Welcome to Your Brain: Why You Lose Your Car Keys but Never Forget How to Drive and Other Puzzles of Everyday Life

Welcome to Your Brain

Why You Lose Your Car Keys but Never Forget How to Drive and Other Puzzles of Everyday Life

Sandra Aamodt, ph.D. and Sam Wang, ph.D.

Bloomsbury USA

www.bloomsburyusa.com

From Sandra, to Ken and Aquila

From Sam, to Dad, Becca, and Vita

Contents

Acknowledgments

Quiz How Well Do You Know Your Brain?

Introduction Your Brain: A User’s Guide

Part 1—Your Brain and the World

Chapter 1 Can You Trust Your Brain?

Chapter 2 Gray Matter and the Silver Screen: Popular Metaphors of How the Brain Works

Chapter 3 Thinking Meat: Neurons and Synapses

Chapter 4 Fascinating Rhythms: Biological Clocks and Jet Lag

Chapter 5 Bring Your Swimsuit: Weight Regulation

Part 2—Coming to Your Senses

Chapter 6 Looking Out for Yourself: Vision

Chapter 7 How to Survive a Cocktail Party: Hearing

Chapter 8 Accounting for Taste (and Smell)

Chapter 9 Touching All the Bases: Your Skin’s Senses

Part 3—How Your Brain Changes Throughout Life

Chapter 10 Growing Great Brains: Early Childhood

Chapter 11 Growing Up: Sensitive Periods and Language

Chapter 12 Rebels and Their Causes: Childhood and Adolescence

Chapter 13 An Educational Tour: Learning

Chapter 14 Reaching the Top of the Mountain: Aging

Chapter 15 Is the Brain Still Evolving?

Part 4—Your Emotional Brain

Chapter 16 The Weather in Your Brain: Emotions

Chapter 17 Did I Pack Everything? Anxiety

Chapter 18 Happiness and How We Find It

Chapter 19 What’s It Like in There? Personality

Chapter 20 Sex, Love, and Pair-Bonding

Part 5—Your Rational Brain

Chapter 21 One Lump or Two: How You Make Decisions

Chapter 22 Intelligence (and the Lack of It)

Chapter 23 Vacation Snapshots: Memory

Chapter 24 Rationality Without Reason: Autism

Chapter 25 A Brief Detour to Mars and Venus: Cognitive Gender Differences

Part 6 — Your Brain in Altered States

Chapter 26 Do You Mind? Studying Consciousness

Chapter 27 In Your Dreams: The Neuroscience of Sleep

Chapter 28 A Pilgrimage: Spirituality

Chapter 29 Forgetting Birthdays: Stroke

Chapter 30 A Long, Strange Trip: Drugs and Alcohol

Chapter 31 How Deep Is Your Brain? Therapies that Stimulate the Brain’s Core

A Note on the Authors

Acknowledgments

In our careers so far, we have written over half a million words about the brain, but that experience only partially prepared us for writing this book. We have wondered why acknowledgments run so long. Now we know.

When Jack Horne learned that both of us were planning to write the same book, he suggested we combine our efforts. Sandy Blakeslee and Jeff Hawkins recommended their agency, Levine Greenberg, to us, and vice versa. Our agent, Jim Levine, and his assistant, Lindsay Edgecombe, helped us shape the book’s tone and content. All authors should have such expert guides for their first book. Beth Fisher connected us with publishers around the world. At Bloomsbury USA we have been lucky to work with our editor, Gillian Blake, who has been enthusiastic from the beginning and has provided an experienced hand. She, Ben Adams, and the Bloomsbury crew have improved our words and thoughts and kept us moving forward. Thanks are also due to Lisa Haney and Patrick Lane for beautiful illustrations and to Ken Catania, Pete Thompson, Ted Adelson, and Michael MacAskill for permission to use technical images.

We wrote a substantial part of the book at the Villa Serbelloni on the shores of Lake Como in Bellagio, Italy, an experience made possible by the Rockefeller Foundation and words of support from Jane Flint, Bob Horvitz, Charles Jennings, Olga Pellicer, Robert Sapolsky, and Shirley Tilghman. Pilar Palacia, Elena Ongania, and the rest of the Villa Serbelloni staff created an elegant but relaxed atmosphere for thinking, talking, and writing. Our fellow residents provided a great forum and we thank them all: Anne Waldman, Ed Bowes, Seemin Qayum, Sinclair Thomson, Raka Ray, Ashok Bardhan, Richard Cooper, Joan Kennelly, Jane Burbank, Fred Cooper, Russell Gordon, Jennifer Pierce, Dedre Gentner, Ken Forbus, David and Kathy Ringrose, Len and Gerry Pearlin, Bishakha Datta, Gautam Ojha, Sushil Sharma, Helen Roberts, Rodney Barker, Cyrus Cassells, Andrée Durieux-Smith, and Roger Smith.

Friends, colleagues, and students helped and encouraged us tremendously and were the source of invaluable suggestions, discussions, and corrections. We are especially grateful to Ralph Adolphs, Daphne Bavelier, Alim-Louis Benabid, Karen Bennett, Michael Berry, Ken Britten, Carlos Brody, Tom Carmichael, Gene Civillico, Mike DeWeese, David Eagleman, Neir Eshel, Michale Fee, Asif Ghazanfar, Mark Goldberg, Astrid Golomb, Liz Gould, David Grodberg, Patrick Hof, Hans Hofmann, Petr Janata, Danny Kahneman, Yevgenia Kozorovitskiy, Ivan Kreilkamp, Eric London, Zach Mainen, Eve Marder, David Matthews, Becca Moss, Eric Nestler, Elissa Newport, Bill Newsome, Bob Newsome, Yael Niv, Liz Phelps, Robert Provine, Kerry Ressler, Rebecca Saxe, Clarence Schutt, Steven Schultz, Mike Schwartz, Mike Shadlen, Debra Speert, David Stern, Chess Stetson, Russ Swerdlow, Ed Tenner, Leslie Vosshall, Larry Young, and Gayle Wittenberg. Sam thanks his entire laboratory for accommodating his preoccupation, especially Rebecca Khaitman for excellent assistance. The Princeton University library was an essential resource. Finally, we thank Ivan Kaminow for telling us about the cell phone trick. Any remaining problems with the science, of course, are our responsibility and not theirs.

Our spouses went far beyond the call of duty in supporting us and this project, keeping us as sane as possible. Sandra thanks Ken Britten for his tolerant amusement at the prospect of entertaining himself for yet another weekend while she worked on the book and for his enthusiastic contributions to many shared adventures. She also thanks her parents, Roger and Jan Aamodt, for teaching her that girls too can take risks in pursuit of their dreams. Sam thanks Becca Moss for her partnership, her aplomb in the face of yet another crazy idea that got out of hand, and for providing a light when things got dark. Finally, Sam thanks his parents, Chia-lin and Mary Wang, for planting the seeds of a lifelong love of science and learning.

Quiz

How Well Do You Know Your Brain?

Before you start reading this book, find out what you already know about your brain.

1) When are your last brain cells born?

(a) Before birth

(b) At age six

(c) Between the ages of eighteen and twenty-three

(d) In old age

2) Men and women have inborn differences in

(a) spatial reasoning

(b) strategies for navigation

(c) ability to leave the toilet seat down

(d) Both a and b

(e) Both b and c

3) Which of the following is not likely to improve brain function in old age?

(a) Eating fish with omega-3 fatty acids

(b) Getting regular exercise

(c) Drinking one or two glasses of red wine per day

(d) Drinking a whole bottle of red wine per day

4) Which of the following strategies is the best one for overcoming jet lag?

(a) Taking melatonin the night after you arrive at your destination

(b) Avoiding daylight for several days

(c) Getting sunlight in the afternoon at your destination

(d) Sleeping with the lights on

5) Your brain uses about as much energy as

(a) a refrigerator light

(b) a laptop computer

(c) an idling car

(d) a car moving down a freeway

6) Your friend is trying to tickle your belly. You can reduce the tickling sensation by

(a) putting your hand on his to follow the movement

(b) biting your knuckles

(c) tickling him back

(d) drinking a glass of water

7) Which of the following activities is likely to improve performance in school?

(a) Listening to classical music while you sleep

(b) Listening to classical music while you study

(c) Learning to play a musical instrument as a child

(d) Taking breaks from studying to play video games

(e) Both c and d

8) Which of the following things is a blow to the head least likely to cause?

(a) Loss of consciousness

(b) Memory loss

(c) Restoration of memory after suffering amnesia

(d) Personality change

9) Which of the following activities before a test might help you to perform better? (You may choose more than one.)

(a) Having a drink

(b) Having a cigarette

(c) Eating a candy bar

(d) Telling yourself with great conviction that you are good at this kind of test

10) You are in a noisy room, attempting to talk to your friend on your cell phone. To have a clearer conversation, you should

(a) talk more loudly

(b) cover one ear and listen through the other

(c) cover your ear when you talk

(d) cover the mouthpiece when you listen

11) Which of the following is an effective way to reduce anxiety?

(a) Antidepressant drugs

(b) Exercise

(c) Behavioral therapy

(d) All of the above

12) Which of the following is the hardest thing your brain does?

(a) Doing long division

(b) Looking at a photograph

(c) Playing chess

(d) Sleeping

13) Blind people are better than sighted people at which of the following?

(a) Understanding words

(b) Hearing sounds

(c) Remembering stories

(d) Training dogs

14) Your mother was improving your brain capacity when she told you which of the following things?

(a) Turn that music down

(b) Go out and play

(c) Practice your instrument

(d) All of the above

15) Memory starts to get worse in which decade of life?

(a) Thirties

(b) Forties

(c) Fifties

(d) Sixties

16) Which activities kill brain cells?

(a) Drinking three bottles of beer in an evening

(b) Smoking a joint

(c) Dropping acid

(d) All of the above

(e) None of the above

17) Which depiction of neurological damage is least realistic?

(a) Guy Pearce’s character Leonard in Memento

(b) Drew Barrymore in 50 First Dates

(c) Dory in Finding Nemo

(d) John Nash in A Beautiful Mind

18) What percentage of mammalian species are monogamous?

(a) 5%

(b) 25%

(c) 50%

(d) 90%

19) What percentage of your brain do you use?

(a) 10%

(b) 5% when you are sleeping, 20% when you are awake

(c) 100%

(d) Varies according to intelligence

20) When Einstein’s brain was compared with the average person’s, it

(a) was larger

(b) was indistinguishable in size

(c) had more folds on the surface

(d) had an extra part

Answers: 1) d, 2) d, 3) d, 4) c, 5) a, 6) a, 7) e, 8) c, 9) b and d, 10) d, 11) d, 12) b, 13) c, 14) d, 15) a, 16) e, 17) b, 18) a, 19) c, 20) b

Introduction

Your Brain: A User’s Guide

I used to think my brain was my most important organ. But then I thought: wait a minute, who’s telling me that?

—Emo Phillips

In our decades of studying and writing about neuroscience, we have often found ourselves discussing the brain in strange places: at the salon, in taxicabs, and even in the occasional elevator. Believe it or not, people don’t run away (usually). Instead, they ask us all sorts of interesting questions: When I drink, am I killing my brain cells? Does cramming for an exam work? Will playing music during pregnancy make my baby smarter? What is wrong with my teenager [or parent]? Why can’t you tickle yourself? Do men and women think differently? Can you really get amnesia from being hit on the head?

All these questions lead to your brain, the amazing three pounds in your skull that make you yourself. Your brain lets you watch a sunset, learn a language, tell a joke, recognize a friend, run from danger, and read this sentence.

In the last twenty years, neuroscientists have learned a lot about how your brain does all these things. It’s a complicated subject, but we think it doesn’t have to be intimidating. This book will give you the inside scoop on how your brain really works—and how you can help it work better.

Your brain has many ways of doing its job, including tricks and shortcuts that help it work efficiently—but may lead you to make predictable mistakes. By reading this book, you’ll find out how you accomplish the things you do every day. Along the way we’ll explode some of the myths that you might believe because everybody knows they’re true. For instance, you don’t really use only 10 percent of your brain. (Come on.)

Knowing your brain better can be both fun and useful. We will show you simple changes that will allow you to do more with your brain and help you lead a happier and more productive life. We’ll also show you how disease can damage your brain—and suggest ways to prevent or repair this damage.

This book is like a guided tour: we’ll see all the best sights and most important spots. But you don’t have to start at the beginning. You can dip in anywhere and read this book in small pieces because each chapter stands on its own. In each one, you’ll find fun facts, cocktail party-ready stories to amuse your friends, and practical tips to help you use your brain better.

• In part 1, we introduce the star of the show, your brain. We pull aside the curtain to show what is happening behind the scenes and explain how your brain helps you survive in the world.

• In part 2, we take a tour of your senses, explaining how you see, hear, touch, smell, and taste.

• In part 3, we show how your brain changes through life, from birth to old age.

• In part 4, we examine your brain’s emotional systems, focusing on how they help you navigate life effectively.

• In part 5, we discuss your reasoning abilities, including decision making, intelligence, and gender differences in cognition.

• In part 6, we examine altered states of your brain—consciousness, sleep, drugs and alcohol, and disease.

Leave this book by your bedside or on your coffee table, and dip in anywhere, anytime. We hope you’ll be enlightened and entertained, and that after reading a few pages you will want to read the whole book. Now pull up a chair and get ready to find out about your brain—and about yourself!

Part One

Your Brain and the World

Can You Trust Your Brain?

Gray Matter and the Silver Screen: Popular Metaphors of How the Brain Works

Thinking Meat: Neurons and Synapses

Fascinating Rhythms: Biological Clocks and Jet Lag

Bring Your Swimsuit: Weight Regulation

Chapter 1

Can You Trust Your Brain?

Your brain lies to you a lot. We’re sorry to have to break the news to you, but it’s true. Even when your brain is doing essential and difficult stuff, you’re not aware of most of what’s going on.

Your brain doesn’t intend to lie to you, of course. For the most part, it’s doing a great job, working hard to help you survive and accomplish your goals in a complicated world. Because you often have to react quickly to emergencies and opportunities alike, your brain usually aims to get a half-assed answer in a hurry rather than a perfect answer that takes a while to figure out. Combined with the world’s complexity, this means that your brain has to take shortcuts and make a lot of assumptions. Your brain’s lies are in your best interest—most of the time—but they also lead to predictable mistakes.

One of our goals is to help you understand the types of shortcuts and hidden assumptions that your brain uses to get you through life. We hope this knowledge will make it easier for you to predict when your brain is a source of reliable information and when it’s likely to mislead you.

The problems start right up front, when the brain takes in information from the world through the senses. Even if you are sitting quietly in a room, your brain receives far more information than it can hold on to, or than you need to decide how to act. You may be aware of the detailed pattern of colors in the rug, the photographs on the wall, and the sounds of birds outside. Your brain perceives many other aspects of the scene initially but quickly forgets them. Usually these things really aren’t important, so we don’t often notice how much information we lose. The brain commits many lies of omission, as it discards most of the information in the world as soon as it is deemed to be unremarkable.

Lawyers know this principle. Eyewitnesses are notoriously unreliable, in part because they imagine—as most of us do—that they see and remember more details than they really can. Lawyers can use this knowledge to discredit witnesses by tempting them to say they saw something that the lawyer can disprove, casting doubt on the rest of the witness’s testimony.

Did you know? Looking at a photograph is harder than playing chess

You may think that you know what your brain does, but you actually notice only a small fraction of its activity—and what your brain accomplishes behind your back is some of its hardest work. When computer scientists first began trying to write programs to mimic human abilities, they found that it was relatively easy to get computers to follow logic rules and do complex mathematics, but very hard to get them to figure out what they were seeing in a visual image or to move smoothly through the world. Today’s best computer chess programs can beat a grand master, at least some of the time, but any normal toddler can kick the butt of the top programs when it comes to making sense of the visual world.

One difficult step, as it turns out, is identifying individual objects in a visual scene. When we look at, say, a dinner table, it seems obvious that the water glass is one object that is in front of another object, like a vase of flowers, but this turns out to be a sophisticated calculation with many possible answers. You only notice this ambiguity occasionally, when you see something briefly enough to misidentify it, like when that rock in the middle of the dark road suddenly turns into the neighbor’s cat. The brain sorts out these possibilities based on its previous experience with objects, including having seen the two objects separately and in other combinations. Have you ever taken a picture in which a tree seemed to be growing out of someone’s head? When you snapped the photo, you didn’t notice the problem because your brain had efficiently separated the objects based on their different distances from your eyes. Later on, the two-dimensional photo didn’t contain the same information about distances, so it looked like the two objects were on top of each other.

In addition to throwing away information, the brain also has to decide whether to take shortcuts, depending on how it values speed against accuracy in a particular situation. Most of the time, your brain favors speed, interpreting events based on rules of thumb that are easy to apply but not always logical. The rest of the time, it uses the slow, careful approach that’s appropriate for doing math or solving logic puzzles. Psychologist Daniel Kahneman won the Nobel Prize in Economics for studying these rules of thumb and how they influence real-life behavior. (His longtime collaborator, Amos Tversky, passed away before he could share the honor.)

Did you know? Are we in our right minds?

When people talk about the right brain and the left brain, they’re referring to the two sides of the cortex. While there are some real differences in function between them, the distinctions are often misunderstood.

Most people’s speech is controlled by the left side of the brain, which is also responsible for mathematics and other forms of logical problem solving. Curiously, it is also the source of many misremembered or confabulated details, and it is the home of the interpreter discussed on the next page. All in all, the left side of the brain seems to have an intense need for logic and order—so intense that if something doesn’t make sense, it usually responds by inventing some plausible explanation.

The right side is much more literal and truthful when it reports what happened. It controls spatial perception and the analysis of objects by touch, and excels at visual-motor tasks. Rather than being artistic or emotional, the right brain is simply more grounded.

It’s a Joe Friday type, and if it could talk, it would probably say, Just the facts, ma’am.

The take-home message from their research is that logical thinking requires a lot of effort. For example, try to solve the following problem quickly: A bat and a ball together cost $1.10. The bat costs $1 more than the ball. How much does the ball cost? Most people say 10¢, which is intuitive but wrong. (The bat costs $1.05, and the ball costs 5¢.) Mental shortcuts like this are very common: in fact, people are likely to use them in almost all situations unless they’re strongly cued that they should be using logic instead. Most of the time, the intuitive answer is good enough to get by, even when it is wrong.

In everyday life, we’re not typically asked to solve logic problems, but we are often asked to make judgments about people we don’t know very well. Kahneman and Tversky used another approach to show that these judgments aren’t logical either. For example, they would start an experiment by telling people about Linda: Linda is thirty-one years old, single, outspoken, and very bright. She majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice and also participated in antinuclear demonstrations. Then they asked people to pick the phrase that seemed most likely to describe Linda from a carefully contrived list of traits.

Most people thought it was more probable that (a) Linda is a bank teller who is active in the feminist movement than (b) Linda is a bank teller. Choice (a) makes intuitive sense because many of Linda’s other characteristics—concern about social justice and so on—suggest that she might be active in the feminist movement. Yet that is not the right answer, because everyone who is (a) a bank teller who is active in the feminist movement is also (b) a bank teller. And of course the group in (b) includes other bank tellers who are reactionary or apathetic.

In such a case, even sophisticated participants like graduate students in statistics make the error of reaching a conclusion that directly contradicts logic. This strong tendency to attribute groups of related characteristics to people without much evidence is a quick way of estimating likely outcomes, but it may also be a root cause of many of the stereotypes and prejudices that are common in society.

To make matters worse, many of the stories we tell ourselves don’t even reflect what’s actually happening in our own heads. A famous study of brain-damaged patients demonstrates this idea. The patients had been treated for severe epilepsy by a surgical operation that disconnected the right and left halves of their brain’s cortex, to prevent seizures from spreading from one side to the other. This meant that the left half literally didn’t know what the right half was doing, and vice versa.

In one experiment, the scientists showed a picture of a chicken claw to the left side of a patient’s brain, where the language areas are located, and a picture of a snow scene to the right side of the brain, which cannot produce speech. Asked to pick a related image from another set of pictures, he correctly chose a shovel with his left hand (controlled by the right side of the brain) and a chicken with his right hand (controlled by the left side of the brain). When asked to explain his choices, he responded: Oh, that’s simple. The chicken claw goes with the chicken, and you need a shovel to clean out the chicken shed. The scientists concluded that the left side of the brain contains an interpreter whose job is to make sense of the world, even when it doesn’t understand what’s really happening.

These problems of throwing away information, taking mental shortcuts, and inventing plausible stories come together in what psychologists call