the brain’s activity: Most of the brain is active, much of the time.
the left to control the left. Things are not that simple, however. There are many crossed connections to and from the primary cortex, leading to asymmetries, or differences in function between the hemispheres. Input from our visual, auditory, and somatosensory systems is at least partially crossed, for example. The left part of somatosensory cortex receives tactile input from the right part of the body and vice versa. Crossed connections also contribute to asymmetries in the primary motor cortex. The left part of the primary motor cortex controls movement on the right part of the brain and vice versa. Furthermore, as we describe later in this chapter, not everybody’s hemispheres are the same. There are some fascinating individual differences in the two halves of our brain. A treatment sometimes used when people have severe epilepsy is to sever the corpus callosum, to stop the spread of seizures from one side of the brain to the other. People who have undergone this surgery are called split-brain patients. These patients are normal in many respects, but they lack the ability to integrate information from the two hemispheres (Gazzaniga, 2005). Studies on these patients have highlighted the fact that the two hemispheres need the corpus callosum to communicate. Preventing this can sometimes result in one part of the brain acting in opposition to the other.
The Integrated Brain
FIGURE 4-14 The corpus callosum This cross section of the human brain shows the large bundle of axons that allows communication between the two hemispheres.
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It’s important to remember that many of the above mentioned brain areas, including the cortical regions, can be subdivided into multiple areas or nuclei, each of which is involved in different functions. However, no brain region works alone. To process information, integrate it with previous information, and then to formulate and execute a reaction requires neural circuitry undoubtedly not contained within a single brain region. For example, a person whose brain contained only a hippocampus would not be able to store information about anything because it would lack the sensory pathways necessary to provide stimuli about events or the spatial environment. Understanding how a brain region works requires sophisticated knowledge about information that flows into the area, that which flows out of the areas, and of course, the important computations that occur within the neurons of that given brain region.
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Before You Go On What Do You Know? 14. Which part of the brain is essential to basic functioning, such as breathing? 15. Describe the role of the brain in regulating hormones throughout the body. 16. Which part of the brain has been linked with our fear responses? 17. What behavior is most closely linked to the hippocampus? 18. Which of our senses is linked primarily with the occipital cortex? Which with the temporal cortex? Which with the parietal cortex? 19. What are the primary functions of Broca’s and Wernicke’s areas, and where are they located? 20. What mental functions are associated with the frontal cortex? 21. How do the two hemispheres of the brain communicate, and how are functions distributed between the two?
What Do You Think? What are the potential pitfalls in making inferences about brain function from studying a single brain area?
Building the Brain How we Develop LEARNING OBJECTIVE 6 Describe the processes of neurogenesis, synaptogenesis, and programmed cell death, and their role during development and throughout the lifespan.
Development of the nervous system begins during the embryonic phase of prenatal life, before we are born, and continues throughout the lifespan.
Brain Development Before We Are Born Embryos have three layers of rather undefined tissue that later specialize to become all of our recognizable body parts. Nervous tissue originates from one of the layers, called the ectoderm. A portion of the ectoderm thickens and eventually folds to form a tube called the neural tube. As cells lining the wall of the neural tube divide and produce more cells, eventually the process of differentiation begins. Differentiation refers to the achievement of characteristics specific to a certain type of cell—in this case a neuron. The production of new neurons is called neurogenesis. Young neurons are born near the center of the neural tube and migrate away from their birthplaces to create new brain regions, as shown in Figure 4-15. The migrating young neurons can travel in several different ways, including moving along the specialized glia called radial glia (Marín & Rubenstein, 2003). They can also move along axons of other neurons that have already been formed or travel through the extracellular space itself. As these new neurons take up residence in areas where certain brain regions are forming, they grow axons and dendrites and quickly make synaptic contact with other neurons. The process of forming new synapses is called synaptogenesis. Gradually, through neurogenesis and synaptogenesis, a young brain is formed with many functions, including hearing and touch, working before we are even born. It seems most intuitive that brain development would require mostly constructive processes—a new brain needs to synthesize new neurons and those new neurons need to make dendrites, axons, and synapses. However, neuroscientists were surprised to find that destructive cellular events are just as important for brain development as are constructive events. As we described in Chapter 3, during development, our brains overproduced neurons in large numbers. The extra, unused neurons are culled, through a process called programmed cell death (Levi-Montalcini, 1988). In some brain regions, cell death claims the lives of over three-fourths of the neurons originally produced by the brain. Why would the brain waste so much energy making neurons only to kill them off? The answer seems to be that producing a large number of neurons will insure that a
neural tube area of an embryo from which the CNS arises. neurogenesis the production of new neurons. synaptogenesis the process of forming new synapses.
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FIGURE 4-15 How the nervous system develops (a) The brain and spinal cord originate from the embryonic neural tube. (b) Neurons are born in tissue that surrounds the central canal (the ventricle) and migrate away from the center to build the CNS.
Developing neural tube
Undefined embryonic tissues
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(a) Brain surface Developing cortex Neural tube in cross section Radial glia
Radial glial process
Migrating neuron
Migrating neuron
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reasonable number make appropriate connections. Those that fail to make the needed connections ultimately die. Developmental cell death is special because it involves the activation of a program of suicide genes within the neuron itself (Steller, 1995). Importantly, it does not trigger any inflammation or reactive events as occurs with other types of cell death as a result of trauma. For example, developmental cell death does not attract microglia or astroglia, nor does it lead to the formation of a glial scar. This insures that the young neurons that did not make the cut were eliminated without wreaking havoc on the brain region. Of those neurons that survive, most undergo some form of regressive structural remodeling before development is complete. That is, many neurons initially develop more dendrites and synapses, or more elaborate axons, than they will eventually need. Only those that are necessary and make appropriate connections survive (Luo & O’Leary, 2005). The rest are retracted and reabsorbed, so that in the long-term, the brain spends energy only on those circuits that work most efficiently. 118 Chapter 4
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Brain Development Across the Lifespan For humans, many of the cellular events, such as neurogenesis, neuronal migration, dendrite formation, axon extension, synaptogenesis, and their regressive counterparts that take place before birth, reflect the unfolding of a preprogrammed, maturational plan that can only be altered by toxic influences, such as the ingestion of drugs or alcohol by a pregnant woman. Although there are some interesting exceptions, presented in Chapters 5 and 7, that describe evidence for fetal sensation and learning, our brains are generally much more open to being physically shaped by our experiences after we are born than before. Both progressive and regressive developmental events occur after birth, too—these are affected by experience. For example, our experiences may determine which synapses are maintained and which are pruned during infancy and childhood. Other events, such as myelination, occur at different time points in our development, depending on the brain region. As described in Chapter 3, myelination in humans occurs mostly after we are born. It begins relatively rapidly in some of the primary sensory areas and continues through late adolescence or early adulthood. Myelination of the prefrontal cortex, for example, is not finished until after puberty, which may explain why adolescents are generally less efficient at planning and executing complex behaviors than are adults. You may think that developmental events in the nervous system stop once you became an adult. In fact, a very common myth about the brain is that you have all of the neurons you will ever have once you are born and any that die cannot be replaced. Neuroscientists have recently overturned this fallacy by showing that some populations of neurons continue to be produced well into adulthood (Gould, 2007). As discussed earlier in this chapter, a brain region that exhibits substantial neurogenesis in adulthood is the hippocampus (Cameron & McKay, 2001). Adult neurogenesis may be important for the functions of the hippocampus, which as we saw earlier, is involved in learning and memory (Leuner et al., 2006). Although still a controversial issue, it is possible that the plastic nature of new neurons may provide the substrate needed for us to change as a result of our experiences, in other words, to learn.
New neurons (green), shown here in this fluorescent photomicrograph, are produced in the hippocampus of adult mammals, including humans.
Dying Cells in a New Brain? Early neuroanatomists studied growth and development of the nervous systems in a variety of species. One important developmental phenomenon they overlooked, however, was the role of cell death in sculpting the brain. It wasn’t until the 1940s that an Italian medical doctor, Rita LeviMontalcini, began investigating this possibility. Ousted from her post at the Turin medical school during World War II because she was Jewish, Levi-Montalcini made a discovery that changed how we view brain development and eventually led to a Nobel Prize. Though she was under constant threat of deportation and death, Levi-
Montalcini continued to study neural development in her apartment, using fertilized eggs from a nearby farm as her experimental animal. Through careful microscopic work, she was the first to discover that neurons are overproduced during development and that neural circuits are sculpted by cell death, as we described in this chapter. She was also able to determine which neurons were most likely to survive. The survival of a new neuron, she found, was critically dependent on whether or not that neuron made contact with an appropriate target site. Levi-Montalcini found that amputating a limb bud from a developing chick embryo resulted in the survival of fewer motor neurons, whereas grafting an extra limb to a developing chick embryo led to the survival of more neurons. Levi-Montalcini eventually made it to the United States where she was the first to identify trophic factors, the chemicals that promote neuron growth. In 1986 she was awarded the Nobel Prize in Medicine (Levi-Montalcini, 1988). She later returned to Italy, where she continues her active life, serving in the Italian Senate past the age of 100.
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In addition to the incorporation of entirely new neurons into pre-existing neural circuits, the adult brain also shows evidence of ongoing dendritic remodeling (McEwen, 2001) and synaptogenesis, or forming of new synapses (Cooke & Woolley, 2005). Although evidence for these changes was first observed decades ago, using traditional methods of examining brain sections under the microscope, recent studies using genetically-engineered mice with fluorescent neurons have allowed researchers to examine and determine the size and shape of individual neurons in live animals through transparent windows implanted into their skulls. These studies have confirmed the earlier reports by showing that dendrites and synapses change in shape, size, and number throughout adult life (Knott et al., 2006). The extent to which this structural plasticity contributes to normal brain function remains unknown, but its occurrence indicates that the adult brain is not a rigid, static place. Researchers studying structural plasticity in the adult brain hope that identifying the mechanisms controlling these events may someday help us to actually change the shape and connections of neurons in order to repair circuits that are abnormal as a result of brain damage or birth defects.
Before You Go On What Do You Know? 22. How are neurons formed before we are born? 23. What is synaptogenesis? Does it ever stop?
What Do You Think? What advantages does cell death have for the developing brain?
Brain Side and Brain Size HOW we Differ LEARNING OBJECTIVE 7 Explain the neuroscience evidence about brain lateralization and the significance of brain size.
You may have heard popular theories about “left-brained” or “right-brained” types of people, or jokes about the female brain versus the male brain. Neuroscience tells us that, although the importance of them may be exaggerated in the public mind, there are, indeed, some differences among the brains of different groups of individuals.
Differences in Brain Lateralization
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Can the brain understand the brain? —David Hubel, neuroscientist and Nobel laureate in medicine
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In most people, there are some parts of cortex that exist only on one side of the brain. Wernicke’s and Broca’s areas related to speech and language, for example, are on the left side of most people’s brains; but not everybody’s. The exceptions occur most often in left-handed individuals. Left-handers are more likely to have these language areas located on the right side of their brains or on both sides, than are right-handers, suggesting that lateralization of more than one function (handedness and language) may be linked in some way. In addition to these rather clear-cut functional and anatomical asymmetries, many people believe that more general thought processes are lateralized, such that people who think a certain way are using proportionately more of one side of their brain than they are the other side. Although this remains controversial, the “word on the street” is that individuals who rely heavily on their right brain are more likely to be creative and use abstract reasoning and imagery to solve problems. This side of the brain is thought to
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be dominant in artists and engineers. By contrast, the left side of the brain is thought to be dominant in individuals with strong analytical and verbal skills. This distinction has been so popularized that it’s difficult to separate fact from fiction. What then is the scientific evidence for “right-brain” and “left-brain” dominant thinking? Neuroscientists have been able to temporarily inactivate one hemisphere, by infusing drugs into the circulatory system that feeds that side of the brain, in order to determine which functions are affected most and fastest. Another way neuroscientists study the hemispheres is by taking advantage of the fact that part of the visual field of each eye crosses over to the opposite side of the brain. Researchers can present visual stimuli to only one hemisphere by requiring the participant to fixate on a point and/or use a special contact lens. They then ask participants to complete a task using just one side of the brain. Studies such as these have shown that the right-brain–left-brain dichotomy is only a general theme, and there are notable exceptions. For instance, the right brain, which is typically believed to excel at spatial perceptual tasks, is actually less accurate at making some spatial perceptual distinctions, such as determining the location of objects in relation to one another. Overall, the research shows that, aside from the language areas noted above, the two hemispheres are more similar than they are different. Indeed, even when right-left differences are detected in function, these differences are usually relative. For example, the left brain can accomplish what the right brain can accomplish, it’s just less efficient at some tasks and more efficient at others.
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What it comes down to is that modern society discriminates against the right hemisphere. —Roger Sperry, neuroscientist and Nobel laureate in medicine
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Gender Differences On average, the brains of women are smaller than those of men. Does this mean men are smarter than women? It does not. The overall size of the brain appears to be more closely related to the size of the body than to function. In fact, a relationship between
PRACTICALLYSPEAKING
How Can You Prevent Age-Related Decline in Brain Function?
A common adage used today with regard to the aging brain is “Use it or lose it!” Stories in the media encourage aging individuals to keep their brains active by spending time on crossword puzzles, Sudoku, or other brainteasers. Some companies have even developed and marketed brain puzzles they claim are specifically designed to keep the brain agile and prevent declines in a wide range of general cognitive abilities, such as day-to-day problem solving and memory.
Unfortunately, the scientific evidence available does not support these claims. While it’s true that people with a higher level of education and also those with multiple interests and socially active lives seem somewhat protected from age-related cognitive dysfunction (Perneczky et al., 2008), there is no evidence that engaging in brain puzzles is beneficial for any purpose other than making you better at solving similar brain puzzles! In other words, mastery of these tasks does not generalize to overall cognitive performance. One type of experience, however, that does seem to make a difference in cognitive performance is physical exercise. In humans, aerobic exercise increases blood flow to the brain, improves performance on cognitive tasks, and elevates mood (Pereira et al., 2007). Studies in experimental animals have shown that physical exercise increases the birth of new neurons in the hippocampus and also stimulates the growth of neurons in general throughout brain structures that support cognitive function (Stranahan et al., 2006; 2007). So add protection of your brain to the list of other reasons of why it’s a good idea to hit the gym regularly. There’s good scientific evidence to support this claim!
Brain Side and Brain Size How we Differ
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brain size and intelligence doesn’t exist, except at the two ends of the spectrum; people with abnormally small or abnormally large brains are both more likely to exhibit mental deficiencies than those with brains whose size falls in the normal range. In addition to the overall size difference, researchers have reported some differences in the size of certain brain regions in humans. For example, part of the corpus callosum, connecting the two hemispheres of the brain, has been shown to be larger in women (Johnson et al., 1994). This finding has contributed to the much-overstated suggestion that women are more likely to use both sides of their brains than men are. Even in cases where differences have been reported in the size of brain regions, the overall differences between men and women are very small, so much so that they really don’t tell us much about the individual person of either gender. An exception to this exists in the hypothalamus where certain nuclei that control the release of reproductive hormones differ in men and women.
Before You Go On What Do You Know? 24. What does research show about “right-brained” creative thinking versus “left-brained” analytical thinking? 25. On which side of the brain do most people have their language-related areas? What about left-handed people? 26. Does overall brain size matter in how well brains function?
What Do You Think? What are some of the ethical problems associated with searching for structural differences in the brains of different groups of people?
Neurological Diseases
“
All the most acute, most powerful, and most deadly diseases, and those which are most difficult to be understood by the inexperienced, fall upon the brain. —Hippocrates, 4th century B.C.E. Greek philospher
”
LEARNING OBJECTIVE 8 Describe four neurological disorders and the current directions in research for treating them.
In general, diseases of the nervous system can be divided into two broad classes characterized by the type of physician designated to care for the patient. These classes are psychiatric illnesses and neurological illnesses. In the case of psychiatric illnesses, such as depression and schizophrenia, the underlying problem is often thought of as primarily a biochemical or neurotransmitter imbalance. In the case of neurological illnesses, such as Parkinson’s disease and Alzheimer’s disease (discussed in Chapter 8), the main problem is thought to be structural, generally involving the degeneration of neurons. Although there is certainly overlap between these two classes of brain diseases (for instance, people with depression are known to have a smaller hippocampus (Sheline et al., 2003) and people with Parkinson’s disease have a deficiency in the neurotransmitter dopamine (Jankovic & Aguilar, 2008), this general distinction holds true. Because psychiatric diseases are taken up in other chapters of this book, we will focus here on some key neurological diseases: • Multiple sclerosis involves demyelination, or loss of myelin, on the axons of neurons. This leads to the inefficient transmission of electrical information among neurons and a range of symptoms, including vision loss, pain, and muscle weakness, depending on where the demyelination occurs. Research on multiple sclerosis has focused on finding ways to stimulate myelination (Franklin & Ffrench-Constant, 2008). • Amyotrophic lateral sclerosis (ALS or Lou Gehrig’s disease, so-named after a famous athlete who had the illness) is another condition that affects movement.
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People with ALS experience degeneration of motor neurons in the spinal cord. The symptoms of this disease begin with localized muscle weakness and ultimately, the entire body is afflicted. People with ALS typically die when the motor neurons that control basic functions, including breathing, die. Interestingly, some populations of motor neurons appear to be more resistant to ALS than others. Examples of the resistant populations include the cells that control eye movements (Laslo et al., 2001) and those that are involved in motor control of the anus and genitals (Mannen et al., 1982). Investigators are studying these neuron groups to determine whether molecular differences between vulnerable and resistant populations of cells can be used to stimulate protective mechanisms in motor neurons that degenerate in this devastating disease. • Parkinson’s disease is a neurological condition that involves the death of dopaminergic neurons—those that rely on the neurotransmitter dopamine—in the substantia nigra. Patients with this condition often have a tremor in their hands and muscle rigidity. Parkinson’s disease can have many different causes and affects a relatively large percentage of the population. In most cases, however the cause is not known. People with Parkinson’s disease can be treated with drugs that replace the dopamine that is lost when the neurons in the substantia nigra die. However, this replacement is only temporary. As time passes, patients become resistant to the dopamine drugs and/or develop intolerable side effects to the drugs. Because drug therapy is only temporary and so many people suffer from the condition, scientists have spent considerable effort searching for novel therapies. Among them include the transplantation of stem cells, which can be induced to produce new neurons that make dopamine. Although these treatments are promising, there is much work to be done before they can be used routinely (Isacson & Kordower, 2008).
multiple sclerosis neurological disease that causes a loss of myelin on the axons of neurons. amyotrophic lateral sclerosis (ALS or Lou Gehrig’s disease) neurological disease that causes degeneration of motor neurons in the spinal cord, leading to loss of movement and eventual death. Parkinson’s disease neurological disease that involves the death of dopaminergic neurons in the substantia nigra, leading to tremors, muscle rigidity, and other motor problems. Huntington’s disease inherited neurological condition that results in the death of neurons in the striatum. stem cell undifferentiated cell that can divide to replace itself and create new cells that have the potential to become all other cells of the body, including neurons.
• Huntington’s disease is an inherited condition that results in the death of neurons in the striatum. People suffering from this disease exhibit awkward movements and often, symptoms of psychosis (Paulsen, 2009). Like ALS and Parkinson’s disease, Huntington’s disease is progressive and as yet, there is no cure.
Transplanting Stem Cells to Treat Neurological Disorders Medical and neuroscience researchers have not yet developed truly effective medicines for these devastating neurological diseases, so some neuroscientists have turned their attention to the possibility of repairing damaged brain regions by transplanting new tissue into the brain. Early work ruled out the possibility of transplanting fully differentiated brain tissue into a damaged region. In most cases, these transplants did not survive or integrate properly into the existing circuitry. Subsequent attempts to transplant fetal brain tissue into brains of adults suffering from Alzheimer’s or Parkinson’s disease also met with limited, if any, success. Fetal tissue may integrate into the damaged brain, but it remains foreign and often does not function normally for extended periods of time. Thus, transplantation research has focused primarily on the possibility of restoring damaged circuits by transplanting stem cells. Stem cells, as described earlier, are undifferentiated cells that have the potential to grow into any cell type if given the appropriate environmental cues. The most versatile stem cells come from embryonic tissue (Srivastava et al., 2008). Researchers have obtained stem cells from embryos created as part in vitro fertilization, a procedure sometimes used to help infertile couples have babies. Eggs are fertilized with sperm in the laboratory, and some of the resulting embryos are implanted into a woman’s uterus. Remaining, or extra, embryos, at very early stages of development, can provide a source for stem cells. This source, however, is very controversial among those who question whether the embryos could be considered humans yet.
Neural stem cells shown in this microscopic image have been used to repopulate damaged brain regions. These cells can divide and produce different types of neurons depending on their environment.
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Because, as we will see, stem-cell research has shown great promise, researchers are now working to find other sources of stem cells, including reproducing them from adult tissue. Thus far, stem cell transplantation studies in animals have been successful in some cases, particularly in animal models of Parkinson’s disease (Takahashi et al., 2009; Hovakimyan et al., 2008). The effectiveness of stem-cell treatment may depend on what kind of brain cell is damaged and where the damaged cells are located. For instance, Parkinson’s disease arises predominantly from the death of dopaminergic neurons in the substantia nigra. Thus, restoring this population of neurons, providing they make appropriate connections and synthesize the correct neurotransmitter, is likely to repair the deficit. Other neurological diseases that cause more widespread damage might not respond as well. For example, patients with Alzheimer’s disease (which we discuss in some detail in Chapter 8) lose neurons throughout their brains. The disease also causes the formation of abnormal clusters of nondegradable protein that interfere with neuronal function (Rafii & Aisen, 2009). Replacing only certain types of dead neurons may not be sufficient to overcome the widespread devastation characteristic of this disease.
Before You Go On What Do You Know? 27. What goes wrong in the nervous system to cause multiple sclerosis, ALS, Parkinson’s disease, and Huntington’s disease? 28. What have neuroscientists learned to date about transplants of brain tissue as a way to treat neurological diseases?
What Do You Think? What are the technical and ethical pitfalls stem cell researchers must contend with?
Summary How Do Scientists Study the Nervous System?
• Neurons communicate with other cells by producing and sending electrochemical signals. • Glia are involved in various functions, such as forming the bloodbrain barrier, producing myelin, and clearing the brain of debris.
LEARNING OBJECTIVE 1 Understand the key methods that scientists use to learn about brain anatomy and functioning. • Neuroscientists examine autopsy tissue and patients with localized brain damage to learn about brain anatomy and brain function. • EEGs and neuroimaging, such as PET scans and fMRI, allow us to study brain function in the living brain.
What Cells Make Up the Nervous System? LEARNING OBJECTIVE 2 Name the two major types of cells in the nervous system, and describe the primary functions of each. • The two major types of brain cells are neurons and glia.
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How Do Neurons Work? LEARNING OBJECTIVE 3 Describe what happens when a neuron “fires,” and how neurons send messages to one another. • Communication within a neuron occurs electrically by means of the action potential, whereas communication between neurons occurs at the synapse via chemical signals called neurotransmitters. • Neurotransmitters are released by the presynaptic neuron, diffuse across the synapse, and bind to receptors on the postsynaptic site. • The response of a receiving neuron to a neurotransmitter is determined by the receptor on the postsynaptic, or receiving, neuron’s membrane. Depending on the type of receptor, the postsynaptic neurons will fire or not.
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How is the Nervous System Organized?
Building the Brain
LEARNING OBJECTIVE 4 Name and describe the functions and subdivisions of the two major parts of the nervous system.
LEARNING OBJECTIVE 6 Describe the processes of neurogenesis, synaptogenesis, and programmed cell death, and their roles during development and throughout the lifespan.
• The two major divisions of the nervous system are the central nervous system, which consists of the brain and spinal cord, and the peripheral nervous system, which consists of nerves that extend throughout the body outside the central nervous system. • The peripheral nervous system has two divisions: the somatic nervous system, which sends information about the senses and movement, and the autonomic nervous system, which controls involuntary functions and responses to stress. • The autonomic nervous system is divided into the sympathetic nervous system, which responds to stress, and the parasympathetic nervous systems, which is responsible for digestion and other processes that occur when the body is at rest.
• Cellular processes that build the brain are neurogenesis, which produces new neurons, and synaptogenesis, which forms new synaptic connections with other neurons. • Cellular processes that sculpt or fine-tune the brain are cell death, axon retraction, and synapse elimination. • Changes in brain structure, including neurogenesis and synaptogenesis, occur throughout life, into old age.
Brain Side and Brain Size LEARNING OBJECTIVE 7 Explain the neuroscience evidence about brain lateralization and the significance of brain size.
Structures of the Brain LEARNING OBJECTIVE 5 List key structures of the brain, and describe their relationships to our behavior. • The brain can be subdivided into many regions, each of which serves one or more specialized functions. • The brainstem participates in movement and sensation of the head and neck as well as in basic bodily functions, such as respiration and heart rate. • The midbrain includes the substantia nigra, an area important for movement. • The hypothalamus controls basic drives (food, drink, sex) and hormones while the thalamus serves as a relay station for sensory information on its way to the cerebral cortex. • Many brain regions participate in different types of learning—the hippocampus is important for spatial navigation learning and learning about life’s events; the amygdala is important for fear learning; the cerebellum and striatum are important for motor learning; and the nucleus accumbens is important for reward learning. • A large part of the brain consists of the neocortex. The neocortex can be subdivided into frontal, parietal, temporal, and occipital regions. The cortex controls movement, integrates sensory information, and serves numerous cognitive functions.
• Research shows that the two hemispheres are more similar than different and that any differences are usually relative. • Brain size appears to be related to overall body size and not to brain function.
Neurological Diseases LEARNING OBJECTIVE 8 Describe four neurological disorders and the current directions in research for treating them. • Multiple sclerosis involves the loss of myelin on the axons of neurons. • In amyotrophic lateral sclerosis, the motor neurons in the spinal cord degenerate. • Parkinson’s and Huntington’s diseases are primarily the result of neuronal destruction in the substantia nigra and striatum, respectively. • Some regeneration occurs in the brain after it is injured, but repair is typically not complete and functional impairment often remains. Researchers believe transplantation of brain tissue, particularly embryonic stem cells, may provide relief for some neurological diseases.
Key Terms neuroscience 98
action potential 102
plasticity 105
reticular formation 108
neuroimaging 98
myelin 103
somatic nervous system 105
serotonin 108
neuron 98
absolute refractory period 103
autonomic nervous system 106
pons 109
dendrites 98
relative refractory period 103
sympathetic nervous system 106
norepinephrine 109
axon 98
synapses 103
cerebellum 109
axon terminal 98
neurotransmitters 103
parasympathetic nervous system 106
glia 101
synaptic vesicles 103
spinal cord 106
dopamine 109
resting potential 102
neurotransmitter receptors 103
interneuron 106
thalamus 109
ion channels 102
postsynaptic potentials 103
brainstem or medulla 108
hypothalamus 111
substantia nigra 109
Key Terms
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endocrine system 111
association cortex 113
Broca’s area 115
multiple sclerosis 123
pituitary gland 111
occipital cortex 113
prefrontal cortex 115
amyotrophic lateral sclerosis 123
amygdala 111
temporal cortex 113
corpus callosum 115
Parkinson’s disease 123
hippocampus 111
Wernicke’s area 115
hemispheres 115
Huntington’s disease 123
striatum 111
parietal cortex 115
neural tube 117
stem cell 123
nucleus accumbens 113
somatosensory strip 115
neurogenesis 117
neocortex 113
frontal cortex 115
synaptogenesis 117
CUT/ACROSS CONNECTION What Happens in the
BRAIN? • The human brain contains about 100 billion neurons. In addition, some parts of the brain contain 10 times that many nonneuronal cells, called glia. • If you put a recording electron into a “resting” neuron, it will read a negative charge of approximately –70 millivolts. At the peak of a neuron’s action potential, the membrane charge is around ⫹50 millivolts. • Action potentials of neurons follow an all-or-none principle. When sufficiently stimulated, a neuron fires; otherwise, it does not. • Synaptic spaces are about 20 nanometers wide. A nanometer is 1 billionth of a meter. • The sympathetic nervous system is responsible for the “fightor-flight” reaction; the parasympathetic nervous system helps control the basic functions of life, such as digestion. • The hypothalamus helps regulate eating, drinking, sex, maternal behavior, and the endocrine system. • Although the two halves of the brain are called hemispheres, the brain is not completely symmetrical.
HOW we Differ • Although the speech and language areas—Wernicke’s and Broca’s areas—are on the left side of most people’s brains, these areas may be located on the right side or both sides for some people—particularly left-handed people. • On average, the brains of women are smaller than those of men, although such size differences have no relationship to intelligence or other faculties. • Some theorists believe that women are more likely than men to use both sides of their brain.
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• When the spinal cord is damaged and information to and from the brain interrupted, individuals become paralyzed. The higher up the damage—the closer it occurs to the brain—the larger the proportion of body affliction. • People with damage to the frontal cortex region called Broca’s area, cannot generate speech but can understand language. • With some notable exceptions, psychiatric disorders (for example, clinical depression) seem tied most often to biochemical imbalances in the brain, while neurological disorders (for example, Parkinson’s disease and Alzheimer’s disease) seem tied to brain-structure abnormalities, including the degeneration of neurons. • Many neuroscientists currently are trying to develop treatments for certain neurological diseases in which they restore damaged neural circuits by transplanting new tissue into those areas of the brain, particularly by transplanting stem cells—undifferentiated cells that can grow into particular cell types.
How we Develop • Over the course of development, a process of programmed cell death, or cellular pruning, results in the death of over 75 percent of the neurons initially produced by the brain. • Our environmental experiences also help determine which synapses are maintained and which are pruned during infancy and childhood. • Myelination of the frontal cortex is not completed until after puberty. • Contrary to past beliefs, some populations of neurons continue to be produced well into adulthood—for example, neurons in the hippocampus. • Adult brains also continue to undergo dendrite remodeling and synaptogenesis.
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Psychology Around Us The Amazing Brain
Video Lab Exercise
A teenager who’s had his left-brain hemisphere removed to alleviate very severe epilepsy. A young woman recovering from a car accident. A middle-aged man undergoing rehabilitation after a stroke. The cognitive and physical functioning of each of these individuals reflects various kinds of brain damage. For years, prior to the development of neuroimaging technologies, neuroscientists learned about the brain largely by observing the behaviors of brain-impaired individuals, and then working backward, figuring out what those altered behaviors seemed to say about the operation of the affected brain areas. You have a similar task in this video lab exercise. Observe the behaviors and functioning of each of the individuals in the video and suggest which of their brain areas have been damaged, how those brain areas probably operate when they are not damaged, and how rehabilitation might help change the brain and restore the behaviors and functioning of the individuals. As you are working on this online exercise, consider the following questions: 1. What examples of brain lateralization are on display for each of the individuals in the lab video? 2. What do the treatment gains of each individual reveal about brain integration and brain plasticity? 3. How might stem cell transplantations, if such techniques are successfully developed and socially approved, improve on the rehabilitation techniques applied in this lab video?
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CHAPTER 5
128 Chapter 5
Sensation and Perception
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Sensation and Perception chapter outline •
Common Features of Sensation and Perception •
H
and
Off
The Chemical Senses: Smell and Taste
The Tactile or Cutaneous Senses: Touch, Pressure, Pain, Vibration •
On
•
The Auditory Sense: Hearing •
Sensation
ave you ever noticed how enticing the aroma of your favorite restaurant is when you first walk through the front
door? The smell of foods you enjoy coming from the kitchen make your mouth water. Depending on how long it’s been since you last ate a meal, you might develop an urgent craving to order as soon as possible! After you order, while you wait for your meal to arrive, you may not even notice it, but your awareness of the food odors in the room is probably gradually diminishing. By the time your meal is delivered to your table, you are probably not even noticing the smells that seemed so strong when you first entered the restaurant. When the server places your plate on the table, right under your nose, however, you might suddenly begin to notice the smell of food again—this time your own. Our sense of smell contributes greatly to our enjoyment of a good meal. In fact, all of our senses become involved when we enjoy a meal. We use vision, our sense of sight, to admire the food on the plate. Hearing lets us listen to the sizzle of a particularly hot dish, or enjoy conversation with our dining companions. Obviously, our sense of taste is involved once we actually take a bite of food, but so are our senses of touch, as we discern the temperature and texture of the food. Without
The Visual Sense: Sight
our touch senses, we could not tell a rough, cool salad from a smooth, warm soup. Psychologists have generally agreed that there are five senses: smell, taste, touch, sound, and sight. Touch is actually a complex of senses collectively referred to as the cutaneous senses or the somatosenses. These include pressure, vibration, pain, temperature, and position. Although we will discuss each of these five major senses separately in this chapter, in most of our day-to-day experiences, we actually use these sensory systems or modalities to experience the world. We use our senses in two almost inseparable processes. One process is sensation, the act of using our sensory systems to detect stimuli present in the environment around us. Once acquired, sensory information must be interpreted in the context of past and present sensory stimuli. This process, which also involves recognition and identification (for example, the realization that you recognize the smell in a restaurant as pizza cooking), is broadly defined as perception. Sensation and perception are both critical for our interpretation of, and interaction with, the environment. Accurate functioning of our sensory systems is critical for survival. Imagine how greatly diminished your chances of survival would be if you could not see a fire, feel its heat, hear others crying “fire,” smell the smoke, or interpret any of these sensations appropriately. Aside from the clear adaptive significance of our ability to sense and perceive the world, our life experiences are greatly enriched by these processes. Let’s explore them in more detail.
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sensation the act of using our sensory systems to detect environmental stimuli. perception recognition and identification of a sensory stimulus. sensory receptor cells specialized cells that convert a specific form of environmental stimuli into neural impulses. sensory transduction the process of converting a specific form of environmental stimuli into neural impulses. absolute threshold the minimal stimulus necessary for detection by an individual.
Smell
Taste
Touch
Hearing
FIGURE 5-1 Sensory receptor cells Each sensory system contains specialized cells that are activated by particular physical stimuli.
Common Features of Sensation and Perception LEARNING OBJECTIVE 1 Describe characteristics shared by all the senses, including receptor cells, transduction, and thresholds, and differentiate between top-down and bottom-up processes of perception.
Each of our sensory systems is set up to convert the physical stimuli we receive from the world outside our bodies into neural information. Sensation and perception occur differently in each of our sensory modalities, but our senses also share some common processes. Each of the senses has a set of specialized cells called sensory receptor cells that convert a specific form of environmental stimuli into neural impulses, the form of communication used in our brains and nervous systems (see Figure 5-1). This conversion is called sensory transduction. For each sensory system, the different physical stimuli that are converted to brain activity through sensory transduction are listed in Table 5-1. Our sensory receptors can be activated by very weak stimuli. A stimulus must, however, reach a certain level of intensity before we can detect it, because the conversion of physical stimuli into neural impulses only occurs when the stimuli reach this level or threshold. The minimal stimulus necessary for detection by an individual is called the absolute threshold (Table 5-2). Although the absolute threshold varies from person to person, in most cases, it is surprisingly small. For instance, many normal humans are capable of detecting a candle flame a mile away on a clear night (Galanter, 1962). Researchers have also worked to determine the smallest difference that we can detect between two stimuli, called the difference threshold or just noticeable difference. When sensory systems are working optimally, the difference threshold is also remarkably small. Our senses are generally organized to detect change. This makes adaptive sense since most stimuli we are exposed to are not important enough to warrant our attention. Imagine how difficult it would be to concentrate on reading this chapter if sensory information about the odors of your breath, the taste of your mouth, the sound of the clock ticking, and the touch of your clothing were all competing with your ability to read! To combat the possibility of being unable to focus on the salient or important cues, our sensory systems respond to the continual presence of the same stimulus with a decreased response to that stimulus, a process called sensory adaptation. Although it’s possible that the diminished sense of smell people Sight experience as they sit in a restaurant may be due to blocked sinuses, it’s
TABLE 5-1 Sensory Transduction Converts Environmental Stimuli
into Neural Activity
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Sensory System
Physical Stimuli
Olfactory (smell)
Odorants (airborne chemicals)
Gustatory (taste)
Chemicals (typically in food)
Somatosensory (touch, heat, pain)
Pressure or damage to the skin
Auditory (hearing)
Sound waves
Visual (sight)
Light (photons)
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difference threshold or just noticeable difference the minimal difference between two stimuli necessary for detection of a difference between the two.
TABLE 5-2 Absolute Thresholds for Various Senses Sense
Absolute threshold
Smell
A drop of perfume diffused throughout a six-room apartment
Taste
One teaspoon of sugar in two gallons of water
Touch
An insect’s wing falling on your cheek from a height of about half an inch
Hearing
The tick of a watch at 20 feet in a quiet room
Sight
A candle flame 30 miles away on a clear, dark night
sensory adaptation the process whereby repeated stimulation of a sensory cell leads to a reduced response. bottom-up processing perception that proceeds by transducing environmental stimuli into neural impulses that move onto successively more complex brain regions. top-down processing perception processes led by cognitive processes, such as memory or expectations.
much more likely that this experience occurs as a result of sensory adaptation. Our ability to detect odors gradually fades when we are in their presence for a prolonged period. Sensory adaptation can be overcome by providing a much stronger stimulus, which is what happens when your restaurant meal is delivered to your table. Now that the source of the smell is more concentrated in your vicinity, your ability to smell is renewed. Although the sense of smell is perhaps most prone to this response, all of our sensory systems exhibit some form of adaptation. Sensation and perception almost always happen together. Researchers, however, have worked to study each process separately and to determine how the two work together. Perception can occur through bottom-up processing, which begins with the physical stimuli from the environment, and proceeds through transduction of those stimuli into neural impulses. The signals are passed along to successively more complex brain regions, and ultimately result in the recognition of a visual stimulus. For example, when you look at the face of your grandmother, your eyes convert light energy into neural impulses, which travel into the brain to visual regions. This information forms the basis for sensing the visual stimulus and ultimately its perception. Equally important to perception, however, is top-down processing, which involves previously acquired knowledge. When you look at grandma’s face, for example, brain regions that store information about what faces look like, particularly those that are familiar to us, can help you to perceive and recognize the specific visual stimulus. Typically, perception involves both bottom-up and top-down processing occurring at the same time. The combination lets us rapidly recognize familiar faces and other stimuli. Bottom-up and top-down processing are involved in sensation and perception of all sensory modalities. For example, recognizing familiar songs involves not only information carried from the ear to the brain but also the matching of that information with previously stored information about the music. We also combine bottom-up and top-down processes to help us recognize the smell or taste of a familiar food.
A critical difference A radiologist carefully examines a mammogram, looking for the slightest indication of a tumor. An individual’s ability to detect a difference between two visual stimuli (such as normal versus abnormal tissue) can be increased by special training, practice, and instruments, but it is still limited to some degree by sensory difference thresholds.
Before You Go On What Do You Know? 1. What is sensory transduction? 2. What are absolute and difference thresholds? 3. Compare and contrast bottom-up and top-down processing.
What Do You Think? Describe examples of sensory adaptation that you have experienced in two or more of your sensory modalities.
Common Features of Sensation and Perception
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The Chemical Senses: Smell and Taste LEARNING OBJECTIVE 2 Summarize the biological changes that underlie smell and taste.
“
When nothing else subsists from the past, after the people are dead, after the things are broken and scattered . . . the smell and taste of things remain. –Marcel Proust, novelist
”
Smell and taste are usually called the chemical senses because they involve responses to particular chemicals. Smell, our olfactory sense, and taste, our gustatory sense, emerged early in our evolutionary history (Doty, 1986). The sense of smell, in particular, is more sensitive and of greater significance to less complex animals, who use it for social communication as well as finding food and avoiding predators (Yahr, 1997; Mech & Boitani, 2003). This is less so for humans who rely more heavily on vision. However, the contributions of both smell and taste to the safety, social communication, and overall quality of life in humans are often underestimated. The ability to detect dangerous odors, such as smoke or a gas leak, or dangerous flavors, such as tainted food or poison, can be critical to our survival. In addition, some of our greatest pleasures in life come from the ability to smell and taste—to smell a rose or, as we all know, to enjoy a good meal. In this section, we’ll explore the environmental stimuli that create aromas and flavors, the organs we use to sense those stimuli, and how we transform environmental stimuli into brain signals that eventually help us perceive different smells and tastes. We’ll also discuss the development of these abilities, some very interesting differences among people in their ability to taste and smell things, and some problems that can go wrong in the olfactory and gustatory systems.
Taste and Smell: How They Work
olfactory sense our sense of smell. gustatory sense our sense of taste. odorants airborne chemicals that are detected as odors. olfactory receptor neurons sensory receptor cells that convert chemical signals from odorants into neural impulses that travel to the brain. papillae bumps on the tongue that contain clumps of taste buds. taste buds clusters of sensory receptor cells that convert chemical signals from food into neural impulses that travel to the brain. olfactory bulb the first region where olfactory information reaches the brain on its way from the nose.
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Sensation in the smell or olfactory system begins when chemicals called odorants enter the nose, as shown in “What Happens in the Brain When We Eat Pizza” on the following pages. Odorants are converted to neural signals at sensory receptors located in our nasal mucosa. These sensory receptors are located on the cilia, or hairlike structures, of olfactory receptor neurons (McEwen, 2008). When odorants enter the nose, these chemicals bind to specific receptors located on the olfactory receptor neurons in a lock-and-key fashion. Only certain airborne chemicals bind to specific receptors (Buck, 1996). When enough odorant molecules have bound to receptors, the combination sets off an action potential in the olfactory receptor neuron. As we described in Chapter 4, the action potential or firing of a neuron sends a message to other neurons. The firing of olfactory receptor neurons is transmitted to the brain, as we’ll see next. Continuous binding of certain odorants, such as those contained in the main ingredients of a restaurant dinner, will result in fatigue of the olfactory receptor neurons to which they bind. In other words, the cell will stop responding to the odorant unless it’s given a chance to recover so it can fire again (Dalton, 2000). If you were to step outside the restaurant to make a phone call, for example, you would probably notice the food smells again when you stepped back into the restaurant, because your olfactory receptor neurons would have gotten a break from constant exposure to the food odorants. When a stimulus is continuously present, however, as when you remain sitting in the restaurant, the only way the olfactory receptor neurons will respond to the odorant would be if the stimulus is increased in magnitude. As we saw, this is the case when the food is brought directly to your table. Many more odorant molecules are now available to your nose and its olfactory receptor neurons. In humans, the sense of smell is very closely tied to the sense of taste. Have you ever noticed how dull your sense of taste is when you have a bad cold? This is due, in large part, to mucous blocking the access of odorants to the olfactory receptors located on the cilia. What we normally refer to as taste is really flavor, a combination of smell and taste.
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Taste, the gustatory sense, is itself independent of smell and its major organ is the tongue. Your tongue is covered with bumps, called papillae. As shown in Figure 5-2, papillae contain clumps of taste buds, each of which contains sixty to one hundred sensory receptor cells for taste. Taste receptor cells have cilia that contain the actual receptors. These cilia extend through the pores of the taste receptor and are exposed to the contents of your mouth. There are four major kinds of taste receptors. Each responds to a specific taste in our food: 1) sweet, 2) sour, 3) bitter, and 4) salt (Sugita, 2006). A fifth type of taste receptor has also been discovered—umami. Umami is the taste of monosodium glutamate (MSG). It is a chemical additive used in cooking some Asian food and American fast food. Each of these five types of taste receptors uses a slightly different mechanism for transduction of the chemicals in food to neural impulses in the gustatory system. For example, salt activates its taste receptors by sending sodium ions into the channels on the taste receptor cell. Since sodium ions are positively charged, the electrical charge of the taste receptor then becomes more positive. Taste buds are not evenly distributed across the tongue but most tastes can be recognized to a greater or lesser degree on most parts of the tongue. The overall sensations we experience when we eat food are not just the result of combined interactions between olfactory and gustatory senses. Much of the information we get about food is delivered to us through one of the touch or tactile senses. The consistency of a particular food is not relayed to the brain via the taste receptors, but rather by inputs from touch receptors located on the tongue. The role of food consistency in determining preference is much greater than you might imagine. Many adult humans reject certain foods, such as raw oysters or cooked okra, specifically because those foods have a “slimy” texture. In addition, the sensation we experience when we eat a “hot,” as in spicy, meal is related to a component of the tactile system that communicates information about pain. A chemical called capsaicin, from chili peppers, activates pain receptors located in the tongue (Numazaki & Tominaga, 2004). These pain impulses, in conjunction with tactile information about the food texture, as well as the flavors (smell and taste) associated with the food, can combine to produce a sensation that is pleasurable to many people. Suppose a food is not spicy, but is hot in the other meaning of the word in that it just came out of the oven. We’ve all had the experience of burning our mouths, which can damage the taste receptors on the tongue. As the box accompanying this section points out, the sensory receptors of taste are unusual because they regenerate when this happens. What Happens in the
Taste pore
Taste receptor cells
Gustatory nerve
FIGURE 5-2 A taste bud The receptor cells for taste are clustered within the taste buds found in the bumps, or papillae, covering your tongue.
Olfactory bulb
Inside the brain
Olfactory axons
Smell and Taste B R A I N ? Signals from our olfactory receptor neurons travel to the brain via the olfactory nerve. As the figure on the right shows, information carried along the olfactory nerves travels first to a structure called the olfactory bulb, located at the base of the front of the brain, beneath the frontal lobes. Olfactory information is then sent to regions of the cerebral cortex that are important for recognizing and discriminating among odors, including the piriform cortex (Wilson, 2001). The ability of our cortex to recognize patterns of inputs from a variety of olfactory receptors is most likely responsible for our detection of certain odors. Studies have shown that the piriform cortex is plastic or changeable in adulthood (Li et al., 2008). That is, the parts of piriform cortex that normally recognize specific odorants can change with experience, actually remapping this brain region. The chemical structures of some pairs of molecules are so similar that untrained humans can’t discriminate between them (the two odors are usually below the just noticeable difference).
Olfactory receptor neuron Supporting cell
Mucous Odorants
Nasal cavity
The smell route Olfactory receptor neurons (shown here in blue) transduce information from odorant molecules that enter the nose. This information is carried by the olfactory nerve into the brain where it synapses in the olfactory bulb.
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What Happens In The Brain When We Eat Pizza s this the best pizza you have ever had or does it fall
I
smell information to produce flavor. Olfactory receptor
short? When you dig into a slice of pizza, several
neurons transduce pizza odorants and send this
neural circuits are activated to give you the overall
information on to the olfactory bulb and then the
experience. The appearance of your food can play an
olfactory cortex (smell is the only sensory modality that
important role in its enjoyment. Photoreceptors in the
bypasses the thalamus on its way to the cortex).
eye transmit this information to the brain via the optic nerve which synapses in the brainstem, followed by the
Information about taste, smell, texture, temperature and
thalamus and finally the visual cortex. Taste receptor cells,
appearance is integrated in various association regions of
as well as sensory cells that respond to touch and tem-
the neocortex. These circuits, together with those that
perature, are activated on your tongue. These nerves
store memories related to your previous pizza
carry impulses into the brain where they synapse in the
experiences, work together to produce your perception
brainstem, thalamus and sensory cortex (gustatory
of this particular slice.
cortex and somatosensory cortex). Taste is combined with
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SENSING MORE THAN TASTE A large part of somatosensory cortex (shown here with neurons genetically engineered to produce fluorescent dyes) is devoted to processing information about texture, temperature and pain from the tongue. Somatosensory information from the tongue is critical for the enjoyment of food - many people prefer their crust crispy while others like it soft.
Somatosensory Cortex
MAXIMIZING THE EXPERIENCE Visual cortex
Thalamus Gustatory Cortex Brain stem Olfactory bulb
Olfactory cortex
When you eat something delicious and close your eyes, you may be maximizing the experience by turning up the activity in certain parts of cortex. When your eyes are open, activity in parts of cortex serving nonvisual senses is decreased. Closing your eyes increases activity in these areas, including in taste and smell cortex. This fMRI image shows such increased activation in the olfactory cortex (yellow).
Visual pathway Smell pathway
Taste pathway
Somatosensory pathway
BURNING YOUR TONGUE Taste buds contain taste receptor cells (shown here marked with fluorescent dyes) that continually regenerate. The process is hastened when tissue is damaged, such as when you burn your tongue.
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Regeneration in the Taste and Smell Systems If you, like most people, have had the experience of burning your tongue on too-hot food, you’ve probably noticed that by the next day or so, your ability to taste has returned and your tongue is no longer painful. This is due to the remarkable regenerative characteristics of the taste buds. Taste receptor cells normally turn over—they die and are replaced— in a matter of days. The process happens even faster when they are damaged. Our olfactory receptor neurons are also constantly turning over under normal circ*mstances (Farbman, 1997). The capacity to regenerate on such a large scale and so rapidly is probably necessary because the receptor neurons for both taste and smell are exposed to the external environment.
Unspeakable pleasure The ecstasy demonstrated on this woman’s face as she bites into a chocolate covered strawberry serves as a vivid reminder that taste information is integrated with the reward circuits in the brain.
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Unlike the sensory receptors of the eye, which are protected by the eyeball, or those of the ear, which are protected by the eardrum, the surface of the tongue and the mucosa of the nose are directly exposed to any number of noxious chemical molecules that may enter our mouths or noses. Because destruction of receptors is likely under such circ*mstances, we need to constantly regenerate receptor cells just to continue normal functioning of our smell and taste systems. Neurobiologists study the regenerative capabilities of the taste buds and olfactory receptor neurons in hopes of understanding exactly how these cells are constantly rejuvenating. Scientists and medical professionals hope that understanding these mechanisms may someday enable replacement of other types of cells, ones that currently don’t seem capable of repair when they are damaged.
However, if exposure to one of the chemicals is paired with a painful shock to the leg, humans can be taught to discriminate between the odors (Li et al., 2008). This is a remarkable example of top-down processing. Learning about associations between odors and other experiences (such as a shock) can influence our ability to perceive sensory information in the future. In parallel with the new ability to discriminate the odors of closely related molecules, the areas of the piriform cortex that are activated by each of the previously indistinguishable molecules become more distinct from each other. The olfactory bulb also sends information to the amygdala, an area important for emotions and fear, as well as indirectly to the hippocampus, an area important for learning and memory. Many people report that certain smells are evocative of past events (Lehrer, 2007). The smell of baking might remind you of visiting your grandmother as a young child, the smell of peanut butter might remind you of your elementary-school cafeteria, and so on. The ability of smells to call up memories is probably related in part to olfactory connections to the hippocampus and amygdala. Taste receptor cells do not have axons but instead synapse with sensory neurons in the tongue to send information to our brains. Taste information is sent to the thalamus and eventually, the cerebral cortex. We’ll see throughout this chapter that the thalamus is a relay station for incoming sensory information of many kinds; all of our sensory systems except olfaction have a main pathway through the thalamus. Taste information is integrated with reward circuits in the brain (Norgren et al., 2006) and rewarding tastes seem to be processed separately from aversive tastes. Tastes that are considered to be rewarding, such as salty and sweet, activate overlapping areas in the taste cortex. By contrast, tastes generally considered to be less pleasurable, such as bitter and sour, activate regions that overlap less with rewarding tastes and more with one another in the taste cortex (Accolla et al., 2007). Taste and smell information are processed through separate pathways but there is convergence in the association parts of neocortex, namely in the prefrontal cortex. In addition to integrating information about taste in general, part of the cortex that receives taste information, called the insula, is associated with the emotion of disgust.
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Neuroimaging studies have shown that this brain region becomes activated not only when we smell or taste something revolting but also when we view repulsive visual images (Calder et al., 2007; Schienle et al., 2008).
Smell and Taste How we Develop The sense of smell is relatively well developed at birth. Research suggests that, within hours of birth, a newborn baby is capable of telling his or her own mother from another woman using only the sense of smell. In fact, olfactory functioning seems to be in place even before birth. Newborn infants show a learned preference to the odors of their mother’s amniotic fluid. After birth, infants quickly learn to recognize the smell of their own mother’s milk. Exposure to odors of their mother’s milk has a calming effect on infants when they are experiencing a brief, minor painful stimulus, such as a needle stick in the heel (Nish*tani et al., 2009). This effect doesn’t appear to be as specific to the milk as it is to the mother—exposure to other odors that the baby has associated with the mother, such as vanillin, has the same calming effect as mother’s milk odor (Goubet et al., 2007). The ability to taste is also well formed at birth in humans. Newborn humans show an innate preference for sugar and aversion to bitter or sour tastes. Babies move their faces toward a sweet substance and make sucking movements with their mouths, but turn away and grimace when presented with a sour or bitter substance (Rosenstein & Oster, 1988). Researchers have shown that by about seven years of age, children develop a preference for sour tastes (Liem & Mennella, 2003) . This may explain the popularity of candies such as Sour Patch Kids. However, the aversion to bitter tastes typically lasts until adulthood. At this time, bitter foods, such as blue cheese and dark chocolate can emerge as favorites. Many of these developmental changes are the result of learning. As children grow, they become accustomed to different tastes. However, there is some evidence to suggest that the gustatory system itself changes from infancy to adulthood. We form taste buds before we are even born, and as newborns, have higher concentrations of them on our tongues than we will as adults. Children also have taste buds on their palates, inside the cheeks, and the back of their mouths (Nilsson, 1979). Although these regions continue to contain taste buds in adults, their numbers decline with time. The high number of taste buds in children may explain why they are often picky eaters. The tastes of certain foods may seem too strong to children, because their larger number of taste buds produces more neural impulses than adults would generate from the same food. Some researchers suggest that this developmental phenomenon might actually be adaptive in helping us survive. If young children enjoyed ingesting substances with strong or bitter tastes, they might be at higher risk of poisoning. Children often refuse or eat very little of unfamiliar foods (Koivisto Hursti, 1999). Although neuroimaging studies on developing humans have yet to be done with regard to taste, it’s tempting to speculate that as individuals grow and their tastes broaden, areas in the taste cortex represented by certain tastes are modified. It’s likely that increased exposure to certain foods, especially when paired with positive social interactions and encouragement from parents, result in a remapping of previously aversive taste information on the gustatory cortex.
Smell and Taste HOW we Differ Among humans, there is a wide range in the ability to detect certain odors. Some people seem relatively insensitive to even pungent odors, while others are particularly sensitive. Some of these individual differences are related to learning. Childhood exposure to particular odors decreases the reaction to those odors in adulthood. The Chemical Senses: Smell and Taste 137
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A special gift? These scent testers (or “noses”) determine whether a new deodorant produces a pleasant result. People who are highly sensitive to odors often find employment that puts their special ability to use.
In addition to these learned differences, research suggests that females are generally more sensitive to smell than males are, and that this sensitivity varies with the stage of the menstrual cycle (Pause et al., 1996). Around the time of ovulation, women are more sensitive to odors than during other stages of the cycle. Women’s ability to detect different odors also diminishes after menopause (Hughes et al., 2002). The exact biological mechanisms that underlie these differences are not known, but it is possible that reproductive hormones, such as estrogen, alter the excitability, or the likelihood of firing of olfactory neurons. There is also considerable individual variability in the ability to taste. Researchers group people into three different categories with respect to taste sensitivity: nontasters (25 percent of people), medium tasters (50 percent), and supertasters (25 percent). These groups are distinguished based on their ability to detect and respond negatively to a specific bitter substance (Bartoshuk et al., 1996). Supertasters are repulsed by the bitter chemical. Nontasters do not even notice the bitter taste although they are capable of detecting other tastes. Medium tasters notice it, but do not find the taste particularly offensive. These functional differences are the result of variations in the concentration of taste buds on the tongue. Women make up a higher proportion of supertasters than do men (Bartoshuk et al.,1994). This heightened sensitivity of both chemical sensory systems, smell and taste, is likely to have had adaptive significance for women. Since the chemicals in women’s diets are passed along to their children when women are pregnant or nursing, the ability to detect and avoid potentially harmful odors and tastes may have contributed to survival of the species by protecting infants from toxic substances.
Smell and Taste
anosmia inability to smell. ageusia inability to taste. free nerve endings sensory receptors that convert physical stimuli into touch, pressure, or pain impulses. Meissner’s corpuscles sensory receptors that convert physical stimuli about sensory touch on the fingertips, lips, and palms. Merkel’s discs sensory receptors that convert information about light to moderate pressure on the skin.
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True taste disorders are rare. In fact, most people who seek medical assistance complaining that they cannot taste are actually suffering from problems with their olfactory, as opposed to gustatory, systems. People with a condition called anosmia have lost the ability to smell. They can often still taste sweet, salt, sour, bitter, and umami, but they can no longer detect other flavors, since those require the additional information provided by food odorants. In some rare cases—typically as a result of head trauma or oral surgery—humans lose the ability to taste itself, a condition called ageusia. Head trauma is also a leading cause of anosmia (Haxel et al., 2008). Sometimes the nerves that carry olfactory information from the olfactory receptor neurons to the olfactory bulb can be sheared, cutting off the pathway by which information about smell reaches the brain. People with Alzheimer’s disease also suffer from a diminished sense of smell that is probably due to a combined degeneration of olfactory receptor neurons and neurons located in olfactory brain regions (Djordjevic et al., 2008). Although humans can certainly survive without the ability to smell, their quality of life is considerably diminished. Many people with anosmia report feelings of depression. In addition, there are safety and social issues to consider. Since we use our sense of smell to detect dangers, such as smoke or spoiled food, anosmia increases the risk of injury. Moreover, socially acceptable cultural practices of hygiene may become difficult to follow with anosmia, since humans often use olfactory cues to make decisions about bathing, washing clothes, and brushing teeth. People with anosmia can learn to cope effectively with their condition by using other sensory systems to detect danger. They might, for example, use sound cues, such as a blaring smoke detector to notice smoke, or visual cues, such as appearance and freshness dates, to detect spoiled food.
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The chemical senses are also involved in the symptoms of some people with migraine headaches or epilepsy. For instance, a specific odor can initiate the onset of a migraine (Kelman, 2007). Likewise, patients with a certain form of epilepsy, called reflex epilepsy, will experience a seizure only after exposure to a specific odor. Although the reasons for this remain unknown, these individuals find it necessary to avoid specific intense odorants. In other patients suffering from migraines or epilepsy, stimuli from the other sensory systems, such as touch, sound, and sight, can initiate the headaches or seizures. Some people experience hallucinations called auras either before or during migraine headaches or epileptic seizures. Auras can involve any of the sensory systems. People with these conditions might have touch, sound, or sight hallucinations, and some experience strong, often unpleasant, smells or tastes. The involvement of different senses indicates which brain circuits are compromised in these conditions. For example, if a person’s seizure is preceded by strong olfactory hallucinations, it’s likely that his or her olfactory pathways are initiating the seizure, or at least participating in its generation.
Migraines and the senses Migraine sufferers often experience sensory distortions—for example, a strange light or unpleasant smell—just before or during their headaches. In some cases, specific odors actually trigger migraines.
Before You Go On What Do You Know? 4. 5. 6. 7.
What five tastes have specific receptors? Which parts of the brain are involved in sensing and perceiving odors? What are supertasters? How are smell and taste involved with migraines and epileptic seizures?
What Do You Think? This section of the chapter listed some ways, such as using smoke detectors, for people with anosmia to compensate for their lack of smell. What other ways can you suggest that people with anosmia might use to replace the safety and pleasures that a sense of smell provides?
The Tactile or Cutaneous Senses: Touch, Pressure, Pain, Vibration LEARNING OBJECTIVE 3 Describe how the different senses of touch work and what can happen when things go wrong.
As with the chemical senses, there are rewarding and aversive types of tactile stimuli. The pleasure associated with a relaxing back massage or stroking a baby’s cheek stands in stark contrast to the discomfort of getting a scrape or burn. The tactile or somatosensory system is actually a complex sense. As shown in Figure 5-3, our skin contains a variety of sensory receptors to register different types of physical stimuli (Munger & Ide, 1988). • Free nerve endings are located mostly near the surface of the skin and function to detect touch, pressure, pain, and temperature. • Meissner’s corpuscles transduce information about sensitive touch and are found in the hairless regions of the body, such as the fingertips, lips, and palms. • Merkel’s discs transduce information about light to moderate pressure against the skin.
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FIGURE 5-3 Sensory receptors in the skin The tactile senses rely on a variety of receptors located in different parts of the skin. Fine touch and pressure
Pain and temperature
Meissner's corpuscle (touch)
Free nerve endings for pain (sharp pain and dull pain)
Merkel's disc (light to moderate pressure against skin) Ruffini's end organ (heavy pressure and joint movements)
Free nerve endings for temperature (heat or cold)
Hair receptors (flutter or steady skin indentation)
Pacinian corpuscle (vibrating and heavy pressure)
• Ruffini’s end-organs are located deep in the skin. They register heavy pressure and movement of the joints. • Pacinian corpuscles are also buried deep in the skin and respond to vibrations and heavy pressure. Depression of the skin activates free nerve endings that give us the sense of being touched. As you may have noticed, your skin is not equally sensitive to tactile stimuli over your whole body. Certain parts of your body, for example, the skin on your elbow, are much less sensitive to touch than other areas, such as your face and hands. These differences likely arise as a result of different densities of free nerve endings. Areas that are more sensitive have more free nerve endings. We can also experience sensory adaptation, resulting in reduced tactile sensation from depression of the skin that continues for a period of time. This happens to you every day when you put on your clothing; shortly after getting dressed, you are no longer aware of the tactile stimulus your clothing provides (unless of course it is too tight).
What Happens in the
Tactile Senses B
RAIN?
Our brains use a variety of related processes to help us perceive general information about a range of nonpainful touch sensations, including pressure, temperature, and general touch. Pain perception is also an important, but not yet fully understood, function. Using the brain to counteract pain Anesthesia is a procedure that helps block pain sensations, enabling patients to undergo surgery. Drug-induced anesthetic approaches that act through the brain are general anesthesia (seen here) and sedation.
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The Touching Brain When we touch something, or something touches us, our free nerve endings send tactile information into the spinal cord. The signals travel up the spinal cord to the brain, as shown in Figure 5-4. In the brain, touch information is
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first received in the thalamus, and then routed from there to the Somatosensory 4 The somatosensory cortex cortex receives the information somatosensory cortex (located in the parietal lobe). Information about pressure and vibration is generally transmitted to the brain in a similar way, after being converted to neural impulses by the specialized receptors described above. Our brain processes tactile information contralaterally, or on the opposite side of the brain from the side of the body where the touch occurred. So, if you touch something with your left hand, the information is eventually processed by the somatosensory cortex on the right side of your brain. 3 The thalamus sends the Thalamus information to the As we discussed in Chapter 4, the somatosensory corsomatosensory cortex tex does not have an equal representation of all parts of the body (Kakigi et al., 2000). For example, tactile inputs 2 The information is relayed up the spinal cord from the hands take up proportionately more space in the to the thalamus Pathway for somatosensory cortex than those from the back. This pressure and Pathway for touch vibration seems reasonable, given the fact that our hands are specialized for object manipulation, and we need to process information from them in great detail. As described in the box accompanying this section, other animals have somatosensory systems that are adapted to provide high-resolution tactile information from the parts of their bodies that are especially important to their daily lives. Spinal cord Information about pressure and vibration is generally 1 Tactile receptors respond to touch and pressure transmitted to the brain in a similar way after being conand send information to the spinal cord verted to neural impulses by the specialized receptors FIGURE 5-4 Somatosensory pathways in the cendescribed above. tral nervous system
Pain and the Brain Like general touch information, painful sensations are also transmitted to the brain via free nerve endings. Pain information travels to the brain via two different types of pain fibers. One system, called the fast pathway, uses myelinated axons that, as we discussed in Chapter 4, carry signals faster than unmyelinated axons. Messages about sharp, localized pain travel along the fast pathway directly up the spinal cord to the thalamus and to areas of the somatosensory cortex. Pain information received via the fast pathway helps us to respond quickly with a withdrawal reflex, such as pulling a hand away after touching a hot stove. The slower pain pathway uses more unmyelinated axons—these inputs communicate with brain regions involved in processing emotions. Pain we perceive via the slow pathway is more often burning pain than sharp pain. Like all other sensory systems we’ve discussed so far, the pain system shows evidence of sensory adaptation. A common example of this can be experienced when eating a spicy meal. Recall that the sensation of eating chili peppers is mostly due to the activation of pain fibers located on the tongue. Oftentimes, when a very “hot” food is first ingested, the pain response seems great. However, as the meal progresses, the response diminishes and we are less likely to experience discomfort. This is due to adaptation of the pain fibers and a subsequent decrease in their activity. However, when pain is associated with actual tissue damage or an abnormality in the pain system, as discussed below, pain can be persistent and debilitating.
The Tactile Senses How we Develop The tactile senses are generally in place at birth. In fact, studies have shown that fetuses can respond to the touch of a hair at a relatively early stage in prenatal development (Lagercrantz & Changeux, 2009). However, the ability to recognize and respond to different somatosensory stimuli occurs only after birth and involves further brain development as well as learning.
Ruffini’s end-organs sensory receptors that respond to heavy pressure and joint movement. Pacinian corpuscles sensory receptors that respond to vibrations and heavy pressure.
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Specialized Somatosensory Systems: Whiskers and Star-Shaped Noses Humans have a very high concentration of tactile receptors on our hands, particularly on the fingertips. The many receptors provide us with very detailed, highresolution tactile information. This level of detail is The star-nosed mole very adaptive to us, because our hands are our primary tools for making fine movements. Other mammals, particularly those without hands, have concentrated tactile receptors on different parts of their bodies. They rely on these specific body parts for fine touch information, much in the same way we rely on our hands. Rats and mice, for example, have movable whiskers that they use to detect information in their environments (Feldman & Brecht, 2005). Their whiskers are sensitive to movements of air and physical stimuli. When rats or mice move through small openings
or dig tunnels, they use the movement of their whiskers to help them determine the location of the walls of these confined spaces. The star-nosed mole is named for its specialized nose, shaped like a star, which has 21 appendages. This creature lives mostly underground and is almost completely blind. It navigates throughout its dark environment by using its star-shaped nose as a blind person would use his or her hands, to accomplish such tasks as finding food and exploring its spatial environment (Catania & Remple, 2004). Just as a good deal of the somatosensory cortex in our brains is used to process information from the hands, a large amount of space in the brains of other animals is devoted to processing information from their specialized somatosensory features, The somatosensory cortex in the brain of a rodent devotes a proportionately large amount of space to processing information from the whiskers, for example, and the nose representation in the star-nosed mole somatosensory cortex is proportionately larger than that devoted to other body parts.
For children, one of the most enjoyable types of somatosensory input is being tickled. Although rough or prolonged tickling can become abusive, when tickled under the right circ*mstances, children often explode with laughter. The reaction we have to tickling is a result of activation of somatosensory pathways in an uneven, uncontrollable and unexpected manner. Not only are our sensory systems organized to detect change, but they are most tuned to stimuli that are unexpected and surprising. When you move your body and produce tactile sensations, these stimuli are less noticeable to you than are sensations produced by another individual. The sensations of your own legs touching one another when you cross your legs, for example, is generally less noticeable than a similar touch on your leg would be if someone sitting next to you brushed their leg against yours. Likewise, your reaction to your cat jumping onto your lap is likely to be much greater if you have your eyes closed when it happens. This differential response to surprising tactile stimuli appears to be a defense mechanism that has adaptive significance. It is probably also the reason why being tickled by someone else is more effective at producing an emotional reaction than trying to tickle yourself. Our enjoyment of being tickled generally diminishes as we age. This is likely due to the fact that adults are better at anticipating stimuli, and hence are more difficult to surprise, than are children.
Tactile Senses HOW we Differ Humans differ greatly in their ability to detect physical stimuli on the skin. In addition, they differ in the degree to which they find certain tactile stimulation pleasurable or aversive. For example, some people enjoy an intense back massage while others do not. Of all the somatosensory experiences, the one that has received the most research attention is that of pain. Pain management for surgical procedures and other medical conditions is a critical part of patient care. There are dramatic differences in both the threshold to detect pain and the degree to which pain causes emotional suffering. Some 142 Chapter 5
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of these differences can be attributed to ethnicity. For example, studies have shown that Japanese people have a lower pain threshold than Caucasians. These differences extend to reports of the detection of nonpainful stimuli as well (Komiyama et al., 2009). Although learning plays some role, groups of people also differ in the actual sensation and perception of pain as a result of physical differences in their sensory systems. Studies have shown, for example, that women have a lower threshold for detecting pain than do men. They report greater pain intensity than men in response to the same stimulus (Garcia et al., 2007). One interpretation of this sex difference is that women are just less able to cope psychologically with painful stimuli since they haven’t been “toughened up.” In fact, research suggests that women may have about twice as many pain receptors in their facial skin than men. This suggests a physical cause for at least some of the differences in pain sensitivity. It is not yet known whether this difference exists throughout the body or whether it is specific to the face. Neuroimaging studies show that people’s brains react differently depending on their sensitivity to pain (Dubé et al., 2009). People exposed to a high temperature stimulus in one study exhibited varied responses, for example. Those who reported feeling pain showed changes in activity in their thalamus, somatosensory cortex, and cingulate cortex areas. Those who did not report feeling pain, showed similar activity in the thalamus, but no changes in the cortical regions. Although there may be differences in the two groups’ sensory receptors in their skin, these findings suggest that differences in activation of brain circuitry may also underlie varied responses to painful stimuli. One theory, the gate control theory of pain attempts to explain the relationship of brain activity to pain by suggesting that some patterns of neural activity can actually create a “gate” that prevents messages from reaching parts of the brain where they are perceived as pain (Melzack, 1999). Early versions of this theory hypothesized that pain signals were blocked in the spinal cord, but later research has focused on neurochemicals or patterns of activity in the brain itself. Individual differences in gating mechanisms may result in the wide range of pain sensitivity across people.
High pain threshold This performer lifts concrete blocks and other heavy objects with a chain attached to his pierced tongue—an act that is unbearable for most people to even watch. Although hours of practice and conditioning and certain tricks of the trade each play a role in this behavior, a high pain threshold is certainly a prerequisite.
Tactile Senses As we’ve seen, sensing and perceiving pain are normal, and important, functions of our tactile senses. Some people, however, experience either too much pain or too little. Sometimes, people even feel pain and other sensations in limbs or other body parts that have actually been removed. Chronic Pain The most common abnormality associated with the somatosensory system is that of chronic pain, pain that lasts longer than three months. In the United States, a relatively large percentage of the population, about one in six people, suffers from chronic pain. There are multiple causes of chronic pain, although in some cases the cause cannot be identified. In all cases, however, pain management is a critical issue, since prolonged pain sensations can interfere with daily functioning, and may lead to depression or even suicide. Researchers have identified two groups of chemicals naturally produced by our nervous systems that have pain relieving properties, endorphins and enkephalins. Endorphins and enkephalins belong to a class of molecules called opiates. As we will see in Chapter 6, this class of chemicals also includes pain-killing drugs, such as morphine and heroin. When opiates are present in the nervous system naturally, they are referred to as endogenous opiates. These molecules are released by neurons after intense physical exercise, stress, and sexual experience. They are thought to be responsible for the so-called runner’s high as well as for the ability of some people to perform heroic physical actions under extreme duress.
gate control theory of pain suggests that certain patterns of neural activity can close a “gate” to keep pain information from traveling to parts of the brain where it is perceived. endorphins naturally-occurring pain-killing chemicals in the brain. enkephalins naturally-occurring pain-killing chemicals in the brain.
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Medical practitioners use opiate drugs that mimic or stimulate the endogenous opiate system for pain relief. However, this approach has been problematic because people easily become addicted to opiate drugs. Opiate drugs are not only addictive when they are abused illegally, such as heroin, but when they are prescribed medically, as happens with morphine. Repeated use of these drugs to treat chronic pain can produce a physiological dependence that is very difficult to overcome. In addition, these drugs become less effective with continual use, so higher and higher doses are needed to achieve pain relief. Opiates suppress breathing, however, so they can be very dangerous at high doses. Eventually, people with chronic pain can reach a point where the dose of medicine needed to reduce their pain would be enough to stop their breathing and kill them, but lower doses do not provide them with pain relief. Scientists continue to explore new avenues for pain relief that do not produce addictions or unwanted side effects. In extreme debilitating cases of chronic pain, physicians have turned to neurosurgery. Destroying the pathways that carry information about pain stimuli to the brain can be effective for some people. An extreme form of neurosurgery to relieve intractable chronic pain is a cingulotomy, destruction of the cingulate cortex (Cetas et al., 2008). No Pain Some people are incapable of detecting painful stimuli. While the idea of feeling no pain may sound appealing at first, the fact is that our ability to recognize and respond to discomfort is critical for preventing physical damage to the body. Consider how often you shift position in your chair when you are studying or sitting in a lecture. If you were unable to receive signals of discomfort from your body, you would not move to relieve pressure on your skin. The parts of your skin under continuous pressure would develop sores or bruises. Since many everyday experiences would be damaging to our bodies if we were not able to detect discomfort, a lack of ability to detect pain can be very dangerous.
PRACTICALLYSPEAKING
Quick Ways to Reduce Acute Pain
As we discuss in this chapter, medical practitioners are constantly seeking ways to provide relief to patients in chronic, or continuing, pain. But what about acute pain, the short-term pain you feel when you bump your leg on a table, for example? Gate control theory suggests that touch sensations, which frequently travel along fast fibers, can help prevent some pain sensations traveling on the slow pathways from reaching areas of your brain where they are perceived. According to this theory, the brain only processes so much input, so touch can help to set up a “gate” that stops pain. This explains why we have a tendency to rub the skin of areas of our body that have been injured. For example, if you walk into a piece of furniture, you might rub your leg to dampen the pain.
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Focusing on your breathing may also help. We often tend to gasp and then hold our breath when we injure ourselves, such as bumping a leg. Formal methods of pain control, such as the Lamaze method for childbirth, work in part by altering this natural tendency, by teaching people to breathe in short, panting gasps (Leventhal et al., 1989). Distraction can also help, whereas anxiously focusing on pain can make it worse (al Absi & Rokke, 1991). Some studies have suggested that simply looking at a pleasant view, can affect pain tolerance (Ulrich, 1984). Other evidence suggests that in order for a distraction to be effective, the experience must be active. Studies have shown that playing an interesting videogame can dampen pain detection, whereas passive watching of a TV show has little effect. Stress and sexual experience also decrease the perception of pain. So, if you bump your leg on the way into a big job interview or on a hot date, perhaps you would not notice the pain as much as you would under other circ*mstances!
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Some people are born unable to feel pain. A rare genetic condition called familial dysautonomia is associated with an inability to detect pain or temperature (Axelrod, 2004). Children with this disorder are at grave risk of life-threatening injuries and must be monitored very carefully. Loss of pain sensation can also be acquired later in life. Some medical conditions, including diabetes, can cause neuropathies, or nerve dysfunction, that block pain sensations arising from the person’s extremities. People with such neuropathies may not notice if they sustain an injury in an affected area, such as a toe. Sometimes tissue can get so damaged that it must be amputated. Phantom Limb Sensations Many individuals with amputated limbs report tactile hallucinations or phantom sensations of touch, pressure, vibration, pins and needles, hot, cold, and pain in the body part that no longer exists. Some people even feel the sensation of a ring on the finger or a watch on the wrist of an amputated arm. Similar phantom experiences have been reported in woman who have undergone mastectomy for the treatment of breast cancer (Björkman et al., 2008). Researchers believe that such phantom sensations are the result of abnormal activity in the somatosensory cortex of the brain. When a body part is removed, the part of somatosensory cortex that previously received its input does not become inactive. Instead, somatosensory inputs from intact body parts expand to occupy those regions of the cortex (Ramachandran, 2005). Since information from the face is represented in an area of the somatosensory cortex located near that of the arm and hand, a person whose arm was amputated is likely to experience an expansion of the somatosensory inputs from his or her face into the arm and hand regions of cortex. Although researchers do not fully understand how reorganization of somatosensory cortex produces phantom sensations, there is clearly a memory component to the phenomenon. People are more likely to experience phantom sensations that they actually felt previously, as opposed to random sensations. For example, someone who previously wore a ring or a watch is more likely have the sense of wearing one after an amputation than is a person who didn’t wear a watch or ring. Similarly, people who previously experienced considerable pain in their now-missing body part are much more likely to feel phantom pain.
She feels no pain The child on the right looks like any other 3-year-old welcoming her big sister home from school, except for the goggles she is wearing. The child, who suffers from a severe case of familial dysautonomia, cannot detect any pain to her body and must wear goggles to protect her eyes from excessive rubbing and scratching and the effects of various injuries. She has lost one eye, damaged the other, and inadvertently chewed apart portions of her tongue and mouth.
Before You Go On What Do You Know? 8. 9. 10. 11.
List the different types of tactile receptors in the skin and the primary functions of each. Compare and contrast slow and fast pain pathways. Why do children so often enjoy getting tickled? What are some possible explanations for individual differences in pain sensitivity?
What Do You Think? Have you experienced an occasion when your senses have worked together to either enhance or diminish pain or another touch sense? For example, did certain sights or sounds make pain better or worse?
The Auditory Sense: Hearing LEARNING OBJECTIVE 4 Summarize what happens when we hear.
Hearing, the auditory sense, plays a very important role in social communication as well as in our ability to detect danger. In addition to these clearly adaptive roles, the ability to hear enriches our lives through music and other pleasurable sounds. The Auditory Sense: Hearing 145
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sound waves vibrations of the air in the frequency of hearing. tympanic membrane the ear drum.
The auditory system is designed to convert sound waves, vibrations of the air, into neural impulses. Sound waves have two major qualities that produce our perceptions of different sounds:
ossicles tiny bones in the ear called the hammer, anvil, and stirrup. oval window a membrane separating the ossicles and the inner ear, deflection of which causes a wave to form in the cochlea.
• Frequency. The frequency of a sound wave refers to the number of cycles the wave completes in a certain amount of time. Frequency of a sound wave is measured in units called Hertz (Hz) which represent cycles per second. The frequency of a sound wave is responsible for producing the pitch of a sound. The voice of Mickey Mouse is a high-frequency sound wave that produces a high-pitched sound. Although the range of human hearing is quite large, we hear sounds best within the range of 2,000–5,000 Hz, which encompasses the frequencies of most sounds that humans actually make, such as babies crying and people talking. • Amplitude. The amplitude of a sound wave refers to the strength of a given cycle. Waves with higher peaks and lower bottoms are higher amplitude than those that do not reach such extremes. The amplitude of a sound wave is responsible for our detection of loudness. Waves with high amplitudes produce loud sounds, while those with low amplitudes sound soft. Loudness is measured in units called decibels (dB).
cochlea fluid-filled structure in the inner ear, contains the hair cells. basilar membrane structure in the cochlea where the hair cells are located. hair cells sensory receptors that convert sound waves into neural impulses.
Our detection of sound begins, of course, in the ear. Sound waves are converted to neural impulses in the ear through several steps, as shown in Figure 5-5. 1. First, sound waves enter the outer ear and at its deepest part, deflect the ear drum or tympanic membrane.
1 Sound waves enter ear and deflect tympanic membrane.
2 Vibrations of tympanic membrane strike the ossicles (hammer, anvil, and stirrup). Stirrup hits oval window.
Hammer
3 Vibrations of the oval window create waves in the cochlea fluid which deflects the basilar membrane. This movement bends the hair cells.
4 The hair cells communicate with the auditory nerve, which sends neural impulses to the brain.
Anvil Stirrup Oval window Auditory nerve
Auditory cortex
Sound waves
Auditory nerve
Tympanic membrane
Cilia
Cochlea Cross-section through one turn of cochlea
Outer ear
Middle ear
Inner ear
FIGURE 5-5 How the ear hears Basilar membrane
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Hair cells
Auditory nerve
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2. Vibrations of the tympanic membrane set in motion a series of three tiny bones or ossicles, called the hammer, anvil, and stirrup. The stirrup, which is the last bone in the chain, hits the oval window, a membrane separating the ossicles and the inner ear. 3. Deflection of the oval window causes a wave to form in the fluid-filled cochlea of the inner ear. When fluid moves in the cochlea, it deflects the basilar membrane that runs down the middle of the cochlea. The basilar membrane is covered with rows of hair cells, the auditory sensory receptors. Movement of the basilar membrane bends the hair cells that transduce the “fluid sound wave” into electrical activity. 4. The hair cells communicate with nerves in the cochlea that, in turn, send the neural impulses to the brain.
Unlike in humans, damaged hair cells in the bird cochlea are regenerated. Scientists are studying the regeneration of bird hair cells to find ways to repair hearing loss in humans.
There are two major theories about how the auditory system converts sound waves into all the various sounds we can perceive. The first, called frequency theory, suggests that different sound frequencies are converted into different rates of action potentials or firing in our auditory nerves. According to this theory, high-frequency sounds produce a more rapid firing than do low-frequency sounds. Although there may be some truth to frequency theory—different firing rates contribute to sound perception of low tones—researchers agree that this theory cannot fully explain sound perception. The second theory, called place theory, seems to account for a greater degree of auditory perception. Place theory holds that differences in sound frequency activate different regions on the basilar membrane. Regions along the basilar membrane send inputs to the brain that are encoded according to the place along the membrane where the inputs originated. As with the other sensory systems we’ve discussed, adaptation also occurs in the auditory system when we are continuously exposed to sounds. We can adapt to sounds in several ways. First, our ears respond to very loud sounds by contracting muscles around the ear’s opening so that less of the sound wave can enter the ear. This also happens when you talk, so that the sound of your own voice, which is so close to your ear, is not deafening. Second, the hair cells of the ear also become less sensitive to continuous noises. Unfortunately, if the noise is loud enough, it can actually damage the hair cells (Petrescu, 2008). Unlike receptors for the chemical senses, our sensory receptors in the ear are not readily replaced, so such damage to the hair cells makes the ear permanently less sensitive. To protect your own hair cells from such permanent damage, which is associated with hearing loss, avoid prolonged exposure to loud noises—including the music coming through your iPod! Finally, the brain can filter out many sounds that are not important, even if they are relatively loud. This ability enables you to carry on a conversation with your friends at a noisy party. This phenomenon, often referred to as the co*cktail party effect, is another example of top-down processing. The brain is able to attend to, and pick up on, relevant sounds even in a very noisy environment. These relevant sounds, such as your name or the names of people who interest you, grab your attention and focus your auditory perception because you have previously learned their importance. So background noise, even if it’s also the sounds of people talking, interferes minimally with hearing a conversation, as long as the conversation is of interest to us. To determine the importance of a particular sound, it’s necessary to localize it in space, to figure out where it is coming from. For example, if you’re driving in a car and you hear the sound of an ambulance siren, you need to determine whether the ambulance is far away or close up in order to decide whether or not to pull over to the side of the road to let the ambulance pass. You also need to determine from which direction the sound is approaching you. The auditory system uses several cues to help localize sound: • General loudness We learn from many early experiences that loud sounds are usually closer to us than are quiet sounds, so that eventually we automatically use the loudness of a sound to assess the distance between ourselves and the source of the sound.
What television? This father, who has set up shop in his family room, seems oblivious to the loud sounds coming from the television that his son is watching. He is concentrating on his phone conversation and professional work while filtering out the irrelevant TV noise.
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tonotopic map representation in the auditory cortex of different sound frequencies.
• Loudness in each ear Because of the distance between our ears and the presence of the head between our ears, there are slight differences between each ear in the loudness of the same sound wave. The ear closer to the sound hears a louder noise than the ear farther from the sound. This difference is particularly useful in detecting the location of high-frequency sounds. • Timing Another cue used to localize sound is differences in the time at which sound waves hit each ear. Sound waves will reach the ear closer to the source of the sound before they reach the ear farther away. Since the ears are separated in space, a sound wave will also hit each ear at a slightly different part of its wave cycle, creating a phase difference. This cue is particularly useful to us in localizing sounds with low frequencies. We also adjust our heads and bodies to assess the location of sounds. These movements allow us to hear how the sound changes while we’re in different positions and to use those changes to help make a reasonable approximation of its location. Finally, the use of other sensory systems, such as vision, may come into play. For instance, you might confirm the location of the ambulance when you look into your rearview mirror and see it approaching.
What Happens in the
Hearing B
They can’t fool the brain (yet) M.I.T. professor Neil Gershenfield and a graduate student work on project Digital Stradivarius, an attempt to build a digital model that can match the sound of the great violins of Stradivarius. When digital-produced and instrument-produced sound waves are each converted into neural impulses in the brains of musical experts, the experts can detect a difference. The instrument remains the champ.
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RAIN?
After auditory information is transduced from sound waves by the hair cells in the basilar membrane of the cochlea, it travels as signals from nerves in the cochlea to the brainstem, the thalamus, and then the auditory cortex, which is located in the temporal lobe. Part of the primary auditory cortex is organized in a tonotopic map. That is, information transmitted from different parts of the cochlea (sound waves of different frequency and, hence, sounds of different pitch) is projected to specific parts of the auditory cortex, so that our cortex maps the different pitches of sounds we hear. Auditory information from one ear is sent to the auditory cortex areas on both sides of the brain. This enables us to integrate auditory information from both sides of the head and helps us to locate the sources of sounds. From the primary auditory cortex, auditory information moves on to the auditory association areas in the cortex. As we described in Chapter 4, association areas of the brain’s cortex are involved in higher-order mental processes. Association areas help to link the sounds we hear with parts of the brain involved in language comprehension. Association areas also integrate, or coordinate auditory information with signals from other sensory modalities. Have you ever noticed how distracting it is to watch a movie that has an audio slightly out of synchrony with the video image? This is because the brain is set up to integrate information from multiple sensory systems. Over time, we learn to have expectations about the coincidence of certain visual stimuli with specific sounds. When the sounds in a movie do not match the visual images the way they would in real life, our expectations are violated and our attention is drawn to this discrepancy from the norm. In some people, the integration of sensory systems in the brain can sometimes lead to abnormal crossover of different modalities. As described in the box accompanying this section, people who experience a condition known as synesthesia, perceive sensations in a different modality from that of the original stimulus. Synesthesia is not a debilitating abnormality; in fact it has sometimes been described as enriching, particularly when it occurs in artistic or musical individuals.
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Specialized Somatosensory Systems: Synesthesia Can you see noise or taste words? Some people can. This condition is called synesthesia. The name comes from two Greek words: syn, meaning together, and aesthesis, meaning perception, and therefore refers to “The best kaleidoscope ever” “joined perception.” People Performer and songwriter Tori Amos has who have synesthesia expesaid that she often experiences the notes rience a stimulus that norand chords in her music as colors and mally would be perceived by light filaments. She says, “Try to imagine the best kaleidoscope ever.” one sense in a different sensory modality. They may actually see colors or images when they hear music. The most common form of synesthesia is called colored letters or numbers. A person who has this form always sees a color
in response to a specific letter or number. There are also synesthetes who smell particular odors in response to touch, who hear noises in response to smell, or who feel a tactile stimulus in response to sight. There are even some individuals who possess synesthesia involving three or more senses, but this is especially unusual. People who experience synesthesia are not simply imagining their unusual sensations. Neuroimaging studies have shown that sensory areas normally not affected by particular stimuli are activated if that sense is involved in the synesthetic experience (Nunn el al., 2002). For example, the auditory cortex of sight–sound synesthetes, as well as the visual cortex, becomes active in response to particular visual stimuli that cause synesthesia. The brain of a person who can hear a picture or color really does respond as though the stimulus were producing sound waves, as well as reflecting light waves.
Hearing How we Develop Our ears are formed and capable of transducing sound waves before we are even born. In fact, human fetuses have been shown to respond to noises long before birth. Research has shown that fetuses respond to loud noises with a startle reflex and that after birth, they are capable of recognizing some sounds they heard while in utero. However, the ability to recognize and respond appropriately to a wide variety of sound stimuli is acquired over many years of postnatal life. Sounds associated with language, for example, become recognizable over postnatal development, as do those associated with music. We describe language development in more detail in Chapter 9. Sensitive periods exist for the development of both language and music learning (Knudson, 2004). As we described in Chapter 3, we acquire certain abilities during sensitive periods of development much more easily that we do after the sensitive period has ended. The tonotopic map in the primary auditory cortex of the brain is organized during such a sensitive period of development (deVillers-Sidani et al., 2007). Studies in experimental animals have shown that exposing animals to pure tones during a certain time in development, leads to a larger representations of those sounds in the auditory cortex. The same exposure after the sensitive period in development is over has no such effect. If a sound is made important to the animal, however, by pairing it either with a reward, such as water, or a punishment, such as an electric shock, the primary auditory cortex can be reorganized so that more of it responds to the relevant tone (Bakin et al., 1996). Such top-down processing of tones indicates that this region of the brain still shows plasticity after the sensitive period is over. It is not as easy, however, to remap the brain after a sensitive period as it is during one. The stimuli needed to produce changes in older animals must be very strong and important, compared to those needed for younger animals (Kuboshima & Sawaguchi, 2007). In humans, the auditory brain is set up to acquire information about speaking and music most readily relatively early in life, during the preschool years. It is more difficult, but by no means impossible, for us to learn additional languages or certain music skills after we mature.
A bit too early A pregnant woman tries to introduce music to her fetus by positioning headphones on her stomach. Although fetuses do indeed respond to loud noises and can detect certain sounds, the acquisition of musical skills cannot take place until sensitive periods unfold during the pre-school years.
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Hearing HOW we Differ
Breaking the bad news One of the guilty pleasures for many American Idol fans is that special moment when judge Simon Cowell calls a contestant “tone deaf.”The show includes performers whose musical abilities vary from absolute pitch to tone deafness.
We differ greatly in our ability to detect specific sounds. People show particular differences in their ability to identify certain notes in a scale. Absolute pitch refers to the ability to recognize an individual note in isolation. This is very difficult for most people. Only about 1 in 10,000 people in Western countries has absolute pitch. This ability seems to originate in childhood, between the ages of three and six years, through musical training, and it is associated with differences in brain anatomy (Zatorre, 2003). Research has shown that portions of the cortex are actually thinner in individuals with absolute pitch (Bermudez et al., 2009). Although it’s not clear whether people with absolute pitch start out with a thinner cortex or whether they develop it through training, it’s possible that synaptic pruning contributes to this structural difference. Studies have shown, however, that people who speak tonal languages, or languages in which differences in tone convey meaning, such as Vietnamese and Mandarin Chinese, are more likely to develop absolute pitch than those speaking Western languages. This again suggests the possibility that early learning of auditory information related to tones can have a permanent effect on the functioning of this sensory system. Just as some people exhibit absolute pitch, others are tone deaf, or unable to discern differences in pitch. Although tone deafness or amusia is sometimes the result of damage to the auditory system, it can be present from birth, and researchers believe it may be related to genetics (Peretz et al., 2007). Tone deafness affects up to 4 percent of the population and mostly results in a diminished appreciation for music. Although music appreciation is an important enriching ability, people with tone deafness are able to enjoy all other aspects of life. This condition only presents serious social problems when it occurs in cultures where the language is tonal.
Hearing There are many conditions that lead to abnormalities in the auditory system. Some cause either partial or total deafness, the loss of hearing. Abnormalities in the auditory system can also add unwanted auditory perceptions.
A world of new possibilities After undergoing successful cochlear implant surgery, this four-year-old child practices the violin under the instruction of his music teacher at the Memphis Oral School for the Deaf.
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Deafness Deafness has a variety of causes. It can be genetic or caused by infection, physical trauma or exposure to toxins, including overdose of common medications such as aspirin. Since speech is an important mode of communication for humans, deafness can have dramatic consequences for socialization. This is particularly a concern for children, because young children need auditory stimulation in order to develop normal spoken language skills. For this reason, physicians try to identify auditory deficits at an early life stage. Parents can then make choices among different options to help their children with deafness. Some deaf individuals learn to use sign language and other methods of communication that rely on the senses other than hearing. Research over the past years has made progress in the construction of cochlear implants that help individuals with deafness to hear sounds (Sharma et al., 2009). Although this work is developing at a rapid pace, there remain many deaf people who are not helped by cochlear implants, however. (Battmer et al., 2009). This is one reason that many individuals and families choose to avoid them. Some in the deaf community also believe that hearing is not necessary in order to lead a productive and fulfilling life. For them, the potential benefits of implants may not outweigh the potential risks of surgery required to place them in the cochlea (Hyde & Power, 2006).
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Hearing Unwanted Sounds About one of every 200 people is affected by tinnitus, or ringing in the ear. Tinnitus has multiple causes, some of which are related to abnormalities in the ear itself (Lanting et al., 2009). Most people are able to cope with the noise, but some find it too loud and distracting to ignore. Patients with epilepsy in the temporal cortex have reported the perception of hearing complex auditory stimuli, such as a musical tune (Wieser, 2003). This symptom, which can be completely distracting and disturbing to the patient, is the result of abnormal electrical activity in brain circuits that store complex auditory memories. Treatment for epilepsy sometimes involves neurosurgery to remove the part of the brain that is responsible for starting the seizures. Brain surgery in the temporal lobes, where auditory information is processed is particularly dangerous, however, because the temporal lobe also houses Wernicke’s area, which is critical for language comprehension.
“
I have unwittingly helped to invent and refine a type of music that makes its principal exponents deaf. Hearing loss is a terrible thing because it cannot be repaired. –Pete Townshend, rock musician of the band The Who
”
Before You Go On What Do You Know? 12. 13. 14. 15.
What What What What
happens in the ear to transduce sound waves into neural signals? is a tonotopic map? are sensitive periods and how are they important for hearing? is tinnitus?
What Do You Think? What would you suggest including in an ideal early school curriculum, to develop children’s auditory systems to their maximum capabilities?
The Visual Sense: Sight LEARNING OBJECTIVE 5 Describe key processes in visual sensation and perception.
The ability to see and make sense of the visual world around us plays a very important role in human life. We use our vision in virtually all of our activities. Most of our social experiences have a visual component, for example. Vision is important for communication: facial expressions and “body language” or nonverbal communication help to convey information that is often lost in spoken language. No doubt related to its importance to us, the visual sense is particularly well developed in humans. Some estimates suggest that about half of the cerebral cortex of our brains is devoted to processing some type of visual stimuli. The stimulus for vision is light. Light is made up of particles called photons. The light that we can see is part of the electromagnetic spectrum of energy that also includes many forms we cannot see, such as X-rays and radio waves. Like sound, light travels in waves. The visible spectrum of light ranges from about 400 to 700 nanometers in wavelength (a nanometer is a billionth of a meter). As shown in Figure 5-6, different wavelengths within our visible spectrum appear to us as different colors. Objects in the world absorb and reflect light in varying levels and patterns—those that reflect more light are perceived as brighter.
absolute pitch the ability to recognize or produce any note on a musical scale. deafness loss or lack of hearing.
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FIGURE 5-6 Visible light and the electromagnetic spectrum The part of the electromagnetic spectrum that our visual receptors can detect is restricted to a narrow range.
Visible light AC circuits
Broadcast bands
Radar
Microwaves
IR
UV
X rays
Gamma Cosmic rays rays
Amplitude Wavelength Invisible Long Waves
Invisible Short Waves
Visible Light Spectrum
Infrared rays (beyond red)
1500
800
Ultraviolet rays (beyond violet)
700
600
500
400
300
Wavelength (in nanometers)
Seeing the Light
The photoreceptors This colorized scanning electron micrograph shows the retina’s photoreceptors—the rods and cones—which help pass visual signals through the optic nerve to the brain. Rods (pink) are the photoreceptors that detect light. Cones (olive) are photoreceptors that detect color.
retina a specialized sheet of nerve cells in the back of the eye containing the sensory receptors for vision. photoreceptors the sensory receptor cells for vision, located in the retina. rods photoreceptors most responsive to levels of light and dark. cones photoreceptors responsive to colors.
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Vision begins when light enters the eye, as shown in Figure 5-7. Muscles in the iris— the colored part of the eye that you can see—adjust the size of our pupils to let in more or less of the light reflected from objects around us. These muscles also adjust the shape of the lens, focusing the light that enters the eye onto a specialized sheet of nerve cells in the back of the eye, called the retina. The retina is where we transduce light waves into neural impulses that the brain can process. Two major classes of visual receptors or photoreceptors exist in the retina, the rods and the cones. The rods predominate. There are over 100 million rods in the human retina. Rods are important for detecting light; they are highly sensitive to small amounts of light and are critical for night vision. The cones are much fewer in number, with only about 6 million per human retina. Cones respond to light of different wavelengths, which is how we detect color. When light reaches the photoreceptors, a series of chemical reactions take place. The rods and cones stimulate the bipolar cells that, in turn, cause ganglion cells to then fire. The axons of the ganglion cells are bundled together to form the optic nerve. Signals from the ganglion cells travel along the optic nerve out of the eye and into the brain. Rods and cones are not evenly distributed throughout the retina. Cones are concentrated more in the center than the periphery of the retina. The fovea, the region of the retina where our vision is at its sharpest, is entirely made up of cones. Rods are distributed throughout the rest of the retina and, unlike cones, are concentrated at the peripheral edges of the retina. Have you ever noticed that your peripheral vision is not particularly acute? It mostly enables you to detect movement, but not necessarily details. This is due to that fact that rods dominate the peripheral parts of the retina. The retina also contains a region that is completely lacking in rods and cones. This area produces a blind spot in your visual field. The blind spot is the location where your optic nerve leaves your retina. Because the visual parts of the brain are very good at filling in incomplete images, the blind spot is not noticeable under normal circ*mstances. With some manipulation of your visual inputs as instructed in Figure 5-7, however, you can experience your blind spot. Like the other sensory systems we previously discussed, the visual system undergoes sensory adaptation. Dilation and constriction of the pupil, the opening in the center of the iris, is one way that the visual system adapts to the light. When you go from inside your home to outside on a bright, sunny day, you may immediately feel the need
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FIGURE 5-7
Lens
How the eye sees Retina 1 Light enters the eye -
Eye lid
Muscles in the iris adjust the size of the pupil to let in more or less light. Light
Fovea
Pupil Optic nerve
Iris Blind spot
Receptor cells
2 Light is transduced by the
photoreceptors [rods and cones] in the retina, at the very back of the eye. Changes in the excitability of photoreceptors are passed along to other neurons in the retinal circuitry.
Ganglion cells
Bipolar cells
Cones Rods
Optic nerve axons
Optic nerve to brain
Blind spot
Neural impulses
3 Photoreceptors project to interneurons
Light
which communicate with ganglion cells in the retina. Ganglion cells send visual input from the retina to the brain via the optic nerve. Neural impulse
Find your blind spot The blind spot is not normally noticeable. To find yours, hold this book about a foot away, close your right eye, and stare at the X with your left eye. Very slowly, bring the book closer to you. The worm should disappear and the apple become whole.
to squint, and shade your eyes. Your eyes quickly adapt to light, however, in part by constriction of the pupil that decreases the amount of light entering the eye. Conversely, to allow vision to occur in dark places, the pupil will open further to let in more light.
Seeing in Color As we noted earlier, cones enable us to see color. The color of a visual stimulus can be described along three dimensions: hue, saturation, and brightness. The variety of colors we can perceive is related to the different combinations of these three characteristics. • Hue refers to the wavelength of light that the visual stimulus produces. This is the most basic aspect of color, whether the stimulus is red, blue, yellow, or some other color.
optic nerve the bundle of axons of ganglion cells that carries visual information from the eye to the brain. fovea center of the retina, containing only cones, where vision is most clear.
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• Saturation refers to how pure and deep the color appears—in other words, how much white is mixed into the color. • Brightness of a color refers to how much light emanates or is reflected from the visual stimulus.
Changing one’s view These two people at the Sensorium museum exhibit at M.I.T. wear wireless head gear that causes each of them to view the world from the visual perspective of the other. This visual manipulation is eventually adjusted to, but, for a while, it interferes with many aspects of visual functioning, including shape, light, and color perceptions; activity in visual regions of the brain; depth perception; and perceptual constancies.
FIGURE 5-8 The afterimage effect Afterimages occur when one color in an opponent pair inhibits the other. When you look away from the first color, the previously inhibited color is turned on. To see opponent processing in action, stare at the white dot in the center of the flag for about 30 seconds, then look away at a white sheet of paper.
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No single theory yet entirely explains how we perceive color. Two theories of color vision in combination help to explain a good deal, however. One theory, called the trichromatic theory of color vision, maintains that there are three different sensors for color and that each type of sensor responds to a different range of wavelengths of light (Balaraman, 1962). We can certainly see more than just three colors, however. The rich variations we can detect in color arise from combinations in relative activation of these three types of sensors. This theory is largely correct, in that people with normal color vision have three different kinds of cones. One type responds to light in the yellowish-red wavelengths, another to the green wavelengths, and the third to light in the bluish-purple wavelengths. Typically, at least two of the cone types will respond to a certain wavelength of visible light, but in varying increments. The combination of the signals produced by cones is what enables the brain to respond to a multitude of colors. An alternative theory about color vision is called the opponent process theory (Buchsbaum & Gottschalk, 1983). This theory maintains that color pairs work to inhibit one another in the perception of color. For example, red inhibits the perception of green, yellow inhibits the perception of blue, and black inhibits the perception of white. There is also some truth to this theory because we cannot mix certain combinations of colors. For example, we cannot see reddish green or bluish yellow; instead we see brown or green, respectively. Opponent processing may be the result of activity in a region of the thalamus that receives visual information, called the lateral geniculate nucleus. Inputs to this nucleus from one color of an opposing pair inhibit those from the other color in the pair. So inputs carrying red information prevent the firing of neurons that convey green information, and so on for the other opponent pairs. You can observe opponent processing at work by staring at the white dot in the middle of the green and black flag in Figure 5-8. After about 30 seconds, stare at a white sheet of paper. You will see an afterimage that is red and white. This also works with other colors in the opponent pairs. A white-on-black image will produce a black-onwhite afterimage, and a yellow image will produce a blue afterimage. Afterimages happen when one color in an opponent pair inhibits the other. When we release this inhibition by looking away from the first color, the previously inhibited color overcompensates and creates an image in the opponent color.
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The two theories can be used together to explain color blindness. Very few people are actually unable to see any colors at all. Most people who have what is called color blindness are really just unable to distinguish certain colors. Most common is red-green color blindness, which is tested with images, such as the one shown in Figure 5-9. Studies suggest that people with this problem have a shortage of cones that respond to either the greenish or reddish wavelengths. Therefore, the lateral geniculate nucleus of their thalamus does not receive sufficient inputs that enable it to inhibit either red or green colors, making people unable to distinguish between the two colors (Weale, 1983; Wertenbaker, 1981).
What Happens in the
Sight B
RAIN?
Visual information leaving the retina travels via the optic nerve to the brainstem. After synapsing with neurons in the superior colliculus, visual information then communicates with the thalamus. From the thalamus, visual input travels to the primary visual cortex, located in the occipital lobe. Basic visual information is transmitted throughout the brain via a partially crossed set of axons (Figure 5-10). Visual information from the middle part of your visual field, closest to your nose, is sent, via axons that cross to the other side of your brain, to the opposite side of your visual cortex. Visual information from the lateral part of your visual field, closest to your temples, travels to the same side of the visual cortex. Once visual information reaches the primary visual cortex, it is processed to enable the detection of very simple features, such as lines and edges (Hubel & Wiesel, 1959). However, we don’t see the world as a collection of lines and edges. Instead, we see a rich set of complex visual stimuli that change as we and the world around us move. Detection of complex visual stimuli occurs as a result of circuitry that involves association areas of visual cortex. Recall from our discussion of hearing that association areas are involved with higher-order processes of perception: thinking and memory. The pathways that process information about complex visual stimuli can be roughly divided into the “what” and the “where” pathways, as shown in Figure 5-11 (Ungerleider & Haxby, 1994). That is, the regions that process visual information to help us determine what is the identity of an object (is it an apple, a car, or a house) are different from those where
FIGURE 5-9 Color blindness Most people who are color blind cannot distinguish between red and green; they would see only a random pattern of dots in this figure.
Primary visual cortex
Optic nerve Eye
V i s u a l f i e ld
FIGURE 5-10 The crossed visual pathway Before entering the brain the optic nerves partially cross. Visual information from the middle part of your visual field travels to opposite sides of your visual cortex, while information from the lateral part of the field (closest to your temples) travels to the same side of the visual cortex.
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we process the visual information to figure out where in space the object is located (is the apple on the table, under the table, or behind the table). The “what”pathway involves axons that travel from the occipital cortex to the temporal cortex. The “where” pathway involves axons that travel from the occipital cortex to the parietal cortex. How do researchers know about the brain regions that serve these complex functions? Recall from Chapter 4 that one way scientists have determined the funcOccipital cortex tion of certain brain regions is by examining the deficits displayed by people who have sustained damage in particular areas of their brains, usually as a result of stroke, disease, or head trauma. Patients with damage to the parts of the temporal cortex, which houses the “what” pathway, exhibit a condition called visual agnosia. Although their vision remains intact, they cannot recognize objects visually. When shown a rose, they can describe it, but they cannot name it. If they are allowed to touch or smell the rose, however, they can immediately identify it as a rose. A more specified form of visual agnosia that happens to people with damage to a certain part of the “what” pathway is called prosopagnosia. Individuals with prosopagnosia cannot recognize faces (Farah et al., 1995). Sometimes these patients can recognize familiar individuals by concentrating on some visual characteristic that is not directly related to facial features, such as the person’s hairstyle or eyeglasses, but their ability to recognize the face itself is lost (Sacks, 1985). Patients with damage to the “where” pathway also have normal vision, but they have lost the ability to locate objects in space. For example, when given the task of pouring water from a pitcher into a glass, they will invariably miss and pour the water onto the table or floor. A very interesting form of damage to the “where” pathway results in a condition called hemi-neglect (Mesulam, 1981). Patients with hemi-neglect completely ignore one side of their visual field. Because nerves that carry visual information cross to the opposite sides of the brain, people with damage to the left side of their “where” pathways neglect the right side, and vice versa (Figure 5-12). When asked to copy a drawing, people with hemi-neglect will leave out one half of it. Women with this condition have been known to apply makeup and do their hair only on one side. In addition to the information researchers have gained from studying patients with brain damage, neuroimaging studies of people without brain damage have confirmed the presence of the “what” and “where” pathways. Indeed, these types of studies have shown that brain activity changes in specific parts of the “what” pathways when the participants are viewing objects (Reddy & Kanwisher, 2006). So far we have discussed vision from a bottom-up perspective. Light comes in through the eye and the neural impulses generated are passed to successively more complex brain regions that ultimately result in the perception of a visual stimulus. Equally important to visual perception, however, is top-down processing, which involves previously acquired knowledge. Like perception involving the other sensory systems, visual perception involves both bottom-up and top-down processing occurring at the same time. Brain regions that store information about what objects look like can help us to perceive visual stimuli that are partially hidden or of different size from when we originally encountered them. Parietal cortex
W
he
re
Temporal cortex
What
FIGURE 5-11 The “what” and “where” pathways The “what” pathway of the brain processes information that helps us identify an object, while the “where” pathway helps us identify its location in space. Communication between the two pathways allows us to integrate complex visual stimuli.
FIGURE 5-12 Seeing only half the picture When asked to copy a drawing of a house with a driveway, parked car, and garden to its left, a patient with hemi-neglect copies only the right side of the drawing—the house and a tree. She completely ignores the left side of her visual field.
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Putting Together the Parts: Gestalt Principles We don’t see images as a series of small patches of color or a series of simple features. Instead, our visual system assembles this information into coherent objects and scenes. Even when we see a small part of an object or scene partially obscured by another object, we are able to perceive it as a whole, given limited visual information. Our brains are organized to fill in the missing parts so that we perceive and recognize meaningful stimuli. As we described earlier, part of our ability to perceive images comes from our use of cognitive processes, such as memory and learning, to help us recall from prior experience images that match the stimuli we are sensing. The area of study focused on understanding principles by which we perceive and recognize visual stimuli in their entirety despite limited information is called Gestalt
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psychology. As mentioned in Chapter 1, Gestalt psychologists believe that perception helps us to add meaning to visual information, so that “the whole is greater than the sum of the parts” of what we see. Gestalt psychologists have identified several laws by which visual information is organized into coherent images:
:) O
• Proximity The law of proximity indicates that visual stimuli near to one another tend to be grouped together. For example, AA AA AA is seen as three groups while AAA AAA is seen as two groups despite the fact that each set has six As. • Similarity The law of similarity indicates that stimuli resembling one another tend to be grouped together. So AAaa is viewed as two groups because of the dissimilar appearance of upper and lowercase letters. • Continuity The law of continuity indicates that stimuli falling along the same plane tend to be grouped together. AAA AAA would be organized into two perceptual groups because they are not on the same line. • Good form The law of good form indicates that stimuli forming a shape tend to be grouped together while those that do not remain ungrouped. Compare to O:) . The former are perceived as a smiley face while the latter are perceived as three separate symbols. • Closure The law of closure indicates that we tend to fill in small gaps in objects so that they are still perceived as whole objects. These laws of visual organization work to create meaningful information out of the vast array of photons our eyes typically encounter when we look at something. Sometimes, however, our brain’s tendency to impose order can lead us to perceive sights that are, in fact, illusions, such as those shown in Figure 5-13. Only careful examination reveals that the drawings depict physically impossible situations.
FIGURE 5-13 Impossible figure The brain is organized to perceive meaningful images; with impossible figures such as this, the brain tries but cannot form a stable perception. (M.C. Escher’s “Convex and Concave” ©2009 The M.C. Escher CompanyHolland. All rights reserved. www.mcescher.com)
Getting in Deep When you look at the items on the table in a restaurant, how do you know which items are closer to you and which are farther away? We use a number of methods for depth perception, determining the distance of objects away from us and in relation to one another. Because our eyes are set a slight distance apart, we do not see exactly the same thing with each eye. This retinal disparity, the slightly different stimuli recorded by the retina of each eye, provide us with a binocular cue of depth. Our brains use the discrepancies between the visual information received from our two eyes to help us judge the distance of objects from us. You can observe your own retinal disparity by holding up a finger at arm’s length away from your face. Close first one eye, then the other, and note how the position of your finger seems to change relative to objects in the background beyond the finger. Another binocular cue to depth is actually tactile. We feel the changes in the muscles around our eyes as we shift them to look at objects at various distances. Closer objects require more convergence, turning our eyes inward toward our noses. Use your finger again to demonstrate convergence. Start with the finger at arm’s length from you and watch it as you bring it closer and closer to your face. Note the sensations you feel as you do so. We also use a number of other cues to determine depth. The following are sometimes called monocular cues, because, if needed, they can help us judge depth based on information from only one eye. You can see them all in the photo in Figure 5-14:
retinal disparity the slight difference in images processed by the retinas of each eye.
• Interposition When one object blocks part of another from our view, we see the blocked object as farther away. • Elevation We see objects that are higher in our visual plane as farther away than those that are lower.
convergence inward movement of the eyes to view objects close to oneself. monocular cues visual clues about depth and distance that can be perceived using information from only one eye.
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• Texture gradient We can see more details of textured surfaces, such as the wood grain on a restaurant table, that are closer to us. • Linear perspective Parallel lines seem to converge in the distance. • Shading We are accustomed to light, such as sunlight, coming from above us. We use differences in the shading of light from the top to the bottom of our field of view to judge size and distance of objects. • Familiar size Once we have learned the sizes of objects, such as people or restaurant plates, we assume that they stay the same size, so objects that look smaller than usual must be farther away than usual. • Relative size When we look at two objects we know are about the same size, if one seems smaller than the other, we see it as farther away than the other.
FIGURE 5-14 Monocular depth cues How many monocular depth cues can you identify in this photograph of the Taj Mahal in India?
Although some studies show that we can perceive depth at very early ages, and may even be born with some depth perception abilities, top-down processing also plays a part in depth processing (Banks & Salapatek, 1983). We use our memories of the sizes of objects around us, for example, to help judge depth. Artists use monocular depth cues to help us “see” depth in their two-dimensional representations. In essence, they create an illusion of depth. Because visual perception happens nearly automatically, we are quite susceptible to such visual illusions. For example, people from cultures that have a lot of architecture and structures featuring straight edges, such as the United States, are easily fooled by the Ponzo illusion and Müller-Lyer illusion, shown in Figure 5-15, which both take advantage of our tendency to use linear perspective to judge distance (Berry et al, 1992; Brislin & Keating, 1976).
perceptual constancies our top-down tendency to view objects as unchanging, despite shifts in the environmental stimuli we receive.
Seeing What We Expect to See: Perceptual Constancies Top-down processing also contributes to perceptual constancies, our tendencies to view objects as unchanging in some ways, even though the actual visual sensations we receive are constantly shifting. We tend to see the food on our plate as the same colors, for example, even when a restaurant owner dims the lights for the evening and the actual light waves we are receiving change in intensity, a phenomenon known as color constancy (Schiffman, 1996). Once we have learned the shape of an object, we also experience shape constancy (Gazzaniga, 1995). We may get visual input of only the edge of a plate as server sets it on a restaurant table in front of us, but we perceive the plate as a round disk. Another consistency, size consistency, helps us in depth perception, as noted above. Once we have learned the size of an object, we expect it to stay the same. Top-down processing, based on our memory of the object’s size, leads us to assume that if it looks smaller than usual, it is probably far away, instead of thinking that the object has somehow shrunk. As with our other perceptual processes, perceptual constancies, while usually very useful in helping us understand the world, can sometimes lead us to “see” illusions. A common size illusion, for example, is the moon illusion. The moon stays the (b) (a)
FIGURE 5-15 Perceptual illusions (a) The Müller-Lyer illusion: The line on the right appears longer, but both lines are the same length.
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(b) The Ponzo illusion: The converging lines make the upper bar seem larger, but both bars are identical in length.
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same size all the time, but when we view it close to a horizon it appears much bigger than when we see it farther from the horizon (see Figure 5-16) (Kaufman & Rock, 1989).
Sight How we Develop Newborn infants are capable of seeing, but their visual acuity is much less than it will be after a few months. For a short time after birth, human babies focus mostly on contrasts. For example, a baby will stare at the hairline of his or her caregiver, instead of the face. By the time we are about two months old, visual acuity has improved and infants seem to focus intently on faces. Their focal range is limited, though. They see objects best that are within a foot away. Perhaps not coincidentally, this is about the distance people tend to place their faces when interacting with babies. Over the next several months, our visual acuity improves so that by the end of the eighth month, vision in babies is quite similar to that of normal adults. These early life changes in vision are due to the postnatal development of the visual nervous system. As we’ll see next, proper development of the visual system requires visual experience during a specific part of early life.
Sight Many common vision problems can be corrected today. Increasingly common laser surgeries or the lenses in glasses or contacts can help people cope with nearsightedness, or difficulty seeing things clearly far away, and farsightedness, problems seeing near objects clearly, for example. Eye-care practitioners help with a variety of other problems as well. Sometimes, however, there is no treatment available, or treatment is begun too late to prevent people from losing vision in one or both eyes. Amblyopia To see the world as a whole, both eyes must work together to produce not two separate images, but one comprehensive image. To do this, motor control of both eyes is important. Newborn infants often do not move their eyes in tandem. It is not uncommon for parents to report concern that their young infants sometimes appear to have crossed eyes. This is a normal characteristic that typically resolves itself within a few months after birth as the eye muscles and the motor system that controls them mature. Some people, however, do not naturally develop coordinated movement of both eyes. This condition is called strabismus and affects about 2 percent of the population. To avoid seeing double images, children with strabismus will rely on the visual information from one eye while ignoring information from other. Strabismus is commonly treated by having the child wear a patch over the stronger eye, thus forcing the child to use the weaker one, or by surgery. If children are treated during early life, their normal binocular vision can be preserved. If strabismus remains uncorrected past the age of about six years, however, it will eventually lead to a loss of visual abilities in the weaker eye, or amblyopia. Amblyopia can be a permanent condition that results from abnormal development of the brain’s visual cortex. As we discussed in Chapter 3, many development psychologists suggest that there are not only sensitive periods, when we can develop certain skills with greater ease than at other time in our lives, but also “critical periods,” which are the only times during which certain developments can take place. Amblyopia develops if we do not receive visual stimulation from both eyes during the critical period of development for the normal maturation of the visual brain. After about the age of six, the brains of children with strabismus seem to lose the ability to use information from both eyes and instead process inputs only from one eye.
FIGURE 5-16 The moon illusion The moon is the same size all the time but it appears larger near the horizon than higher in the sky, partly because no depth cues exist in space.
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A life of accomplishment Braille, devised in 1821 by blind Frenchman Louis Braille, has greatly improved the level of accomplishment and quality of life of people who are sightless. Here a blind computer developer reads Braille at his workstation.
Blindness About 12 million people in the United States suffer from visual impairments that are either total or so severe and uncorrectable that these individuals are characterized as blind. There are many potential causes of blindness. Some are congenital, or present at birth, while others are acquired later in life. Diseases that can produce blindness include diabetes, glaucoma, and macular degeneration. Since humans rely so heavily on visual information, living without adequate visual input is very challenging. A number of devices have been created to help blind people live independently. Braille, a system of reading that involves touch, has significantly improved quality of life for the blind. Braille uses various combinations of raised dots to replace traditional printed letters and numbers. Visually impaired individuals can become so proficient at reading Braille that they can actually read faster than people with normal vision typically read printed material. Researchers have found that blind individuals who become experts at reading Braille are actually using parts of their “visual” brain to process the sophisticated tactile information. Neuroimaging studies have shown that parts of the occipital and temporal cortices that normally process visual information are activated in blind individuals while they read Braille. It is also noteworthy that the individuals with congenital blindness use more of their visual brains to read Braille than did those who became blind later in life. This may be another example of a critical period at work. The acquisition of Braille reading skills as a child may allow for the reorganization of the visual system to serve some new function. Learning Braille later in life may lead to less dramatic reorganization because those parts of the visual brain have already become “hard-wired,” or less plastic and open to change.
Before You Go On What Do You Know? 16. What are rods and cones? 17. What are the two theories of color vision and how do they work together? 18. What do the “what” and “where” pathways in the brain do? 19. What are the two major types of depth perception cues and what is the difference between them? 20. What is strabismus, how is it treated, and what can happen if it is not treated promptly?
What Do You Think? Is the cliché, “Seeing is believing,” really true? Why or why not?
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Summary • Sensation is the process of converting physical stimuli from our environment into neural impulses that the brain can process. Perception is the process of interpreting the neural signals to understand the information we receive.
Common Features of Sensation and Perception LEARNING OBJECTIVE 1 Describe characteristics shared by all the senses, including receptor cells, transduction, and thresholds, and differentiate between top-down and bottom-up processes of perception. • Our sensory systems convert physical stimuli into neural information with specialized cells called sensory receptor cells that convert a specific form of environmental stimuli into neural impulses by a process called sensory transduction. • The conversion of physical stimuli into neural impulses only occurs when the stimuli reach a certain level, or threshold. The absolute threshold is the minimum level of a stimulus we can detect. The difference threshold is the smallest difference we can detect between two similar stimuli. • Our sensory systems are set up to detect change. With continuous exposure to a stimulus, adaptation occurs.
The Chemical Senses: Smell and Taste LEARNING OBJECTIVE 2 Summarize what happens when we smell and taste. • Smell, our olfactory sense, converts chemical odorants into neural signals that the brain can use. Taste, our gustatory sense, is closely intertwined with smell. Most flavors are a combination of scents with the five basic tastes we can discern: sweet, salty, sour, bitter, and umami. • Our tactile sense combines with taste and smell, to help us appreciate, or dislike the textures of foods and to experience temperature and “hot” sensations from capsaicin in spicy foods. • Taste buds in papillae on the tongue convert chemicals in our food to neural signals the brain can use. Taste receptors and
smell receptors are routinely replaced, since they are more vulnerable to damage than other sensory receptors. • Information about smell goes directly from the olfactory bulb to the olfactory cortex. Areas of the brain that process smells and tastes are plastic, or changeable. Processing of smells also sometimes overlaps with emotions and memories. • Our preferred tastes change as we mature from childhood to adulthood, probably from a combination of learning and physical changes in the mouth. • True disorders of taste are rare; people more frequently lose part or all of their sense of smell. Anosmia can present safety risks and diminish pleasure in life.
The Tactile or Cutaneous Senses: Touch, Pressure, Pain, Vibration LEARNING OBJECTIVE 3 Describe how the different senses of touch work and what can happen when things go wrong. • A variety of sensory receptors throughout our bodies convert touch, pressure, or temperature stimuli into neural impulses that our brains can perceive. • The sensory cortex of the brain maps touch sensations. Especially sensitive or important body parts receive disproportionately large representation in the cortex. • Pain travels to the brain via both a fast pathway and a slow pathway. • People differ greatly in the perception of pain. Some of the differences are related to culture and gender. Others are individual. • The gate control theory of pain suggests that certain patterns of neural activity can close a “gate” so that pain information does not reach parts of the brain where it is perceived. • Medical professionals continue to search for ways to relieve people’s chronic pain. Opiate drugs that simulate natural pain-killing endorphins or enkephalins are addictive. Sometimes practitioners resort to neurosurgery, which stops a patient from receiving all touch signals. • The inability to feel pain can put people at high risk for injuries. • People who have lost body parts surgically or through accidents often feel phantom sensations in the missing body part. These may be related to reorganization of the somatosensory cortex after an amputation.
Summary
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The Auditory Sense: Hearing
The Visual Sense: Sight
LEARNING OBJECTIVE 4 Summarize what happens when we hear.
LEARNING OBJECTIVE 5 Describe key processes in visual sensation and perception.
• The frequency and amplitude of sound waves produce our perceptions of pitch and loudness of sounds.
• Vision is very important to humans, and a great deal of our brain is involved in processing visual information. • Rods and cones in the retina at the back of the eye change light into neural impulses. Cones provide detailed vision and help us perceive color, while rods provide information about intensity of light. • Two different theories in combination—trichomatic theory and opponent process theory—explain a good deal of how we perceive color. • The fovea at the center of the retina contains only cones and provides our sharpest vision. We have a blind spot where the optic nerve leaves the retina to carry information to the brain. • In the brain, visual information is processed through the “what” and “where” pathways. • Damage to the brain can produce deficits in sensation, as well as abnormal sensory experiences. • Top-down processing is involved in much visual perception. Gestalt theorists have identified several principles by which we recognize stimuli even when visual inputs are limited. We use binocular and monocular cues for depth perception. Perceptual constancies, based on learning from previous experiences, help us to see things as stable despite constant shifts in our visual inputs. These top-down processes can be “fooled” by visual illusions. • Without adequate visual stimulation through both eyes during a critical period of life, we may not develop binocular vision, a condition known as amblyopia. • Blind individuals can use other sensory modalities to compensation for the loss of visual information. Learning Braille with touch involves the use of brain areas normally used for vision.
• When sounds enter the ear, they move the ear drum, which sets in motion the ossicles. The last of these, the stirrup, vibrates the oval window, setting into motion fluid in the cochlea. Hair cells on the basilar membrane in the cochlea transduce movements along the basilar membrane into neural signals the brain can interpret. • Frequency theory suggests that patterns in the firing rates of the neurons are perceived as different sounds. Place theory suggests that information from different locations along the basilar membrane is related to different qualities of sound. • Top-down processing lets us use the general loudness of sounds, as well as differences in the signals received from each ear, to determine location of a sound. • Different pitches are represented in a tonotopic map in the auditory cortex of the brain. Association areas of the cortex help us recognize familiar sounds, including speech. • The brain integrates information from multiple sensory systems to enable the appropriate recognition and response to stimuli. Some people experience an overlap of sensory systems known as synesthesia. • As young children, we experience a sensitive period during which it is especially easy for us to learn auditory information, including language and music. Some people, particularly those exposed to pure tones during this sensitive period, develop absolute pitch. • Common hearing problems include hearing loss and deafness, as well as hearing unwanted sounds, such as tinnitus.
Key Terms sensation 130
odorants 132
gate control theory of pain 143
deafness 151
perception 130
olfactory receptor neurons 132
endorphins 143
retina 152
sensory receptor cells 130
papillae 132
enkephalins 143
photoreceptors 152
sensory transduction 130
taste buds 132
sound waves 146
rods 152
absolute threshold 130
olfactory bulb 132
tympanic membrane 146
cones 152
difference threshold or just noticeable difference 131
anosmia 138
ossicles 146
optic nerve 153
ageusia 138
oval window 146
fovea 153
sensory adaptation 131
free nerve endings 138
cochlea 146
retinal disparity 157
bottom-up processing 131
Meissner’s corpuscles 138
basilar membrane 146
convergence 157
top-down processing 131
Merkel’s discs 138
hair cells 146
monocular cues 157
olfactory sense 132
Ruffini’s end-organs 141
tonotopic map 148
perceptual constancies 158
gustatory sense 132
Pacinian corpuscles 141
absolute pitch 151
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CUT/ACROSS CONNECTION What Happens in the
BRAIN? • The brain normally integrates information from multiple sensory systems. In people who experience synesthesia, brain areas for one sense are activated by stimuli related to different senses, so that they might, for example, hear colors. • Different parts of our brains are active in figuring out what we see from those that help us figure out where things are when we see them. • Blind people who learn to read Braille at early ages actually use parts of their visual cortex to do so, in addition to areas normally associated with touch.
HOW we Differ
• People rarely lose their sense of taste. Most problems with taste are related to loss of sense of smell. • When we damage taste buds or odor receptors in the nose, they are replaced, but damage to other sensory receptors, such as photoreceptors and hair cells, is permanent. They are not replaced. • People who experience phantom sensations in missing body parts usually feel things they actually felt before losing the body part.
How we Develop
• About a fourth of all people are supertasters, able to discern bitter tastes that many others do not even notice. • On average, women have more sensory receptors for pain in their faces than men do. • Only about 1 person in 10,000 in Western countries develops absolute pitch, the ability to identify tones heard in isolation. More people who speak tonal languages have absolute pitch. • About 4 people in 100 in the United States are tone deaf.
• All of our sensory systems begin to develop during fetal life. We can hear, feel, smell, and taste before we are born. • Sight is our least developed sense at birth. • Children have more taste buds in more locations in their mouths than adults, which may explain in part why they dislike many new foods.
Psychology Around Us The Ups and Downs of Visual Perception
Video Lab Exercise
Seeing is Not Always Believing Whether driving through the streets of a city, looking out a train window at the passing landscape, or viewing events on the ground from a plane above, you are relying on your visual senses. Come along for a video ride in which nothing can be taken for granted and during which you will be asked to not only enjoy the view, but to explain it, ignore it, adjust to it, or change it. As you are working on this on-line exercise, consider the following questions: • What does this lab exercise say about both the power and the limits of visual perception? • What’s going on in your brain as you correctly observe objects, adapt to visual events, or are fooled by visual illusions? • What role does attention play in visual perception? • How might your auditory sense affect what you see?
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Consciousness chapter outline •
When We Are Awake: Conscious Awareness •
Preconscious and Unconscious States •
•
Hypnosis
Meditation
When We Are Asleep •
Love and Awareness on an Errand
I
•
magine yourself driving a car, perhaps to drop off some clothes at the dry cleaners on a Saturday morning. You’ve
slept in, so you’re feeling pretty relaxed and alert. Traffic is light and driving easy. You’re singing along with some music playing. One song reminds you of a former love, and you begin to recall a special intimate moment with that person. But since he or she dumped you, you try to shift your focus to your psychology homework assignment. You slow as you see a stop-
Psychoactive Drugs
Consciousness is often defined as our immediate awareness of our internal and external states. But how aware is “aware”? Sometimes we are keenly aware of something and other times only dimly so. In addition, sometimes we do not seem to be paying much attention to complex stimuli, yet we wind up recalling information from them later. Consider people who are just learning how to drive. New drivers must concentrate carefully on checking the rearview mirror, gauging how hard to press on the gas and brake pedals, and the like. In time and with experience, drivers come to perform most of these activities almost automatically; they stop being particularly aware of them while driving. An experienced driver can stop the car while simultaneously pondering a topic for his or her psychology paper, for example.
light turn yellow, then stop for the red light. What will you write about, you wonder, as you wait for the light? Maybe the pain of ending relationships would be a good paper topic. You begin to accelerate as the light turns green, but then jerk to a halt when you notice another car sailing through the intersection against the red light on the cross street. The driver is obviously distracted by yakking on his cell phone, and you wonder whether he might be drunk, too, judging by his excessive speed. You’re suddenly back to thinking entirely about driving as you avoid this driver. Crisis averted, you notice the song that made you think of your ex is over and a new song is playing. This one reminds of your new sweetie, and you recall a nice dream you had last night, in which your current love featured quite heavily.... Quite a lot can occur to you when running a simple errand, such as going to the dry cleaners!
Heightened awareness Navigating an automobile requires full concentration for new drivers such as this nervous individual. This is not the case, however, for people who have been at it for years, many of whom are barely conscious of the driving-related tasks they are performing.
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Going toward the Light: Near-Death Experiences A man lies dying. He hears himself pronounced dead by his doctor. He feels himself rushing through a long, dark tunnel and suddenly finds himself outside his body, observing it from a distance as the doctor tries to revive him Soon, a loving, warm spirit—a being of light—comes to meet him and directs him through a panoramic review of the major events of his life. He feels himself approaching a barrier—a sort of border between earthly existence and some other state. He is overwhelmed by joy but must return to his body, for the time has not come for him to die. Later, he has trouble describing this experience, but it profoundly affects his life and his feelings about death. Thus does Dr. Raymond Moody describe a typical near-death experience (NDE) in his best-selling 1975 book, Life after Life, which introduced NDEs into the popular culture. Typically these
consciousness our immediate awareness of our internal and external states.
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experiences include some or all of the features just described—the tunnel, the out-of-body experience, the bright light, and so forth. Over the past several decades, many people have reported having such experiences (Carey, 2009). The question is, what causes them? Some observers offer a religious or supernatural explanation, that the soul leaves the body during an NDE and encounters a “spirit of light” (Sheikh et al., 2007). Moody himself has adopted this view. But many researchers disagree and look instead to more scientific explanations (Nelson et al., 2006). Some point out, for example, that certain drugs produce the same effects as NDEs. Perhaps the brain, under great stress, releases chemicals that, like these drugs, induce hallucinations (Augustine, 2007). Others attribute NDEs to the brain’s constant efforts to process our sensory experiences and maintain a stable sense of reality. As a person nears death, the senses shut down, sending faulty information that the brain tries to interpret as best it can. This effort may lead to misinterpretations about where the body is in space or produce the sensation of being in a dark tunnel with bright light at the end. These and other scientific explanations share the notion that NDEs often reflect an altered state of consciousness that is brought about by sensory arousal, a heightened state of awareness, and the brain’s ongoing efforts to determine what we experience as real.
In addition to these constant, mostly effortless, shifts in our awareness, we can also experience shifts that occur as the result of special events or efforts, such as being asleep, dreaming, meditating, or ingesting alcohol or other substances. In this chapter, we shall examine conscious awareness, changes in consciousness, and some of the major ways in which these changes come about. The study of consciousness has undergone many historical shifts. As you may recall from Chapter 1, early psychologists defined psychology entirely as the study of consciousness. The influential American psychologist William James, for example, noted that our conscious awareness continually shifts based on what we’re paying attention to and how intensely we are attending (Singer, 2003). Nevertheless, we feel continuity from moment to moment. As the opening story describes, many thoughts and fantasies—all different in meaning and feeling—can occur within a short period of time, yet we maintain a sense of sameness. Whether thinking of former lovers or dry cleaning, we have a sense of ourselves as the same person. James coined the term “stream of consciousness” to signify how we experience our conscious life, because consciousness, like a running stream, keeps moving, yet seems to be the same. You may also recall from Chapter 1 that one of psychology’s most influential theories of consciousness has been Sigmund Freud’s psychoanalytic theory. Freud introduced the idea that we can have unconscious thoughts and feelings of which we are not even aware. Right up to his death in 1939, Freud kept defining and revising his ideas about states of consciousness, and we will discuss these in some detail later in this chapter.
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Partly in response to the difficulties of conducting research on elusive concepts, such as the unconscious mind, many researchers during the first half of the twentieth century, especially those in North America, shifted their interest from consciousness to observable behavior and, as you read in Chapter 1, equated psychology with behaviorism (Baars, 2003). Theorists and researchers in Europe, however, continued to pay significant attention to consciousness and even unconsciousness. During the latter part of the twentieth century, with important developments in neuroscience and computer technology, consciousness reemerged as a topic of major interest in psychology (Frith, 2003). With the help of neuroimaging techniques, investigators have been able to explore meaningfully the relationship between brain activity and various states of consciousness (Keenan, Gallup, & Falk, 2003). Indeed, a considerable body of research now is directed at the study of conscious, less conscious, and nonconscious states (Baruss, 2003).
Test your own powers of attention. Before finishing this introduction, take a break and watch the video at http://viscog.beckman. illinois.edu/flashmovie/15.php. Count how many times the players in white shirts complete a pass of the basketball.
When We Are Awake: Conscious Awareness LEARNING OBJECTIVE 1 Define different levels of conscious awareness and describe key brain structures and functions associated with those levels.
As the opening vignette illustrates, attention plays a key role in conscious awareness. Psychiatric researcher John Ratey (2001) has pointed out, “Before we can be conscious of something...we have to pay attention to it.” At the same time, attention does not equal consciousness. We need something more. To be fully conscious of something, we must be aware that we are attending to it. Conscious awareness of ourselves, our needs, and how to satisfy them has directly aided us in survival, contributing mightily to our evolutionary progress. To be conscious of our thirst, for example, is to understand that water is necessary to quench it, and to know that certain actions are necessary to obtain water, helps us compete successfully for water—more successfully than creatures that operate without consciousness. Clearly, conscious awareness involves elements beyond attention, and in fact, a number of such elements have been suggested by theorists. Three of the most prominent are monitoring, remembering, and planning: • We monitor ourselves and our environment as we decide (implicitly) what items to be aware of (Glaser & Kihlstrom, 2005). A quickly moving car approaching us might catch our awareness, for example. • In order to be aware of a current event, we often must bring forth memories of past experiences and previously acquired knowledge and skills (Baars, 2003; Osaka, 2003). Such memories establish a context for our current situation, provide us with the motivation and ability to focus on it, and may even become part of the present situation. A driver has to have a memory related to red lights in order to be aware that a yellow light is a signal to slow down. • Control and planning are also often at work. In fact, to help us plan for the future—from which route to take to the dry cleaners to our choice of a mate or career—we often bring into conscious awareness images, events, and scenarios that have never occurred. In such cases, conscious awareness may help us to initiate more effective behaviors or make wiser decisions.
No room for error As we interact with our environment, we constantly monitor both ourselves and the situations at hand to help ensure that we attend to key features of the interactions. When performing a dangerous task, such as climbing a mountain, careful monitoring can take on life-and-death importance.
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What Happens in the
When We Are Awake B R A I N ?
Think back to the basketball video. Did you immediately notice the gorilla among the players, or did you miss it? What do you think that implies about your consciousness?
Multiple brain processes and structures must be operating simultaneously in order for us to be conscious of our world or ourselves (Kolb & Whishaw, 2009). In fact, research has shown that when we are awake, most if not all the neurons in our brains are constantly active. Of course, certain neurons become particularly active when an individual is stimulated by objects or events, but even in the absence of such stimulation, neurons are still active at a steady, low level and are communicating with other neurons (Llinas, 2001; Llinas & Ribary, 2001). Recall from Chapter 4 that neurons tend to work together in groups, or networks, and those networks become more and more efficient with repeated use. For us to experience conscious awareness of something, such as a thought or an oncoming car, many of these networks must become particularly active at once. While one set of networks is enabling us to pay attention to the stimulus, other biological events must also be at work, enabling us to be aware and recognize that we are attending. Still others are allowing us to monitor, remember, and control. Researchers have not yet pinpointed all of the brain areas and events that are responsible for such parallel processing, but research has suggested that two areas of great importance to consciousness are the cerebral cortex, the brain’s outer covering of cells, and the thalamus, the brain structure that often relays sensory information from various parts of the brain to the cerebral cortex. The Cerebral Cortex Evidence has accumulated that some areas of the brain are responsible for attention, while other areas—particularly ones in the cerebral cortex— are in charge of one’s awareness of that attention. Investigations by Lawrence Weiskrantz (2002, 2000, 1997) on blindsight illustrate how this works in the visual realm. Weiskrantz studied people whose visual areas in the cerebral cortex had been destroyed, leaving them blind, so far as they were aware. When Weiskrantz presented such people with a spot of light on a screen and asked them to point to it, the individuals were totally unaware of the light and could not fulfill the request. Yet, when he told the same individuals to “just point anywhere,” they typically pointed in the direction of the light. Similarly, these individuals could generally avoid chairs, tables, and other objects as they walked through a room, denying all the while that they were seeing anything at all. In short, the patients in Weiskrantz’s studies could and did readily attend to visual objects, yet because the visual areas in their cerebral cortex had been destroyed, they were unaware of those objects. Weiskrantz and others have concluded that the areas of the brain that help us attend to visual stimuli are different from the visual areas in the cerebral cortex that help us to be aware that we are attending to such stimuli. Remarkable studies of “split-brain” patients, conducted by investigators Roger Sperry (1998, 1995, 1985, 1982) and Michael Gazzaniga (2000, 1995, 1988, 1983), also point to the cerebral cortex as a center of conscious awareness. As you’ll recall from Chapter 4, people with severe seizure disorders can sometimes be helped by cutting the nerve fibers of their corpus callosum, the brain structure that connects the two hemispheres of the brain, to keep abnormal activity from traveling from one side of the brain to the other. By carefully studying such split-brain patients, Sperry and Gazzaniga learned that the left and right sides of the cerebral cortex may play different roles in conscious awareness. As shown in Figure 6-1, in the split-brain patients, the objects in the left visual field project only to the visual area in the right hemisphere (Thompson, 2000). Similarly,
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FIGURE 6-1 Split-brain research (a) When “What did you see?”
“What did you see?”
“With your left hand, pick up what you saw”
“I saw nothing.”
a picture of a screwdriver is flashed to a split-brain patient’s left visual field, the information goes to his nonverbal right hemisphere and he cannot name the object. (b) When instructed to feel behind a screen among a variety of objects and select the one that matches the picture just seen, the patient correctly selects the screwdriver. (c) When a picture of a baseball is flashed to the patient’s right visual field, he easily names it.
“I saw a baseball.”
Verbal left Nonverbal right hemisphere hemisphere
visual information presented to the right visual field projects only to the visual area in the left cortex. Using this information, the investigators found that when they showed a word to a patient’s left hemisphere, the individual was readily able to say and write the word. When a word was flashed to the right hemisphere, however, the individual could not say or write it. Apparently, the left cerebral cortex is responsible for verbal awareness. In contrast, the right cerebral cortex seems to be responsible for nonverbal forms of conscious awareness. In one study, for example, the experimenters flashed a picture of a screwdriver to each patient’s right hemisphere. The individuals were then instructed to feel, from behind a screen, a variety of real objects, including a real screwdriver, and on the basis of touch, to select the object that matched the picture they had just seen: all correctly selected a screwdriver. Apparently, the right cerebral cortex can produce tactile awareness and perhaps other kinds of nonverbal awareness as well, but not verbal awareness. Of course, for most of us, our two hemispheres are connected and these various kinds of awareness occur simultaneously, helping to produce a broad and complete sense of conscious awareness. The Thalamus We might think of the networks of neurons in the brain as similar to the different train lines in a complicated subway system, like that of New York City. In order for trains to get from place to place on schedule without collision, a train conductor (or even a whole group of them) must oversee the process. Researchers have nominated several brain areas as potential conductors, involved in routing messages along the proper neural network “subway lines” of our brains. Two of the most prominent candidates are the intralaminar nuclei and midline nuclei of the thalamus (Van der Werf et al., 2002; Ratey, 2001). Research indicates that the intralaminar and midline nuclei receive and project long axons to neurons throughout the cerebral cortex, including areas that, as we have seen, are involved in conscious awareness (Ratey, 2001). Consistent with this theory, investigators have observed that people actually lose all consciousness and enter a deep coma if their intralaminar and midline nuclei are broadly damaged. If, however, the damage to the nuclei occurs in only one hemisphere, individuals lose awareness of only half of their bodies. They become unaware of all
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events that occur on one side of their visual field, for example, or unaware of all objects that touch one side of their body. In short, the intralaminar and midline nuclei seem to play an important role in conscious awareness, with different nuclei responsible for different dimensions of consciousness.
Alert Consciousness
Hello there When babies look into a mirror and realize that they are looking at themselves, it means that they are finally experiencing a sense of self. That is, they are aware of themselves as separate beings from others.
How we Develop
There have been a number of attempts to identity consciousness in infants. As we saw in Chapter 3, there is evidence that even before the age of 2, babies may be able to direct their attention, hold concepts in mind, and engage in planned or intentional behaviors—the component skills of consciousness. Because babies are not yet able to talk very well, however, it’s difficult to determine how aware they are that their experiences are things happening to them, or even whether they are fully aware of themselves as separate beings from others, a concept known as sense of self. Researchers have developed some ingenious ways to try to determine when babies first experience a sense of self. In one test, experimenters secretly dabbed red make-up on babies’ foreheads while pretending to wipe them. Then they placed the babies in front of a mirror. The researchers reasoned that babies who had developed a sense of self would see the makeup and touch their own heads, while those who did not understand they were looking themselves in the mirror would try to touch the makeup by touching the mirror. Based on such tests, it seems that most children develop a stable concept of the self by around 18 months of age (Gallup, 1970; Lewis & Brooks-Gunn, 1979). Some researchers suggest that the early cognitive development we discussed in Chapter 3 and the development of consciousness contribute to one another. That is, if infants demonstrate the ability to develop concepts and to think through their behaviors—even if they cannot express such thinking—they should be viewed as having a rudimentary sense of self-consciousness. Without this rudimentary sense of consciousness, babies would not be able to develop any concept at all (Mandler, 2004). Other theorists suggest that consciousness itself is rooted in language. Because babies do not have language, they cannot reflect on their thoughts and behaviors and do not have consciousness yet (Rakison, 2007; Zelazo, 2004). These theorists suggest that a shift happens at around 22 months of age, when babies show the abilities to reason inductively and to name and categorize concepts, which in turn enable them to represent concepts in a richer and deeper way. Thus, describing how consciousness develops during awake states remains both a philosophical and empirical question, influenced in large part by how we define consciousness. The matter is further complicated by the question we asked at the beginning of this chapter: Just how aware is “aware”? We’ll see next that there may be levels of alert consciousness at which we are not fully aware of all our thoughts.
Before You Go On What Do You Know? 1. List the core cognitive processes of consciousness. 2. What is blindsight?
What Do You Think? What characteristics do you believe are essential to define alert consciousness?
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Preconscious and Unconscious States
preconsciousness level of awareness in which information can become readily available to consciousness if necessary.
LEARNING OBJECTIVE 2 Summarize the ideas of preconscious and unconscious states, including Freud’s thinking on the unconscious.
unconscious state state in which information is not easily accessible to conscious awareness.
© The New Yorker Collection 1983 Edward Frascino from cartoonbank.com. All Rights Reserved.
Theorists often talk about different “levels of consciousness” or “degrees of consciousness,” and some believe that consciousness should be distinguished from two alternative states, preconsciousness and unconsciousness. Preconsciousness is a level of awareness in which information can become readily available to consciousness if necessary. Have you ever tried to remember something that you’re certain you know but just cannot recall at the moment? When something is on the tip-of-your-tongue (a phenomenon we’ll talk about again in Chapter 8), it is in your preconsciousness. When (or if) you finally do remember it, the memory has reached consciousness. Many of our most familiar behaviors occur during preconsciousness. Take a second—can you remember exactly what your morning ritual was this morning? What song was playing when you woke up? Did you count every tooth as you brushed it? For many morning activities, you probably do things in the same order, but you do not necessarily need to plan all the steps or think about what you’re doing as you move through your ritual. Preconscious behaviors of this kind are sometimes called automatic behaviors. As we saw at the beginning of the chapter, driving can involve automatic behaviors. An unconscious state is one in which information is not easily accessible to conscious awareness. Perhaps at a particularly beautiful moment while watching a movie, you become teary-eyed, with no idea why. Psychoanalytic theorists, influenced by the ideas of Sigmund Freud, would suggest that the movie triggered a memory in your unconscious. It may be a memory of an especially happy or difficult time in your childhood, but chances are, you will never find out for sure. Information, feelings, and memories held in the unconscious are—by definition—not readily available to conscious awareness. So, at the movies, you may just have to enjoy the tearful moment without fully appreciating why you are so moved.
Freud’s Views of the Unconscious Although there are many current views about the unconscious, most have some relationship to the explanation advanced by Sigmund Freud (Kihlstrom, 1999). As we discussed in Chapter 1, Freud believed that the vast majority of our personal knowledge is located in our unconsciousness, and thus is not readily accessible (see Figure 6-2). According to him, one of the key functions of the unconsciousness is to house thoughts and memories too painful or disturbing to us to remain in our consciousness (Gomes, 2003). Indeed, he maintained that at some level, we may repress such thoughts and memories, keeping them in our unconscious and preventing them from entering our conscious experience. Even though we cannot access unconscious material directly, Freud still believed the unconscious is an important driver of human behavior. Freud also suggested that, although it is typically inaccessible, unconscious material does come into conscious awareness on occasion (Ross, 2003). Have you ever meant to say one thing, but something very different comes out, often to your embarrassment? Freud identified this slip of the tongue (called a Freudian slip) as a moment when the mind inadvertently allows a repressed idea into consciousness. Let’s say that you do not Preconscious and Unconscious States
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Conscious
Preconscious Repression
Wishes, fears, memories, emotions Unconscious
FIGURE 6-2 Freud’s view of the unconscious According to Freud, material that is relegated to the unconscious, such as repressed material, enters preconscious awareness or conscious awareness only accidentally or indirectly.
implicit memory knowledge that we have stored in memory that we are not typically aware of or able to recall at will. hypnosis a seemingly altered state of consciousness during which individuals can be directed to act or experience the world in unusual ways.
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enjoy your job but you’re not sure why. One day you arrive at work 15 minutes late and your boss is waiting for you. Whereas you intend to say, “I’m sorry I’m late, boss,” you say instead, “I’m sorry I hate boss.” Suddenly you—and your boss—are well aware of why you don’t like your job! Freud also believed that our unconscious can work against us and that people who store too many emotionally-charged memories and needs in their unconscious may eventually develop psychological disorders (as we will discuss in further detail in Chapters 13 and 16). His theory suggests that the knowledge and memories stored in the unconscious maintain their ability to influence how we think, feel, and relate to others. If we repress too much, we may experience distortions in how we feel or relate to others, and, at the same time, we may feel helpless to change. Based on this part of Freud’s theory, psychoanalytic psychotherapy attempts to bring patients’ unconscious material into their conscious awareness.
Cognitive Views of the Unconscious Throughout much of the twentieth century, scientists paid little, if any, attention to the unconscious. Rejecting Freud’s psychoanalytic ideas, they also rejected the notion that people’s behaviors, thoughts, and feelings may be influenced by mental forces of which they are totally unaware. This dismissal of the unconscious has shifted dramatically in recent decades. Today, most psychologists believe that unconscious functioning does occur and a number of explanations—particularly cognitive explanations—have been proposed. Perhaps the most prominent cognitive explanation for unconscious processing points to the concept of implicit memory (Kihlstrom et al., 2007, 2000). As we shall observe more closely in Chapter 8, cognitive theorists distinguish two basic kinds of memory—explicit memory and implicit memory. Explicit memories are pieces of knowledge that we are fully aware of. Knowing the date of your birth is an explicit memory. Implicit memories refer to knowledge that we are not typically aware of — information that we cannot recall at will—but that we use in the performance of various tasks in life. Implicit memory is usually on display in the skills we acquire, such as reading, playing an instrument, driving a car, or speaking a second language. Our performance of such skills improves as we gain more and more of the knowledge, motor behaviors, and perceptual information required for the skills. These gains—that is, these implicit memories—are usually revealed to us indirectly by our improved performances, not by our consciously recalling the acquired information and experiences that led to the improvements. Shortly after learning to drive, you may realize one day that you are able to drive and talk to a passenger at the same time, for example, but not recall the exact moment you learned how to control the wheel and pedals well enough to add the additional activity of carrying on a conversation. Implicit memory may also involve factual information. When we vote for a particular candidate on election day, a wealth of past experiences and information may be at the root of that behavior—childhood discussions with our parents about political parties, Web sites we’ve seen, articles we’ve read, political science classes we’ve taken, interviews or “news-bites” we have heard, and more. As we pull the election lever, however, we typically are not aware of all these past experiences or pieces of information. Cognitive and cognitive neuroscience theorists see implicit memories as a part of everyday functioning rather than as a way to keep difficult information from reaching our awareness (Kihlstrom et al., 2007, 2000). They have discovered research methods to test our unconscious—implicit—memories and have gathered evidence that explicit and implicit memories are stored in different pathways in the brain.
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Before You Go On What Do You Know? 3. What is the difference between preconscious and unconscious states? 4. What is the importance of implicit memory to the notion of the unconscious?
What Do You Think? Do you think there are unconscious forces driving people’s behaviors? If not, is it all conscious choice, or do you believe there are other explanations?
Hypnosis LEARNING OBJECTIVE 3 Discuss theories and evidence about what hypnosis is, how it works, and how it can be used.
In movie and cartoon portrayals of hypnosis, a creepy guy dressed in black tells an unsuspecting person to stare at a swinging pocket watch and says, “Relax, just relax.” Soon, the person is completely under the power of the hypnotist, who often makes him or her do something completely out of character or, in more sinister films, illegal and dangerous. As you might expect, this image is exaggerated and distorted. It is true, however, that in real life, hypnosis is considered by many psychologists to be an altered state of consciousness (Kihlstrom, 2007; Farvolden & Woody, 2004). During hypnosis, people can be directed to act in unusual ways, experience unusual sensations, remember forgotten events, or forget remembered events. People typically are guided into this suggestible state by a trained hypnotist or hypnotherapist. The process involves their willing relinquishment of control over certain behaviors and their acceptance of distortions of reality. In order for hypnosis to work, individuals must be open and responsive to suggestions made by the hypnotist. Some people are more open to a hypnotist’s suggestions than others, a quality that often runs in families (Kihlstrom, 2007). Approximately 15 percent of adults are very susceptible to hypnosis, while 10 percent are not at all hypnotizable. Most adults fall somewhere in between (Hilgard, 1991, 1982). People who are especially suggestible, in touch with their fantasy worlds, and comfortable playing with their imaginations are particularly likely to approach the experience with a positive and receptive attitude (Roche & McConkey, 1990). Perhaps not surprisingly, therefore, children tend to be particularly open to hypnotic suggestion (Wallace & Persanyi, 1989).
The power of suggestion People can be directed to experience unusual sensations and act in unusual ways when in a hypnotic state—a trance-like altered state of consciousness marked by extreme suggestibility. Here a hypnotized young man believes that a balloon is tied to his left hand and that his right hand is extremely heavy.
Hypnotic Procedures and Effects Hypnotists use various methods to induce the hypnotic state. Sometimes—in a much tamer version than the movie portrayals—a person is asked to relax while concentrating on a single small target, such as a watch or an item in a painting on the wall. At other times, the hypnotist induces a hyperalert hypnotic trance that actually guides the individual to heightened tension and awareness. In either case, the hypnotist delivers “suggestions” to the subject, not the authoritarian commands on display in the movies.
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dissociation a splitting of consciousness into two dimensions.
One area of functioning that can be readily influenced by hypnotists is motor control. If the hypnotist suggests that a person’s hand is being drawn like a magnet to a nearby stapler, the individual’s hand will soon move to the stapler, as if propelled by an external force. In some cases, people can be directed to respond after being roused from the hypnotic trance. A predetermined signal prompts such posthypnotic responses. During hypnosis the hypnotist may suggest, for example, that the person will later stand up whenever the hypnotist touches a desktop. After being roused, and with no understanding of why, the person will in fact stand when the hypnotist touches the desk. Related to posthypnotic responses is the phenomenon of posthypnotic amnesia. The hypnotist directs the person to later forget information learned during hypnosis. Once again, after being roused from the hypnotic trance, the person does not remember the learned material until the hypnotist provides a predetermined signal to remember. The degree to which the earlier information is forgotten varies. Some people will not remember any of the learned material, while others will remember quite a bit. Hypnosis can also induce hallucinations, mental perceptions that do not match the physical stimulations coming from the world around us. Researchers have distinguished two kinds of hypnotic hallucinations: positive and negative. Positive hallucinations are those in which people under hypnosis are guided to see objects or hear sounds that are not present. Negative hallucinations are those in which hypnotized people fail to see or hear stimuli that are present. Negative hallucinations are often used to control pain. The hypnotized person is directed to ignore—basically, to simply not perceive—pain. The hallucination may result in a total or partial reduction of pain (Gruzelier, 2003). Some practitioners have even applied hypnosis to help control pain during dental and other forms of surgery (Auld, 2007). Although only some people are able to undergo surgery while anesthetized by hypnosis alone, combining hypnosis with chemical forms of anesthesia apparently helps many individuals (Hammond, 2008; Fredericks, 2001). Beyond its use in the control of pain, hypnosis has been used successfully to help treat problems, such as anxiety, skin diseases, asthma, insomnia, stuttering, high blood pressure, warts, and other forms of infection (Shenefelt, 2003). Many people also turn to hypnosis to help break bad habits, such as smoking, nail biting, and overeating. Does hypnosis help? Research has shown that hypnosis has little effect in helping people to quit smoking over the long term (Spanos et al, 1995; Valbo & Eide, 1996). However, greater success has been noted in efforts at weight loss, particularly if hypnosis is paired with cognitive treatments, interventions that help people change their conscious ways of thinking (Ginandes, 2006; Lynn & Kirsch, 2006).
Why Does Hypnosis Work? FIGURE 6-3 Explaining hypnosis Two theories
There are various theories about why hypnosis works (Kallio & Revonsuo, 2003). One, proposed by the pioneering researcher Ernest Hilgard, views hypnosis as a state of divided consciousness. Another theory sees it as an How is the participant's implementation of common social and cognitive processes attention diverted from the pain? (see Figure 6-3). As a professor, Hilgard hypnotized a student to become deaf during a classroom demonstration. The student could not hear even loud noises. Another student asked Hilgard whether “some part” of the Social/cognitive process theory: hypnotized student could still hear noise. In The participant is highly motivated to believe in hypnosis, and, without response, Hilgard instructed the hypnotized awareness, works hard to ignore student to raise his finger if some part of him the pain. could still hear. Surprisingly, the student did raise a finger.
explain how a hypnotized individual is able to ignore pain.
Divided consciousness theory: Hypnosis splits awareness into two parts; one part responds to the hypnotist's suggestion, the other part continues to process pain information but at a less conscious level.
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From this experience, Hilgard concluded that consciousness splits into two parts and that both act at once during hypnosis, an experience called dissociation (Hilgard, 1992). One part of our consciousness becomes fully tuned into and responsive to the hypnotist’s suggestions. The second part, which Hilgard called the hidden observer, operates at a subtler, less conscious level, continuing to process information that is seemingly unavailable to the hypnotized person. According to Hilgard, the hidden observer was the part of the student’s mind that was still able to hear while hypnotized. Another leading theory of hypnosis is that, instead of resulting from a divided consciousness, hypnotic phenomena consist simply of highly motivated people performing tasks or enacting roles that are asked of them. Because of their strong beliefs in hypnosis, the people fail to recognize their own active contributions to the process (Spanos et al., 1995). What Happens in the
Hypnosis B R A I N ? Neuroimaging studies show that hypnosis affects neuron activity in brain areas previously implicated in conscious awareness, suggesting to some theAnterior orists that the procedure does indeed produce altered consciousness, as sug- cingulate cortex gested by Hilgard’s theory (Rainville et al., 2002, 1999, 1997). When people are hypnotized, they are usually first guided into a state of mental relaxation. Studies have found that during this state, neural activity in key areas of the cerebral cortex and thalamus—brain regions that, as we noted earlier, are implicated in conscious awareness—slows down significantly (Rainville et al., 2002). Hypnotized individuals are next guided into a state of mental absorption, during which they focus carefully on the hypnotist’s voice and instructions and actively block out other sources of stimulation, both internal and environmental. In fact, mental absorption has often been described as a state of total focus. During this state, cerebral blood flow and neural activity actually pick back up in key areas of the cerebral cortex, thalamus, and other parts of the brain’s attention and conscious awareness systems (Rainville et al., 2002). Neuroimaging research suggests that one part of the brain’s cerebral cortex, the anterior cingulate cortex, may be particularly involved when hypnosis is used to anesthetize or reduce pain. This region has been implicated both in general awareness and in the unpleasantness we feel during pain. In one study, participants were hypnotically induced to ignore their pain while placing their hands in painfully hot water (Rainville et al., 1997). While the individuals were in a hypnotic pain-free state, neurons in their anterior cingulate cortex became markedly less active. Although the activity of other neurons that receive pain messages continued as usual in these people’s brains—suggesting that they were indeed receiving sensations of pain—the decreased activity in the anterior cingulate cortex seemed to reduce their awareness of the pain. They did not perceive the pain sensations.
Cingulate cortex
Before You Go On What Do You Know? 5. What are hypnotic hallucinations and how might they be useful? 6. How does Hilgard use the idea of a divided consciousness to explain hypnosis?
What Do You Think? What are the ethical implications of using hypnosis to control behavior?
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meditation technique designed to turn one’s consciousness away from the outer world toward one’s inner cues and awareness.
Meditation
adaptive theory of sleep theory that organisms sleep for the purposes of self-preservation, to keep away from predators that are more active at night.
LEARNING OBJECTIVE 4 Describe the techniques and effects of meditation.
restorative theory of sleep theory that we sleep in order to allow the brain and body to restore certain depleted chemical resources and eliminate chemical wastes that have accumulated during the waking day. circadian rhythm pattern of sleep-wake cycles that in human beings roughly corresponds to periods of daylight and night.
Meditation is a technique designed to turn one’s consciousness away from the outer world, toward inner cues and awareness, ignoring all stressors (Fontana, 2007). The technique typically involves going to a quiet place, assuming either a specific body position or simply a comfortable position, controlling one’s breathing, limiting one’s outward attention, and forming internal images. The result of such efforts is an altered state of consciousness, accompanied by deeply relaxing and pleasant feelings. Experienced meditators are often said to attain a “wider consciousness.” Meditation is an ancient practice that can be traced through the history of all the world’s major religions. Perhaps the best known practices derive from the yoga traditions of the Hindu religion and from the Zen traditions of Buddhism. Yoga is a form of meditation that involves adjusting the body into different positions, or poses, in an attempt to also regulate blood flow, heart rate, and digestive processes. Two major techniques to meditation seem to use opposite approaches. In openingup approaches, the meditator seeks to clear his or her mind in order to receive new experiences. One opening-up technique is to imagine oneself as another person; a related opening-up technique involves the performance of a common task in a slightly different way, in order to call better attention to one’s daily routine. In the other kind of meditation approach, concentrative meditation, the person actively concentrates on an object, word, or idea, called a mantra. In some versions of this approach, the person concentrates instead on a riddle, called a koan. A well-known koan involves answering the question, “What is the sound of one hand clapping?” One of meditation’s greatest appeals is that it can help people relax. In fact, studies have shown that people in meditative states experience increases in the same brain waves that are associated with the relaxation phase individuals experience just prior to falling sleep (Aftanas & Golasheiken, 2003). Research has found that meditation also can lower respiration, heart rate, blood pressure, and muscle tension. Because of its positive impact on physical functioning, it has been used to help treat pain, asthma, high blood pressure, heart problems, skin disorders, diabetes, and viral infections (Wootton, 2008; Goodman et al., 2003). One form of meditation that has been applied in particular to patients suffering from severe pain is mindfulness meditation (Carey, 2008; Kabat-Zinn, 2005). Here, meditators pay attention to the feelings, thoughts, and sensations that are flowing through their minds during meditation, but they do so with detachment and without judgment. By just being mindful but not judgmental of their feelings and thoughts, including feelings of pain, the individuals are less inclined to label or fixate on them and, in turn, less likely to react negatively to them.
Before You Go On What Do You Know? 7. What are the physical effects of meditation? 8. What are the main benefits of altering consciousness through meditation?
What Do You Think? Which approach to meditation appeals more to you, opening-up meditation or concentrative meditation? Why?
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When We Are Asleep LEARNING OBJECTIVE 5 Describe what happens when people sleep, key theories of why we sleep and dream, and problems with sleep and how they affect functioning.
To Benjamin Franklin’s famous acknowledgment that the only sure things in life are death and taxes could be added a third: that sooner or later we must—absolutely must— fall and stay asleep. Sleep is so central to our lives—indeed, most people spend 25 years of their lives asleep—that we first need to ask what important purpose does it serve?
Why Do We Sleep?
“Everyone needs to sleep” These two bees take time out from their busy agenda to sleep in a comfortable flower.
Interestingly, despite considerable research into the matter, no consensus exists about why people need to sleep (Moorcroft, 2003). After all, as we shall see, the brain does not rest when we are sleeping, nor, on the surface, does sleep offer the body much more rest than it would get by sitting down and relaxing for awhile. Yet all animals sleep, and they would, in fact, die if they were deprived of sleep for too long (see Figure 6-4). One theory, the adaptive theory of sleep, suggests that sleep is the evolutionary outcome of self-preservation. Proponents of this view suggest that organisms sleep in order to keep themselves away from predators that are more active at night. Our ancestors, for example, tucked themselves away in safe places to keep from being eaten by nocturnal animals on the prowl. Animals that need to graze and so have less chance of hiding from predators tend to sleep less. An elephant, for Donkey example, sleeps only two or three hours a day, whereas a bat sleeps around twenty. This evolutionary argument, however, seems to account more for why Human we sleep at night than for why we sleep in the first place. Several biological theories of sleep have also been proposed. One suggests that sleep plays a role in the growth process, a notion consistent with the findGuinea pig ing that the pituitary gland releases growth hormones during sleep. In fact, as we age, we release fewer of these hormones, grow less, and sleep less (Gais et al., Rat 2006). Researchers have also observed changes in neuron activity in other areas of the Rabbit brain during sleep, including the reticular formation and the pons, as well as the forebrain region. As we described in Chapter 4, these regions are important in alertness Cat and arousal. Researchers have not established, however, that changes in the activity of these areas cause us to sleep. Opossum Another biological theory, the restorative theory of sleep, suggests that sleep allows the brain and body to restore certain depleted chemical resources, while eliminating 0 15 3 6 9 12 18 21 24 chemical wastes that have accumulated during the waking day (Smith & Baum, 2003; Average time spent in sleep per day (hours) Irwin, 2001). Which chemicals might be depleted, and which ones might build to excess? We do not really know (Thompson, 2000). While we may not yet know exactly what FIGURE 6-4 Sleep needs of various animals Animals vary greatly in how much sleep they need each day. Their sleep causes sleep, we do know that sleep occurs in regular patterns, or rhythms, and that these needs are related in part to how much awake time is needed rhythms reflect changes in the body’s chemistry (Moorcroft, 2003). to obtain food and protect themselves from predators.
Rhythms of Sleep Human beings’ basic pattern is called the circadian rhythm (see Figure 6-5). Within each 24-hour cycle, we experience a sustained period of wakefulness that gives way to a period of sleep. Although we tend to be awake during the day and to sleep at night, our circadian rhythms are not fully dependent on the cycles of daylight (Schultz & Kay, 2003; Thompson, 2000).
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Sleep
Alertness
High
Low Degree of alertness
0.4 0.2 0.0 –0.2
(b)
Time of Day
FIGURE 6-5 Circadian rhythms Two prime examples of circadian rhythms are our cycles of alertness and shifts in body temperature.
6 AM
Midnight
6 PM
Noon
6 AM
Midnight
6 PM
–0.4 Noon
Change in body temperature (°F)
(a)
During the circadian cycle, we also experience other, more subtle patterns of biochemical activity. As morning nears, for example, our temperature rises and continues to rise until it peaks at midday. Then it dips and we feel fatigued. Many people around the world take naps during this early afternoon lull. Later in the afternoon, body temperature rises once more, only to drop again as we approach our full evening sleep (Johnson et al., 2004). Research has suggested that, on average, we are most alert during the late morning peak in the circadian rhythm. This “rule,” however, varies with age (Yoon et al., 2003). Younger people tend to peak later in the day, while older people peak earlier. Along with shifts in body temperature, we also experience changes throughout the 24-hour period in blood pressure, the secretion of hormones, and sensitivity to pain. As we have discussed, for example, the release of growth hormones tends to occur during periods of sleep. The circadian rhythm has been called our biological clock because the pattern repeats itself from one 24-hour period to the next. This clock, however, can be made to go haywire by certain events (Waterhouse & DeCoursey, 2004). For example, the clock can be disrupted by long-distance airplane flights when we are awake at times that we should be sleeping—a problem compounded by crossing time zones. The result: jet lag. Similarly, people who work nightshifts, particularly those who keep irregular schedules of dayshifts and nightshifts, may experience sleep disorders and, in some instances, develop problems such as depression or health difficulties. People with a pattern called circadian rhythm sleep disorder experience excessive sleepiness or insomnia as a result of a mismatch between their own sleepwake pattern and the sleep-wake schedule of most other people in their environment (Lack & Bootzin, 2003).
“Owls” and “Larks” HOW we Differ Do you get up at the crack of dawn, head to the gym, and complete all of your class assignments before noon? Then you are probably a morning person (a “lark”). Or do you have trouble getting up before noon and can’t really concentrate on your work until much later in the day? If so, you are likely an evening person (an “owl”). Most people have no preference for the time of day when they are most alert and active; they may shift their sleep-wake rhythms two hours earlier or later than normal with no adverse affects on their alertness or activity level (Sack et al., 2007). But for some, there is a strong preference for either earlier or later in the day. Researchers now believe that genetics plays an important role in determining these variations in sleep-wake rhythms, and that age, ethnicity, gender, and socioeconomic factors have almost no influence (Paine, Gander & Travier, 2006). Every cell in your body has its own internal clock, and scientists are able to measure your unique body clock at the cellular level (Cuninkova & Brown, 2008). As we shall see, the master control center for your body’s internal clock and your own sleep-wake rhythm is found in the brain area known as the suprachiasmatic nucleus.
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What Happens in the
When We Sleep B R A I N ?
Hypothalamus
Research has uncovered what happens in our brains to control the circadian rhythms of when we wake and sleep, as well as what happens in the brain while we sleep.
Suprachiasmatic nucleus
Controlling the Clock The suprachiasmatic nucleus (SCN), a small group of neurons in the hypothalamus, is ultimately responsible for coordinating the many rhythms of the body (Waterhouse & DeCoursey, 2004; Honma et al., 2003). As daylight fades into night, the SCN “notices” the change and directs the pineal gland to secrete the hormone melatonin. Increased quantities of melatonin, traveling through the blood to various organs, cause sleepiness. Melatonin production peaks between 1:00 and 3:00 A.M.As dawn approaches, this production decreases and sleepers soon awaken. During the day, photoreceptors in the retina of the eye communicate the presence of sunlight to the SCN and melatonin secretions remain low. Photoreceptors are also sensitive to artificial light. In fact, the invention of the lightbulb just over a hundred years ago has disturbed the human experience of the circadian rhythm by increasing the number of hours of light people are exposed to in a given day. This may be one reason why many people today sleep much less than our forbearers. What happens if a person is entirely deprived of access to environmental shifts in sunlight and darkness? In a number of sleep studies, participants have been placed in special settings where they are totally deprived of natural light. In such settings, the SCN extends the body’s “day,” by as much as an hour, to about 25 hours (Lavie, 2001). When we are deprived of light, the various circadian rhythms also become out-of-synch with each other. The normal cycles of body temperature and melatonin production, for example, no longer coordinate with one another (Lavie, 2001). If we speak of a biological clock, we should also be able to speak of setting, or resetting, the clock (Waterhouse & DeCoursey; 2004). In fact, when a person who has been kept in an environment without sunlight is returned to normal living conditions, the usual 24-hour circadian rhythm is quickly restored. Patterns of Sleep Every 90 to 100 minutes while we sleep, we pass through a sleep cycle that consists of five different stages (Lavie, 2001). Researchers have identified these stages by examining people’s brain-wave patterns while they sleep, using a device called an electroencephalograph (EEG). EEG readings indicate that each stage of sleep is characterized by a different brain-wave pattern, as shown in Figure 6-6. When we first go to bed and, still awake, begin to relax, EEG readings show that we experience what are called alpha waves. As we settle into this drowsy presleep period, called the hypnagogic state, we sometimes experience strange sensations. We may feel that we are falling or floating in space, or “hear” our name called out, or we may hear a loud crash. All of these sensations seem very real, but none actually has happened. Such sensory phenomena are called hypnagogic hallucinations (Sherwood, 2002). Also common during this presleep stage is a myoclonic jerk, a sharp muscular spasm that generally accompanies the hypnagogic hallucination of falling. When we finally doze off, EEG readings show that our brain waves become smaller and irregular, signaling that we have entered Stage 1 sleep. Alpha-wave patterns are replaced by slower waves, called theta waves. This first stage of sleep actually represents a bridge between wakefulness and sleep; it lasts only a few minutes. Our conscious awareness of street noises or the hum of an air conditioner fades. If we are roused from this stage, we might recall having just had ideas that seem nonsensical. Falling deeper into sleep, we next pass into Stage 2 sleep. A still further slowing of brain-wave activity occurs during this stage, although we may also exhibit sleep spindles—
Pineal gland
suprachiasmatic nucleus (SCN) small group of neurons in the hypothalamus responsible for coordinating the many rhythms of the body. hypnagogic state a presleep period often characterized by vivid sensory phenomena. sleep spindles bursts of brain activity lasting a second or two; occur during Stage 2 sleep.
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Alert
Awake and Alert
Relaxed (Alpha waves)
Awake and Drowsy
(Thetawaves)
Stage 1
(Dreaming) Spindles
REM
Stage 2 (Delta waves appear)
Stage 3 (Mostly Delta waves)
Stage 4
FIGURE 6-6 The stages of sleep As people move from an awake state to a state of deep sleep, their brain waves become less and less frequent, and at the same time, larger and larger. REM sleep waves resemble alert-state brain waves.
rapid eye movement sleep (REM) stage of sleep associated with rapid and jagged brainwave patterns, increased heart rate, rapid and irregular breathing, rapid eye movements, and dreaming. nonREM sleep (NREM) Stages 1 through 4 of normal sleep pattern.
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bursts of brain activity that last a second or two. During Stage 2, breathing becomes steadily rhythmic. Occasionally, the body twitches, although generally our muscle tension relaxes. During this stage, which lasts 15 to 20 minutes, we can still be awakened fairly easily. Towards the end of Stage 2 sleep, our brain waves slow even further and delta waves start to appear in addition to the theta waves. Delta waves indicate delta sleep, or deep sleep. The next two stages of sleep, Stage 3 and Stage 4, are characterized by very deep sleep. In Stage 3, between 20 and 50 percent of our EEG waves are delta waves. During Stage 4, the percentage of delta waves increases to more than 50 percent (Bertini et al., 2007; Cooper, 1994). During Stage 4, heart rate, blood pressure, and breathing rates all drop to their lowest levels and the sleeper seems “dead to the world.” Interestingly, although our muscles are most relaxed during this deepest phase of sleep, this is also the time that people are prone to sleepwalking and might go for a stroll. Similarly, children who wet their beds tend to do so during this stage. Passing through all of the first four stages takes a little more than an hour of each 90 to 100-minute sleep cycle. After that, we experience the most interesting stage of sleep, rapid eye movement, or REM, sleep. In fact, all the preceding stages (Stages 1–4) are collectively called nonREM sleep, or NREM. During REM sleep, we experience rapid and jagged brain-wave patterns, in contrast to the slow waves of NREM sleep. REM sleep has been called paradoxical sleep because, even though the body remains deeply relaxed on the surface—almost paralyzed—we experience considerable activity internally (Wickwire et al., 2008). The rapid brain-wave pattern of REM sleep is accompanied by increased heart rate and rapid and irregular breathing, for example. Moreover, every 30 seconds or so, our eyes dart around rapidly behind our closed eyelids. Perhaps most interesting, people’s brains behave during REM sleep just as they do when we are awake and active (Ratey, 2001). Along with this brain activity, the genitals become aroused during REM sleep. Indeed, except during nightmares, men are usually experiencing erections and women vagin*l lubrication and cl*toral engorgement during REM sleep, even if the content of the dream is not sexual (Mann et al., 2003; Solms, 2007). Men often retain their erections beyond the REM stage, explaining the occurrence of “morning erections.” As we will discuss shortly, dreams usually occur throughout REM sleep. If people are awakened during this stage, they almost always report that they have been dreaming. Unlike the hypnagogic hallucinations of presleep, which are often fleeting and isolated images, dreams tend to be emotional and are experienced in a story-like form. Dreams are less common during NREM sleep, and when they do happen, they are less vivid or fantastic than REM dreams.
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Many researchers believe that REM sleep serves a particularly important function—the consolidation of memories of newly learned material, a process that we will be talking about more in the coming chapters on learning and memory (Fenn et al., 2003). In fact, REM sleep tends to extend longer than usual in both animals and humans if the organisms go to sleep after just having learned a new task (Smith, 2006, 1996). In one study, a group of volunteers were trained on a perceptual task just before going to sleep (Karni et al., 1994). Half of the sleepers were awakened during REM sleep, while the other half were awakened later, during the next cycle of NREM sleep. The next day, those who had been awakened during REM sleep performed more poorly on the perceptual task than those who had been awakened during the later NREM phases. Presumably, the REM-awakened volunteers had not yet had the opportunity to fully consolidate their memories of the newly learned task. This memory consolidation theory has, however, been challenged by some studies showing that when animals are administered antidepressant drugs, which typically disrupt REM sleep, they nevertheless continue to learn and remember quite well (Vertes & Eastman, 2003). Research also finds that people with lesions to the pons portion of the brain, which is active during REM sleep, learn, remember, and function quite normally. It is worth noting that every kind of mammal whose sleep patterns have been studied, including birds, experience both NREM and REM sleep. Thus, many theorists believe that animals also dream. Of course, this comes as no surprise to dog owners who have, no doubt, frequently observed their pets twitch their paws in a regular rhythm during REM sleep, as if running in a dream (Thompson, 2000).
Almost like being awake When we are in REM sleep, our brains behave much like they do when we are awake and active, and indeed it is during this stage of sleep that we dream. The PET scan of a brain during REM sleep (left) reveals much more activity (indicated by the colors “red” and “orange”) than does the scan of a brain during nonREM sleep (right).
Dreams Dreams—emotional, story-like sensory experiences that usually occur during REM sleep—have proven to be endlessly fascinating to scientists, clinicians, philosophers, artists, and laypeople, probably because of how vivid and mysterious they are. A woman dreams of being punched in the stomach and doubling over in pain. In thinking about the dream the next day, she notices that she feels very vulnerable. She also recalls that earlier on the day of the dream she had learned that her investment portfolio lost a great deal of money, and she remembers having felt vulnerable because all of that money was gone. Could the dream and the loss of money be related? Some psychologists would say yes, while others would be skeptical. In this section we shall examine ways in which different theorists and researchers have come to understand dreams (Moorcroft, 2003).
Research suggests that actions in dreams run in real time—that is, it takes you as long to accomplish something in the dream as it would if you were performing the action while you were awake.
Freudian Dream Theory Sigmund Freud argued that dreams represent the expression of unconscious wishes or desires. He believed that dreams allow us to discharge internal energy associated with unacceptable feelings (Freud, 1900). Freud suggested that dream interpretation, in which a psychoanalytic therapist facilitates insight into the possible meaning behind a dream, may help clients appreciate their underlying needs and conflicts with the goal of being less constrained by them during waking life. For example, if a lonely and morally upstanding young man is sexually attracted to his brother’s wife, he might have a dream in which he goes swimming in a private pool that is marked “No Trespassing.” His therapist might help the man arrive at the conclusion that the dream about swimming in an off-limits pool symbolizes his wish to be with his sisterin-law. Such an insight eventually might help the man to overcome inhibitions he feels about finding a suitable partner for himself. Freud called the dream images that people are able to recall the manifest content. The unconscious elements of dreams are called the latent content. In our example, the young man’s desire for his sister-in-law (latent content)—a scandalous idea that he would never allow himself to have—is symbolized in the dream by a swim in the pool When We Are Asleep
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Brain stem
FIGURE 6-7 Activation-synthesis According to the activation-synthesis theory of dreaming, neurons in the brainstem activate neurons in other areas throughout the brain. The brain combines these various signals into a story, or dream.
(manifest content). His dream of a happy swim in forbidden territory is his mind’s solution to a problem that he could not work out consciously. Many of today’s theorists, including a number of psychoanalytic ones, criticize Freud’s theory. For example, object-relations theorists, psychoanalytic theorists who place greater emphasis on the role of relationships in development, focus more on relationship issues when interpreting dream material. Regarding the earlier dream in which a woman gets punched, an object-relations therapist might be inclined to help the patient explore her feelings of vulnerability in various relationships rather than her financial fears.
Information-Processing Theory Information-processing theory offers an alternative, more cognitive, view of dreaming. According to this view, dreams are the mind’s attempt to sort out and organize the day’s experiences and to fix them in memory. Consistent with this perspective, studies have revealed that interrupting REM sleep—and so interrupting dreams—impedes a person’s ability to remember material that he or she has learned just before going to sleep (Empson, 2002). Also, in support of this view, researchers have found that periods of REM sleep (during which we dream) tend to extend longer when people’s days have been filled with multiple stressful events or marked by extensive learning experiences (Palumbo, 1978). Thus, according to an information-processing perspective, the woman who dreamed of being punched may simply have been attempting to process and give order to the stressful financial events that she had experienced earlier in the day. Activation-Synthesis Hypothesis Researchers J. Allan Hobson and Robert W. McCarley have proposed a more biological hypothesis about dreaming, the activationsynthesis model (Hobson, 2005; Hobson & McCarley, 1977) (see Figure 6-7). They argue that as people sleep, their brains activate all kinds of signals. In particular, when dreams occur, neurons in the brainstem are activated. These, in turn, activate neurons in the cerebral cortex to produce visual and auditory signals. Also aroused are the emotion centers of the brain, including the cingulate cortex, amygdala, and hippocampus. Neuroimaging scans of people who are experiencing REM sleep confirm heightened activity and neuron communication in each of these brain regions. Hobson and McCarley suggest that the activated brain combines—or synthesizes— these internally generated signals and tries to give them meaning. Each person organizes and synthesizes this random collection of images, feelings, memories, and thoughts in his or her own personal way—in the form of a particular dream story (Hobson et al., 1998). The woman who dreamed of being punched might be trying to synthesize activation in brain areas that normally receive signals from the muscles of the stomach with signals from areas of the brain that process emotions, for example. What remains unclear in this model is why different people synthesize their onslaught of brain signals in different ways. Freud, of course, might suggest that each person’s particular synthesis is influenced by his or her unfulfilled needs and unresolved conflicts.
Nightmares, Lucid Dreams, and Daydreams
Dream stories People often experience similar dream stories. For example, 80 percent of all people have had repeated dreams of running toward or away from something.
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Dreams evoke many different feelings. Dreams filled with intense anxiety are called nightmares. The feeling of terror can be so great that the dreamer awakens from the dream, often crying out. Nightmares generally evoke feelings of helplessness or powerlessness, usually in situations of great danger. They tend to be more common among people who are under stress. People who experience frequent nightmares and become very distressed by their nightmares are considered to have a nightmare disorder.
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It appears that nightmares are more common among children than adults, although there is some dispute on this issue. When children have a nightmare, simple reassurances that they are safe and that the dream does not reflect real danger are usually helpful. It is important to help the child appreciate the difference between inner and outer reality (Halliday, 2004; Josephs, 1987). In contrast to nightmares, during which dreamers feel they are caught in a real and terrifying situation, lucid dreams are dreams in which people fully recognize that they are dreaming (Baars et al., 2003). Some lucid dreamers can even willfully guide the outcome of their dreams (LaBerge, 2007). In a lucid dream, the woman who dreamed of being punched might tell herself—while still asleep—that she is only dreaming and is actually fine; she even might try to guide the outcome of the dream so that she prevails over her attacker. Although not necessarily subscribing to psychoanalytic theory, people who attempt to engage in lucid dreaming often believe that it is a way to open up another phase of human consciousness. A third dream-related phenomenon is actually associated with waking states of consciousness—the daydream. Fantasies that occur while one is awake and mindful of external reality, but not fully conscious, are called daydreams (Schon, 2003; Singer, 2003). Recall, for example, that the driver in the opening story of this chapter had an elaborate daydream about an old romantic interest. Sometimes a daydream can become so strong that we lose track of external reality for a brief while. Although we may be embarrassed when caught daydreaming, such experiences may also afford us opportunities for creativity; we are, after all, less constrained during the fantasies than we would be if attending strictly to the outside world.
Sleep
information-processing theory hypothesis that dreams are the mind’s attempt to sort out and organize the day’s experiences and to fix them in memory. activation-synthesis model theory that dreams result from brain’s attempts to synthesize or organize random internally generated signals and give them meaning. lucid dreams dreams in which the sleeper fully recognizes that he or she is dreaming, and occasionally actively guides the outcome of the dream.
How we Develop
Parents or older siblings know all too well that young babies do not sleep quite like older children or adults. Through the first four months of life, babies sleep between 14 and 17 hours each day. The amount of time that they spend sleeping declines steadily as they get older (Sadeh et al., 2009). Although babies spend a lot of time asleep overall, the lengths of their sleep periods can last anywhere from minutes to hours before they are stirred and crying out for attention. For parents, the good news is that sleep tends to become more structured at around six months of age. Babies appear to spend a great deal more time than adults in REM sleep—around 8 hours per day for infants, compared with 2 hours for adults (Siegel, 2005). The size of this difference has led theorists to suspect that infant sleep patterns are crucial to development in various ways. Several have speculated, for example, that REM sleep aids in the development of the central nervous system by facilitating synaptic pruning and preventing the formation of unnecessary connections, although research has not yet confirmed this belief. Also, by slowing body activity, the extended REM sleep of babies may help to regulate the temperature of their developing brains. REM sleep tends to decrease to adult levels somewhere between the ages of two and six years (Curzi-Dascalova & Challamel, 2000). By early childhood, an individual’s total daily sleep requirement also decreases significantly (see Figure 6-8). Most children sleep around 9 hours each day, although pediatricians recommend between 12 and 15 hours of sleep for anyone between two and five years of age (Acebo et al., 2005). Teenagers average around 7 hours of daily sleep although pediatricians recommend at least 8 hours for them. As adults, our sleep patterns continue to change. As we age, we spend less and less time in deep sleep and
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FIGURE 6-8 The effects of aging on the sleep cycle As we get older, our total daily sleep and our REM sleep decrease. The largest shifts occur during out first three years of life.
24 16
Awake 12 40%
30%
10
25% 20%18.5% 18.5% 20%
8
22% 6
18.9%
REM
15%
13.8%
4
70–85 yrs
31–49 yrs
19–30 yrs
14–18 yrs
5–9 yrs 10–13 yrs
3–5 yrs
2–3 yrs
6–23 mos
3–5 mos
1–15 days
50–69 yrs
Non-REM
2
Total daily sleep
Mean number of hours per day
14
Age
A graduate student in physiology, Eugene Aserinsky, discovered REM sleep when he attached electronic leads to his 8-year-old son’s head and eyelids to monitor his sleep and waking brain waves and found unexpected brain-wave activity, suggesting his son “had woken up even though he hadn’t. (Aserinsky, 1996).”
REM sleep, our sleep is more readily interrupted, and we take longer to get back to sleep when awakened (Garcia-Rill et al., 2008). As discussed earlier, our sleep-awake cycle is tied to our bodies’ circadian rhythms. These biological clocks are also affected by environmental demands and expectations. Studies have, for example, contrasted parenting practices in the United States with those in the Kipsigis tribe (you may remember them from Chapter 2). Many American parents structure their babies’ sleep by putting them down at designated times and not responding to their cries. In contrast, Kipsigis mothers keep their babies with them constantly. As a result, Kipsigis babies sleep for much shorter periods of time later into infancy than do American babies; in many cases, they do not sleep for long stretches even as adults (Super & Harkness, 2002, 1972). The body clocks of teenagers also seem to be compromised by the increased social and academic pressures that they encounter (Crowley, Acebo, & Carskadon, 2007). Many adolescents in the United States, for example, stay up late largely because that’s what it takes for them to finish their homework or to keep up with their friends.
Sleep Deprivation and Sleep Disorders How much sleep a person needs varies, depending on factors such as age, lifestyle, and genetic disposition. The amount of sleep a person actually gets may also be different from how much they need. Their lifestyles deprive many people of sleep, and sleep disorders and may also make it impossible to sleep properly. Sleep Deprivation Left unhindered, most people would sleep for nine or ten hours a day in order to awaken alert and refreshed. However, we’ve all had the opposite experience—that of not getting enough sleep. We become generally sleepy and maybe a little cranky. After a while, we may yearn for sleep. Researchers have found that without enough sleep, people also experience a general malaise (Fredriksen et al., 2004). They display lower productivity and are more apt to make mistakes (Van Dongen, 2007, 184 Chapter 6
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2003). Not surprisingly, accidents and deaths sometimes occur when drivers and pilots do not get enough sleep. While it is possible to make up for the lost sleep of one night by sleeping a little longer the next night, it becomes increasingly difficult for persons to “pay off ” their “sleep debt” if they chronically miss sleep (Moorcroft, 2003). Adolescents are particularly likely to be sleep deprived (Carskadon, 2002). Interestingly, teenagers today get about two hours less sleep per night than teens did 80 years ago. In fact, the distinguished sleep researcher William Dement has asserted that 80 percent of students at his institution, Stanford University, are “dangerously sleep deprived” (Dement & Vaughan, 1999). Ironically, students who pull all-nighters in order to complete their work actually wind up working less efficiently and effectively than they would if they were to sleep the eight or nine hours that they need. Despite such problems among young persons, researchers have not conducted much research on how sleep deprivation specifically affects physical, cognitive, and emotional development (Loessl et al., 2008). Sleep researchers used to spend most of their time examining the impact of lost sleep on simple or monotonous tasks. Today’s researchers, however, often look at the impact of sleep deprivation on more complex activities (Moorcroft, 2003; Harrison & Horne, 2000). Studies suggest, on the one hand, that sleep deprivation does not necessarily lower one’s performance on complex logical tasks. Sleep-deprived participants in such tasks often are able to avoid poor performances by being highly interested in the complex tasks at hand. Many sleep-deprived college students, for example, seem able to conduct research or write papers, particularly if those works interest them a lot. Problems arise, on the other hand, when a sleep-deprived person faces unexpected turns of events, distractions, or innovations while working on a complex task, or needs to revise the task. If, for example, someone turns on the television while you’re studying in a sleep-deprived state, your learning is likely to suffer considerably. In an important set of findings, researchers have also learned that sleep loss can lower the effectiveness of people’s immune systems (Benedict et. al., 2007; Dement & Vaughan, 1999). Sleep deprived people apparently have a more difficult time fighting off viral infections and cancer, for example. Thus, it may not be surprising that people who average at least eight hours of sleep a night tend to outlive those who get less sleep (Dement & Vaughn, 1999). Sleep Disorders Sleep disorders occur when normal sleep patterns are disturbed, causing impaired daytime functioning and feelings of distress (Espie, 2002; APA, 2000). Almost everyone suffers from some kind of sleep disorder at one time or another in their lives. The sleep disorder may be part of a larger problem, such as life stress, a medical condition, or substance misuse, or it may be a primary sleep disorder, in which sleep difficulties are the central problem. Primary sleep disorders typically arise from abnormalities in the people’s circadian rhythms and sleep-wake mechanisms. People who suffer from insomnia, the most common sleep disorder, regularly cannot fall asleep or stay asleep (Taylor et al., 2008; Morin & Espie, 2003). More than 20 percent of the entire population experience significant extended episodes of insomnia each year (APA, 2000). The National Sleep Foundation claims that 43 percent of adults experience at least one symptom of insomnia a few nights or more each week. As you might expect, many cases of insomnia are triggered by day-to-day stressors. In particular, job or school pressures, troubled relationships, and financial problems have been implicated. For many people, a subtle additional stress is worrying about not getting enough sleep while trying to fall asleep. This vicious cycle can further intensify anxiety and make sleep all the more elusive (Espie, 2002). Insomnia is more common among older people than younger ones (Knight et al., 2006). Elderly individuals are particularly prone to this problem because so many
Sleep wins Whether it’s a bassist collapsing in midplay on a couch or a gardener dozing on a bench, the need to drift off eventually catches up with those who are sleep deprived.
insomnia sleep disorder characterized by a regular inability to fall asleep or stay asleep.
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Studying narcolepsy Some people with narcolepsy, a sleep disorder marked by uncontrollable urges to fall asleep, further experience sudden losses of muscle tone during their narcoleptic episodes. To learn more about this abnormal pattern, famous sleep researcher William Dement studies dogs such as Tucker, seen here before and during a sudden narcoleptic episode.
of them have medical ailments, experience pain, take medications, or grapple with depression and anxiety—each a known contributor to insomnia (Taylor et al., 2008). In addition, some of the normal age-related sleep changes we described earlier may heighten the chances of insomnia among elderly people. As individuals age, for example, they naturally spend less time in deep sleep and their sleep is interrupted more readily (Edelstein et al., 2008). Twenty million people—typically older men who are heavy snorers—suffer from sleep apnea, the second most common sleep disorder. People with this condition repeatedly stop breathing during the night, depriving the brain of oxygen and leading to frequent awakenings. Sleep apnea can result when the brain fails to send a “breathe signal” to the diaphragm and other breathing muscles or when muscles at the top of the throat become too relaxed, allowing the windpipe to partially close. Sufferers stop breathing for up to 30 seconds or more as they sleep. Hundreds of episodes may occur each night. Often the individual will not remember any of them, but will feel sleepy the next day. Narcolepsy, marked by an uncontrollable urge to fall asleep, afflicts more than 135,000 people in the United States (NINDS, 2006). People with this disorder may suddenly fall into REM sleep in the midst of an argument or during an exciting football game. When they wake, they feel refreshed. The narcoleptic episode is experienced as a loss of consciousness that can last up to 15 minutes. This disorder can obviously have serious consequences for people driving cars, operating tools, or performing highly precise work. Its cause is not fully known. Narcolepsy seems to run in families, and some studies have linked the disorder to a specific gene or combination of genes (Quinnell et al., 2007). Sleepwalking most often takes place during the first three hours of sleep. Sleepwalkers will often sit up, get out of bed, and walk around. They usually manage to avoid obstacles, climb stairs, and perform complex activities. Accidents do happen, however: tripping, bumping into furniture, and even falling out of windows have all been reported. People who are awakened while sleepwalking are confused for several moments. If allowed to continue sleepwalking, they eventually return to bed. The disorder appears to be inherited (Hublin et al., 2001). Up to 5 percent of children experience this disorder for a period of time (Wickwire et al, 2008). Related to sleepwalking is night terror disorder. Individuals who suffer from this pattern awaken suddenly, sit up in bed, scream in extreme fear and agitation, and experience heightened heart and breathing rates. They appear to be in a state of panic and are often incoherent. Usually people suffering from night terrors do not remember the episodes the next morning. Night terror disorder is not the same thing as a nightmare disorder, discussed earlier in the chapter, in which sufferers experience frequent nightmares. Sleepwalking and night terrors are more common among children than among adolescents or adults. They tend to occur during Stages 3 and 4, the deepest stages of NREM sleep (Hublin et al., 1999).
Before You Go On What Do You Know? 9. What are the major theories of why people sleep? 10. What is the difference between the manifest content of a dream and its latent content? 11. What is the role of the suprachiasmatic nucleus in human consciousness? 12. What is the difference between a nightmare and a night terror?
What Do You Think? Which of the theories of dreams described in this section seems to make most sense to you and why? Could another idea or a combination of theories better explain dreaming?
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Psychoactive Drugs © New Yorker Collection 2000 Tom Cheney from cartoonbank.com. All Rights Reserved.
LEARNING OBJECTIVE 6 List and describe common depressant, stimulant, and hallucinogenic psychoactive drugs and their effects.
What is one of the first things you do every day? For millions of people, the answer is to have a cup of coffee (maybe more than one). Why do so many people do this? For most, it is to give themselves a bit of a jolt and get the day going. Similarly, people often use other substances to help improve, or at least change, how they feel or function. Many people smoke cigarettes to feel more alert, less anxious, or both. Others may have a glass of wine or beer in the evening in order to wind down from a hectic day. These substances—coffee, cigarettes, and alcohol—along with many others, alter our state of consciousness and influence our moods and behaviors. Collectively, they are examples of psychoactive drugs, chemicals that affect awareness, behavior, sensation, perception, or mood. Some such drugs are illegal chemicals (heroin, ecstasy, marijuana), while others are common and legal. Table 6-1 shows the three broad categories of drugs and lists examples of specific drugs that fall within those categories. TABLE 6-1 Psychoactive Drugs and Their Effects DRUG CLASS
EFFECTS
Depressants
Depress activity of central nervous system
Alcohol
Slows down brain areas that control judgment, inhibition, behavior (speech, motor functioning, emotional expression)
Sedative-hypnotics (benzodiazepines)
Produce relaxation and drowsiness, relieves anxiety
Opioids (opium heroin, morphine, codeine, methadone)
Reduce pain and emotional tension, produce pleasurable and calming feelings
Stimulants
Increase activity of central nervous system
Caffeine
Increases alertness
Nicotine
Increases alertness, reduces stress
Cocaine
Increases energy and alertness, produces euphoric feelings of well-being and confidence
Amphetamines
Increase energy and alertness, reduce appetite, produce euphoric feelings
Hallucinogens
Enhance normal perceptions
LSD
Dramatically strengthens visual perceptions (including illusions and hallucinations) along with profound psychological and physical changes
sleep apnea sleep disorder characterized by repeatedly ceasing to sleep during the night, depriving the brain of oxygen and leading to frequent awakenings.
Cannabis (marijuana, THC)
Produces a mixture of hallucinogenic, depressant, and stimulant effects
narcolepsy sleep disorder marked by uncontrollable urge to fall asleep.
MDMA (Ecstasy)
Enhances sensory perceptions, increases energy and alertness, produces feelings of empathy and emotional well-being
psychoactive drugs chemicals that affect awareness, behavior, sensation, perception, or mood.
Psychoactive Drugs
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Addictions: Living out of control
Fighting addiction Thousands of people from alcohol and drug recovery programs march across the Brooklyn Bridge in 2008 as part of The Recovery Rally, a campaign to spread the message that addiction is treatable.
Most of us know someone who has an addiction problem. According to some clinical theorists, addictions are not only about alcohol and substance abuse; they may also cover dependencies such as food, the Internet, gambling, caffeine, shopping, sex, and exercise, to name a few (Page & Brewster, 2009; Stein, 2008). Addictive patterns do not suddenly appear; they are usually long-standing and may be rooted in various psychological problems. Whereas it takes time for an individual to lose control of his or her life to a dependency, it also takes time, motivation, commitment, discipline, and often the help of a professional treatment program to regain control and recover from an addiction. There are no quick fixes for recovery.
How do you know whether you or someone close to you is experiencing an addiction? This is a complex issue that typically requires careful clinical assessment for a definitive answer. Nevertheless, there are some straightforward questions that you can use to determine whether professional attention is in order. For example, is the person unable to meet responsibilities at home, school, or the office? Has the person tried to stop the repeated behavior but cannot, and continues to engage in it despite the apparent dangers? Although most clinicians agree that there is no substitute for careful clinical assessment and treatment of addictions, some have developed basic detection devices that can help get the ball rolling. For example, a brief tool to detect alcohol addiction is known as the CAGE questionnaire. It asks these questions: 1) Has the person ever felt that he or she should CUT DOWN on the drinking? 2) Has the person ever been ANNOYED by people criticizing the drinking? 3) Has the person ever expressed remorse or GUILT about drinking? 4) Has the person ever started to drink in the morning as an EYEOPENER to start the day or get rid of a hangover? A “yes”’ answer to at least two of these questions may indicate a problem with alcohol addiction and a corresponding need for professional assessment and treatment. More than a quarter century after the CAGE questionnaire was first developed, it has been validated in many studies as an effective, quick indicator of the need for help (O’Brien, 2008).
Some of the changes brought about by psychoactive drugs are temporary, lasting only as long as the chemicals remain in the brain and body. But certain psychoactive drugs can also bring about long-term changes and problems. People who regularly ingest them may develop maladaptive patterns of behavior and changes in their body’s physical responses, a pattern commonly called addiction. We will also be discussing addiction in Chapter 11 when we examine the motives and drives that direct behavior, including chronic drug-taking behavior. Those addicted to a drug feel compelled psychologically and physically to keep taking it. They rely on the drug excessively and chronically and may damage their family and social relationships, function poorly at work, or put themselves and others in danger. Addicted individuals may also acquire a physical dependence on the drug. They may develop a tolerance for the drug, meaning they need larger and larger doses in order to keep feeling its desired effect. And, if they try to stop taking or cut back on the drug, they may experience unpleasant and even dangerous withdrawal symptoms, such as nausea, cramps, sweating, or anxiety. People in withdrawal may also crave the drug that they had been taking regularly. Even if they want to quit taking it, the knowledge that they can quickly eliminate the unpleasant withdrawal symptoms by simply ingesting the
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drug makes it difficult for many users to persevere through the withdrawal period. In any given year, 9.2 percent of all teens and adults in the United States, around 23 million people, display addiction (NSDUH, 2008).
Depressants Psychoactive drugs that slow down the central nervous system are called depressants. They reduce tension and inhibitions and may interfere with a person’s judgment, motor activity, and concentration. The three most widely used groups of depressants are alcohol, sedative-hypnotic drugs, and opioids. Alcohol Alcohol, a depressant that is taken in liquid form, is one of the most commonly used psychoactive drugs. More than half of the people in the United States drink beverages that contain alcohol, at least from time to time (NSDUH, 2008). Purchases of beer, wine, and liquor amount to many billions of dollars each year in the United States alone. Nearly 7 percent of people over 11 years of age are heavy drinkers, having at least five drinks in a row on at least five occasions each month (NSDUH, 2008). Among heavy drinkers, males outnumber females by more than two to one, around 8 percent to 4 percent. All alcoholic beverages contain ethyl alcohol, a chemical that is quickly absorbed into the blood through the lining of the stomach and the intestine. The ethyl alcohol immediately begins to take effect as it is carried in the bloodstream to the central nervous system (the brain and spinal cord), where it acts to slow functioning by binding to various neurons, particularly those that normally receive a neurotransmitter called gamma aminobutyric acid, or GABA.
addiction psychological or physical compulsion to take a drug, resulting from regular ingestion and leading to maladaptive patterns of behavior and changes in physical response. tolerance mark of physical dependence on drug, in which person is required to take incrementally larger doses of the drug to achieve the same effect. withdrawal symptoms unpleasant and sometimes dangerous side effects of reducing intake of a drug after a person has become addicted. depressants class of drugs that slow the activity of the central nervous system.
Binge Drinking and College Students Binge drinking—the consumption of five or more drinks in a row—is a major problem in many settings, not the least of which are college campuses (NSDUH, 2008, Read et al., 2008). According to research, 40 percent of college students binge drink at least once each year, many of them multiple times per month (NCASA, 2007; Wechsler et al., 2004). These are higher rates than those among similar aged individuals who do not attend college (Ksir et al., 2008). On many campuses, alcohol use often is an accepted part of college life. But consider these statistics: • Binge drinking by college students has been associated with 1,700 deaths each year, 500,000 injuries, and tens of thousands of cases of sexual assault, including date rape (NCASA, 2007; Wechsler et al., 2000). • Alcohol-related arrests account for 83 percent of all campus arrests (NCASA, 2007).
• Binge drinking by female college students has increased 31 percent over the past decade. • Alcohol may be a factor in 40 percent of college problems (Anderson, 1994). Given such trends, many researchers and clinicians have turned their attention to the problem of college binge drinking. Surveys of more than 50,000 students across the United States find that the students most likely to binge drink are those who live in a fraternity or sorority house, pursue a party-centered lifestyle, and engage in highrisk behaviors, such as substance misuse or having multiple sex partners (Wechsler & Nelson, 2008; Wechsler et al., 2004, 1995, 1994). Efforts to reduce college binge drinking have begun to make a difference. Some universities, for example, now provide substance-free dorms. One study found that 36 percent of the residents in such dorms were binge drinkers, compared to 75 percent of students who lived in a fraternity or sorority house (Wechsler et al., 2002). The implications are clear: college drinking, including binge drinking, is more common and harmful than previously believed. And most experts agree that the time has come to attack this enormous problem head on.
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TABLE 6-2 Alcohol’s Effects on the Body and Behavior
Cultural endorsem*nt? Five men and hundreds of others around them celebrate at Oktoberfest, Germany’s annual 16-day festival, marked by eating, special events, and perhaps most prominently, drinking. Almost 7 million liters of beer are served to thousands of revelers at each year’s festival, an excessiveness that many believe contributes to binge drinking and alcoholism.
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Number of drinks(a) in two hours
Blood alcohol content (%)(b)
Effect
(2)
0.06
Relaxed state; increased sociability
(3)
0.09
Everyday stress lessened
(4)
0.10
Movements and speech become clumsy
(7)
0.20
Very drunk; loud and difficult to understand; emotions unstable
(12)
0.40
Difficult to wake up; incapable of voluntary action
(15)
0.55
Coma and/or death
a
A drink refers to one 12-ounce beer, a 4-ounce glass of wine, or a 1.25-ounce shot of hard liquor.
b
In America, the legal blood alcohol lever for “drunk driving” varies from 0.05 to 0.12.
At first, ethyl alcohol slows down the brain areas that control judgment and inhibition; people become looser and more talkative, relaxed, and happy. When more alcohol is absorbed, it slows down additional areas in the central nervous system, causing the drinkers to make poorer judgments, become careless, and remember less well. Many people become highly emotional, and some become loud and aggressive. As drinking continues, the motor responses of individuals decline and their reaction times slow. They may be unsteady when they stand or walk, for example, Their vision becomes blurred and they may misjudge distances. They can also have trouble hearing. As a result, people who have drunk too much alcohol may have enormous difficulty driving or solving simple problems. As summarized in Table 6-2, the concentration, or proportion, of ethyl alcohol in the blood determines how much it will affect a person (Ksir et al, 2008). When the alcohol concentration reaches 0.06 percent of the blood volume, a person usually feels relaxed and comfortable. By the time it reaches 0.09 percent, the drinker crosses the line into intoxication. If the level goes as high as 0.55 percent, death will probably result. Most people, however, lose consciousness before they can drink enough to reach this level.The effects of alcohol subside only when the alcohol concentration in the blood falls. Though legal, alcohol is actually one of society’s most dangerous drugs, and its risks extend to all age groups. In fact, 10 percent of elementary school students admit to some alcohol use and nearly 45 percent of high school seniors drink alcohol each month (usually to the point of intoxication), with 3 percent of them drinking every day (Johnston et al., 2007). Surveys indicate that over a one-year period, 6.6 percent of all adults in the world fall into a long-term pattern of alcohol addiction, known as alcoholism (Somers et al., 2004). More than 13 percent of adults experience the pattern at some time in their lives, with men outnumbering women by at least two to one (Kessler et al., 2005). The prevalence of alcoholism in a given year is similar (from 7 to 9 percent) for white Americans, African Americans, and Hispanic Americans (SAMHSA, 2008). Native Americans, particularly men, display a higher alcoholism rate (15 percent) than any of these groups. Generally, Asians in the United States and elsewhere have lower
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rates of alcoholism than do people from other cultures. As many as one-half of Asians have a deficiency of alcohol dehydrogenase, a chemical responsible for breaking down and eliminating alcohol from the body, so they react very negatively to even a small intake of alcohol. Such extreme reactions help prevent heavy use (Wall et al., 2001; APA, 2000). People who abuse alcohol drink large amounts regularly and rely on it to help them to do things that would otherwise make them nervous. Eventually the drinking disrupts their social behavior and their ability to think clearly and work effectively. Many build up a tolerance for alcohol and they need to drink greater and greater amounts to feel its effects. They also experience withdrawal when they stop drinking. Within hours, for example, their hands and eyelids begin to shake, they feel weak, they sweat heavily, their heart beats rapidly, and their blood pressure rises (APA, 2000). Alcoholism can wreak havoc on an individual’s family, social, and occupational life (Murphy et al., 2005). Medical treatment, lost productivity, and losses due to deaths from alcoholism cost society many billions of dollars each year. The disorder also has been implicated in more than one-third of all suicides, homicides, assaults, rapes, and accidental deaths, including 30 percent of all fatal automobile accidents in the United States (Ksir et al., 2008). Intoxicated drivers are responsible for 12,000 deaths each year. One of every eight persons has driven while intoxicated at least once in the past year (NSDUH, 2008). The 30 million children whose parents have alcoholism are also severely affected by this disorder. The home life of these children often features much conflict and, in some cases, sexual or other forms of abuse. The children themselves have elevated rates of psychological problems and substance-related disorders over the course of their lives (Hall & Webster, 2002). Many display low self-esteem, weak communication skills, poor sociability, and marital problems (Watt, 2002; Lewis-Harter, 2000). Long-term excessive drinking can also cause severe damage to one’s physical health (Myrick & Wright, 2008). It so overworks the liver—the body organ that breaks down alcohol—that people may develop an irreversible condition called cirrhosis, in which the liver becomes scarred and dysfunctional (CDC, 2008). Alcohol abuse may also damage the heart and lower the immune system’s ability to fight off infections and cancer and to resist the onset of AIDS after infection. Finally, women who drink during pregnancy place their fetuses at risk (Finnegan & Kandall, 2008). Heavy drinking early in pregnancy often leads to a miscarriage. Excessive alcohol use during pregnancy may also cause a baby to be born with fetal alcohol syndrome, a pattern that can include mental retardation, hyperactivity, head and face deformities, heart defects, and slow growth. It has been estimated that in the overall population approximately 1 of every 1,000 babies is born with this syndrome (Ksir et al., 2008). The rate increases to as many as 29 of every 1,000 babies of women who are heavy drinkers. Sedative-Hypnotic Drugs At low dosages, sedative-hypnotic drugs produce feelings of relaxation and drowsiness. At higher dosages, they are sleep inducers, or hypnotics. Benzodiazepines, antianxiety drugs developed in the 1950s, are today’s most popular sedative-hypnotic drugs available. More than 100 million prescriptions are written each year for this group of chemical compounds (Bisaga, 2008). Xanax®, Ativan®, and Valium® are three of the benzodiazepines in wide clinical use. This group of drugs reduces anxiety without making people as overly drowsy as alcohol or other depressant substances. Nevertheless, in high enough doses, benzodiazepines can cause intoxication and lead to addiction (Dupont & Dupont, 2005). As many as 1 percent of the adults in the United States become addicted to these drugs at some point in their lives (Sareen, Enns, & Cox, 2004).
Spreading the word Perhaps the most successful public effort to reduce drunk driving fatalities has been undertaken by Mothers Against Drunk Driving (MADD). Raising public awareness through ads, campaigns, and lobbying efforts, this organization has helped reduce the number of alcohol-related automobile deaths by 47 percent since it was formed in 1980.
alcoholism long-term pattern of alcohol addiction. sedative-hypnotic drugs class of drugs, the members of which produce feelings of relaxation and drowsiness.
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opioids class of drugs derived from the sap of the opium poppy. endorphins neurotransmitters that help relieve pain and reduce emotional tension stimulants substances that increase the activity of the central nervous system.
Opioids The term opioids refers to opium and drugs derived from it, including heroin, morphine, and codeine. Opium, a substance taken from the sap of the opium poppy, has been used for thousands of years. In the past, it was used widely in the treatment of medical disorders because of its ability to reduce both physical pain and emotional distress. Physicians eventually discovered, however, that the drug was addictive. Morphine and heroin, each of which was later derived from opium for use as a safer painkiller, also proved to be highly addictive. In fact, heroin is even more addictive than the other opioids. Additional drugs have been derived from opium, and several synthetic (laboratoryblended) opioids such as methadone have also been developed. Each of these various drugs has a different strength, speed of action, and tolerance level. Today, morphine and codeine are used as medical opioids, usually prescribed to relieve pain. Heroin is illegal in the United States under all circ*mstances. Outside of medical settings, opioids are smoked, inhaled, snorted (inhaled through the nose), injected by needle just beneath the skin (“skin popped”), or injected directly into the blood stream (“mainlined”). An injection quickly produces a rush—a spasm of warmth and joy that is sometimes compared with an org*sm. The brief spasm is followed by several hours of a pleasant feeling and shift in consciousness called a high or nod. During a high, the opioid user feels very relaxed and happy and is unconcerned about food or other bodily needs. Opioids depress the central nervous system, particularly the brain areas that control emotion. The drugs attach to brain receptors that ordinarily receive endorphins, neurotransmitters discussed in the previous chapter, that help reduce pain and emotional tension (Ksir et al., 2008). When neurons receive opioids at these receptors, the opioids produce the same kinds of pleasant and relaxing feelings that endorphins would produce. The most direct danger of heroin use is an overdose, which shuts down the respiratory center in the brain, almost paralyzing breathing and in many cases causing death. Death is particularly likely during sleep, when individuals cannot fight the respiratory effects by consciously working at breathing. Each year 2 percent of those addicted to heroin and other opioids are killed by the drugs, usually from an overdose (Theodorou & Haber, 2005; APA, 2000).
Stimulants Psychoactive drugs that speed up the central nervous system are called stimulants. They produce increases in blood pressure, heart rate, alertness, thinking, and behavior. Among the most problematic stimulants are caffeine, nicotine, cocaine, and amphetamines,
“
”
Caffeine. The gateway drug. —Eddie Vedder, singer/guitarist, Pearl Jam
Caffeine Caffeine, a mild (and legal) stimulant, is the world’s most widely used stimulant. It is found in coffee, tea, chocolate, cola, and so-called energy drinks. Worldwide, 80 percent of all people consume caffeine in one form or another every day (Rogers, 2005). Like many other psychoactive drugs, caffeine is addictive, although this addiction does not cause the significant social problems that are associated with substances such as alcohol, heroin, and cocaine (Paton & Beer, 2001; Silverman et al., 1992). Still, quitting caffeine can cause unpleasant withdrawal symptoms for chronic users, including lethargy, sleepiness, anxiety, irritability, depression, constipation, and headaches. Withdrawal symptoms can start only a few hours after the individual’s last consumption of caffeine. Nicotine Although legal, nicotine is one of the most highly addictive substances known (Ksir et al., 2008). Most commonly, it is taken into the body by smoking tobacco. Nicotine is then absorbed through the respiratory tract, the mucous membranes of the nasal area, and the gastrointestinal tract. The drug procedes to activate nicotine receptors located throughout the brain and body. Inhaling a puff of cigarette smoke delivers a dose of nicotine to the brain faster than it could be delivered by injection into the blood stream.
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Regular smokers develop a tolerance for nicotine and must smoke more and more in order to achieve the same results (Hymowitz, 2005). When they try to stop smoking, they experience withdrawal symptoms such as irritability, increased appetite, sleep disturbances, and a powerful desire to smoke (Dodgen, 2005; APA, 2000). Almost one third of all individuals over the age of 12 in the United States regularly smoke tobacco (NSDUH, 2008). Surveys also find that nearly 22 percent of all high school seniors have smoked within the past month (Johnston et al., 2007). All of this smoking eventually takes a heavy toll: 440,000 people in the United States alone die each year as a result of smoking (George & Weinberger, 2008). Chronic smoking is directly tied to lung disease, high blood pressure, coronary heart disease, cancer, strokes, and other fatal medical problems. Moreover, pregnant women who smoke are much more likely than nonsmokers to deliver premature and underweight babies (NSDUH, 2008). Cocaine Cocaine, the key active ingredient of South America’s coca plant, is the most powerful natural stimulant currently known. The drug was first separated from the plant in 1865. For many centuries however, native people, have chewed the leaves of the plant to raise their energy and increase their alertness. Processed cocaine—a white, fluffy powder—is snorted and absorbed through the mucous membrane of the nose. Some users, however, prefer the more powerful effects of injecting cocaine intravenously or smoking it in a pipe or cigarette. Around 28 million people have tried cocaine, and 2.4 million—the majority of them teenagers or young adults—are using it currently (NSDUH, 2008). In fact, 6 percent of all high school seniors have used cocaine within the past year (Johnston et al., 2007). Cocaine brings on a rush of euphoria and well-being—an org*smic-like reaction if the dose is high enough. Initially, cocaine stimulates the higher centers of the central nervous system, shifting users’ levels of awareness and making them excited, energetic, and talkative. As more cocaine is taken, it stimulates additional areas of the central nervous system, resulting in increases in heart rate, blood pressure, breathing, arousal, and wakefulness. Cocaine apparently produces these effects largely by increasing activity of the neurotransmitter dopamine at key neurons throughout the brain (Haney, 2008). As the stimulating effects of cocaine subside, the user experiences a depression-like letdown, popularly called crashing (Doweiko, 2006). Regular use of cocaine may lead to a pattern of addiction. Tolerance to the drug may develop, and suddenly withdrawing from it results in depression, fatigue, sleep problems, anxiety, and irritability (Ksir et al., 2008). Today, almost 1 out of every 100 persons over the age of 12 in the United States is addicted to cocaine (NSDUH, 2008).
The early days In the early twentieth century, cocaine was an ingredient in such products as Cocaine Toothache Drops and Coca-Cola soft drinks.
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Cocaine also poses serious physical dangers (Kosten et al., 2008). Use of the drug in powerful, smokable, forms known as freebasing and crack, has caused the annual number of cocaine-related emergency room incidents in the United States to increase 100fold since 1982, from around 4,000 cases to 450,000 (SAMHSA, 2008). In addition, cocaine use has been linked to as many as 20 percent of all suicides among people under 61 years of age (Garlow, 2002).The greatest danger of cocaine use is an overdose, which may impair breathing, produce major—even fatal—heart irregularities, or cause brain seizures (Doweiko, 2006).
“
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Drugs are a bet with your mind. —Jim Morrison, singer, The Doors. Died of suspected overdose in 1971
hallucinogens substances that dramatically change one’s state of awareness causing powerful changes in sensory perception. flashbacks recurrence of the sensory and emotional changes after the LSD has left the body.
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Amphetamines Amphetamines are manufactured in the laboratory. These stimulants are most often taken in pill or capsule form, although some individuals inject the drugs intravenously or smoke them for a quicker and more powerful effect. Like cocaine, amphetamines increase energy and alertness and lower appetite in small doses, produce intoxication and psychosis in higher doses, and cause an emotional letdown when they leave the body. Also like cocaine, these drugs produce such effects by increasing the activity of the neurotransmitter dopamine (Haney, 2008). Tolerance to amphetamines builds very rapidly, thus increasing the chances of users becoming addicted (Acosta, Haller, & Schnoll, 2005). People who start using the drug to help reduce their appetite, for example, may soon find they are as hungry as ever and increase their dose in response. Athletes who use amphetamines to increase their energy may also soon find that they need increasing amounts of the drug. When people who are addicted to the drug stop taking it, they fall into a pattern of deep depression and extended sleep identical to the withdrawal from cocaine. Around 1.5 to 2 percent of the population in the United States become addicted to amphetamines at some point in their lives (APA, 2000; Anthony et al., 1995). One powerful kind of amphetamine, methamphetamine (nicknamed crank), currently is experiencing a major surge in popularity. Almost 6 percent of all persons over the age of 12 in the United States have now used this stimulant at least once. It is available in the form of crystals (known as ice or crystal meth) which are smoked by users. Most of the nonmedical methamphetamine in the United States is made in small, illegal “stovetop laboratories,” which typically operate for a few days and then move on to a new location (Ksir et al., 2008). Although such laboratories have been around since the 1960s, they have increased eightfold over the past decade. A major health concern is that the secret laboratories produce dangerous fumes and residue (Burgess, 2001). Since 1989, when reports first emerged about the dangers of smoking methamphetamine crystals, the rise in usage has been dramatic. In 1994, fewer than 4 million Americans had tried this stimulant at least once. That number rose to more than 9 million in 1999 and is 15 million today (NSDUH, 2008). Initially, the drug was available primarily in western parts of the United States (NSDUH, 2007), but its use has been spreading east steadily. Indeed, treatment admissions for methamphetamine abuse are on the increase in New York, Atlanta, Minneapolis/St. Paul, and St. Louis (Ksir et al., 2008; CEWG, 2004), and methamphetamine-linked emergency room visits are rising in hospitals throughout all parts of the country (DAWN, 2008). Around 60 percent of current methamphetamine users are men (NSDUH, 2008). The drug is particularly popular among biker gangs, rural Americans, and urban gay communities, and has gained wide use as a “club drug,” the term for drugs of choice at all-night dance parties, or “raves” (Ksir et al., 2008). Like other kinds of amphetamines, methamphetamine increases activity of the neurotransmitter dopamine, producing increased arousal, attention, and related effects. This particular drug also may damage nerve endings—a neurotoxicity that is
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compounded by the drug’s tendency to remain in the brain and body for a long time— more than six hours (Rawson & Ling, 2008). But, among users, such dangers are less important than methamphetamine’s immediate positive impact, including perceptions by many that it makes them feel hypersexual and uninhibited (Jefferson, 2005). All of this has contributed to major public health problems. For example, one-third of all men who tested positive for HIV in Los Angeles in 2004 reported having used this drug (Jefferson, 2005). Similarly, according to surveys, a growing number of domestic-violence incidents, assaults, and robberies have been tied to the use of methamphetamine (Jefferson, 2005).
Hallucinogens Hallucinogens, or psychedelic drugs, are substances that dramatically change one’s state of awareness by causing powerful changes in sensory perception, such as enhancing a person’s normal perceptions and producing illusions and hallucinations. The substanceinduced sensory changes are sometimes called “trips,” and these trips may be exciting or frightening, depending on how a person’s mind reacts to the drugs. Many hallucinogens come from plants or animals; others are laboratory-produced. LSD Lysergic acid diethylamide, or LSD, is a very powerful hallucinogen that was derived by the Swiss chemist Albert Hoffman in 1938 from a group of naturally occurring substances. During the 1960s, a period of rebellion and experimentation, millions of users turned to the drug in an effort to raise their consciousness and expand their experiences. Within two hours of being swallowed, LSD brings on hallucinosis, a state marked by a strengthening of visual perceptions and profound psychological and physical changes. People may focus on small details—each hair on the skin, for example. Colors may seem brighter or take on a shade of purple. Users often experience illusions in which objects seem distorted and seem to move, breathe, or change shape. LSD can also produce strong emotions, from joy to anxiety or depression. Past thoughts and feelings may return. All these effects take place while the user is fully alert, and wear off in about six hours. Scientists believe that LSD produces these effects primarily by binding to many of the neurons that normally receive the neurotransmitter serotonin, changing the neurotransmitter’s activity at those sites (Julien, 2008). More than 14 percent of all people in the United States have used LSD or another hallucinogen during their lives (NSDUH, 2008). A key problem is that LSD is so powerful that any dose, no matter how small, is likely to produce very strong reactions. Sometimes the reactions are quite unpleasant, an experience called a “bad trip.” In addition, some LSD users have flashbacks, recurrences of the sensory and emotional changes even after the LSD has left the body (Doweiko, 2006).
Bad trip Ingesting LSD brings on hallucinosis, a state of sensory and perceptual distortions. Sometimes this state can be very frightening and disorienting, as captured in this photo illustration of a hallucination of hands and arms burning.
Cannabis The hemp plant Cannabis sativa grows in warm climates. Collectively, the drugs produced from varieties of hemp are called cannabis. The most powerful of them is hashish; the weaker ones include the best-known form of cannabis, marijuana, a mixture derived from the buds, crushed leaves, and flowering tops of hemp plants. Although there are several hundred active chemicals in cannabis, tetrahydrocannabinol (THC) is the one most responsible for its effects. The greater the THC content, the more powerful the cannabis. When smoked, cannabis changes one’s conscious experiences by producing a mixture of hallucinogenic, depressant, and stimulant effects. At low doses, the smoker typically has feelings of happiness and relaxation, although some smokers become anxious or irritated, especially if they have been in a bad mood. Many smokers have sharpened perceptions and become fascinated with the intensified sounds and sights that they are experiencing. Time seems to slow down, and distances and sizes become greater. This
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reward learning pathway brain circuitry that is important for learning about rewarding stimuli. reward-deficiency syndrome theory that people might abuse drugs because their reward center is not readily activated by usual life events.
overall reaction is often called getting “high.” In strong doses, cannabis produces particularly unusual visual experiences, changes in body image, and even hallucinations (Mathew et al., 1993). Most of the drug’s effects last two to six hours. Because marijuana can interfere with complex sensorimotor tasks and cognitive functioning, it has been tied to many automobile accidents (Kauert & Iwersen-Bergmann, 2004). In addition, many people on a marijuana high fail to remember information, especially recently learned material; thus, heavy marijuana smokers may function poorly at school or work (Lundqvist, 2005). Some research also suggests that regular marijuana smoking may contribute to long-term medical problems, including lung disease (Ksir et al., 2008; NIDA, 2002), lower sperm counts in men, and abnormal ovulation in women (Schuel et al., 2002). Due to changes in growing patterns, today’s marijuana is at least four times higher in THC content than was the marijuana of the early 1970s (Doweiko, 2006; APA, 2000). As a result, many people, including 5 percent of high school seniors, are now caught in a pattern of heavy and regular use, getting high on marijuana daily, although it is not clear whether such use represents a true addiction or a strong habit (Johnston et al., 2007). Either way, a number of these users do indeed find their social, occupational, or academic lives affected greatly. Around 1.7 percent of people in the United States have displayed heavy and regular marijuana use in the past year; between 4 and 5 percent have fallen into a pattern of such use at some point in their lives (NSDUH, 2008; APA, 2000).
Marijuana as Medicine Movies, such as Dazed and Confused, Half Baked, and The Big Lebowski—so-called “stoner films”—have helped to popularize the image of a marijuana user as a mellow hippie trying to avoid the wrath of inept authority figures (Meltzer, 2007). In fact, however, the many millions of individuals who have tried marijuana come in all sizes, shapes, and personalities (Earleywine, 2007). Indeed, tens of thousands of them An uncommon medicine A man suffering from chronic arthritis smokes mariuse marijuana for a very serijuana at a protest rally, calling on the ous purpose—as medicine. government to implement a medical Common medicinal marijuana program. uses of marijuana, or cannabis, include treatment of chronic pain, nausea associated with chemotherapy, glaucoma, and disease-related anorexia (Okie, 2005). A key difficulty for many patients, however, lies in gaining access to the drug; in the United States, federal law holds that possession or distribution of marijuana for any purpose is illegal—a law upheld by the Supreme Court in 2005 (Sunil, Carter, & Steinborn, 2005). Despite this, 31 states formally recognize that
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marijuana can have medicinal value, and 14 of them allow their residents to grow, possess, or use marijuana when approved by a physician. Moreover, the U.S. Attorney General recently announced that federal prosecutors would not prosecute cases against medical marijuana users as long as they are complying with the laws of their states. The federal anti-marijuana laws are based, in part, on assessment by the National Institute for Drug Abuse and the Food and Drug Administration that evidence to support medical marijuana usage is lacking. To address this concern, a randomized, double-blind, placebo-controlled study—the gold standard of research design— was recently conducted to investigate the effectiveness of marijuana in reducing pain associated with nerve damage. The researchers found that smoking marijuana, even at a low dose, did indeed reduce pain in comparison to a placebo. In this study, the patients considered the negative side effects to be minimal and tolerable, although the effects did include slight declines in learning and recall abilities, especially with higher doses (Wilsey et al., 2008). Some countries are already convinced—the Netherlands and Canada now allow the sale of medical marijuana in select pharmacies. In the United States, however, it appears that more studies of the kind just described will be required before the medical use of marijuana is accepted by the federal government and its legislators. In the meantime, the mind of the public may already be set; surveys indicate that more than 70 percent support medical marijuana use (Earleywine, 2007).
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What Happens in the
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BRAIN?
Cingulate cortex Prefrontal cortex
As you have seen, an ingested drug increases the activity of certain neurotransmitters in the brain—chemicals whose normal purpose is to reduce pain, calm us, lift our mood, or increase our alertness—and these neurotransmitters, in turn, help produce the particular effects of the drug.Alcohol, for example, heightens activity of the neurotransmitter GABA; opioids raise endorphin activity; and cocaine and amphetamines increase dopamine activity. Similarly, researchers have identified a neurotransmitter called anandamide (from the Sanskrit word for “bliss”) that operates much like THC (Hitti, 2004). It used to be thought that each drug, along with its corresponding neurotransmitters, sets in motion a unique set of brain reactions. However, recent Nucleus brain-imaging studies suggest that while each drug has its own starting point in accumbens the brain, most (perhaps all) of them eventually activate a single reward learning pathway, or “pleasure pathway,” in the brain (Haney, 2008; Koob & LeMoal, Ventral tegmental 2008). This brain reward learning pathway apparently extends from the midarea of midbrain brain to the nucleus accumbens and on to the frontal cortex (see Chapter 4). The key neurotransmitter in this pathway appears to be dopamine. When The brain's reward learning pathway, or "pleasure pathway," extends dopamine is activated there, a person wants—at times, even craves—pleasurefrom an area in the midbrain called the ventral tegmental area to the nucleus accumbens, as well as to the prefrontal cortex. able rewards, such as music, a hug, or, for some people, a drug (Higgins & George, 2007; Higgins et al., 2004). Certain drugs apparently stimulate the reward learning pathway directly. You’ll recall that cocaine and amphetamines directly increase dopamine activity. Other drugs seem to stimulate it in roundabout ways. The biochemical reactions triggered by alcohol and opioids each set in motion a series of chemical events that eventually lead to increased dopamine activity in the reward learning pathway. Research also suggests that people prone to abuse drugs may suffer from a rewarddeficiency syndrome—their reward learning pathway is not activated readily by the events in their lives (Blum et al., 2000; Nash, 1997)—so they are more inclined than other people to turn to drugs to keep their pathway stimulated. Abnormal genes have been pointed to as a possible cause of this syndrome (Finckh, 2001; Lawford et al., 1997). But how might persons become ensnared in a broad pattern of addiction, marked by tolerance and withdrawal effects? According to one explanation, when a person takes a particular drug chronically, the brain eventually makes an adjustment and reduces its own production of the neurotransmitter whose activity is being increased by the ingested drug (Kleber & Galanter, 2008; Kosten, George, & Kleber, 2005). That is, because the drug is increasing neurotransmitter activity, natural release of the neurotransmitter by the brain is less necessary. As drug intake increases, the body’s production of the neurotransmitter continues to decrease, and the person needs to take more and more of the drug to feel its positive effects. In short, drug takers are building tolerance for a drug, becoming more and more dependent on it, rather than on their own biological processes to feel comfortable or alert. In addition, if they suddenly stop taking the drug, their supply of neurotransmitters will be low for a time, producing symptoms of withdrawal that will continue until the brain resumes its normal production of the necessary neurotransmitters.
Before You Go On What Do You Know? 13. What are the major drug categories and the characteristics of each category? 14. What is addiction, and what are two key features of addiction to a drug? 15. Why is alcoholism realtively less common among Asians than in individuals of other ethnic groups?
What Do You Think? Why do you think alcohol is more acceptable culturally than some of the other drugs we are discussing here?
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Summary • Consciousness is defined as our immediate awareness of our internal and external states. • The study of consciousness has proven difficult for researchers, because of the difficulty measuring its associated phenomena, such as dreams and awareness. In part, the rise of behaviorism in the United States during the 1950s was a reaction to these difficulties, focusing more on objective behaviors that could be easily measured. • Recent developments in neuroimaging have allowed researchers to look at brain activity during various states of consciousness.
When We Are Awake: Conscious Awareness LEARNING OBJECTIVE 1 Define different levels of conscious awareness and describe key brain structures and functions associated with those levels. • Attention is one of the key aspects of conscious awareness. Other key cognitive activities underlying cognitive awareness include monitoring (our implicit decisions about what to attend to), memory, and planning. • Most biological investigators believe that consciousness results from a combination of brain activities in several brain regions. Two key brain structures appear to be the cerebral cortex, which helps regulate our awareness of attentional processes, and the thalamus, which relays sensory information from various parts of the brain to the cerebral cortex for processing.
Preconscious and Unconscious States LEARNING OBJECTIVE 2 Summarize the ideas of preconscious and unconscious states, including Freud’s thinking on the unconscious. • In addition to our conscious level of awareness, many psychologists believe there are other levels or degrees of consciousness, and distinguish conscious awareness from two other states— unconsciousness and preconsciousness. • Preconsciousness is a level of awareness in which information can become readily available to consciousness if necessary. • Unconsciousness is a state in which information is not easily accessible to conscious awareness. • Freud viewed the human unconscious as an important storehouse for knowledge and experience, which although not directly accessible to our conscious awareness, still influences our behavior. • Although Freud’s ideas fell into disfavor for several years, in recent years, scientists have begun to reexamine the unconscious
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from different points of view. For example, implicit memory describes knowledge that we have and are able to apply to various tasks, without being able to recall it at will.
Hypnosis LEARNING OBJECTIVE 3 Define hypnosis and discuss theories and evidence about what hypnosis is, how it works, and how it can be used. • Hypnosis is a suggestible state during which people can be directed to act in unusual ways, experience unusual sensations, remember forgotten events, or forget remembered events. • Ernest Hilgard’s theory suggests that hypnosis divides consciousness into two parts: one focused on the suggestions of the hypnotist, and the other a hidden observer. Other theorists suggest that motivated role-playing is at work in hypnosis. • Hypnosis has been used to successfully help control pain, as well as treat problems , such as anxiety, skin diseases, asthma, insomnia, stuttering, high blood pressure, warts, and other forms of infection.
Meditation LEARNING OBJECTIVE 4 Define meditation and describe the techniques and effects of meditation. • Meditation is designed to help turn one’s consciousness away from the outer world toward inner cues and awareness, and to ignore all stressors. • Like hypnosis, meditation has been suggested to have numerous positive benefits, including successfully treating many of the same illnesses, and helping people to relax.
When We Are Asleep LEARNING OBJECTIVE 5 Describe what happens when people sleep, key theories of why we sleep and dream, and problems with sleep and how they affect functioning. • Every 90 to 100 minutes when we sleep, we pass through a sleep cycle consisting of five different stages. The fifth stage of sleep, rapid eye movement, or REM sleep, is characterized by rapid and jagged brain-wave patterns and eye movements and irregularities in heart rate and breathing. Dreaming usually occurs during this phase of sleep. • Scientists have identified brain activities that maintain the regular rhythms of life. Our move from a sustained period of wakefulness into a period of sleep during each 24-hour period is known as a circadian rhythm.
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• Scientists have not reached a definitive conclusion about why people sleep, although some scientists have suggested sleep serves an evolutionarily adaptive function, keeping our ancestors away from predators that hunted at night. Others have suggested that sleep might play a role in growth, or allow us time to restore depleted chemical resources in the brain and body and eliminate chemical wastes that have accumulated throughout the day. • We also do not understand why people dream. Freud believed that dreams represent expressions of the internal desires and wishes that have been repressed and stored in the unconscious. Recent theories about dreams emphasize more cognitive approaches. The information-processing theory of dreams suggests that dreams are the mind’s attempt to sort out and organize the day’s experiences and fix them in memory. The attention-synthesis hypothesis suggests that dreams are the mind’s attempts to give meaning to internally generated signals firing throughout the brain during deep sleep. • Sleep deprivation can lead to feelings of fatigue, irritability, and malaise, resulting in lower productivity and a tendency to make mistakes. Loss of sleep can also affect the functioning of the
immune system. The regular inability to fall asleep or stay asleep is called insomnia. Other sleep disorders include sleep apnea, narcolepsy, sleepwalking, and night terrors.
Psychoactive Drugs LEARNING OBJECTIVE 6 Define and describe common depressant, stimulant, and hallucinogenic psychoactive drugs and their effects. • The three main classes of psychoactive drugs are depressants (substances that slow down brain activity), stimulants (substances that excite brain activity), and psychedelic or hallucinogenic drugs (substances that distort sensory perceptions). • Regular ingestion of some drugs can lead to maladaptive changes in a person’s behavior patterns and physical responses, a pattern known as addiction. Signs of addiction can include increased tolerance, the need for larger and larger doses of a substance to get the desired effect, and symptoms of withdrawal when one discontinues the drug.
Key Terms consciousness 166
lucid dreams 183
sedative-hypnotic drugs 191
preconsciousness 171
suprachiasmatic nucleus (SCN) 177
insomnia 185
opioids 192
unconscious state 171
hypnagogic state 177
sleep apnea 187
endorphins 192
implicit memory 172
sleep spindles 177
narcolepsy 187
stimulants 192
hypnosis 172
rapid eye movement sleep (REM) 180
psychoactive drugs 187
hallucinogens 194
addiction 189
flashbacks 194
tolerance 189
reward learning pathway 196
withdrawal symptoms 189
reward-deficiency syndrome 196
dissociation 174 meditation 176 adaptive theory of sleep 176 restorative theory of sleep 176 circadian rhythm 176
nonREM sleep (NREM) 180 information-processing theory of dreams 183 activation-synthesis model 183
depressants 189 alcoholism 191
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CUT/ACROSS CONNECTION What Happens in the
BRAIN? • People who are blind because of damage to visual areas in the cerebral cortex are still able to point in the direction of light projected onto a screen, even though they are not aware of attending to the light. That’s because the areas in the cerebral cortex that are in charge of awareness of attention are not the same as the areas responsible for attention itself. • Similarly, hypnosis used to anesthetize or reduce pain doesn’t keep sensations of pain from reaching neurons. Instead, it reduces awareness of the pain by decreasing activity in a particular part of the cerebral cortex. • Humans are probably not the only animals that dream. Dreaming takes place during rapid eye movement (REM) sleep, the final stage of the brain’s five-stage sleep cycle, and every kind of mammal that has been tested experiences these sleep stages. • There are various theories to explain dreaming. Some researchers, for instance, believe that we dream because the brain, while we sleep, produces a variety of visual and auditory signals and then tries to combine these self-produced signals in a way that makes sense. • Most, or perhaps all, psychoactive drugs eventually work by activating a single reward learning pathway in the brain. The key neurotransmitter in this reward learning pathway is dopamine.
HOW we Differ • Although most of us don’t have a strong preference, some of us are “morning people” who like to get everything done early in the day, while others are “night people” who prefer to sleep late and do our work in the evening. • Such preferences depend on our internal clocks, and the settings of those clocks are thought to be determined primarily by genetic factors. • Alcoholism is displayed by at least twice as many men as women. • Native Americans, particularly men, display a higher rate of alcoholism than other racial minority groups or white Americans.
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• Adolescents are especially likely to suffer from sleep deprivation. In fact, teenagers today get about two hours less sleep per night than teens 80 years ago. • Going without sleep, over time, causes a variety of problems: general malaise, lower productivity, and an increased tendency to make mistakes, and even lower immune system functioning. • The most common sleep disorder is insomnia. Insomnia sufferers, who are generally older people, regularly have trouble falling asleep or staying asleep. Less common is narcolepsy, which involves suddenly falling asleep for short periods of time—sometimes even in the midst of an argument or during an exciting football game. • In any given year, more than 9 percent of all teens and adults in the United States display drug or alcohol addiction. • Intoxicated drivers cause 12,000 deaths each year.
How we Develop • The question of when babies develop alert consciousness is a matter of debate. On the one hand, some researchers argue that early cognitive development, such as that discussed in Chapter 3, shows that babies do have a rudimentary sense of consciousness. Others argue that consciousness comes later, with the development of language. • During the first four months of life, babies sleep between 14 and 17 hours a day, but the time spent sleeping declines steadily as they get older. • Environmental demands and expectations affect babies’ sleepawake cycles. In the Kipsigis tribe, for example, babies sleep for much shorter stretches longer into infancy than American babies. That’s because Kipsigis mothers keep their babies with them constantly, while American parents structure their babies’ sleep by putting them to bed at regular times.
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Psychology Around Us Sleep’s Impact on Daily Functioning
It’s Not Nice to Fool Mother Nature Video Lab Exercise
Try though we might, we cannot exercise a lot of control over sleep. Whether we like it or not, we are at the mercy of our circadian rhythms; once we are asleep, we are along for a ride through our sleep cycle; and if we deprive ourselves of too much sleep, we function poorly while we are awake. In this video lab exercise, your job is to perform video tasks and react to various scenes at various times throughout the day and under various states of sleep deprivation. You may think you’re on top of your game most of the time, but as you’ll see, sleep-awake rhythms and sleep deprivation strongly affect how you think, how you learn, and how you feel about various people, objects, and situations. As you are working on this on-line exercise, consider the following questions: • What does this lab exercise say about our sleep needs and the impact of sleep on our daily lives? • Do we become “morning people” or “night owls” based on our experiences or on our biological predispositions? • How might dreams fit into the equation? • Are there any ways to get around sleep rhythms and sleep needs?
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Learning Chapter Outline •
What Is Learning? •
•
Classical Conditioning •
Observational Learning •
that
Learning and Gender •
Tune
Operant Conditioning
Factors that Facilitate Learning
When We Learn What Happens in the Brain? • •
Name
•
Prenatal and Postnatal Learning
Learning Disabilities
specific
study
techniques
to
learn
the
material.
At the very least, concentration and extensive studying are
I
f you have a favorite musical group, you probably eagerly
critical for learning in such a course.
await the release of their latest album and scan the Internet
for signs that they will be touring in your area. When you first hear a new song performed by the group, it’s likely to feel a little familiar, given your attachment to the group’s style. The lyrics and tune will be new, however, and you won’t know them right away. If you listen to the album several times on your iPod, even if you are not intently concentrating on the music and are instead engaged in other activities while listening, the music will seem increasingly familiar each time you hear it. You may find yourself humming or whistling the tune without realizing it. After you’ve heard the song a few times, you will probably know most, if not all, of the lyrics. All of this learning is likely to occur without much effort. For most people, it’s much easier than learning a poem or an essay of comparable length. The reasons for the ease with which learning occurs in this situation are multifaceted and most likely involve emotional engagement with the material and the fact that having the lyrics set to music makes them “catchier.” This type of automatic learning experience may stand in stark contrast to your efforts to master the information presented in a course that is dense with facts and figures, such as organic chemistry. For a course like this, students often use
Why are these two learning experiences so different? There are most likely several reasons. First, there is the difficulty factor. Material in your most challenging courses is likely to be conceptually difficult. Thus, learning the material requires first gaining an understanding of it and then finding a way to remember it. By contrast, information presented to you in most entertainment is relatively simple and usually does not require concentrated effort to understand. Second, attention probably plays an important role. Attention is critical for certain types of learning and it’s probably not difficult to attend to the lyrics of a new song from your favorite group. Even for organic chemistry aficionados, however, it may be difficult to sustain attention long enough to learn labor-intensive course material effectively in one sitting. This type of material often requires repeated presentation, perhaps first in class, then by reading in your text, and finally by studying your notes. Third, emotional factors facilitate learning information. Numerous studies have shown that emotionally charged material is easier to learn (although this can sometimes present a problem, as we will see later in the chapter). Since new music from your favorite group is likely to elicit an emotional reaction, be it one of sadness or happiness, this material is learned more readily. Finally, differences between these two types of learning experiences may be related to our biology. Humans evolved living in groups where social cooperation was essential for survival. Thus, we are biologically ready to learn about social interactions and relationships, the subject matter of many
Learning
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song lyrics. Facts about organic chemistry, on the other hand, were not critical information for the survival of early people, and as a result, our brains are not as prepared to learn this type of information. All of these variables—task difficulty, attention, emotions, and biological readiness—are important for learning. The study of each will come up later in this chapter. The overall picture underscores how learning is complex and multidimensional.
What Is Learning? learning a lasting change caused by experience.
LEARNING OBJECTIVE 1 Define learning and distinguish between associative and nonassociative learning.
learning curve a graph that shows change in performance on a learning task over time.
Put simply, learning is defined as a lasting change caused by experience. In the laboratory, scientists study learning by measuring changes in behavioral responses. This is particularly true for studies of animals, where it’s impossible to verbally assess the degree to which the subject has learned. However, it’s clear that considerable learning occurs in the absence of overt behavioral change. You might not show any new behavior for example, even though you’ve learned the lyrics of a new song from hearing it several times. This is likely to be the case if the song does not end up as one of your favorites. It may seem strange to separate a discussion about learning with a closely related subject: memory, which is covered in the next chapter. Although learning and memory are indeed interrelated and many of the biological mechanisms (and brain regions) that underlie learning are also critical for memory, the study of these topics has diverged in the laboratory. Traditionally, animals (dogs, monkeys, rats, and mice) were the focus of studies on learning, whereas humans were the predominant focus of studies on memory. With the advent of neuroimaging technology and a greater public concern for understanding learning disabilities, more research on learning is focused on humans as well. Wherever possible throughout this chapter, we’ll apply information that scientists have gained from animal experimentation to questions of human learning. Scientists typically display data from learning studies in a learning curve, a graph that shows change in performance on the learning task over time, as shown in Figure 7-1. The learning curve can be used to determine whether or not mastery of the task occurs rapidly (in other words, is the task relatively easy?) or whether it occurs gradually, which is the case when the task is relatively difficult. The graph of a learning curve for an easy task will be very steep initially, perhaps leading to a plateau when peak performance is reached. In general, learning can be divided into two major categories: associative and nonassociative. Associative learning is a change that occurs as the result of experiences that lead us to link two or more stimuli together. An example of associative learning would be learning the words to a song in conjunction with the tune. Nonassociative learning also involves change based on experience, but happens without a person connecting two or more different pieces of information.
associative learning learning that involves forming associations between stimuli. nonassociative learning learning that does not involve forming associations between stimuli. habituation a form of nonassociative learning whereby repeated presentation of a stimulus leads to a reduction in response. sensitization a form of nonassociative learning whereby a strong stimulus results in an exaggerated response to the subsequent presentation of weaker stimuli.
Nonassociative Learning Nonassociative learning is by far the simpler of the two types; the most basic forms of learning are nonassociative. This means that they do not involve linking together information about more than one stimulus. Rather, nonassociative learning refers to a change that occurs as a result of our experiences with a single sensory cue. There are two major types of nonassociative learning, habituation and sensitization. 204 Chapter 7
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FIGURE 7-1 Learning curves Learning study data are typically displayed on learning curve graphs that show the mastering of a task over time. The learning curves reveal whether the task was an easy or difficult one.
DIFFICULT TASK
High
Level of mastery
Level of mastery
EASY TASK
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Low Time
High
Low Time
Habituation We discussed habituation of our senses in Chapter 5: Sensation and Perception. Habituation happens when our senses begin to respond less strongly to repeated presentations of the same sensory cue. A smell, such as baking cookies, might hit you with the power of a freight train when you first walk into your home, but after a while, you may barely notice it. Even though the cookies continue to give off just as much aroma, you have become habituated. You respond less and less strongly, though the same stimulus repeatedly reaches the sensory receptors in your nose. In most cases, sensory habituation occurs without our awareness. You might notice it occurred afterwards, but it does not require attention to the stimulus for learning to occur. When we use the term habituation to talk about learning, it also refers to a decrement in response after repeated stimulus presentation. Learned habituation, however, is not the exclusive result of sensory adaptation or fatigue of neurons in the sensory receptors. Instead, learning theorists study habituation that involves changes in neurons in our central nervous system. If a decrease in response occurs because of a change in neurons in the brain or spinal cord, then the effect qualifies as learning. Sensitization Sensitization is another form of nonassociative learning that involves an altered response after the presentation of a single sensory cue. Unlike habituation, sensitization involves an increase, as opposed to a decrease, in response with learning. A good example of this can be drawn from a common experience we’ve all had: being
Habituation in action When this child is initially presented with letter blocks, she responds to them happily and learns various ways to enjoy them (left). However, after months of repeated presentations with the same stimuli, her response to the blocks is decidedly more muted and less enthusiastic (right).
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startled. Imagine you are home alone at night reading quietly. Without any warning, your pet cat knocks over a lamp. You may jump or even shout out in fear before realizing what has happened. And, for some time after you regain your senses and scold poor kitty, you are still likely to startle again, even in response to a normal auditory stimulus, such as the ring from your cell phone. Your enhanced response to this typical stimulus may reflect the fact that sensitization has occurred. Both habituation and sensitization make good adaptive sense. In the case of habituation, when harmless stimuli are repeatedly presented, continuing to respond to them is a waste of energy and may prevent you from noticing an important change in the environment. In the case of sensitization, an extreme unexpected stimulus may signal danger, so a greater than usual response to stimuli that follow may be helpful for survival. What Happens in the
Learning from the slug By studying sea slugs, scientists have gained insights about how the nervous system changes in response to learning.
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Nonassociative Learning: B R A I N ? Since habituation and sensitization are very basic forms of learning, they occur in animals with very simple nervous systems. Neuroscientists have taken advantage of this and used one of the simplest—the nervous system of a sea slug—to study the biological basis of nonassociative learning (Kandel, 2001). Sea slugs do not have brains or spinal cords. They do, however, have some of the largest neurons in the animal kingdom; their neurons can actually be seen with the naked eye. This makes it easy to record from the neurons, using electrodes as described in Chapter 4. Researchers have been able to use electrode recordings from sea slugs to develop a thorough understanding of how simple nervous systems change in response to learning. If you touch a sea slug once lightly, it will withdraw two vulnerable parts of its body, the gill and the siphon. If you touch it multiple times lightly, eventually this response will diminish as habituation sets in. Recordings from the sea slug’s neurons have shown that in habituation, the amount of neural activity in the motor neurons (the neurons that control the gill and siphon muscles) goes down as the animal is repeatedly touched (Gingrich & Byrne, 1985). The decrease in activity is largely due to the fact that the neurotransmitter in the synapse between the sea slug’s sensory neuron and the motor neuron gets depleted with repeated presentations of the tactile stimulus. Eventually, the same level of sensory stimulus becomes ineffective at causing the gill and siphon withdrawal response because the amount of neurotransmitter has diminished to the point that the synapse can no longer be activated (Figure 7-2). To study sensitization, scientists apply an electric shock to the tail of the sea slug. The slug responds with a strong gill and siphon withdrawal reflex. Then they apply a very mild tactile stimulus to the slug’s body. It still strongly withdraws its gill and siphon because it is sensitized. Sensitization can occur even when a slug has undergone trials of habituation (Hawkins Cohen, & Kandel, 2006). If habitation occurs as a result of neurotransmitter depletion, how can sensitization result in an almost immediate restoration of activity in the same motor neuron? The answer lies in the fact that the tail shock recruits another population of neurons, called interneurons, into the circuitry. Interneurons work to enhance the weakened sensory neuron input to the synapse of the sensory and motor nerves. The combined action stimulates the motor neurons enough to produce the augmented withdrawal response. You may be wondering what all of these experiments on sea slugs can tell us about learning in more complex animals, including humans. Although there are many important differences between sea slugs and humans, it’s likely that these basic mechanisms, or something very close to them, also operate in more complex nervous systems, such
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Tactile stimulation
Gill
Tactile stimulation
Tail Siphon Gill and siphon withdraw
Gill and siphon do not withdraw Depletion of neurotransmitter molecules produces habituation
Tactile stimulation to body
Gill and siphon muscles Sensory neuron
Sensitization
Electrical shock
Motor neuron
Tactile stimulation
Gill and siphon withdraw
Gill and siphon withdraw further
Electrical shock to tail Sensory neuron Interneurons +
+
Activation of interneurons produces sensitization
Tactile stimulation to body
Gill and siphon muscles Sensory neuron
Motor neuron
FIGURE 7-2 Habituation and sensitization in the sea slug (Above) The sea slug gill and siphon withdrawal reflex becomes habituated to a repeated tactile stimulus when the neurotransmitter needed to activate its motor neurons has been depleted. (Below) The sea slug can experience sensitization to mild tactile stimulation if it is first exposed to a noxious stimulus like electric shock—a stimulus that activates a group of neurons called interneurons. These latter neurons stimulate the animal’s motor neurons, which in turn produce responses to mild tactile stimuli.
© The New Yorker Collection 1998 Leo Collum from cartoonbank.com. All Rights Reserved.
as our own. We, too, may experience habituation because of depleted neurotransmitter and sensitization because of the added recruitment of interneurons.
Associative Learning Nonassociative learning does not account for the majority of learning that engages more complex organisms, such as humans. The majority of learning is considered to be associative. It involves making connections between two or more stimuli. Most of the learning you engage in as a student is highly associative. Course material involves connecting numerous concepts and facts to produce an overall picture of a certain subject. Learning song melodies or lyrics also involves forming associations. Two major types of associative learning are classical conditioning and operant, or instrumental, conditioning. In classical conditioning, as we’ll see next, we come to associate two stimuli, eventually responding the same way to both. We’ll then examine operant conditioning, by which we come to associate stimuli with our behaviors.
Before You Go On What Do You Know? 1. What is learning? 2. What happens in synapses during habituation? What happens during sensitization?
What Do You Think? Give an example from your own life of nonassociative learning.
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Pavlovian or classical conditioning a form of associative learning whereby a neutral stimulus is paired with a salient stimulus so that eventually the neutral stimulus predicts the salient stimulus.
Classical Conditioning
unconditioned stimulus (US) a stimulus that on its own elicits a response.
One type of associative learning was accidentally discovered, around the turn of the previous century, by a Russian physiologist named Ivan Pavlov. His discoveries paved the way to a systematic investigation of associative learning in the laboratory, and versions of his original research methods are still being studied in psychology laboratories today. Pavlov was interested in understanding the role of the salivary reflex in digestion and to do so, he conducted research on dogs; his laboratory method is shown in Figure 7-3. As time progressed in his studies, Pavlov noticed that his dogs were salivating even when food wasn’t present. They salivated when the lab assistants arrived or when they heard noises that signaled their arrival. Pavlov recognized this as evidence that the dogs had learned to associate the appearance of a lab assistant with getting food. Thus, they were having a behavioral response (salivation) in anticipation of getting food. Pavlov systematized this basic form of associative learning that is now called Pavlovian or classical conditioning (Windholz, 1987).
unconditioned response (UR) a physical response elicited by an unconditioned stimulus; it does not need to be learned. conditioned stimulus (CS) a neutral stimulus that eventually elicits the same response as an unconditioned stimulus with which it has been paired. conditioned response (CR) a physical response elicited by a conditioned stimulus; it is usually the same as the unconditioned response. extinction reduction of a conditioned response after repeated presentations of the conditioned stimulus alone.
LEARNING OBJECTIVE 2 Describe the basic processes of classical conditioning and explain how classical conditioning is relevant to learning.
How Does Classical Conditioning Work? In classical conditioning, a person or animal learns to associate a previously neutral stimulus with an unconditioned stimulus (US), one that normally elicits a physiological response. Because the response doesn’t have to be learned, it is called the unconditioned response (UR). With repeated pairings, the neutral stimulus alone elicits the physiological response. After that happens the stimulus is no longer neutral. It is now called the conditioned stimulus (CS), and the physiological response it elicits is called the conditioned response (CR). This process is summarized in Figure 7-4.
One-way window
Meat powder Measuring device
Collecting tube from salivary glands
FIGURE 7-3 Pavlov’s setup for collecting and measuring salivation in dogs The dog is placed in a harness and given a bowl of meat powder. A tube from the salivary gland collects the saliva, which is measured and recorded.
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For Pavlov’s dogs, the unconditioned stimulus was food. Their unconditioned response was to salivate. The arrival of a lab assistant was, originally, a neutral stimulus to the dogs. After repeated pairings of the assistant with food, however, the assistant’s arrival became a conditioned stimulus. The dogs salivated when they heard or saw the assistant show up. Their salivation, once an unconditioned response to the food, was now a conditioned response to the assistant. Classical conditioning is not just for the dogs, however. It happens to people, too. Suppose classroom exams (US) made you nervous (UR). If all your exams were given in the same room on campus, the room itself (CS) might begin to make you feel nervous (CR), even though it probably didn’t affect you much one way or another the first time you entered. Timing plays an important role in the formation of learned associations. An effective presentation schedule would be to pair the US and the CS together, with the CS slightly before the US, so that it has predictive value. You enter the room, and then you take the exam, for example. A neutral stimulus that follows an unconditioned one has little or no predictive value and makes it unlikely that an association between the stimuli will form. If you went to the room later in the day after you took exams, instead of taking the test there, the room would probably never grow to make you nervous. Not surprisingly, learning is more robust when the number of CS-US pairings is high. Pavlov also showed that the learned response could be eliminated, by presenting the conditioned stimulus over and over again, without the unconditioned stimulus. The lab assistant might show up many times without offering any food to the dogs. This phenomenon, called extinction, does not represent “unlearning” or forgetting, but rather a process by which the previously learned CR is actively inhibited (Quirk, 2006). Evidence that the information about the previous CS-US pairing still exists after extinction training can be observed by allowing time to pass with no training after
Unconditioned stimulus (US)
Unconditioned response (UR)
UR
Conditioned stimulus (CS)
+
Unconditioned response (UR)
UR
Unconditioned stimulus (US)
A classic moment In this famous photo, Ivan Pavlov (center, with beard) stands with his assistants and students prior to demonstrating his classical conditioning experiment on a dog.
“
While you are experimenting, do not remain content with the surface of things. Don’t become a mere recorder of facts, but try to penetrate the mystery of their origin. –Ivan Pavlov, Russian physiologist
”
Conditioned stimulus (CS)
Conditioned response (CR)
CR
FIGURE 7-4 Classical conditioning The sequence of classical conditioning is shown here, from left to right. (1) The US (meat powder) produces the UR (salivation). (2) During conditioning, the US is paired with a CS, a neutral or conditioned stimulus (a sound such as a doorknob being turned). (3) After conditioning, the CS alone produces the conditioned (learned) response of salivation.
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spontaneous recovery re-emergence of a conditioned response some time after extinction has occurred.
phobia an abnormal fear, often of a stimulus that is not inherently dangerous, that may arise as a result of fear conditioning.
Response rate
stimulus generalization when similar stimuli elicit the same response as a conditioned stimulus after classical conditioning has occured.
High
High
Spontaneous recovery
Response rate
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Extinction curve
Time
Low
Low Extinction trials
Day 1
Day 2
Day 3
When the CS is presented repeatedly without the US, the individual’s learned response
But the information about the previous CS-US pairing is not lost, and the extinguished
gradually decreases until extinction occurs.
response spontaneously reappears.
FIGURE 7-5 Extinction and spontaneous recovery
extinction has occurred. In this case, the CR will often re-emerge at a later date, a phenomenon called spontaneous recovery (Figure 7-5). Even though the assistant didn’t bring food for several visits, the dogs might still salivate a week later when the assistant arrived. Even if you revisited the classroom you took exams in several times to hear a guest lecture, you might re-experience the nervous feeling at a later time when you happen to walk by. What Happens in the
Classical Conditioning B R A I N ?
Cerebellum
Extinction training and spontaneous recovery show that classical conditioning creates lasting changes in the nervous system in order for us to make a CS-US association. After extinction training, these changes persist; the nervous system does not go back to the way it was before conditioning. Instead, the newer extinction learning creates further changes that allow us to suppress the conditioned response. Researchers have used another form of classical conditioning, conditioning of the eye-blink response, to learn more about the location of nervous system changes that occur in classical conditioning. In this procedure, humans or animals are conditioned to associate a tone (CS) with a US, such as a mild shock to the eyelid or a puff of air to the eye that normally elicits an eye blink. Eventually, eye blink becomes a conditioned response, elicited in response to the CS tone alone (Figure 7-6). By studying animals subjected to eye-blink conditioning, scientists have found that the cerebellum is critical for this type of learning (Thompson & Steinmetz, 2009). Changes occur in the synapses among neurons in the cerebellum when animals learn to associate the CS with the US (Christian & Thompson, 2003). This was a very surprising finding, since prior to this work, the cerebellum was considered to be a brain region devoted mainly to coordinated movement.
Training
Tone (CS)
Puff of air (US)
Blink (UR)
After training
Tone (CS)
Blink (CR)
Puff of air (US)
FIGURE 7-6 Eye blink conditioning Researchers have relied on eye blink conditioning in animals to learn more about the brain processes involved in classical conditioning. In this procedure, a CS or neutral stimulus (a tone) is followed by a stimulus (such as a puff of air) that causes the animal to blink (UR). After conditioning, the animal will blink after hearing the tone and before receiving the stimulus. Researchers found that the cerebellum is critical for learning the association between the CS and UR.
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Classical Conditioning and Fears Although the work on classical conditioning of the salivary reflex and the eye-blink response was groundbreaking, you may have trouble seeing what its relevance is to human learning outside of the laboratory. Although some of us experience a mild version of classical conditioning when our stomachs growl around a certain time of day, some other forms of classical conditioning are probably much more relevant to human life. One such example is called fear conditioning. Fear conditioning was first studied by the American psychologist, John Watson, whose most well-known study was classical conditioning of a human baby named “little Albert.” Watson exposed baby Albert to an initially neutral stimulus, a white rat. Immediately after the appearance of the white rat, little Albert was subjected to a loud crashing noise that startled him so much he burst into tears. Repeated pairings of the white rat with the loud noise made Albert cry at the mere presence of the rat. There are serious ethical problems associated with Watson’s line of research. Little Albert’s mother was never informed of the studies, which were carried out without regard for their cruelty or the possibility that they would have a lasting negative effect on his emotional state (Field & Nightingale, 2009). They are, however, the first example of classical conditioning in humans and of fear conditioning in any species. Watson’s studies also led to the discovery of stimulus generalization, which refers to the fact that similar, but not identical, stimuli can take the place of a CS. Albert, for example, came to fear not only the white rat, but also other white stimuli, including a human with a white beard. Subsequent laboratory studies with animals show that fears are very easily learned. Fear conditioning of laboratory rodents involves training them to associate a neutral cue (usually a tone) with a painful stimulus, usually an electric shock to the feet (Figure 7-7). Naïve rodents will respond to foot shock by adopting a characteristic posture of immobilization, or “freezing.” This response probably reflects adaptive behavior small mammals engage in when confronted with a predator and no way to escape; they minimize movement to escape detection. Typically just a few pairings of a tone with foot shock are needed to lead to a lasting CS-US association. The rat will freeze at the CS tone alone (LeDoux, 2003). This type of learning involves the amygdala (LeDoux, 2000). Animal fear-conditioning studies, such as these also provide examples of how emotion can facilitate the learning process. Since shock is painful, and thus fear-inducing, its presence in a learning situation can speed up the formation of an association between the CS and US.
Phobias Some scientists believe fear conditioning is the basis of the development of a category of anxiety disorders called phobias (LeDoux, 1998; Morgan, Romanski, & LeDoux, 1993). Phobias are exaggerated fears of stimuli, many of which have little or no inherent danger. Little Albert was conditioned to have a phobia to white fur. People who suffer from phobias are believed to have learned an association (hopefully not in the laboratory) between neutral and dangerous stimuli, thus being conditioned to fear a relatively harmless cue.
Teaching a child to fear In an ethically-questionable study by today’s standards, John Watson and his colleague Rosalie Rayner used classical conditioning principles to teach 11-month-old “Little Albert” to fear white rats.
Rat is given electrical shock to the feet in combination with a tone.
Tone plus shock
Later Rat freezes in fear to the tone alone.
Tone only
FIGURE 7-7 Fear conditioning in rats In fear conditioning, a laboratory rat is given an electrical shock (US) to the feet just after exposure to a neutral stimulus (CS), such as a tone. Only a few pairings of the US and CS are needed for the rat to freeze in fear at the tone alone.
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Learning To Love Pain?
Tough love This peaceful domestic scene belies the fact that female rats are often very rough with their young pups—perhaps explaining why many rat pups are attracted to, instead of repelled by, stimuli associated with pain.
Some researchers made an interesting discovery when attempting to use olfactory cues to fear condition very young rat pups. Adult rats will avoid stimuli that are associated with punishment. If an odor is paired with a shock, rats will learn to distinguish that odor and avoid it in the future. This response to olfactory learning, however, is not present during the first week of life for rats. Instead, rat pups will display the opposite effect of such conditioning. Odor pairings with shock produce an approach response in the pups (Moriceau & Sullivan, 2006). Why would rat pups learn to move toward, instead of away from, an odor that predicts pain?
systematic desensitization a process used to condition extinction of phobias through gradual exposure to the feared object or situation. conditioned taste aversion a form of classical conditioning whereby a previously neutral stimulus (often an odor or taste) elicits an aversive reaction after it’s paired with illness (nausea).
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The answer may lie in rats’ normal lifestyles. Rat pups live in the nest, staying close to their mothers for the first two weeks of life, until they start weaning. During this early time in the nest, the mother is likely to do many things to the pups that elicit pain. Mothers retrieve pups by picking them up by their teeth, and they routinely step on their babies. Thus, a tendency to form avoidant reactions to odors associated with pain would be detrimental to the survival of a very young rat. As time passes, however, and the pup becomes less dependent on the mother and more capable of avoiding her sharp teeth and heavy foot, pups develop a healthy aversion to painful stimuli. Around this time, avoidance becomes the natural response to odor pairings with noxious stimuli; rats at this age learn, for example, to avoid smells associated with electric shock. Some investigators have speculated that a similar conditioning process may contribute to the development of attachment disorder in humans. This condition is characterized by an inability to form healthy emotional relationships with others. People with attachment disorder do not respond positively to nurturing behavior, and they often seek out situations that are likely to result in physical and emotional pain. Since a major cause of this condition is early childhood abuse and neglect, it’s possible that excessive strengthening of associations between painful stimuli and one’s caregiver during development lead to persistent maladaptive responses to social interactions.
The theory that phobias arise from fear conditioning has led to the development of therapies that are also based on classical conditioning. In one common process, known as systematic desensitization, people who suffer phobias undergo a series extinction trials, repeated exposure to the feared object or situation in the absence of pairing with a US. There was no follow up on Little Albert, so we don’t know whether or not he carried his phobia throughout his life. If he had been treated with systematic desensitization, however, Watson might have created a pleasant, quiet situation and placed Albert and the white rat together in this pleasant situation many times until Albert no longer cried at the sight of the rat. Systematic desensitization sometimes helps people with phobias to overcome their anxiety and function normally in the presence of the fear-inducing cue. Remember, however, that extinction trials do not produce “unlearning,” but instead involve active inhibition of the previously learned association (Quirk, 2006). This means that the previously learned fear may reappear. Neuroimaging studies suggest that phobias involve abnormal activity in the amygdala, a part of the brain that is active when we experience emotions, including fear. People with phobias show rapid activation of this brain region when exposed to the stimuli they fear most. Extinction training, by contrast, is known to activate part of the prefrontal cortex as phobias diminish (Quirk, Garcia, & González-Lima, 2006). Recall from Chapter 4 that our prefrontal cortex can help us to inhibit emotional impulses. Thus, phobias that have been desensitized still exist. As a result, they are prone to spontaneous recovery, similar to other classically-conditioned behaviors.
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Arachnophobia An extreme fear of spiders is one of the most common of all phobias. Around half of all women and 10 percent of all men have at least a mild fear of spiders.
Phobias and the brain This colored brain scan of a cross section of the brain reveals increased activity in a phobic individual’s amygdala (region circled in yellow) while the person is looking at a feared object.
Classical Conditioning and Taste Aversions Another type of classical conditioning that has been studied in the laboratory has relevance to human learning. Conditioned taste aversion involves learning an association between a particular food and a subsequent stomach illness (Garcia et al., 1985). Many of us have had this type of experience. You eat a certain type of food and a short time later, you are stricken with nausea and vomiting. Whether or not the symptoms are related to the food, you will probably have an aversion to that particular dish for some time afterwards. In this case, the US is whatever agent actually made you nauseous, be it bacterial, viral, or chemical. The food is the CS. The unconditioned physiological response (UR), which becomes the CR, is nausea itself. Nausea will be elicited by exposure to the food in the future. Some people are especially vulnerable to conditioned taste aversions. Pregnant women with severe morning sickness may develop intense aversions to foods that are followed by nausea. Similarly, people undergoing chemotherapy for cancer treatment can develop aversions to foods they ingest right before a chemotherapy session, due to the nausea that is a side effect of the drug. Conditioned taste aversions happen very quickly. Laboratory research has shown that a single pairing of food and nausea may be all that’s necessary. Maybe you still feel queasy at the thought of a food that was associated with stomach sickness in your past. This is particularly impressive, given the length of time that can intervene between exposure to the CS and the illness—sometimes on the order of several hours. Separation of a tone from a shock by several hours would make it very difficult, if not impossible, to produce fear conditioning, and yet conditioned taste aversion is highly successful with just one pairing. Scientists suggest that we have a biological readiness to learn certain associations (Gaston, 1978). Clearly, the link between taste and stomach illness is physiological. This biological readiness may be rooted in our evolutionary history. The ability to associate potentially tainted food with a subsequent illness was most likely highly adaptive during human evolution. Those who could not do this were more likely to be poisoned and to risk poisoning members of their families. Those who readily formed such associations and avoided potentially risky food were more likely to survive and successfully reproduce.
Producing a taste aversion In pioneering work, researcher John Garcia and his colleagues used classical conditioning to teach coyotes to not eat sheep. The researchers laced freshly killed sheep with a vomit-inducing chemical. Whenever the coyotes ate such tainted meat, they became ill; eventually, they ran away from the mere sight and smell of sheep.
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Biological preparedness also may help explain why taste aversions are easy to learn for animals that use odor and taste for food detection. In these same animals, it is difficult to form an association between a visual or auditory cue and nausea. However, in animals such as birds, that select their food using visual cues, conditioned aversions to flavors or odors are difficult to produce. Birds can be more readily conditioned to avoid visual cues (such as a certain colored bead) when those cues have been paired with stomach illness. Since birds often search out food using vision (consider the bird searching for a wiggly worm), it’s more natural for them to associate a visual cue, than a gustatory or olfactory one, with a subsequent stomach illness.
Before You Go On What Do You Know? 3. You take your dog in the car when going to the veterinarian. After several visits, Rover cowers and whimpers whenever he sees the car. Identify the US, UR, CS, and CR in this example of conditioned fear. 4. What is conditioned taste aversion? How does it happen?
What Do You Think? How might the principles of classical conditioning be used in advertising?
Operant Conditioning LEARNING OBJECTIVE 3 Describe the basic processes of operant conditioning and explain how shaping can be used to teach new behaviors.
FIGURE 7-8 Thorndike’s puzzle box Edward Thorndike used a puzzle box to study operant conditioning in cats. When the cat accidentally stepped on a pedal that pulled a string, the cat escaped from the box and received a fish reward. Once the cat had done this, it performed the action more quickly when it was put back into the box, until eventually it stepped on the pedal immediately each time.
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Classical conditioning, although relevant outside of the laboratory, does not account for the vast majority of learning by complex organisms. Classical conditioning is a passive form of learning that does not involve the active participation of the learner. In fact, most forms of classical conditioning occur without awareness that the association is being formed. In everyday life, however, the majority of our learning is active. Most of us are not passive participants in the environment. Instead, we seek out pleasurable experiences, such as good food, good company, and good grades, and we do our best to avoid unpleasant experiences. We react to our environments and modify our behavior according to the responses we receive. As we continue to learn more about the environment, we change our behavior accordingly. Psychologists use the terms operant or instrumental conditioning to describe learning that occurs in an attempt to receive rewards and avoid punishment. For some of the earliest laboratory studies of operant conditioning, psychologist Edward Thorndike created a contraption called a “puzzle box.” This was a cage, into which Thorndike placed a hungry cat. As shown in Figure 7-8, the animal could escape from the box by pressing a pedal that pulled a string. Escape from the box led to a food reward. The first escape from the box probably occurred through the random actions of the experimental animal. In moving about, the cat would accidentally step on the pedal and thus receive temporary freedom and a fish reward. Once this occurred, however, Thorndike’s cats began to more quickly engage in that same behavior when he put them back into the box. Eventually, the cat would immediately step on the pedal when placed into the puzzle box. This work led Thorndike to develop a theory known as the law of effect (Thorndike, 1933), which states that behaviors leading to rewards are more likely to occur again, and behaviors producing unpleasantness are less likely to occur again. He proposed that the law of effect applied not only to other animals, but also to humans.
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How Does Operant Conditioning Work? Thorndike’s ideas about instrumental conditioning eventually became highly influential. For several decades of the twentieth century, the dominant school of thought in psychology was behaviorism, the systematic study of observable behavior (Gantt, 1980). A major goal of behaviorist psychologists was to understand the principles of instrumental, or operant, conditioning. Many researchers, such as leading behaviorist, B. F. Skinner, conducted learning research with laboratory animals such as rats and pigeons. Reinforcement and Punishment In typical experiments, stimuli are provided in response to the animal’s behavior. These stimuli make it more or less likely that the animal will engage in the behavior again. For example, if a laboratory rat presses a lever and receives a food pellet reward, the food works as a reinforcer, a consequence that increases the likelihood that the rat will repeat the behavior or press the lever again. If, on the other hand, the rat receives an electric shock in response to a lever press, the shock works as punishment, a consequence that decreases the likelihood that the rat will press the lever again. What happens in the brain during instrumental conditioning? It appears that somewhat different areas of our brains respond to reinforcement and punishment. Regions important for reward include the ventral tegmental area (Matsumoto & Hikosaka, 2009), the nucleus accumbens, and the prefrontal cortex (Kalivas & Nakamura, 1999), regions that all rely on the neurotransmitter dopamine (we will return to this subject in Chapter 11 on motivation). Learning from punishment, involves some of the same brain regions (Matsumoto & Hikosaka, 2009), as well as those important for fear and pain, including the amygdala and somatosensory cortex (Figure 7-9). Reinforcement and punishment can be either negative or positive. Both forms of reinforcement—positive and negative—increase the likelihood that a response will occur, and both forms of punishment decrease the likelihood of a response recurring.
operant or instrumental conditioning a form of associative learning whereby behavior is modified depending on its consequences. law of effect behaviors leading to rewards are more likely to occur again, while behaviors producing unpleasantness are less likely to occur again. behaviorism the systematic study and manipulation of observable behavior. reinforcer an experience that produces an increase in a certain behavior. punishment an unpleasurable experience that produces a decrease in a certain behavior. positive reinforcement presentation of a pleasant consequence following a behavior. negative reinforcement removal of a negative consequence as a result of behavior. positive punishment presentation of an unpleasant consequence following a behavior. negative punishment removal of a pleasant stimulus as a consequence of a behavior.
• Positive reinforcement is what we consider to be a reward—providing a motivating stimulus. • Negative reinforcement involves removing an aversive stimulus. • Positive punishment involves administering an unpleasant consequence for behavior. • Negative punishment takes away something pleasant. Primary somatosensory cortex
Prefrontal cortex
Nucleus accumbens
Ventral tegmental area
Amygdala
FIGURE 7-9 Brain areas involved in instrumental learning Different regions of the brain are involved in reward and in punishment. Learning from reward involves the ventral tegmental area, nucleus accumbens, and prefrontal cortex. Learning from punishment involves the amygdala and the somatosensory cortex.
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Increases Behavior
Decreases Behavior
ON
Lever pressed
Food delivered
Positive Reinforcement
Lever pressed
Shock delivered
Positive Punishment
OFF
Lever pressed
Shock removed
Negative Reinforcement
Lever pressed
Food removed
Negative Punishment
FIGURE 7-10 Reinforcement and punishment The apparatus shown here is called a Skinner box. The rat can press a lever to receive a food pellet. The floor of the box is wired to give an electric shock. The box is used to test the effects of positive and negative reinforcement and punishment on behavior.
If we take the case of our lever-pressing rat, as shown in Figure 7-10, positive reinforcement would provide a food reward and negative reinforcement would turn off an electric shock. Both would likely increase the rat’s rate of lever pressing. Positive punishment would provide an electric shock, and negative punishment would remove food. Both would decrease lever pressing.We frequently encounter reinforcers and punishments in our day-to-day lives. If you buy one of a band’s songs and really like it, your pleasure in the song works as a positive reinforcer that makes you likely to buy more of their songs, for example.
primary reinforcer reinforcer that is intrinsically pleasurable. secondary reinforcer reinforcer that is associated with primary reinforcers. continuous reinforcement when behavior is reinforced every time it occurs. intermittent or partial reinforcement a schedule of reinforcement where the behavior is only followed by reinforcement some of the time.
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Types of Reinforcers Most reinforcers used in the laboratory fulfill basic biological needs. Rats are trained to press levers to get access to food, water, or mates. These rewards are called primary reinforcers because they are intrinsically pleasurable; they are rewarding by their very nature. Outside the lab, however, most (but not all) of our own actions do not involve behavior designed to directly increase the likelihood of getting a primary reinforcer. For example, most people work for money, not food. In this case, money is considered to be a secondary reinforcer, one that is associated with primary reinforcers, so it also increases the likelihood that people will engage in certain behaviors, such as work. Schedules of Reinforcement In real-life situations, we are not usually reinforced or punished every single time we perform a behavior. You may, for example, hold the door open for the person who walks in behind you many times a day, but
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PRACTICALLYSPEAKING
Using Punishments and Rewards to Teach Children • Punishment is effective only when it is clear that the punishment is a consequence of a specific behavior, rather than, say, a result of the teacher or caregiver’s bad mood or general dislike for the child. • Punishment works only when its aversive component outweighs any reward obtained by the behavior. It is difficult and often unethical to devise a punishment that far outweighs the rewarding aspect of the behavior.
Although both reinforcement and punishment are effective ways of altering behavior in laboratory learning studies, evidence from real-life situations suggests these two approaches may not be equally effective. Positive reinforcement seems to be more effective than punishment for teaching young children, for example. One exception to this general rule is in cases where children put themselves in immediate danger. At such times, a harsh scolding might be much more effective at stopping the behavior. One reason that positive reinforcement seems more effective may be because punishment is often misused. Research suggests the following guidelines for using punishment effectively to promote learning: • Positive punishment is most effective when it occurs immediately after the incorrect behavior.
Negative punishment seems to be less problematic ethically than positive punishment, but still may fail in some circ*mstances. Many parents and preschool teachers use a negative punishment technique called “time out” as a consequence for unwanted behavior. This method involves removing the child from his or her surroundings, generally by putting them in a separate location in the classroom or home. The child has thus had a pleasurable stimulus (access to playthings and classmates) removed. Time out also removes the child from the environment that may have contributed to the bad behavior and allows quiet time to think about the situation. The effectiveness of time out depends on the circ*mstances and the individual. If the child was acting out to gain attention, then intervening, even in a negative manner, may not effectively eliminate the behavior. Also, removal from a certain environment, such as the classroom or the dinner table, may not be sufficiently negative to alter the offensive behavior. It might even be rewarding to some children. In general, educators and child psychologists conclude that wherever possible, positive reinforcement of desired behavior is the best motivator for behavioral change.
only receive a pleasant “thank you” once or twice. Researchers have studied the effects of different schedules of reinforcement on behavior (Skinner, 1958; Skinner & Morse, 1958). When a behavior is reinforced every single time it occurs, reinforcement is said to be continuous. In contrast, there are also several possible schedules of intermittent or partial reinforcement, by which the behavior is only sometimes reinforced. The most common types of intermittent reinforcement schedules are described in Table 7-1. In a ratio schedule, reinforcement is based on the number of behavioral responses. In a fixed ratio schedule, a person or animal is rewarded every time they make a predetermined number of responses. The “frequent drinker” card at your local coffee shop may offer you a free cup of coffee after you pay for a dozen other cups, for example. In a variable ratio schedule, reinforcement occurs for a predetermined average number of responses. You may have a new message on average every three times you look at your phone, but sometimes you can look six times in a row and see no messages, and other times you might have a message twice in a row. In an interval schedule, reinforcement is based on elapsed time, rather than on the number of behavioral responses. In a fixed interval schedule, such as occurs with a
fixed ratio schedule reinforcement occurs after a specific number of responses. variable ratio schedule the number of responses required for reinforcement varies. fixed interval schedule reinforcement occurs every time a specific time period has elapsed.
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variable interval schedule reinforcement occurs after varying amounts of time.
TABLE 7-1 Intermittent Reinforcement Schedules
behavior modification a planned effort to change behavior.
Schedules Based on Number of Responses
shaping introducing new behavior by reinforcing small approximations of the desired behavior. learned helplessness a situation in which repeated exposure to inescapable punishment eventually produces a failure to make escape attempts.
Definition
Response rate
Example
Fixed ratio
Reinforcement occurs after a predetermined number of responses
High
Field workers paid by the amount they harvest
Variable ratio
Reinforcement occurs after an average number of responses
High
A slot machine pays out after an average of 20 tries but the payout intervals are unpredictable
Schedules Based on Time Intervals Fixed interval
Reinforcement occurs after a fixed period of time
Increases with time
A worker receives a paycheck every week
Variable interval
Reinforcement occurs after varying lengths of time
Low
Work breaks occur at unpredictable intervals, such as 60 minutes, 72 minutes, and 54 minutes.
©The New Yorker Collection 1993 Tom Cheney from cartoonbank.com. All Rights Reserved.
weekly salaried paycheck, you are reinforced every time a certain period of time passes. Like a variable ratio schedule, a variable interval schedule provides reinforcement after varying lengths of time have passed. Intermittent or partial reinforcement schedules are more effective than continuous reinforcement at maintaining behavior. With continuous reinforcement, the behavior is always paired with the reward. If reinforcement stops, the elimination signals a major change in the relationship between stimulus and response. By contrast, with intermittent reinforcement, the behavior is only followed by reinforcement some of the time. When a response occurs but is not reinforced, it’s not readily apparent whether or not the reward has stopped altogether. Continuing to engage in the behavior makes sense in case a reward might happen. The principles of partial reinforcement can be applied to behavior modification, a planned effort to change behavior, in children. Parents, teachers, and caregivers should avoid providing intermittent reinforcement for behaviors they want to stop. When parents are trying to wean children off a bottle or pacifier, for example, experts agree it is best to do so in an absolute manner. If parents sometimes allow a child who cries or whines to have the bottle or pacifier, he or she will be more likely to cry or whine again in the future than if the crying and whining are never, ever reinforced.
Using Operant Conditioning to Teach New Behaviors Until now, we have described how operant conditioning can lead people and animals to increase or decrease behaviors that they already display at least some of the time. Thorndike’s cats, for example, learned to press the pedal in 218 Chapter 7
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the puzzle box more often than they would have by chance, but they already pressed the pedal at least once in a trial and error fashion before learning the association. Operant conditioning can also be used to teach people and animals entirely new complex behaviors. This method, called shaping, rewards actions that are increasingly closer to a desired final behavior, rather than waiting for the exact behavior to happen before providing reinforcement. Consider training a dog to roll over. First you might provide a treat if the animal lies down on its stomach. Eventually, you would require the dog to perform something closer to rolling over in order to get the same reward. You might offer a treat only when the dog lies down and turns a bit to the side. You carry on in this way, rewarding successive approximations of the desired behavior until the complete behavioral sequence emerges. Shaping is highly effective in modifying the behavior of animals and can be used to teach people, too. Humans regularly learn behavior through shaping. If you are learning to dance the Tango, for instance, your instructor may praise you lavishly at first for simply moving your feet in the correct order. Later, you may win praise only for moving them without stepping on your partner’s toes, and so on, until only graceful, coordinated steps earn positive remarks. As with classical conditioning, we should note that biology plays a role in determining how easy or difficult a particular learning task will be for a certain species. Although some trainers appear to be quite capable of teaching animals to engage in a wide range of unnatural behaviors, it turns out there are, of course, limits to this. Some researchers have tried to train raccoons to put coins in a piggy bank, for example. Through shaping techniques, raccoons can be trained to pick up a single coin and place it in a piggy bank. However, raccoons are known for their natural tendency to wash food before eating it. If they are given more than one coin at a time, their natural tendency to wash objects seems to interfere with the shaping techniques. Instead of putting the coins into the bank, they rub them together. One of the most prominent examples of biological constraints on learning concerns language learning. Other than humans, only certain species of birds, like parrots, can be taught to speak (although their speech is generally thought to be a form of mimicry). No matter how much reinforcement or punishment is provided, biological factors make speech impossible for most animals. (We will return to this topic in Chapter 9.)
A natural surfer? No. This boogie boarding terrier underwent many learning trials and received rewards for many successive approximations of this behavior before it became a skilled wave rider.
Learned Helplessness Sometimes our prior learning experiences can cause problems with later learning situations. One problem that can arise as the result of operant conditioning is a phenomenon, known as learned helplessness, in which prior experiences with inescapable punishment condition people or animals to accept punishing consequences in later situations when they could actually avoid them (Seligman et al., 1980). For instance, research with rats has found that, after repeated inescapable shocks to the tail, if rats are given the option of escaping a foot shock by moving to a different area in the testing cage, many of them fail to do so (Weiss & Glazer, 1975). The rats that could not escape the tail shocks initially failed later to learn how to stop a shock to the foot. Instead, they stayed put and took the punishment. Learned helplessness is thought by some researchers to be an animal model of depression (Porsolt, 2000). Humans with depression are often unmotivated to act in order to change the stimuli they receive from their environments, and some theorists suggest that these people have learned this pattern of inaction from earlier, perhaps unrelated, experiences in which they were unable to make the changes they wanted. Learned helplessness also may partially explain some of the characteristics of battered spouse syndrome (Clements & Sawhney, 2000).
Why do they stay? Spousal abuse occurs in at least 4 million American homes each year. Psychologists believe that many victims develop feelings of helplessness and become convinced that they are incapable of changing the situation.
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What Happens in the Brain in Spatial Learning: Taxicab Drivers
Taxicab drivers, particularly those in London, must learn and remember a large amount of spatial navigation information to perform their jobs efficiently. Perhaps it is not surprising then that this job has been linked to differences in brain regions that are
important for spatial navigation learning. MRI studies of London taxi drivers, for example, showed that they have a slightly larger hippocampus than people of the same age who do not have taxicab training (Maguire et al., 2000). Whether this finding reflects cause or effect remains unknown. It may be that individuals with larger hippocampi gravitate toward jobs that make use of their spatial navigation skills. Alternatively, exposure to a significant amount of spatial information may enlarge the hippocampus through training. Some studies in experimental animals suggest that the second explanation is likely: the hippocampus may grow in response to experience. Living in a complex environment, learning, and physical activity all increase the size and number of neurons in the hippocampus in lab animals (Shors, 2009; Leuner, Gould, & Shors, 2006; Mirescu & Gould, 2006). Something similar many occur in humans as well.
Repeated, inescapable abuse may cause learned helplessness. The victim can become withdrawn and unable to respond in an adaptive way, even if there is an option to escape an abusive situation.
Learning and Thinking Strict behavioral psychologists have argued that all types of learning are forms of conditioning. During the twentieth century, some prominent behaviorist psychologists argued that everything we do comes about as a result of either classical or operant conditioning. Many also suggested that only observable changes in behavior should be taken as evidence of learning. This interpretation of learning as strictly based on behavioral conditioning, however, seems overly simplistic when you consider the wealth of knowledge you have amassed without any overt reinforcement. Indeed, research has shown that learning does seem to happen without any obvious reinforcement.
spatial navigation learning learning that involves forming associations among stimuli relevant to navigating in space. insight learning a sudden realization of a solution to a problem or leap in understanding new concepts.
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Spatial Navigation Learning One good example of learning without reinforcement arose from laboratory studies designed to assess the ability of reinforcement to train rats to learn information about spatial navigation. Perhaps not surprisingly, laboratory rodents can be trained to navigate through a maze by providing them with reinforcement along the way. This approach, which is a form of shaping, involves the presentation of food rewards as rats move in the correct direction. In the absence of reinforcers, rats typically explore a maze, but are not motivated to find the quickest route from start to finish. However, when rats are allowed to first explore the maze and are then provided with reinforcement, they learn the task much faster than naïve rats. Studies of this type show that the rats were learning information about the spatial environment while they were randomly exploring the maze— even though they were not receiving any reinforcement for learning. When reinforcement was introduced, the rats displayed their latent learning (Figure 7-11) (Tolman & Gleitman, 1949).
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FIGURE 7-11 Latent learning in rats Rats are motivated to explore a
10 No food reward
Average errors
8 6
maze, but when given a food reward, they make fewer errors in finding the quickest route to the end of the maze and the reward. When the reward is introduced after the rats explore the maze, the error rate drops sharply, indicating that learning occured all along.
Latent learning displayed once food reward begins on day II
4 Regular food reward 2 0
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It might be easy to imagine yourself in a similar situation. Exploring a particular environment, perhaps by riding your bicycle for fun or as a passenger in a car, would make finding a location in that same environment, such as a new job or a new restaurant, much easier than doing so in a completely unfamiliar locale. This particular example of spatial navigation learning probably represents another form of biological readiness for certain types of learning. Rodents, and probably humans, seem predisposed to form spatial maps of their environments through learning (O’Keefe, 1990). Learning spatial information about their environments would have had adaptive value to our ancestors—and it still does for modern-day rats—in terms of finding food, shelter, and escape routes. Spatial navigation learning requires an intact hippocampus, a brain region that is also important for learning about other nonspatial events (Morris, 1990). Insight Learning In addition to spatial navigation learning, there are other types of learning that cannot be readily explained in behaviorist terms. One additional example of this is insight learning. Most of us have had this experience. We may puzzle and struggle over a difficult problem. Then, some time later—perhaps while we are not even working on the problem—we may have an “ah-ha!” or “eureka” moment, when the solution suddenly becomes evident. Some individuals even report solving problems in their dreams. The Nobel laureate Otto Loewi, the discoverer of the actions of neurotransmitter chemicals, claims to have come up with his definitive study while sleeping, after pondering the question over and over while awake (Loewi, 1957). Although finding the solutions to our problems in our dreams is fairly rare, insight learning is widespread and is another type of learning that doesn’t involve any obvious reinforcement. Language learning also does not neatly fit into a behavioral explanation. As we discuss in detail in Chapter 9, the principles of association and reinforcement cannot fully explain a number aspects of how we learn to understand and use our native languages.
“Ah-hah” During the 1920s, psychologist Wolfgang Kohler conducted pioneering studies on insight learning. Here one of Kohler’s chimpanzees piles three crates on top of each other to reach a banana that had been placed out of its reach. When first confronted with this complex task, the chimp sat and contemplated the situation; then, in an apparent flash of insight, it stacked and climbed up the crates.
Before You Go On What Do You Know? 5. What are positive reinforcement and negative reinforcement? What are the effects of each on behavior? 6. What is learned helplessness? 7. What is spatial navigation learning and why is it difficult to explain using operant conditioning?
What Do You Think? How could you use operant conditioning principles to get a roommate or child to regularly hang up his or her coat instead of throwing it on the floor?
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Observational Learning LEARNING OBJECTIVE 4 Define observational learning and summarize concerns about observational learning from the media.
Imitating Imo A Japanese macaque washes its sweet potatoes in ocean water. This behavior is displayed only by members of the monkey’s particular troupe. Apparently, they learned it by imitating the innovative behavior of a young monkey named Imo.
Studies of animal behavior in natural habitats have shown that members of certain species learn tasks by watching each other. A good example of this can be seen with a troupe of Japanese macaques. This troupe of monkeys routinely washes sweet potatoes before eating them. This is not an innate behavior, practiced by macaques all over the world. It began with one innovative monkey, who first started washing sweet potatoes after the potatoes were introduced to the macaques by researchers. After observing this behavior, other members of the group started to wash their own sweet potatoes—similar behavior has been observed with other foods (Nakamichi et al., 1998). Other studies have reported that observational learning, learning from watching the behavior of others, led to the use of novel tools by dolphins and certain primate and bird species (Krüetzen et al., 2005). Through observational learning, animals can culturally transmit behaviors across generations. That is, parents or older members of a group engage in behavior that the young observe. Observation leads to mimicry, or modeling, which is concrete proof that learning occurred. In addition to contributing to learning through mimicry, observation can affect other types of behavior that indirectly signal learning has occurred. A good example of this can be seen with reward studies in capuchin monkeys (Brosnan & De Waal, 2003). This species can be rather easily trained to perform a task for a food reward, such as a cucumber slice. If, however, the trained monkey observes another monkey receiving a more desirable reward (for example, a grape) for performing the same task, the monkey will respond by refusing to carry out the task again. This suggests not only that capuchin monkeys have an internal concept of fairness, but also that they have used the experience of observing the consequences of another monkey’s behavior to modify their own. Similar examples abound in our own lives. We learn by observation, using others as positive and negative role models and, perhaps, modifying our own behavior in new ways to accommodate the new information. Suppose a classmate is warmly rewarded with praise for asking a question in lecture. You now have information that the instructor welcomes questions. As a consequence of observing your classmate’s rewarding experience, you may be more likely to ask a question of your own in the future.
Observational Learning and Violence
observational learning learning that occurs without overt training in response to watching the behavior. modeling mimicking others’ behavior.
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Some of the most famous experiments of observational learning in children were carried out by a psychologist named Albert Bandura. Bandura was interested in whether children learned violent behavioral responses by observing aggression. He showed children a movie of a woman beating up an inflatable clown punching bag, called a Bobo doll (see Figure 7-12) (Bandura, Ross, & Ross, 1961). After the movie, the children were allowed to play in a room full of toys, including a Bobo doll. Those who had previously watched the Bobo video were twice as likely as those who did not watch it to display violent behavior toward the doll. The researchers further investigated whether observational learning would be influenced by information about reward and punishment. Indeed, they found such a relationship. The children who saw a video in which beating up the Bobo doll led to rewards, such as candy and praise, were more likely to act aggressively toward the doll than those who observed the woman being punished for beating Bobo. Bandura’s studies, and a great deal of research that followed, raised concerns that violence on television, in movies, and in videogames promotes aggressive behavior among
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viewers, especially children (Bandura, 1978). Some studies have demonstrated a convincing link between excessive television watching and aggressive behavior in children (Johnson et al., 2002). The number of violent acts in a short stretch of children’s programming can be disturbingly high. The number of such acts is typically highest in cartoons, where the consequences of violent actions are usually nonexistent. In fact, cartoon characters seem to have many lives, often returning unscathed after experiencing all manner of horrors. Although there is strong correlational evidence that television watching is associated with aggressive behavior in children, remember from our discussion of correlations in Chapter 2 that a correlation can only tell us that two variables are related. Correlations do not tell whether one variable causes the other. Some studies suggest that kids who already behave aggressively may prefer to watch more violent TV. Recall, too, that correlations only describe the relationship between the two variables specified. Other factors may influence both of those variables. In the studies of TV watching, for example it’s clear that media violence is not the only factor contributing to children’s aggression. Some studies have shown that children who watch excessive television are also less likely than children whose viewing is limited to have other positive environmental influences in their lives. Heavy TV watching is associated with low socioeconomic status and low parental involvement, so these children may lack parental or neighborhood influences against aggression. FIGURE 7-12 Aggressive modeling Bandura found that children learned to abuse an inflatable clown doll by observing an adult hit the doll.
Before You Go On What Do You Know? 8. What is observational learning and what does it demonstrate when it happens? 9. What has research shown about media violence and aggressive behavior in child viewers?
What Do You Think? How might the media be used to get children—or adults—to mimic positive social behaviors?
Factors that Facilitate Learning LEARNING OBJECTIVE 5 Define massed and spaced practice and tell what conditions are best for learning semantic material, such as facts in your classes.
It’s clear that we can learn in a variety of ways: through simple habituation and sensitization, by linking stimuli in classical conditioning, by associating our behavior to its consequences through operant conditioning, or by using our observations of the consequences of another’s behaviors as a model for our own. We also know that several factors can affect how well each of these learning methods works. Timing, as we have seen, is crucial in classical conditioning. It can also affect other types of learning. The amount of attention we pay when trying to learn is another factor that can facilitate, or alternatively, impede our learning, depending on the type of learning.
Timing You have probably noticed that you learn more information when you study for an exam over an extended period of time, as opposed to cramming for the test by pulling an “allnighter.” Why is this? Factors that Facilitate Learning 223
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Oh, those all-nighters! Cramming for a test the night before an exam leads to the acquisition of less information than studying for the test over an extended period of time.
Much of the learning that you, as a student, undertake on a daily basis involves acquiring information about facts. Psychologists distinguish between this type of learning, called semantic learning, and episodic learning, which is learning about events in our own lives. We will return to the distinction between episodic and semantic learning in the next chapter dealing with memory, but we can offer some advice now about how to improve your learning of semantic material. Most importantly, repetition helps. Semantic learning is facilitated by multiple exposures to the same material, such as reading the textbook, then listening carefully in class, and then reviewing your notes and textbook. Multiple exposures make it more likely that learning will occur, compared to a single exposure, such as just reading the book or just going to class. Your learning will also be facilitated by having time intervals between these exposures. When learning trials occur close together, as they do when you try to cram reading the book and reviewing all into the night before a big test, they are referred to as massed. When they are separated in time, they are referred to as spaced. The difference in efficiency between massed and spaced trials for learning has been demonstrated not only in the laboratory, but also in real life. Massed studying, or cramming, is ineffective for two reasons. First, it does not allow enough time between learning trials to maximize learning, and, second, it leads to sleep deprivation.
Awareness and Attention It’s clear that much learning occurs without our awareness. Nonassociative learning and some forms of associative learning—including some forms of classical conditioning and procedural, or motor-skill, learning—often occur without the individual realizing that information has been acquired. Another good example of this is learning the lyrics and tune to a new song, described at the start of this chapter, which often occurs without the intention to memorize. Observational learning also often occurs without awareness, as in the case of children modeling aggressive behavior observed on television. In some instances, awareness and excessive attention can actually interfere with learning. Gymnasts, for example, sometimes find that explicit mental rehearsal breaks their concentration and interferes with their performance when they are trying to learn a new move. In most instances, however, awareness and attention enhance learning. Many forms of associative learning, including semantic and episodic learning, require awareness and are greatly enhanced by attentional processes. You have probably experienced this firsthand on days when you are feeling out of sorts and have difficulty concentrating on your coursework. The information you read or hear in lectures at such times is much less likely to be learned than material presented at a time when you are more attentive. Given the role of attention in learning, it is worth considering an important question: How does attention work? Scientists have found that the answer to this question depends on the circ*mstances. Some attentional processes are automatic and occur when a particular stimulus is very different from those that surround it. Psychologist Anne Treisman studied attention to visual stimuli and showed that in the case of a simple scene, if one stimulus differs considerably from others, it will immediately grab our attention, a phenomenon referred to as “pop-out”. In order for pop-out to work, the stimulus must be singularly different from the surroundings (Treisman & Kanwisher, 1998). As scenes get more and more complicated, pop-out is less likely to help in guiding attentional processes. Instead, we must rely on an active searching method, where we examine material in search of the most relevant stimuli. Anyone who has enjoyed children’s books like “Where’s Waldo” or “I Spy”, where a relevant stimulus is buried in a complex visual scene, has engaged an active searching attentional process. Recall from Chapter 5 the distinction between bottom-up and top-down processing. Pop-out, because of its sim-
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plicity and speed, employs bottom-up processing while active searching, because of the need to draw on cognitive processes and memory, uses top-down processing. Sometimes attentional processes can get in the way—if information is inherently contradictory, for example, attending to one stimulus can block our ability to attend to the relevant one. A good example of this is the Stroop Effect, a psychological test that involves presenting a list of words printed in different colors. Each of the words is a color word (green, red, black, blue), but each is printed in color that differs from that of the word (green, red, black, blue). Participants are asked to list the colors of the ink, thus ignoring the word color—this is very difficult to do quickly because bottom-up attentional processing interferes with the ability to focus on just one contradictory stimulus (Herd et al., 2006). What can we do then to maximize our attention to relevant information while trying to learn? First, it’s a good idea to identify relevant information and focus on those throughout your reading. If your professor mentions topics repeatedly in class, you might use an active searching method to find additional similar material in your readings. Second, avoid dividing your attention. Our attentional processes are generally at their best when they are focused on one task. Performing other behaviors, such as answering text messages or watching TV, while trying to study usually interferes with our ability to attend to relevant material. In fact, a recent study showed that people who engage in a high degree of “multi-tasking” are less likely to perform well overall (Ophira et al., 2009).
Sleep deprivation, attention, and learning Sleep deprivation makes it difficult to pay attention, thus impairing our ability to learn. In addition, sleep deprivation after learning reduces our ability to retain newly learned material.
Before You Go On What Do You Know? 10. Which would be better for helping you learn psychology facts: massed or spaced practice? Why? 11. What kinds of learning benefit from focused attention?
What Do You Think? How could you modify your own schedule or study habits to allow for spaced practice of your material or to take advantage of your most alert and attentive times of day?
What Happens in the
When We Learn B R A I N ? LEARNING OBJECTIVE 6 Discuss synaptic changes that occur in learning, such as long term potentiation.
Throughout this chapter, we have mentioned different brain regions and neural mechanisms that might underlie certain types of learning. One general conclusion we can draw about the neuroscience of learning is that a single learning center does not exist. As we have seen, different types of learning are served by different neural systems: • Habituation and sensitization arise from changes in the sensory neurons themselves and their related corresponding interneurons and motor neurons. • Classical conditioning of the eye blink response is associated with the cerebellum, while fear conditioning involves the amygdala. • Reward learning relies on the midbrain dopamine system, and motor learning involves activation of the basal ganglia, a region near the thalamus. • Spatial navigation learning and episodic learning in general involve the hippocampus.
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Complex environments and learning Humans exposed to stimulating environments and animals raised in stimulating cages each seem to perform better on many learning tests, compared to those living in more deprived settings. This finding is consistent with what we now know about how the brain changes during learning (Pham et al., 2002; Rosenzweig & Bennett, 1996).
“
”
Cells that fire together, wire together. –Donald Hebb, psychologist
long-term potentiation (LTP) a form of synaptic change that involves increased activity in the postsynaptic cells after strong, repetitive stimulation.
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The evidence that some kinds of learning can take place without our awareness, while others require close attention, also emphasizes the fact that there is no single learning system in the brain. See, for example, “What Happens in the Brain When We Learn to Play a Video Game” at the end of this section. Although there are multiple neural systems that underlie different types of learning, neuroscientists suspect that all learning involves some kind of change in the strength of the synapse, the connection between neurons. One of the first ideas about learning involving changes in synaptic strength was put forth in the 1950s by the Canadian psychologist Donald Hebb. Hebb suggested that cells that were activated at or around the same time as one another would have stronger synapses than those that were out of step with one another (Cooper, 2005). Scientists have gathered considerable evidence to support Hebb’s view. Many forms of associative learning have been linked to a form of synaptic plasticity, or change, discussed in Chapter 4, called long-term potentiation (LTP). Recall that a synapse is the tiny gap across which neurons communicate via neurotransmitters. Long-term potentiation refers to a change in activity at the synapse that results in a long-term enhancement in the activity of the postsynaptic neuron—the one that receives the neurotransmitter message (Figure 7-13) (Bliss & Lomo, 1973). LTP has been demonstrated in the synapses in brain areas involved in eye blink conditioning, fear conditioning, and spatial navigation learning (Scelfo, Sacchetti, & Strata, 2008; Whitlock et al., 2006; Maren, 2005). LTP can be associative in nature, occurring only when electrical activity in two related areas occurs around the same time. Moreover, researchers have demonstrated, by blocking the neurotransmitter receptors in the postsynaptic neuron, that preventing LTP inhibits some forms of learning. Another possible mechanism for learning, one that could actually work in tandem with LTP, is the formation of new synapses in our brains. The possibility that learning is accompanied by growth of synapses was first suggested by the early neuroanatomist Ramon y Cajal in the late nineteenth century (DeFelipe, 2002). Since then, numerous studies have shown that Ramon y Cajal was correct. Changes in the number, size, and shape of synapses and dendritic spines, sites of excitatory synapses, have been observed with learning (Leuner, Falduto, & Shors, 2003; O’Malley,
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FIGURE 7-13 Long-term potentiation When a presynaptic neuron is given a strong burst of stimulation, it changes the activity at the synapse of the postsynaptic neuron. Subsequently, a weak stimulation reaching the postsynaptic neuron produces a greater effect than would have occurred before.
O’Connell, & Regan, 1998; Moser, Trommald, & Andersen, 1994). Even the number of entirely new neurons in our hippocampus can increase with certain types of learning (Shors, 2009). These studies present the possibility that structural change may not only occur with learning, but may actually underlie learning. Some evidence suggests that preventing the production of new neurons can inhibit certain types of learning, but not others (Shors, 2009; Leuner et al., 2006). It’s likely that if structural changes participate in learning, then they do so in concert with changes in the function and biochemistry in the relevant circuits.
Before You Go On What Do You Know? 12. Which brain regions are associated with reward and punishment? 13. Name and describe a process referred to in the quotation, “Cells that fire together, wire together.”
What Do You Think? Why are so many different brains regions involved in learning?
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What Happens In The Brain When We Learn to Play a Video Game ou need to find that key, but watch out for
Y
way, we are engaging a number of neural circuits through-
those obstacles!
out the brain. First, spatial navigation learning requires
How do we learn to navigate through virtual reality, avoid-
inputs from the visual cortex to the hippocampus and
ing dangers that prevent us from moving through the
temporal lobe. Second, learning about rewards involves
game to mastery? What parts of the brain enable us to
dopamine projections extending from the ventral
learn the rules of the game and respond to changes in the
tegmental area to the nucleus accumbens and prefrontal
electronic world as we play?
cortex. And third, integration and long-term storage of the information from these systems involves other corti-
When we learn a new video game that involves spatial
cal regions, including the parietal
navigation through a virtual three-dimensional space, try-
and temporal cortex. Will you
ing to avoid punishments and obtain rewards all along the
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make it to the next level?
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PICKING A STRATEGY People use different strategies to solve tasks that involve navigating in space. Some people use a 3D strategy, using their position relative to the environment to find their way. Others use landmarks and numbering strategies (for example, enter the second door on your right). The different strategies engage different neural systems, shown on these fMRI images. Spatial 3D strategies activate the hippocampus (top, yellow) while landmark strategies activate the basal ganglia (bottom, yellow).
STRENGTHENING YOUR SYNAPSES When you learn a task that involves spatial navigation and reward, synapses in a number of brain regions, including the hippocampus and nucleus accumbens, likely undergo long-term potentiation (LTP), a form of synapse strengthening. Most postsynaptic sites that undergo synapse strengthening are located on small extensions off of dendrites, called dendritic spines (shown here labeled with a green fluorescent tracer).
Parietal cortex Primary visual cortex Basal ganglia Nucleus accumbens
Ventral tegmental area Temporal cortex Hippocampus
LEARNING ABOUT SPACE Spatial navigation learning leads to an increase in the number of new neurons in the hippocampus, shown here stained with fluorescent dyes (red). Engaging the hippocampus in this way prevents newly born neurons from dying.
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Prenatal and Postnatal Learning How we Develop LEARNING OBJECTIVE 7 Summarize the types of learning that occur before we are born and during early postnatal life.
Early olfactory learning In this study infants are exposed to bottles containing smells of their mothers, their fathers, and other people. In such research undertakings, babies consistently show highest preference for the smell of their mothers and second highest for that of their fathers.
Several studies suggest that nonassociative learning can occur before we are even born. Fetuses show habituation and sensitization to smells and other sensory stimuli. In one set of studies, for example infants who had been prenatally exposed to garlic—through their mothers’ digestion—showed evidence, after they were born, that they recognized the garlic odor. They did not try to avoid the smell, as babies new to garlic typically do. Habituation studies of newborns also show that they can distinguish between new and familiar sights and sounds. Even very soon after birth babies typically stop moving for a brief time when they are exposed to a new visual or auditory stimulus. This response suggests that they have already become accustomed, or habituated, to “old”sights and sounds. They have learned to recognize them. We are also capable of basic associative learning before birth. One team of researchers reported classical conditioning of human fetuses. Recall from Chapter 5 that hearing is partially developed before birth. These researchers paired specific music (initially a neutral stimulus) with relaxation exercises done by the mother. The maternal relaxation exercises served as an unconditioned stimulus, often leading to a slowing of fetal physical activity (an unconditioned response). After enough pairings of the music and the relaxation, the music became a conditioned stimulus, leading directly to a decrease in fetal movement (CR), with or without the relaxation exercises. Newborn humans also demonstrate olfactory learning by showing an almost immediate preference for their own mothers’ odor, by turning their heads in the direction of their mothers’ odor much more often than toward odors of strangers. The preference for maternal odor has clear adaptive consequences in helping babies to identify the person who, throughout our evolutionary history, has been their primary source of food and care. As we develop from infancy onward, it’s clear that biological factors, such as brain development, guide the development of learning. Psychologists and pediatricians often refer to developmental milestones, many that require learning. The fact that these abilities, such as crawling, walking, language comprehension, and speech, typically emerge during specific time windows suggests that biological changes occuring at certain times are necessary for specific types of learning. The types of learning that occur during the prenatal and early postnatal periods are simple forms that don’t critically involve late-developing brain regions. More complex forms of learning, such as episodic and semantic learning, are not efficient until forebrain regions, such as the hippocampus and neocortex, have developed to a greater extent. This is one reason why young children have a difficult time learning about facts and events in an organized and accurate way. Most of us don’t have clear memories about our lives before the time we were around 3-4 years of age. This phenomenon, called infantile amnesia, is tied to learning episodic information and the development of the hippocampus and neocortex.
Before You Go On What Do You Know? 14. What kinds of learning can happen before we are born?
What Do You Think? What are the advantages and disadvantages of having only very simple forms of learning intact during fetal life? What consequences would arise if we possessed intact learning about events before birth?
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Learning and Gender HOW we Differ LEARNING OBJECTIVE 8 Summarize gender differences in learning and discuss their potential sources.
Within the range of what is considered normal, learning abilities vary greatly. You have likely experienced this firsthand by comparing study techniques and learning requirements of some of your friends and family with your own. Some individuals are gifted at certain subjects and are capable of acquiring that information much more readily than others. Studies of twins have suggested a genetic factor in certain forms of learning, but that does not account for the majority of variability in learning. Other factors clearly play a role. Environmental factors, as well as nongenetic biological factors, are likely to modulate learning abilities.
Gender Differences One highly controversial topic in the study of individual differences in learning is the issue of gender. Many individuals have preconceived notions about learning performance in boys and girls. For instance, it is a relatively common claim that boys are better at mathematics while girls excel at language arts. Since the social and educational implications of such claims are significant, it is important to carefully evaluate scientific evidence related to them. The first question we need ask is whether significant sex differences in learning actually exist. If so, then the cause of these differences becomes the critical issue. Are they biologically governed by chromosomes and/or hormones, or do they arise as a result of environmental influences? Numerous studies have claimed that gender differences exist in a number of different learning tasks. Tasks that require mental rotation of images tend to favor males, while verbal-learning tasks sometimes favor females. Although these overall differences are sometimes statistically significant when a relatively large number of individuals are tested, there is still a substantial overlap between the two genders in performance on both tasks. In addition, the difference between the average for each sex is smaller than the range within a given sex, leading to the conclusion that reports of gender differences in learning ability do not mean much for the individual. In other words, there are plenty of spatially gifted girls and verbally talented boys. Examination of performance on standardized tests, such as the SAT, reveals higher average math scores among boys than girls. Again, these differences are not enormous and say very little about the individual, since the range within a gender far exceeds the average differences. In fact, the range in scores among boys is greater than the range for girls. In other words, although the average for boys is higher, boys earn some of the lowest scores, as well as some of the highest scores. We should also note that standardized tests are typically not actual tests of learning ability, because differences in preparation for such examinations are huge; someone with a high score may have studied for months, while someone with a lower score may have gone into the test without any advance preparation. Even though they are small, and there is a lot of overlap between genders, these consistent gender differences are enough to raise issues about whether biological or environmental factors, such as schooling, influence math learning. Cultural perceptions may influence teachers’ attitudes about gender differences in math ability, for example, leading to unintentional discouragement of girls in math. Studies done by social psychologist Claude Steele have identified a phenomenon called stereotype threat, in which awareness of negative stereotypes about oneself can interfere significantly with test performance. In these studies, Steele and his colleagues observed that mentioning, before a test, a gender difference disadvantaging one gender
Self-fulfilling prophecy? In this math class, a male teacher calls on a male student for the answer. Many psychologists suspect that findings of male superiority in the learning of mathematical tasks and female superiority in the acquisition of language skills have more to do with expectations, biased teaching, misinterpretation of findings, sociocultural factors, and stress reactions than with actual differences in learning potential.
stereotype threat awareness of a negative stereotype that affects oneself and often leads to impairment in performance.
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led to poorer performance on the part of the group experiencing the bias. Members of stereotyped groups performed worse even if researchers called attention to the stereotype in an encouraging way, such as, “Come on girls, I know you can score well on this test and disprove the belief that boys are better at math!” In fact, trying hard to overcome such a stereotype seems to worsen performance even more. This phenomenon, which is incompletely understood, is not specific to gender differences or to math performance. Stereotype threat can also impair the performance of white males on an athletic test if they are informed of the stereotype that Caucasians are less athletically gifted than African Americans. In Chapter 11, we discuss additional effects of stereotype threat on IQ test performance. A biological factor that could affect learning may be our responses to stress. Some studies have shown that gender differences in response to stress can affect not only learning, but also test performance. On average, girls are more emotionally perturbed than boys by the anxiety of test taking. These studies also show that helping girls to reduce test stress by teaching them relaxation exercises or pre-exposing them to the testing environment can eliminate many gender differences in performance. (We discuss stress and coping techniques in further detail in Chapter 15.) This work emphasizes the need to consider other factors, such as stress, when we evaluate claims of individual differences in learning ability.
Before You Go On What Do You Know? 15. What is stereotype threat and what effect does it have on learning?
What Do You Think? What are the ethical problems associated with investigating gender differences in learning abilities? How might positive or negative findings of sex differences in learning affect society’s attitude toward men and women in the workplace?
Learning Disabilities LEARNING OBJECTIVE 9 Define learning disabilities and describe three major types of learning disabilities.
A learning disability is a specific deficiency in one aspect of cognitive functioning, while other aspects function normally. Learning disabilities are different from mental retardation, which is a more global deficit in intellectual abilities. Individuals with learning disabilities can even have very high IQs with impairment only in one type of learning.
Dyslexia
Studying dyslexia A range of factors have been proposed to explain dyslexia, a deficiency in the ability to read, including deficits in visual processing, speech skills, auditory processing, and object or letter identification. Here a young boy with the disorder undergoes a reading test with prism glasses.
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The most common form of learning disability is dyslexia, a deficiency in learning to read. Some estimates suggest that between 5 and 10 percent of school age children have dyslexia. The condition is two to three times more prevalent in boys than girls. Contrary to popular belief, dyslexia doesn’t primarily manifest itself as a reversal of letters of words. Reversal of letters or words is common in young children in the process of learning to read. Most children outgrow this as they acquire reading skills. People with dyslexia display this characteristic for longer periods of time, until they are older than average, in part because they are not as far along on the reading learning curve, but it is a symptom of their larger problems in learning to read.
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There is some evidence that the same people with dyslexia have visual processing deficits that may produce perceptual problems, which in turn, contribute to their difficulty in recognizing written words. Neuroimaging studies comparing children with dyslexia to those without the disability have shown that some children with dyslexia have reduced blood flow in brain regions associated with acquisition of reading skills, such as the left parietal and temporal cortex (Hoeft et al., 2006). Most people with dyslexia can overcome their difficulties in learning to read with the help of extensive tutoring and specific educational programs.
learning disability a specific deficiency in one aspect of cognitive function while other aspects function normally.
Dyscalculia
attention deficit hyperactivity disorder (ADHD) a disorder characterized by an inability to pay attention, accompanied by excessive activity.
A slightly less prevalent learning disability, which may exist with or without dyslexia, is a condition known as dyscalculia. This refers to an inability to readily acquire information about mathematics. Dyscalculia afflicts less than 5 percent of the population and is more prevalent in boys than girls. Dyscalculia can occur in individuals with normal, or even higher than average, reading abilities, suggesting a deficit in specific brain circuitry associated with acquisition of mathematical skills. Less information is available about dyscalculia than about dyslexia, but some evidence suggests that parts of the left parietal and frontal cortex of the brain are less active in individuals with dyscalculia (Price et al., 2007). As with dyslexia, intensive tutoring and specific educational programs can help students with dyscalculia learn mathematical information.
dyslexia a learning disability that involves deficits in learning to read and write. dyscalculia an inability to readily acquire information about mathematics. attention deficit disorder (ADD) a disorder characterized by an inability to pay attention.
Attention Deficit Disorders As we have noted, attention greatly aids some types of learning, especially the semantic learning required in school.Although not specifically designated as learning disabilities, two attention disorders often contribute to difficulties in learning. Attention deficit disorder (ADD) is characterized primarily by an inability to concentrate. Attention deficit hyperactivity disorder (ADHD) is a similar disorder in which concentration problems are accompanied by problematically high activity levels. These attention disorders are sometimes associated with dyslexia and dyscalculia. Both disorders are more prevalent in boys than girls. Neuroimaging studies have identified some brain regions that appear to be different in children with ADD or ADHD, compared to children without these disorders. Some evidence suggests that ADHD is associated with structural abnormalities in the cerebral cortex (Qiu et al., 2009; Wolosin et al., 2009; Shaw et al., 2007). Studies have also shown decreased blood flow in the basal ganglia (Bush,Valera, & Seidman, 2005) and also a portion of the prefrontal cortex called the anterior cingulate (Smith et al., 2008). Some studies have even shown an overall decrease in the size of these brain regions in people with ADHD (Hill et al., 2003). ADD and ADHD can be successfully treated with stimulant drugs, including methylphenidate, widely known by the trade name Ritalin®, and dextroamphetamine, which has the trade name Adderall®. Both drugs enhance attention and, even though they are stimulants, paradoxically diminish hyperactivity. The extent to which these drugs correct abnormalities in the cerebral cortex of people with ADD and ADHD remains undetermined. The identification and study of learning disabilities and attention deficit disorder raise important ethical considerations. First, it is paramount that diagnoses be made early, so that intervention can occur before significant developmental delays occur. Second, it is equally important that diagnoses are accurate, so that children with other behavioral problems are not incorrectly medicated. A third issue concerns misuse of stimulant drugs. The increased diagnosis of attention disorder and subsequent stimulant prescriptions have led to stimulant abuse by some people who most likely do not have attention disorders. Some recent studies have
Learning to “play” attention Various techniques have been used to help explain and treat ADHD, including a computer program called Play Attention. Here a child wears a helmet that measures brain waves while he performs computer tasks requiring various degrees of attention.
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estimated that a significant percentage of college students have used Ritalin and similar drugs without a prescription. Most students surveyed report that they use the drugs to help them study. Since attention-disorder drugs enhance attention and thus learning in normal individuals, this raises ethical questions (Greely et al., 2008). Do stimulants provide an unfair advantage to students who take them in settings—such as college—where success is determined by cognitive function? Is stimulant use among people without attention disorders comparable, for example, to athletes using performance enhancing drugs to improve their competitive standing?
Before You Go On What Do You Know? 16. What are dyslexia and dyscalculia?
What Do You Think? What, in your opinion, are the ethical pros and cons of taking attentionenhancing drugs when they are not needed to treat a disorder?
Summary What Is Learning? LEARNING OBJECTIVE 1 Define learning and distinguish between associative and nonassociative learning. • Learning is a lasting change in the brain caused by experience. • Nonassociative learning is a lasting change that happens as a result of experience with a single cue. Types of nonassociative learning include habituation, in which we display decreased responses to familiar stimuli, and sensitization, in which we display increased responses to stimuli of normal strength after being exposed to an unusually strong stimulus. • Associative learning is a lasting change that happens as a result of associating two or more stimuli. Types of associative learning include classical and operant conditioning.
becomes a conditioned stimulus (CS) when it elicits the same response as the US. The response to the CS is known as a conditioned response (CR). • Repeated presentation of the CS without the US can lead to extinction, or suppression of the CR. Extinction does not mean we forget the CS-US association, however. The CR can be spontaneously recovered. • Eye blink conditioning shows that classical conditioning requires changes in the cerebellum. • Phobias and conditioned taste aversions can result from classical conditioning. Systematic desensitization uses classical conditioning to extinguish phobia responses. Conditioned taste aversions suggest that we are biologically prepared to quickly learn responses important to our survival.
Operant Conditioning Classical Conditioning LEARNING OBJECTIVE 2 Describe the basic processes of classical conditioning and tell how classical conditioning is relevant to human fears and taste aversions. • As a result of classical conditioning, a previously neutral stimulus comes to elicit a response by being paired with an unconditioned stimulus (US) that already generates the response, known as an unconditioned response (UR). The neutral stimulus
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LEARNING OBJECTIVE 3 Describe the basic processes of operant conditioning and explain how shaping can be used to teach new behaviors. • Operant conditioning is a learned association between stimuli in the environment and our own behavior. The law of effect states that we learn to repeat behaviors that will increase our rewards and help us avoid punishment. • Reinforcers are rewarding stimuli from the environment. Positive reinforcement provides a desired stimulus; negative reinforce-
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ment takes away an unpleasant stimulus. Both increase the chance a behavior will be repeated. Primary reinforcers are reinforcing in and of themselves. Secondary reinforcers become reinforcing because of their association with primary reinforcers. Positive punishment provides an unpleasant stimulus; negative punishment takes away a rewarding one. Both types lower the chances that a behavior will be repeated. Schedules of intermittent reinforcement provide reinforcements after either fixed of variable intervals of time or numbers of responses. Any intermittent reinforcement modifies behavior more effectively than continuous reinforcement. Shaping, or rewarding successive approximations of a behavior, uses operant conditioning principles to teach new behaviors. People and animals are limited in the behaviors they can learn, however, by their biological endowments. Learned helplessness occurs when previous learning that punishment is inescapable interferes with the later ability to learn how to avoid escapable punishment. It may be related to depression or the behavior of abuse victims. Insight learning and spatial navigation learning seem to take place in the absence of any obvious reinforcement.
• Learning may also be linked to the addition of more synapses in the brain, either through growing new neurons or by adding dendritic material to existing ones. • Many regions of the brain, including the hippocampus, neocortex, and cerebellum, are involved in different types of learning and have been shown to exhibit LTP and neuron growth.
Prenatal and Postnatal Learning LEARNING OBJECTIVE 7 Summarize the types of learning that occur before we are born and during postnatal life. • We are capable of nonassociative learning, both habituation and sensitization, before birth, as well as basic associative learning, such as classical conditioning. • We become capable of increasingly complex forms of learning as relevant areas of our brains mature after we are born.
Observational Learning
Learning and Gender
LEARNING OBJECTIVE 4 Define observational learning and summarize concerns about learning violent behavior from the media.
LEARNING OBJECTIVE 8 Summarize gender differences in learning and discuss their potential sources.
• Observational learning is learning by watching the behavior of others. We are likely to model, or imitate, others’ behavior that we see rewarded. • Many people are concerned that high levels of violence in the media encourage viewers to model such aggression. Studies about the causal nature of media encouraging violence have been inconclusive.
• Studies show small, but consistent average differences between males and females in learning, with males performing better at spatial rotation tasks and females better at verbal learning. Males also tend to average higher mathematics scores on standardized tests. However, the range of abilities within a sex is much greater than the difference between males and females.
Factors that Aid Learning LEARNING OBJECTIVE 5 Define massed and spaced practice and tell what conditions are best for learning semantic material, such as facts in your classes.
• Environmental factors, such as stereotype threat, may contribute these gender differences. Biological differences in stress reactions may also play a role in test-score differences.
Learning Disabilities
• Repeated, spaced practice aids learning of semantic material, such as classroom information. • We can learn without paying attention and some tasks are easier to learn that way, but focused attention aids semantic learning.
LEARNING OBJECTIVE 9 Define learning disabilities and describe major types of learning disabilities.
When We Learn What Happens in the Brain
• A learning disability is a specific deficiency in one area of learning, while learning in other areas takes place normally. Dyslexia is a common disability in learning to read. Dyscalculia is a disability in learning mathematics.
LEARNING OBJECTIVE 6 Define long-term potentiation and discuss synaptic changes that occur in learning. • Long-term potentiation is a change in the ability of networks of neurons, in which the postsynaptic neuron becomes more active in response to certain presynaptic inputs.
• Attention Deficit Disorder (ADD) and Attention Deficit Hyperactivity Disorder (ADHD) affect concentration and can impair learning. Both are commonly treated with stimulant drugs. The use and misuse of these drugs raises many ethical concerns.
Summary
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Key Terms learning 204
spontaneous recovery 210
positive punishment 215
learned helplessness 218
learning curve 204
stimulus generalization 210
negative punishment 215
spatial navigation learning 220
associative learning 204
phobia 210
primary reinforcer 216
insight learning 220
nonassociative learning 204
systematic desensitization 212
secondary reinforcer 216
observational learning 222
habituation 204
conditioned taste aversion 212
continuous reinforcement 216
modeling 222
sensitization 204
operant or instrumental conditioning 215
intermittent or partial reinforcement 216
law of effect 215
fixed ratio schedule 217
learning disability 233
unconditioned stimulus (US) 208
behaviorism 215
variable ratio schedule 217
dyslexia 233
unconditioned response (UR) 208
reinforcer 215
fixed interval schedule 217
conditioned stimulus (CS) 208
punishment 215
variable interval schedule 218
conditioned response (CR) 208
positive reinforcement 215
behavior modification 218
extinction 208
negative reinforcement 215
shaping 218
Pavlovian or classical conditioning 208
long-term potentiation (LTP) 226 stereotype threat 231
dyscalculia 233 attention deficit disorder (ADD) 233 attention deficit hyperactivity disorder (ADHD) 233
CUT/ACROSS CONNECTION What Happens in the
BRAIN? • All types of learning actually involve changes in our brains, although different types of learning involve different brain regions. • London taxicab drivers, who have intricate spatial knowledge of their cities, tend to have a larger hippocampus than people without similar geographical knowledge. • Some research suggests that our brains might rehearse new information in our sleep, which could explain why sleep deprivation makes learning more difficult.
HOW we Differ • People who watch a lot of violent media or play violent videogames may be more likely to behave aggressively than those who watch less, but no definitive studies have shown this. • There are very small average differences in learning between males and females, but average differences cannot help you predict how well any individual will learn. • If we learn about a negative stereotype about a group to which we belong, our learning and performance often change to reflect that stereotype.
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• Phobias might result from classical conditioning, in which we learn to respond with fear to something that isn’t necessarily threatening. We can learn to extinguish phobic behavior, but can’t “unlearn” the phobia. • We can learn a long-lasting aversion to a food if it makes us sick only once, even several hours after we eat it. • Learned helplessness might play a role in depression. If people have previously been unable to escape punishment, they may fail to act to escape unpleasant situations, even when it becomes possible.
How we Develop • We can learn simple associations before we are even born. • Very early in life, we fail to display efficient complex learning, such as episodic or semantic learning. These forms of learning depend on further development of the hippocampus and neocortex. • Reinforcement is generally more effective and ethical than punishment for teaching children.
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Psychology Around Us Bringing Learning and Conditioning Principles to Life
You Can So Teach an Old Dog New Tricks Video Lab Exercise
We’re constantly learning in life—learning new behaviors, new reactions, new lessons, new skills, and new ideas. Sometimes we are aware of it, sometimes not. We learn some things faster than others. And we learn better in some contexts than others. But we do indeed keep learning. At the same time, we don’t take advantage of every learning opportunity. Moreover, when we do learn something, it may not stay learned indefinitely. And, as we know all too well, we learn a lot of things (certain fears, for example) that we wish we hadn’t learned. This video lab exercise will bring learning principles to life by teaching you some new behaviors and skills—sometimes with your cooperation and sometimes in spite of yourself. And, by the way, while you’re learning, you’ll also be required to identify the conditioning principles and variables at play—just to show that you learned some new material while reading this chapter. As you are working on this on-line exercise, consider the following questions: • How readily does classical, operant, and observational learning occur? • How easy is it to resist conditioning or, at the other end, to extinguish a newlylearned behavior or skill? • How do attention, timing, and insight come into play? • How can learning be enhanced?
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CHAPTER 8
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Memory chapter outline • • •
What Is Memory?
•
How Do We Encode Information into Memory?
How Do We Store Memories?
Why Do We Forget and Misremember? •
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How Do We Retrieve Memories? •
Memory: What Happens in the Brain?
Disorders of Memory
Past
ow a cult classic, the 2000 film Memento fascinated viewers with a series of harrowing situations that confronted
the main character, Leonard. In the movie, Leonard is looking for the person or people who attacked him and brutally murdered his wife. His search is hard and frightening, however, because the attack left Leonard unable to form new memories. To cope with this problem, Leonard takes Polaroid instant pictures and makes notes on them as he acquires information. He also tattoos on his body to help him put the puzzle together. Despite these efforts, however, scenes in the movie frequently open with Leonard being attacked by people he does not know or chased for reasons he cannot explain until he has time to piece the information together. At the same time, Leonard finds himself confronted with other characters who may—or may not—have his best interests
Consider everything that memory lets you do. Obviously there are the everyday tasks, such as passing tests, turning in a paper on time, or remembering a friend’s birthday. But go deeper: Think of the things memory lets you do that you take for granted. Because of memory, you can have favorite foods, favorite musicians, favorite movies, and favorite TV shows. Not only can you remember friends’ birthdays, you can also remember their typical behaviors and their preferences and then predict what they might want for their birthday. You can go deeper still. If you did not somehow encode events and people in your mind, you would not know about anything that you were not directly sensing at that moment. You would only know what was in your line of sight and have no idea how the things that you were seeing connected to you or had any significance or meaning. Without memory, you would, like Leonard, be a stranger to yourself, unable to form the identity, or sense of self, that comes from linking one’s present to one’s past and using this information to make decisions about the future (Kihlstrom, Beer, & Klein, 2003). By keeping a record of our past, our memory takes us out of an infinite present.
at heart as they try to “help” him along his way. On top of everything, Leonard has doubts. Given his own memory loss, how can he be sure that he didn’t kill his wife and then somehow cause his own memory loss to protect himself from his guilt?
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memory the faculty for recalling past events and past learning. encoding a basic activity of memory, involving the recording of information in our brain. storage a basic activity of memory, involving retention of information for later use. retrieval a basic activity of memory, involving recovery of information when we need it later. information-processing model view of memory suggesting that information moves among three memory stores during encoding, storage, and retrieval. parallel distributed-processing (PDP) (or connectionist) model theory of memory suggesting information is represented in the brain as a pattern of activation across entire neural networks.
What is Memory? LEARNING OBJECTIVE 1 Define the basic activities of memory and describe two major models of memory.
Simply put, memory is the faculty for recalling past events and past learning. This definition is perhaps the only thing about memory that is simple. Although psychologists often differ in their ideas about memory, they generally agree that it involves three basic activities: • Encoding—Getting information into memory in the first place • Storage—Retaining memories for future use • Retrieval—Recapturing memories when we need them When, for example, you attend a musical concert, you may transform the sights and sounds produced by the performing band into a kind of memory code and record them in your brain (encoding). This information then remains stored in the brain until you retrieve it at later times—when, for example, you see photos of the band online, watch their music videos, or decide which of the band’s songs to download. At such times of retrieval, the original concert event, including the feelings of exhilaration and discovery that you experienced at the concert, may come rushing back. How do we manage to encode, store, and retrieve information? Psychologists have developed a number of models of explanation, including the information-processing model and the parallel distributed-processing model, or connectionist model. The information-processing model of memory holds that information must pass through three stages, or systems, of mental functioning in order to become a firmly implanted memory—sensory memory, working memory, and long-term memory (see Figure 8-1) (Nee et al., 2008; Buchner & Brandt, 2003). When we first confront a stimulus, our brain retains a sensory image—or sensory memory—of it for less than a second. Sensory memories help us to keep alive a bit longer items that we have experienced briefly, so that we can, in a sense, decide whether to pay further attention to them. If, for example, we look up a person’s e-mail address, our sensory memory records the address and quickly passes it on to our working memory. We can help
Stimulus from the Environment
Sensory Memory
Working Memory Encoding
Long-term Memory Encoding
Retrieval
FIGURE 8-1 The three-stage memory model This model is a useful framework for thinking about the three basic memory stages. Each stage differs in purpose, duration, and capacity.
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Purpose – holds sensory information Duration – lasts up to 1/2 sec for visual; 2-4 sec for auditory Capacity – large
Purpose – holds information temporarily for analysis Duration – up to 30 sec without rehearsal Capacity – limited 5-9 items
Information not transferred is lost
Information not transferred is lost
Purpose – relatively permanent storage Duration – relatively permanent Capacity – relatively unlimited
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Retrieval Recalling memories when we need them
Storage Retaining memories over the long term
FIGURE 8-2 Memory as a computer In the information-processing model of memory, the basic memory stages are analogous to a computer: encoding allows us to enter information into our brain; storage to retain the information over the long term; and retrieval to call up the information as we need it.
Encoding Entering information into memory
retain the new address in working memory by concentrating hard and repeating it over and over as we address an e-mail or type it into our computer’s address book. But working memory itself can hold only so much information at a time. It will eventually fail us and the information will disappear unless it is further passed on to our long-term memory system—the system that can retain a seemingly unlimited number of pieces of information for an indefinite period of time. The three systems of memory proposed by the information-processing model are comparable to the operation of a computer (see Figure 8-2). Have you ever typed faster than your computer can process and then watched it spit out several characters at once? Sensory memory works in a similar way, giving us a quick copy of the information in our environment. In addition, information saved to working memory is equivalent to the information that a computer retains for as long as a document or website is open, but which disappears if you do not save it. And the final memory system, long-term memory, is the equivalent of the computer hard drive, storing information until something causes disruption or loss of the memory. These three systems are sometimes referred to as memory stores. The information-processing model has generated a great deal of research that we will explore further in the sections of this chapter that focus on encoding, storage, retrieval, and forgetting. Although the information-processing model suggests that sensory memory, working memory, and long-term memory correspond roughly to computer memory structures, we need to be clear that this is just a metaphor. If you break open a computer, you can find the dedicated modules where the various forms of memory are in operation. When we look at the human brain, however, there are no equivalent dedicated structures where short -term memory and long-term memory exist. Unlike the information-processing model, which suggests that information is stored and retrieved piece by piece, an alternative model of memory, the parallel distributed-processing model (PDP), or connectionist model, holds that newly encountered pieces of information immediately join with other, previously encountered pieces of relevant information to help form and grow networks of information (Rogers & McClelland, 2008). Such networks result in sophisticated memories, broad knowledge, and the ability to make better decisions and plans in life. Look, for example, at Figure 8-3. When the person in the figure sees an apple, connections to information involving things that are round, the color red, or possibly grandma (because of the apple tree in her backyard) are all activated, while other, less relevant connections are inhibited. These connections are all part of the network of information related to apples that this person has stored. When one part of the
“
Memory isn’t like reading a book; it’s more like writing a book from fragmentary notes. –John Kihlström, psychologist
”
What is Memory?
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FIGURE 8-3 The PDP model of memory The PDP, or connectionist, model of memory suggests that memories are stored in a network of associations throughout our brains.
red
juice tree
sweet
grandmother
pie
round
Apple
“apple” network is activated, related neurons throughout the brain also become active and richer memories spring forth. The PDP model of memory has gained many proponents, largely because its principles fit well with the field’s growing recognition that neurons throughout our brains form networks of association as we respond to repeated learning experiences and events in life.
Before You Go On What Do You Know? 1. What are encoding, storage, and retrieval? 2. What are the three memory stores suggested by the information-processing model of memory?
What Do You Think? Judging from your own experiences, do you think memory works more like a computer, with different memory stores, or more in a connectionist fashion? Could the two ideas both be useful in explaining some of your experiences?
How Do We Encode Information Into Memory? LEARNING OBJECTIVE 2 Describe how information is encoded and transferred among different memory stores and what we can do to enhance encoding.
How many steps are there from the front door of your building to your room? Can’t remember? How about an easier question: what was the first word you said yesterday morning? Most of us probably cannot recall an answer to either of these questions. 242 Chapter 8
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© The New Yorker Collection1996. Arnie Levin from cartoonbank.com. All Rights Reserved.
Even Memory Champions Need To Pay Attention
Contestants in the annual USA National Memory Championship are asked to memorize thousands of numbers and words, pages
of faces and names, lengthy poems, and decks of cards (Schacter, 2001). Would it surprise you to learn that a recent winner considers herself dangerously forgetful? That’s right. “I’m incredibly absentminded,” winner Tatiana Cooley told a reporter. Fearful that she will forget to carry out everyday tasks, Cooley depends on to-do lists and notes scribbled on sticky pads, “I live by Postit*,” she admitted ruefully. The image of a National Memory Champion dependent on Post-Its in her everyday life has a paradoxical, even surreal quality: Why does someone with a capacity for prodigious recall need to write down anything at all? Can’t she call on the same memory abilities and strategies that she uses to memorize hundreds of words or thousands of numbers to help remember that she needs to pick up a jug of milk at the store? Apparently not. The kinds of everyday memory failures that Cooley seeks to remedy with Post-It notes—errands to run, appointments to keep, and the like—reflect absentmindedness: lapses of memory caused by inattentiveness, improper encoding, or carelessly overlooking available memories at the time of information retrieval.
Your lack of recall may be because the information was never encoded, or entered into your memory. Because we fail to encode many pieces of information that we come across in life, we do not actually remember most of the things that we experience. Encoding requires attention—that is, we need to focus on or notice the information in the first place. We can encode only what we attend to.
Using Automatic and Effortful Processing to Encode We are not always aware that we are attending to things in our environment. Sometimes we attend to information—particularly, information about time, space, or frequency— without much conscious awareness and indeed with little or no effort. Even though you might not know how many steps there are from the front door of your building to the door of your room, you probably do not get lost very often along the way and you probably did not need to practice the route to figure out how to get to your room. The encoding process that allowed you to learn this basic route is called automatic processing (Hassin, 2005). Although we use automatic processing to encode many kinds of information, the encoding of other information requires that we make conscious efforts and pay very close attention. This is the type of processing you are engaging in right now as you read this chapter, whether you are preparing for tomorrow’s class or studying for a test. As you read through the present material, you are trying to find ways to bring this new information into your memory, because the facts won’t settle there without your careful attention. This kind of encoding—which is typically needed when a person learns new information, such as new names, songs, or tasks—is called effortful processing (Hassin, 2005). Keep in mind that whether we are encoding information through automatic or effortful processing, we must be paying attention. Our attention might be less apparent
“ ”
The true art of memory is the art of attention. –Samuel Johnson, writer
automatic processing encoding of information with little conscious awareness or effort. effortful processing encoding of information through careful attention and conscious effort.
How Do We Encode Information Into Memory?
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Memory buster This student’s upcoming test performance is clearly at risk. Effortful processing, such as acquiring new information from a textbook, is easily disrupted when one also attends to other tasks during the encoding process.
in automatic processing, but if we do not attend sufficiently to information, in one way or another, we will simply not be able to encode it. There are key differences between these two kinds of processing. First, the encoding of information by effortful processing tends to be disrupted when a person is forced to perform other tasks or to attend to other information while trying to encode the information at hand. You probably will not gather much from this book if you try to read it while carrying on a lively phone or text conversation, for example. In contrast, automatic processing, being so effortless, is disrupted only slightly by the performance of other tasks. Second, as the name might suggest, putting extra effort into effortful processing makes it more effective. Automatic processing is not significantly enhanced by a person’s extra efforts to attend and encode. You could go and rehearse the path from your front door to your room and count the steps, but it’s unlikely that you’ll know any more about the route than you knew this morning. In contrast, extra efforts can make an enormous difference in effortful processing. Reading over the material in this chapter again and again will affect considerably your ability to recall it on a test.
Encoding Information into Working Memory: Transferring from Sensory Memory into Working Memory
K
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FIGURE 8-4 Test of sensory memory In his study of the duration of sensory memory, George Sperling flashed a chart of letters, similar to this one, for 1/20 of a second. He found that participants could recall almost all the letters in a particular row if asked to do so immediately, but half a second later, their performance declined.
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As we observed earlier, when we first confront a stimulus, our brains retain a very brief sensory image of it—an image called a sensory memory. If, for example, we are shown a photograph for just a moment, we retain a detailed image of all the shapes and items in the photograph for a few hundred milliseconds. Studies by researcher George Sperling in the late 1950s and early 1960s provided psychologists with important insights about how sensory memories operate (Sperling, 1960). Sperling wanted to demonstrate the presence of a brief visual storehouse—equivalent to the buffer memory of a computer—that would hold a picture of our environment for a very brief period of time. He also wanted to measure how long this buffer would last. To do so, he exposed participants to a list of random letters, similar to what you might see on an eye chart (although always the same size) (Figure 8-4). He presented those letters extremely quickly and found that, generally speaking, participants did a pretty good job reporting the letters if asked to do so right away. The longer Sperling waited after showing the letters, however, the more performance declined. After about half a second, participants had trouble remembering any letters from the grid. If we do not pay much attention to our sensory memories, as is usually the case, they will disappear forever. Those that are attended to, however, may enter the working memory, the second system of memory. Working memory serves several important functions in our day-to-day lives (Hambrick & Engle, 2003). One of the most important is that of enabling us to hold on to information—such as a phone number— that we need for short periods. We use working memory in this way much of the time. Whenever we read, for example, our working memory enables us to keep the beginning of a sentence in mind while we are reading the last part of the sentence, so that the whole phrase will make sense to us (Just & Carpenter, 2002). It also enables us to relate new sentences, such as this one, to previous sentences we have just read. Similarly, in a conversation, working memory helps us link new comments to previous ones so that we can follow what we are hearing.
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One way of helping to make sure that information is encoded into working memory is rehearsal, consciously repeating the information. As far back as 400 B.C.E., the ancient Greek philosophers recognized the value of rehearsal in memory. They advised students to repeat whatever they heard, on the assumption that hearing and saying the same things would transfer new information into memory (Turkington & Harris, 2009, 2001). We are rehearsing when we keep repeating a phone number we’ve just heard until we can call it or add it to our phone’s contact list. Such rehearsal increases the likelihood that the information will indeed enter our working memory and be available to us as we dial or punch in the phone number.
Encoding Information into Long-Term Memory: Transferring Working Memory into Long-Term Memory
sensory memory memory involving detailed, brief sensory image or sound retained for a brief period of time. working memory a short-term memory store that can hold about seven items at once. rehearsal conscious repetition of information in an attempt to make sure the information is encoded. long-term memory the memory system in which we hold all of the information we have previously gathered, available for retrieval and use in a new situation or task. spacing effect facilitated encoding of material through rehearsal situations spread out over time.
Although concentrated efforts, such as rehearsal, can lengthen the availability of information in working memory, eventually that information is either passed on to the longterm memory system or lost (Jonides et al., 2008, 2003). It is in long-term memory that we hold all of the information we have gathered, available for use—often at a moment’s notice—in a new situation or task. When we remember past events, previously-gathered information, people we once met, past feelings, or acquired skills, we are using our long-term memory system. Just as rehearsal can help move information from the sensory memory system to the working memory system, it can help us move short-term, working memories into the long-term memory system (Neuschatz et al., 2005). Most of us rehearse information from a course’s textbook and lectures, for example, when we are studying for an examination. Information passes into long-term memory best when our rehearsal sessions are spread out over a period of time rather than attempting to take in a great deal of information all at once. As we observed in Chapter 7, this phenomenon is known as the spacing effect. Thus, distributed practice, such as studying material weekly, followed by reviews closer to the time of an exam, is usually more profitable than massed practice, such as studying in one “cram” session just before the exam. As we also saw in Chapter 7, sleep can help or hurt rehearsal. Information acquired in the hours before falling asleep tends to be encoded into long-term memory, as long as we have time to process it before sleep sets in (Backhaus et al, 2008; Stickgold & Walker, 2007). Information learned just as sleep is approaching is rarely retained, however, partly because we fall asleep before we can rehearse. Furthermore, information that comes to us during sleep—a language tape, for example—does not typically enter our memories at all.
In What Form is Information Encoded? We must use some kind of code or representation to encode information. Different codes are available to us (Martin, 2009). When encoding information into working memory— for example, trying to keep a phone number in memory long enough to dial it—we can use a phonological code, repeating the sounds of the numbers again and again, or we can employ a visual code, holding an image of how the digits would look if written down. Research suggests that people tend to favor phonological codes when recording verbal information, such as digits, letters, and words. We rely more on visual codes for nonverbal information, such as a person’s face or a speeding car (Just & Carpenter, 2002).
Putting working memory to good use As people surf through TV channels with their valued remote control, they are making use of working memory. They must briefly remember each video snippet that they come across so that they can make a wise decision about what to watch for the next half-hour.
How Do We Encode Information Into Memory?
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What subway? Because people tend to use semantic codes (codes based on meaning) to record important events into long-term memory, everyone at this nontraditional wedding in Beijing may later remember the day’s events differently. A few may even leave out the fact that it took place on a subway platform!
200 words of poetry 200 words of prose
10 20 90
200 nonsense syllables
20 40 60 80 100 Time to memorize in minutes
FIGURE 8-5 Meaning matters in memory Meaning helped people memorize poetry and prose much faster than nonsense syllables. (Based on Turkington & Harris, 2009, 2001)
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Although adequate for most purposes, the phonological or visual codes that people use to record information in their working memory tend to be flawed. Some people, however, produce visual images with extraordinary detail and near-perfect accuracy. When recalling an object or scene that they have just witnessed, these people almost seem to be looking at a photograph. Thus their detailed images are called eidetic memories, or photographic memories. Eidetic memories usually occur among children: as many as 5 percent of children encode images with this level of detail. The eidetic images can last for several minutes (Hochman, 2001). When we encode nonverbal information into long-term memory, we once again tend to use phonological or visual codes. Similarly, we may use olfactory, gustatory, or tactile codes to help record smells, tastes, or physical sensations. Long after a concert, for example, audience members may remember its intensity by visualizing images of the stage and the lighting effects, re-experiencing the smells of the arena and the crowd, and calling to mind the sounds of the musical instruments, the performers’ voices, and the crowd’s cheers. In contrast, to encode verbal information into long-term memory, people tend to use semantic codes, representations based on the meaning of information. Because we often rely on the meaning of information when transferring items into long-term memory, our later recall of events may be flawed to some degree. Many a family gathering has been spent sharing different versions of an important event—for example, the day Sarah received the news that she was accepted into medical school. Everyone at the gathering may remember the key elements of that special day, but the specific memories of each person—from the size and thickness of the envelope that bore the announcement to the wording of the announcement or the exclamation of various family members—may differ dramatically. Why? In part, because each member used semantic coding to record the important family happening into their long-term memory. It is worth noting that the various codes may operate simultaneously when information is being encoded (Kessels & Postma, 2002). One of these codes—semantic, phonological, or visual—may be used more actively than the others in particular instances, but when we use multiple codes, the combined impact of the these codes increases the likelihood and strength of the memory. Meaning and Encoding Inasmuch as meaning often plays a key role in long-term memory, we should not be surprised that the more meaningful information is, the more readily it is encoded and later remembered. In one study, for example, people were asked to memorize 200 words of poetry, 200 nonsense syllables, and a 200-word prose passage (see Figure 8-5). The poetry took 10 minutes to learn and the prose less than 20 minutes, but the nonsense syllables took an hour and a half! Similarly, the more meaningful a personal event, the more readily it is encoded and later remembered. Sarah’s acceptance into medical school was recognized by everyone in the family as a significant turning point in her life. Thus, Sarah, her parents, and her siblings all remembered the day of her acceptance. A lesser event, such as a day at the circus or a trip to a department store, might not be encoded as readily. People can help ensure that less meaningful information proceeds into long-term memory by artificially adding meaning to it (Ceci et al., 2003). Many a new music student, for example, has come to appreciate that the five lines of printed music of the treble clef are called E-G-B-D-F, by first tying those letters to the sentence “Every Good Boy Does Fine.” The first letter of each word in the sentence is the same as one of the lines of printed music. By giving more meaning to the musical language, the sentence helps the students to encode the information into their long-term memory.
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PRACTICALLYSPEAKING
Make Your Memories More Meaningful
As we have seen, you can use the technique of elaboration, or elaborative rehearsal, to impose meanings on seemingly unrelated pieces of information, such as the names of musical notes. Many mnemonic systems, based on processes and principles discovered by memory researchers, rely on elaboration to help you better encode, store, and retrieve information that you need to remember (Cavallini et al., 2003; Ceci et al., 2003; Kail, 2003). One of the best ways to elaborate is by making the target information personally meaningful. For example, if you want to remember the difference between the spelling of the words dessert (a treat that follows a meal) and desert (a dry, hot, arid place), you might say to yourself, “I like something super sweet after dinner,” to remind you that the food item is spelled with a double s. Two other mnemonic techniques involve imagery, taking a mental picture of something meaningful to you and using information from the picture to increase your memory potential.
• Key Word Method This visualization method was developed by researcher Richard Atkinson (1975) for the learning of foreign-language words. A student trying to learn Spanish, for example, will think about an image that ties the Spanish word to an English key word that sounds similar to a portion of the foreign word. The Spanish word caballo, which means “horse,” sounds like eye in its middle syllable. So a student might imagine a horse kicking a giant eye. When confronted with the word caballo, the sound of the key word, eye, should cue the student to see the image in his or her mind and to retrieve the information that caballo means “horse.” In one experiment, students who were instructed to use this method of study scored an average of 88 percent correct on a test, while those who studied by repetition alone for the same duration scored only 28 percent correct (Pressley, Levin, & Delaney, 1982; Raugh & Atkinson, 1975). The method has also proven helpful in studying unfamiliar vocabulary within a student’s native language, such as medical terms (Troutt-Ervin, 1990). • Method of Loci This method (loci is Latin for “places”) can help you remember information that must be recalled in a specific order, such as a list of words. First, imagine a place that you know well, such as your home. Visualize the layout of that place as you walk through it. At home, for example, you might imagine yourself walking through the front door, past a couch, toward a round table, then past a television set, and finally into the kitchen. Next, form a picture in your mind that connects each word or object to a location in the house. If the first word on a list to be remembered is cat, you might imagine a cat scratching at the front door, for example. Once you have tied the items on the list to these images and practiced them, you can mentally walk through the “place” and list the items one-by-one in the correct order.
Such applications are known as mnemonic devices. Similarly, if people elaborate on the meaning of information, they increase the likelihood that it will be encoded into long-term memory. Throughout this book, we include relevant examples that we hope will make the information more applicable and more relevant and, in turn, make your memories more accessible.
semantic code cognitive representation of information or an event based on the meaning of the information. mnemonic devices techniques used to enhance the meaningfulness of information, as a way of making them more memorable.
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Organizing Your Memories of the body for an anatomy class, you might group them according to their locations or by their actions. One very useful study technique for helping readers—such as yourself—to learn and remember textbook information is, once again, based on the principle of organization (West et al., 2008). The PQRST method is named for its five steps, which are to be undertaken in order.
As you know by now, organizing information is necessary for the proper storage and retrieval of memories. Chunking is one way of organizing information to help enhance memory. Another organizational technique—organizing a list of unrelated words into a story—has also been shown to be very successful. In one study, participants who used this approach were able to recall, on average, over 90 percent of the words presented to them from twelve lists, compared to only 10 percent recalled by participants who did not use this approach. A third way to organize new material is to create a hierarchy of the information, separating it into sections and subsections, much like the chapter of a textbook. For example, if you need to memorize the names of all the muscles
• Preview Skim the entire section you are required to learn. Look for the basic themes, and try to get a rough idea of the information you will have to process when reading the section in more detail. If you were reading a section of a textbook about the assassination of U.S. President John F. Kennedy, your preview might focus on figuring out the principal events and people involved in the assassination. • Question Examine the organization of the section and turn each subsection into a question that you want to answer over the course of your reading. If one of the subheads was, “The Assassination of an Assassin,” ask yourself, “How did the assassin of President Kennedy come to be killed himself?” • Read Read the section with the goal of finding the answers to your questions. • Self-Recitation Ask yourself and answer aloud a set of questions that arose from the reading material, such as: “Who shot John Kennedy?” and “From what location was he shot?” • Test Test yourself by trying to recall as much of the learned information as you can. By organizing your reading in this way—by asking yourself questions about the information at hand before, during, and after reading—you stand a better chance of retaining the information than if you were to spend your time simply reading through the section several times.
Organization and Encoding Another important variable that can enhance the encoding of information into long-term memory is organization. Actually, when people add to or elaborate on the meaning of certain pieces of information or events, they are organizing them. That is, they are giving the information a structure that is more familiar and available to them. As such, they are making it easier to encode into long-term memory. Typically, people do this intuitively. If we asked you to memorize a list of words that included FOX, BEAR, ITALY, ENGLAND, RABBIT, SPAIN, and MOUSE, you might naturally sort the words into rough categories of “Animals” and “European Countries.” Organization by categories can be particularly useful in helping us to encode complicated situations. Cognitive psychologists have identified structures called schemas, 248 Chapter 8
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knowledge bases that we develop based on prior exposure to similar experiences or other knowledge bases. Schemas can be helpful in allowing us to attend to and encode a lot of information in a hurry. Think about the first time you walked into a new restaurant. Did it feel awkward or strange because you weren’t sure of the rules or what to order? If you had visited other, similar restaurants before that one, the schemas you developed during your experiences at those restaurants probably helped you know what to do and what to order in the new restaurant with less effort than you would have needed if you had never been in a restaurant at all.
In need of a schema This young patron seems confused about how things work at Round House Restaurant in Brno, Czech Republic. His previous restaurant schemas simply have not prepared him for the Round House’s unusual use of a model train to deliver food and drinks to its customers.
Before You Go On What Do You Know? 3. How does increased attention affect automatic and effortful processing? 4. Why is it more effective to study all term long, rather than in one massive session right before a final exam? 5. Which type of coding would most people use to remember someone’s face? Which type would most people use to remember a person’s name?
What Do You Think? As we noted earlier in the chapter, the author Samuel Johnson wrote, “The true art of memory is the art of attention.” Can you think of experiences from your own or others’ lives that bring this statement to life?
How Do We Store Memories? LEARNING OBJECTIVE 3 Describe how we organize and store information in working and long-term memory and how we can enhance our long-term memories.
As you have seen, after entering the working memory system, information remains there for only a short period of time, sometimes only a matter of seconds. In contrast, when information moves on to the long-term memory system, it can remain there for hours or a lifetime. The retention of information—whether brief or long—in either of these memory systems is called storage.
Storage in Working Memory Information may enter working memory from two major sources. New information, as we have seen, can be encoded after a short trip through the sensory memory system. In addition, we can bring back into the working memory system information that previously has been encoded in the long-term memory system, for use in a current situation or task.
schemas knowledge bases that we develop based on prior exposure to similar experiences or other knowledge bases. storage the retention of information—whether brief or long—in either working memory or long-term memory.
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During the time that information from either of these sources is residing in the working memory system, it can, as we have seen, serve many important functions in our daily lives, from enabling us to read or carry on conversations to helping us solve current problems. The information stored in working memory also helps us do mental computations, such as mathematical problems (Maybery & Do, 2003). We could not, for example, add together the numbers 12 plus 13 if our working memory were not reminding us that we are computing those particular numbers, that addition is the task at hand, and that 3 plus 2 equals 5 and 10 plus 10 equals 20. In fact, because working memory helps us do mental computations, it is often characterized as a “temporary notepad” that briefly retains intermediate information while we think and solve larger problems.
Research suggests that memory and related cognitive functions peak at approximately age 25 (McGaugh, 2003, 1999).
memory span maximum number of items that can be recalled in correct order. chunking grouping bits of information together to enhance ability to hold that information in working memory. explicit memory memory that a person can consciously bring to mind, such as one’s date of birth. implicit memory memory that a person is not consciously aware of, such as learned motor behaviors, skills, and habits.
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The Storage Limits of Working Memory Once information enters working memory, it can be stored for just a limited period of time (Just & Carpenter, 2002). Concentrated efforts, such as rehearsal can lengthen the availability of information in working memory, but eventually it is either passed on to the long-term memory system or lost (Jonides et al., 2008, 2003). Just as striking as the limited duration of working memory is its limited capacity. On average, only five to nine items can be stored there at a given moment. This number was first uncovered back in 1885 by the German researcher Hermann Ebbinghaus (1850–1909) who pioneered memory research by studying his own memory, and it was confirmed over 70 years later by psychologist George Miller (1956). In a typical study of this phenomenon, researchers present people with a sequence of unrelated digits, letters, words, or the like, and then ask them to restate the items in the correct order. Because the items are unrelated and presented rapidly, it is likely that this procedure is tapping into the storage capacity of working memory only, not into some related information that has been stored in long-term memory. In study after study, almost every adult can recall sequences that consist of five items, but very few can recall lists consisting of more than nine items. Each individual displays his or her own memory span—the maximum number of items that can be recalled in the correct order—but no memory span strays very far from seven. Because research shows that almost everyone has a working memory capacity in this range, Miller described it as the “magical number seven, plus or minus two.” Enhancing Working Memory Actually, the storage capacity of working memory is not quite as limited as it may seem from the Ebbinghaus and Miller studies. Each of the seven or so items that working memory holds can consist of more than a single digit, letter, or word. An item can consist of a “chunk” of information. Chunking pieces of information together into larger units enables us to encode more information in our working memory system, and it also enables our working memory to store more information at a given moment. Let us say that we are presented with a string of 23 letters, o-u-t-l-a-s-t-d-r-i-v-in-g-n-i-g-h-t-w-a-s-i. Because our capacity in working memory is only 7 ± 2 items, we would, on the face of it, be unable to store this entire sequence of items. If, however, we recognized that these letters can be chunked into words—“out,”“last,”“driving,”“night,” “was,” and “I”—our task changes. We now need to store only 6 items (that is, 6 words) in working memory, rather than 23, and the task becomes manageable. In fact, these words can be further chunked into one item: the sentence “Last night I was out driving.” If we store the information in this way, we still have room in our working memory for several other items. Similarly, without realizing it, we may be taking advantage of chunking when we first try to master a song’s lyrics. Rather than learn the song letter by letter or word by word, we may hold on to seven new lines at a time, repeating the lines again and again until we “nail” them.
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Our ability to chunk actually comes from our long-term memory system (Cowan & Chen, 2009). Recall that information may enter working memory as either new information arriving from sensory memory or through retrieval from long-term memory. In chunking, we use our stored, long-term knowledge that certain letters spell certain words or that words can be organized to form sentences to guide us in chunking new information.
Storage in Long-Term Memory Whereas the sensory memory and working memory systems deal only with a limited number of short-term memories, our long-term memory system retains a seemingly unlimited number of pieces of information for an indefinite period of time, extending from minutes to a lifetime (Nairne, 2003). Indeed, memory researcher Elizabeth Loftus has estimated that our long-term memory system may hold as many as one quadrillion separate pieces of information. This expansive capacity and duration is critical to our functioning, for it is in this vast memory store that we hold—ready for use—all of the information that we have ever gathered. When we remember previously-gathered knowledge, past events and people, or acquired skills, we are using our long-term memory system. Several factors influence whether particular events are stored in long-term memory. As we have observed, new information must first be attended to in order to have any chance of eventually winding up in this memory system. Furthermore, items that are attended to must be encoded and briefly stored in working memory and then encoded into long-term memory before they can be stored in this memory system (Ceci et al., 2003). Any shortcomings in these attention and encoding activities may prevent the information from being stored in the long-term system (McGaugh, 2003). Moreover, even after information is successfully stored in long-term memory, some of it may become inaccessible (Loftus & Loftus, 1980). That is, some of the information that we have previously acquired cannot be retrieved from long-term memory. Most of the research on long-term memory storage, including the loss of stored information, has been conducted in the biological realm, as we shall soon see. We have observed that the number of items that can be stored in working memory is rather similar from person to person (7 ± 2). The capacity for long-term memory storage, while enormous for most of us, does, however, vary greatly among people. The differences from person to person may be due to factors, such as attention and the ability to move information from working memory to long-term memory.
Surveys indicate that 16 percent of adults have forgotten their wedding anniversaries (22 percent of men and 11 percent of women). People married only a few years are as likely to forget as those married for many years (Kanner, 1995).
What Types of Memories Do We Store in Long-Term Memory? Various FIGURE 8-6 The long-term memories we store kinds of information are stored in long-term memory, as shown in Figure 8-6. Explicit Our long-term memories are of two main types, with memories consist of the types of memories that you can consciously bring to mind, various subdivisions within each. such as your mother’s birthday, or the movie discussed at the beginning of this chapVarieties of ter. But there are other types of memories that we are not consciously aware of, such Long-Term Memory as learned motor behaviors and perceptual information that help us to develop various skills and habits. These implicit Explicit Memory Implicit Memory memories might include reacting with disgust when you are Memory with Memory without conscious recall conscious recall given a plate of food that made you sick sometime in the past—you might not recall the initial bad meal, but Classically Conditioned you remember to avoid the food. Semantic Memory Episodic Memory Procedural Memory Priming Memory Neuroimaging studies of patients with brain damFacts and Personal Motor skills Conditioned Earlier exposure age suggest that these two kinds of information are general knowledge experiences and habits responses to facilitates retrieval (e.g., bananas and events (e.g., how to conditioned stimuli (e.g., heightened stored in different brain regions (Kandel, 2007; Squire are yellow, (e.g., your high drive a car, brush (e.g., phobias, fears after & Schacter, 2002). Explicit memories are converted into 12 months in school graduation, your teeth, some aspects of reading a a year, spiders the birth of ride a bike) prejudice, and scary novel) long-term memories in the hippocampus and then are have eight legs) your first child) other attitudes) stored permanently in various areas of the neocortex.
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Explicit versus implicit memories (Left) The many details of Star Trek movies that this onlooker and other Trekkies love to recall are explicit memories. (Right) In contrast, the learned motor behaviors and perceptual information that enable this skateboarder to artfully do her thing are implicit memories.
(In a sense, the hippocampus serves as a temporary storage site within the long-term explicit memory system). In contrast, the striatum, the region located toward the midline in the brain, plays a key role in the storage of implicit memories. As we observed in Chapters 4 and 7, when people need to call upon implicit memories to help them carry out various skills and habits, their striatum and its related structures become particularly active. In fact, an individual whose striatum is damaged by injury or disease may have enormous difficulty performing longtime skills and habits, yet retain most of his or her explicit memories. To make things even a bit more complicated, there are two types of explicit memories: semantic memories, your general knowledge, and episodic memories, knowledge of personal episodes from your own life. Some studies further hint that these two subgroups of explicit memories may, themselves, be stored in different ways from one another, but this possibility is far from certain (Rugg et al., 2003).
semantic memory a person’s memory of general knowledge of the world. episodic memory a person’s memory of personal events or episodes from his or her life.
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How Are Long-Term Memories Organized? How does the long-term memory system organize the many pieces of information that are stored there? Is it set up like a bookstore in which the various items are organized first by broad categories, such as fiction and nonfiction, then by subcategories (in the case of nonfiction, for example, “art,” “health,” “nature,” “science,” or “travel”), and finally by sub-subcategories (for example, art books whose authors’ names begin with A, B, and so on)? Despite years of study, we do not fully understand how pieces of information are organized when stored in long-term memory. At the same time, psychologists do now know that, regardless of their precise organization, the pieces of information stored in long-term memory are linked to each other, forming a network of interwoven associations. Thus, when we retrieve one piece of information from long-term memory, a related one will often spring forth, and that piece of information may, in turn, trigger another one. This web of associations enables us to travel rapidly through our long-term memory to retrieve much of the information we need for a current situation or task. As we saw earlier, the PDP, or connectionist, model of memory helps explain such networks by suggesting that our neurons also are activated in networks.
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Before You Go On What Do You Know? 6. What is chunking, and why would you want to use it? 7. What kind of information is stored in semantic memory and episodic memory? Are semantic and episodic memories implicit or explicit memories?
What Do You Think? What are some examples of elaboration and organizational strategies that have helped you in school or other areas of your life? What new ones are you going to try after reading this chapter?
How Do We Retrieve Memories? As we have noted, when information is successfully encoded from working memory into long-term memory, it is not only stored there, but is available for retrieval later. When we retrieve information from our long-term memory, it moves to the front and center of our thinking and becomes available once again for use in our working memory system. Upon its return to working memory, the retrieved information may be used to help clarify current issues, solve new problems, or simply re-experience past events (Hambrick & Engle, 2003; Cook, 2001). Retrieved memories of past political readings and experiences may, for example, enable us to push the right lever in a voting booth. Similarly, retrieved memories of learned math tables help us calculate new mathematical problems, and retrieved memories of how to drive guide us to park our cars in tight spaces. The kind or amount of information stored in long-term memory would mean little if we were unable to retrieve it. Like a library or the Internet, the information in long-term memory must be navigated efficiently and accurately in order to yield needed information. Just as researchers do not fully understand how information is organized when stored in long-term memory, they do not know for sure how retrieval is carried out. Some theorists propose that it is a kind of “search” process (Raaijmakers & Shiffrin, 2002, 1992). In other words, the person focuses on a specific question and scans his or her memory for the specific answer to that question. Other theorists believe that retrieval is more like an “activation” process in which the questions people pose to themselves activate relevant pieces of information that have been stored in long-term memory, after which this activation then spreads simultaneously to every other associated piece of information. The difference between these two operations is akin to the difference between the specific results you get on a Wikipedia search versus the hundreds of results you get from a Google search. If we fail to locate a particular book in a library or bookstore, it can mean either that the book is not there or that we are looking for it in the wrong section. Similarly, our failure to locate a piece of information in our long-term memory may mean that it is not stored there (encoding failure or storage loss) or that we have committed a retrieval failure of some kind.
© The New Yorker Collection 1990. Jack Ziegler from cartoonbank.com. All Rights Reserved.
LEARNING OBJECTIVE 4 Describe how we retrieve information from memory and how retrieval cues, priming, context, and emotion can affect retrieval.
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retrieval cues words, sights, or other stimuli that remind us of the information we need to retrieve from our memory. priming activation of one piece of information, which in turns leads to activation of another piece, and ultimately to the retrieval of a specific memory. recognition tasks memory tasks in which people are asked to identify whether or not they have seen a particular item before. recall tasks memory tasks in which people are asked to produce information using little or no retrieval cues.
We experience many retrieval failures in our daily travels. Often we find ourselves unable to recall a face, an event, or a scheduled appointment, yet it comes to mind later. Obviously the information was available in our memory all along, or we would not recall it later. Similarly, all of us have experienced the frustration of being unable to recall the answer to an exam question, only to remember it soon after the test. And in some instances we may become particularly frustrated when a piece of information feels right at the edge of our consciousness, an experience called the tip-of-the-tongue phenomenon. The retrieval of information from memory is facilitated by retrieval cues—words, sights, or other stimuli that remind us of the information that we need. Essentially, when we come across a retrieval cue, we enter our long-term memory system and activate a relevant piece of information. Because the pieces of information in this memory system are linked to each other in a network of associations, the activation of the first piece of information will trigger the activation of related pieces until a complete memory emerges.
Priming and Retrieval
100 90
Recognition
Retention (%)
80 70 60 50 40 30
Recall
20 10 0 20 1 min. hour
4 1 hours