UPDATED AND EXPANDED

Includes link to Brain Rules film

NEW YORK TIMES BESTSELLER

J O H N M E D I N A

12 Principles for Surviving and Thriving

at Work, Home, and School

br in

rules

“Words leap off the page.”

— USA Today

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B o n u s m a t e r i a l o n l i n e

Film featuring John Medina

take a lively, 45-minute tour of the

12 original Brain rules for home, work,

and school—from “exercise boosts

brain power” to “sleep well, think well.”

Videos of parenting concepts

John medina hosts fun videos on talking

in parentese, the cookie experiment,

dealing with temper tantrums, and more.

Plus, take our parenting quiz.

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BRAIN RULES. Copyright © 2014 by John J. Medina.

All rights reserved. Printed in the United States of America.

No part of this book may be used or reproduced in any manner whatsoever

without written permission except in the case of brief quotations

embodied in critical articles or reviews.

Requests for permission should be addressed to:

Pear Press

P.O. Box 70525

Seattle, WA 98127-0525

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This book may be purchased for educational, business,

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www.pearpress.com

SECOND EDITION

Edited by Tracy Cutchlow

Designed by Greg Pearson

Library of Congress Cataloging-in-Publication Data

is available upon request.

ISBN-13: 978-0-9832633-7-1

10 9 8 7 6 5 4 3 2 1

Printed in the United States of America.

To Joshua and Noah

Gratitude, my dear boys, for constantly reminding me

that age is not something that matters unless you are cheese.

contents

12 Brain Rules

i

Introduction

1

Dumb things we do ~ The grump factor ~ Getting you in the loop ~ A brilliant

survival strategy ~ Your amazing brain

Exercise

17

Our brains love motion ~ The incredible test-score booster ~ Will you age like

Jim or like Frank? ~ How oxygen builds roads for the brain

Sleep

37

The brain doesn’t sleep to rest ~ Two armies at war in your head ~ How to

improve your performance 34 percent in 26 minutes ~ Which bird are you? ~

Sleep on it!

Stress

57

Stress is good, stress is bad ~ Villains and heroes in the toxic-stress battle ~ Why

the home matters to the workplace ~ Marriage intervention for happy couples

Wiring

83

Neurons slide, slither, and split ~ Experience makes the difference ~ Furious

brain development not once, but twice ~ The Jennifer Aniston neuron

Attention

103

Emotion matters ~ Why there is no such thing as multitasking ~ We pay great

attention to threats, sex, and pattern matching ~ The brain needs a break!

Memory

125

Memories are volatile ~ Details get splattered then pieced back together again

~ If you don’t repeat this within 30 seconds, you’ll forget it ~ Spaced repetition

cycles are key to remembering

Sensory integration

161

Lessons from a nightclub ~ How and why all of our senses work together ~

Multisensory learning means better remembering ~ What’s that smell?

Vision

181

Playing tricks on wine tasters ~ You see what your brain wants to see, and it

likes to make stuff up ~ Throw out your PowerPoint

Music

199

Bringing a man back to life ~ Listening and language skills ~ Fine-tuning

emotion detection and empathy ~ Music as therapy

Gender

223

Sexing humans ~ The difference between little girl best friends and little boy best

friends ~ Men favor gist when stressed; women favor details ~ A forgetting drug

Exploration

243

Babies are great scientists ~ Exploration is aggressive ~ Monkey see, monkey do

~ Curiosity is everything

acknowledgments

263

index

267

i

Brain Rules

survival

the human brain evolved, too.

exercise

exercise boosts brain power.

sleep

sleep well, think well.

stress

stressed brains don’t learn

the same way.

wiring

every brain is wired

differently.

attention

We don’t pay attention

to boring things.

memory

repeat to remember.

sensory integration

stimulate more of the senses.

vision

Vision trumps all other senses.

music

study or listen

to boost cognition.

gender

male and female brains

are different.

exploration

We are powerful

and natural explorers.

1. INTRODUCTION

1

go ahead and multiply the number 8,388,628 x 2 in your head.

Can you do it in a few seconds? There is a young man who can

double that number 24 times in the space of a few seconds. He gets

it right every time. There is a boy who can tell you the precise time

of day at any moment, even in his sleep. There is a girl who can cor-

rectly determine the exact dimensions of an object 20 feet away.

There is a child who at age 6 drew such vivid and complex pictures,

some people ranked her version of a galloping horse over one drawn

by da Vinci. Yet none of these children have an IQ greater than 70.

The brain is an amazing thing.

Your brain may not be nearly so odd, but it is no less extraordi-

nary. Easily the most sophisticated information-transfer system on

Earth, your brain is fully capable of taking the little black squiggles in

this book and deriving meaning from them. To accomplish this mir-

acle, your brain sends jolts of electricity crackling through hundreds of

miles of wires composed of brain cells so small that thousands of them

could fit into the period at the end of this sentence. You accomplish

Introduction

BRAIN RULES

2

all of this in less time than it takes you to blink. Indeed, you have just

done it. What’s equally incredible, given our intimate association with

it, is this: Most of us have no idea how our brain works.

12 Brain Rules

My goal is to introduce you to 12 things we know about how the

brain works. I call these Brain Rules. For each rule, I present the sci-

ence, introduce you to the researchers behind it, and then offer ideas

for how the rule might apply to our daily lives, especially at work and

school. The brain is complex, and I am taking only slivers of informa-

tion from each subject—not comprehensive but, I hope, accessible.

Here is a sampling of the ideas you’ll encounter:

• We are not used to sitting at a desk for eight hours a day. From

an evolutionary perspective, our brains developed while we walked

or ran as many as 12 miles a day. The brain still craves this experi-

ence. That’s why exercise boosts brain power (Brain Rule #2) in

sedentary populations like our own. Exercisers outperform couch

potatoes in long-term memory, reasoning, attention, and problem-

solving tasks.

• As you no doubt have noticed if you’ve ever sat through a typ-

ical PowerPoint presentation, people don’t pay attention to boring

things (Brain Rule #6). You’ve got seconds to grab someone’s atten-

tion and only 10 minutes to keep it. At 9 minutes and 59 seconds,

you must do something to regain attention and restart the clock—

something emotional and relevant. Also, the brain needs a break.

That’s why I use stories in this book to make many of my points.

• Ever feel tired about three o’clock in the afternoon? That’s

because your brain really wants to take a nap. You might be more

productive if you did. In one study, a 26-minute nap improved NASA

pilots’ performance by 34 percent. And whether you get enough rest

at night affects your mental agility the next day. Sleep well, think well

(Brain Rule #3).

1. INTRODUCTION

3

• We’ll meet a man who can remember everything he reads

after seeing the words just once. Most of us do more forgetting than

remembering, of course, and that’s why we must repeat to remember

(Brain Rule #7). When you understand the brain’s rules for memory,

you’ll see why I want to destroy the notion of homework.

• We’ll find out why the terrible twos only look like active rebel-

lion but actually are a child’s powerful urge to explore. Babies may

not have a lot of knowledge about the world, but they know a whole

lot about how to get it. We are powerful and natural explorers (Brain

Rule #12). This never leaves us, despite the artificial environments

we’ve built for ourselves.

The grump factor

I am a nice guy, but I am a grumpy scientist. For a study to appear

in this book, it has to pass what some of my clients call MGF: the

Medina Grump Factor. That means the supporting research for

each of my points must first be published in a peer-reviewed

journal and then successfully replicated. Many of the studies have

been replicated dozens of times. (To stay as reader-friendly as pos-

sible, extensive references are not in this book but can be found at

www.brainrules.net/references.)

No prescriptions

There’s a great deal we don’t know about the brain. I am a develop-

mental molecular biologist specializing in psychiatric disorders.

I have been a private consultant for most of my professional life,

working on countless research projects beyond the lab bench. Over

and over in my career, I have seen what a distance there is between a

gene (one’s DNA instructions) and a behavior (how a person actually

acts). It’s very hard to say with certainty that a specific behavior is

caused by a specific gene, or that changing X behavior will produce Y

result. Occasionally, I would run across articles and books that made

startling claims based on “recent advances” in brain science about

BRAIN RULES

4

how we should teach people and do business. The Mozart Effect

comes to mind: the popular idea that listening to classical music

makes students better at math. Or the notion that analytical people

are “left brain” people and creative people are “right brain” people,

and each must be managed accordingly. Sometimes I would panic,

wondering if the authors were reading some literature totally off my

radar screen. I speak several dialects of brain science, and I knew

nothing from those worlds capable of dictating best practices for

education and business. In truth, if we ever fully understood how the

human brain knew how to pick up a glass of water, it would repre-

sent a major achievement. There was no need for me to panic. Brain

research still cannot without equivocation tell us how to become

better teachers, parents, business leaders, or students. In addition to

the ideas you’ll find within each chapter, I end each chapter a few

more potential ways to apply the research in our daily lives. But these

are not prescriptions. They are hypotheses. If you try them, you will

be doing your own little research project to see whether they work

for you.

Back to the jungle

What we know about the brain comes from biologists who study

brain tissues, experimental psychologists who study behavior, cog-

nitive neuroscientists who study how the first relates to the second,

and evolutionary biologists. Though we know precious little about

how the brain works, our evolutionary history tells us this: The brain

appears to be designed to (1) solve problems (2) related to surviving

(3) in an unstable outdoor environment, and (4) to do so in nearly

constant motion. I call this the brain’s performance envelope.

Each subject in this book—exercise, sleep, stress, wiring, atten-

tion, memory, sensory integration, vision, music, gender, and

exploration—relates to this performance envelope. We were in

motion, getting lots of exercise. Environmental instability led to the

extremely flexible way our brains are wired, allowing us to solve

1. INTRODUCTION

5

problems through exploration. To survive in the great outdoors, we

needed to learn from our mistakes. That meant paying attention to

certain things at the expense of others, and it meant creating mem-

ories in a particular way. Though we have been stuffing them into

classrooms and cubicles for decades, our brains actually were built to

survive in jungles and grasslands. We have not outgrown this.

Because we don’t fully understand how our brains work, we do

dumb things. We try to talk on our cell phones and drive at the same

time, even though it is literally impossible for our brains to multi-

task when it comes to paying attention. We have created high-stress

office environments, even though a stressed brain is significantly

less productive than a non-stressed brain. Our schools are designed

so that most real learning has to occur at home. Taken together,

what do the studies in this book show? Mostly this: If you wanted to

create an education environment that was directly opposed to what

the brain was good at doing, you probably would design something

like a classroom. If you wanted to create a business environment that

was directly opposed to what the brain was good at doing, you prob-

ably would design something like a cubicle. And if you wanted to

change things, you might have to tear down both and start over.

Blame it on the fact that brain scientists rarely have a conversa-

tion with teachers and business professionals, education majors and

accountants, superintendents and CEOs. Unless you have the Journal

of Neuroscience sitting on your coffee table, you’re out of the loop.

This book is meant to get you into the loop.

Survival: Why your brain is so amazing

Brain Rule #1: The human brain evolved, too

When he was 4, my son Noah picked up a stick in our backyard and

showed it to me. “Nice stick you have there, young fellow,” I said. He

replied earnestly, “That’s not a stick. That’s a sword! Stick ’em up!”

I raised my hands to the air. We both laughed. As I went back into

BRAIN RULES

6

the house, I realized my son had just displayed virtually every unique

thinking ability a human possesses—one that took several million

years to manufacture. And he did so in less than two seconds. Heavy

stuff for a 4-year-old. Other animals have powerful cognitive abilities,

too, and yet there is something qualitatively different about the way

humans think. How and why did our brains evolve this way?

A survival strategy

It all comes down to sex. Our bodies latched on to any genetic

adaptation that helped us survive long enough to pass our genes on

to the next generation. There’s no bigger rule in biology than evolu-

tion through natural selection, and the brain is a biological tissue. So

it too follows the rule of natural selection.

There are two ways to beat the cruelty of a harsh environment:

You can become stronger or you can become smarter. We did the

latter. It seems most improbable that such a physically weak species

could take over the planet not by adding muscles to our skeletons

but by adding neurons to our brains. But we did, and scientists have

expended a great deal of effort trying to figure out how. I want to

explore four major concepts that not only set the stage for all of the

Brain Rules, but also explain how we came to conquer the world.

We can make things up

One trait really does separate us from the gorillas: the ability to

use symbolic reasoning. When we see a five-sided geometric shape,

we’re not stuck perceiving it as a pentagon. We can just as easily

perceive the US military headquarters. Or a Chrysler minivan. Our

brains can behold a symbolic object as real by itself and yet, simul-

taneously, also representing something else. That’s what my son

was doing when he brandished his stick sword. Researcher Judy

DeLoache calls it Dual Representational Theory. Stated formally, it

describes our ability to attribute characteristics and meanings to

things that don’t actually possess them. Stated informally, we can

1. INTRODUCTION

7

make things up that aren’t there. We are human because we can

fantasize.

We are so good at dual representation, we combine symbols to

derive layers of meaning. It gives us the capacity for language, and

for writing down that language. It gives us the capacity to reason

mathematically. It gives us the capacity for art. Combinations

of circles and squares become geometry and Cubist paintings.

Combinations of dots and squiggles become music and poetry. There

is an unbroken intellectual line between symbolic reasoning and

the ability to create culture. And no other creature is capable of

doing it.

The all-important human trait of symbolic reasoning helped our

species not only survive but thrive. Our evolutionary ancestors didn’t

have to keep falling into the same quicksand pit if they could tell

others about it; even better if they learned to put up warning signs.

With words, with language, we could extract a great deal of knowl-

edge about our living situation without always having to experi-

ence its harsh lessons directly. It makes sense that once our species

evolved to have symbolic reasoning, we kept it. So what was it about

our environment that would give a survival advantage to those who

could reason symbolically?

We adapted to variation itself

Most of what we know about the intellectual progress of our

species is based on evidence of toolmaking. That’s not necessarily

the most accurate indicator, but it’s the best we’ve got. For the first

few million years, the record is not very impressive: We mostly just

grabbed rocks and smashed them into things. Scientists, perhaps

trying to salvage some of our dignity, called these stones “hand axes.”

A million years later, we still grabbed “hand axes,” but we began to

smash them into other rocks, making them more pointed. Now

we had sharper rocks. It wasn’t much, but it was enough to begin

untethering ourselves from a sole reliance on our East African womb,

BRAIN RULES

8

and indeed any other ecological niche. Then things started to get

interesting. We created fire and started cooking our food. Eventually,

we migrated out of Africa in successive waves, our direct Homo

sapiens ancestors making the journey as little as 100,000 years ago.

Then, 40,000 years ago, something almost unbelievable happened.

Our ancestors suddenly took up painting and sculpture, creating fine

art and jewelry. This change was both abrupt and profound. Thirty-

seven thousand years later, we were making pyramids. Five thousand

years after that, rocket fuel.

Many scientists think our growth spurt can be explained by

the onset of dual-representation ability. And many think our dual-

representation ability—along with physical changes that precipitated

it—can be explained by a nasty change in the weather.

Most of human prehistory occurred in junglelike climates:

steamy, humid, and in dire need of air-conditioning. This was com-

fortably predictable. Then the climate changed. Ice cores taken

from Greenland show that the climate staggers from being unbear-

ably hot to being sadistically cold. As little as 100,000 years ago,

you could be born in a nearly arctic environment but then, mere

decades later, be taking off your loincloth to catch the golden rays

of the grassland sun. Such instability was bound to have a powerful

effect on any creature forced to endure it. Most could not. The rules

for survival were changing, and a new class of creatures would start

to fill the vacuum created as more and more of their roommates

died out.

The change was enough to shake us out of our comfort-

able trees, but it wasn’t violent enough to kill us when we landed.

Landing was only the beginning of the hard work, however. Faced

with grasslands rather than trees, we were rudely introduced to the

idea of “flat.” We quickly discovered that our new digs were already

occupied. The locals had co-opted the food sources, and most of

them were stronger and faster than we were. It is disconcerting to

think that we started our evolutionary journey on an unfamiliar

1. INTRODUCTION

9

horizontal plane with the words “Eat me, I’m prey” taped to our evo-

lutionary butts.

You might suspect that the odds against our survival were great.

You would be right. The founding popu ...