Principal The Power of Habit

The Power of Habit

Ano: 2012
Língua: english
Páginas: 258
ISBN 13: 978-0-679-60385-6
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The Power of Habit is a work of nonfiction. Nonetheless, some names and personal characteristics of individuals or events
have been changed in order to disguise identities.
Any resulting resemblance to persons living or dead is entirely

coincidental and unintentional.

Copyright © 2012 by Charles Duhigg
All rights reserved.
Published in the United States by Random House, an imprint of

RANDOM HOUSE and colophon are registered trademarks of Random House, Inc.
Library of Congress Cataloging-in-Publication Data
Duhigg, Charles.

The power of habit : why we do what we do in life and business / by Charles Duhigg.
p. cm.

Includes bibliographical references and index.
eISBN: 978-0-679-60385-6

1. Habit. 2. Habit—Social aspects. 3. Change (Psychology) I. Title.
BF335.D76 2012



Illustration on this page by Andrew Pole

All other illustrations by Anton Ioukhnovets


Title Page
The Habit Cure

The Habits of Individuals
How Habits Work
How to Create New Habits
Why Transformation Occurs

The Habits of Successful Organizations
Which Habits Matter Most
When Willpower Becomes Automatic
How Leaders Create Habits Through Accident
and Design

When Companies Predict (and Manipulate) Habits

The Habits of Societies
How Movements Happen
Are We Responsible for Our Habits?

A Reader’s Guide to Using These Ideas
A Note on Sources


The Habit Cure

She was the scientists’ favorite participant.
Lisa Allen, according to her le, was thirty-four years old, had started smoking and
her le, Lisa had no outstanding debts, didn’t drink, and was in her thirty-ninth month
at a graphic design firm.
“How long since your last cigarette?” one of the physicians asked, starting down the
list of questions Lisa answered every time she came to this laboratory outside Bethesda,
“Almost four years,” she said, “and I’ve lost sixty pounds and run a marathon since
then.” She’d also started a master’s degree and bought a home. It had been an eventful
The scientists in the room included neurologists, psychologists, geneticists, and a
sociologist. For the past three years, with funding from the National Institutes of Health,
they had poked and prodded Lisa and more than two dozen other former smokers,
chronic overeaters, problem drinkers, obsessive shoppers, and people with other
destructive habits. All of the participants had one thing in common: They had remade
their lives in relatively short periods of time. The researchers wanted to understand
how. So they measured subjects’ vital signs, installed video cameras inside their homes
to watch their daily routines, sequenced portions of their DNA, and, with technologies
that allowed them to peer inside people’s skulls in real time, watched as blood and
electrical impulses owed through their brains while they were exposed to temptations
such as cigarette smoke and lavish meals.prl.1 The researchers’ goal was to gure out
how habits work on a neurological level—and what it took to make them change.
“I know you’ve told this story a dozen times,” the doctor said to Lisa, “but some of my
gave up cigarettes?”
“Sure,” Lisa said. “It started in Cairo.” The vacation had been something of a rash
decision, she explained. A few months earlier, her husband had come home from work
hanging up. Then there was the evening Lisa showed up at the girlfriend’s house, drunk,

“It wasn’t a great time for me,” Lisa said. “I had always wanted to see the pyramids,
and my credit cards weren’t maxed out yet, so … ”
On her rst morning in Cairo, Lisa woke at dawn to the sound of the call to prayer
from a nearby mosque. It was pitch black inside her hotel room. Half blind and jetlagged, she reached for a cigarette.
She was so disoriented that she didn’t realize—until she smelled burning plastic—that
angry, all at once. Lying in bed, she broke down. “It was like this wave of sadness,” she
said. “I felt like everything I had ever wanted had crumbled. I couldn’t even smoke
“And then I started thinking about my ex-husband, and how hard it would be to nd
felt all the time. I got up and knocked over a water jug and it shattered on the oor,
least one thing I could control.”
She showered and left the hotel. As she rode through Cairo’s rutted streets in a taxi
the desert.
the bank. She didn’t know the name of the desert she was looking at or if such a trip
expedition, she was certain she would have to make sacrifices.
In particular, she would need to quit smoking.
When Lisa nally made her way across the desert eleven months later—in an airconditioned and motorized tour with a half-dozen other people, mind you—the caravan
radios that throwing in a carton of cigarettes wouldn’t have made much of a difference.
But in the taxi, Lisa didn’t know that. And to the scientists at the laboratory, the
details of her trek weren’t relevant. Because for reasons they were just beginning to
understand, that one small shift in Lisa’s perception that day in Cairo—the conviction
that she had to give up smoking to accomplish her goal—had touched o a series of
buy a house, and get engaged. Eventually she was recruited into the scientists’ study,
and when researchers began examining images of Lisa’s brain, they saw something

remarkable: One set of neurological patterns—her old habits—had been overridden by
—at rst. Everyone in the study had gone through a similar process. By focusing on one
reprogram the other routines in her life, as well.
It’s not just individuals who are capable of such shifts. When companies focus on
changing habits, whole organizations can transform. Firms such as Procter & Gamble,
Starbucks, Alcoa, and Target have seized on this insight to in uence how work gets
don e, how employees communicate, and—without customers realizing it—the way
people shop.
“I want to show you one of your most recent scans,” a researcher told Lisa near the
end of her exam. He pulled up a picture on a computer screen that showed images from
inside her head. “When you see food, these areas”—he pointed to a place near the
center of her brain—“which are associated with craving and hunger, are still active.
Your brain still produces the urges that made you overeat.
“However, there’s new activity in this area”—he pointed to the region closest to her
forehead—“where we believe behavioral inhibition and self-discipline starts. That
activity has become more pronounced each time you’ve come in.”
Lisa was the scientists’ favorite participant because her brain scans were so
compelling, so useful in creating a map of where behavioral patterns—habits—reside
within our minds. “You’re helping us understand how a decision becomes an automatic
behavior,” the doctor told her.
Everyone in the room felt like they were on the brink of something important. And
they were.
When you woke up this morning, what did you do rst? Did you hop in the shower,
teeth before or after you toweled o ? Tie the left or right shoe rst? What did you say to
memo? Salad or hamburger for lunch? When you got home, did you put on your
“All our life, so far as it has de nite form, is but a mass of habits,” William James
wrote in 1892.prl.2 Most of the choices we make each day may feel like the products of
nancial security, and happiness. One paper published by a Duke

performed each day weren’t actual decisions, but habits.prl.3
William James—like countless others, from Aristotle to Oprah—spent much of his life
trying to understand why habits exist. But only in the past two decades have scientists
and marketers really begun understanding how habits work—and more important, how
they change.
This book is divided into three parts. The rst section focuses on how habits emerge
push toothbrushing from an obscure practice into a national obsession. It shows how
Procter & Gamble turned a spray named Febreze into a billion-dollar business by taking
advantage of consumers’ habitual urges, how Alcoholics Anonymous reforms lives by
attacking habits at the core of addiction, and how coach Tony Dungy reversed the
fortunes of the worst team in the National Football League by focusing on his players’
automatic reactions to subtle on-field cues.
The second part examines the habits of successful companies and organizations. It
details how an executive named Paul O’Neill—before he became treasury secretary—
remade a struggling aluminum manufacturer into the top performer in the Dow Jones
Industrial Average by focusing on one keystone habit, and how Starbucks turned a high
school dropout into a top manager by instilling habits designed to strengthen his
willpower. It describes why even the most talented surgeons can make catastrophic
mistakes when a hospital’s organizational habits go awry.
understand how they work.
This book draws on hundreds of academic studies, interviews with more than three
hundred scientists and executives, and research conducted at dozens of companies. (For
and It focuses on habits as they are technically de ned:
to eat and what to focus on when we got to the o ce, how often to have a drink or

rst became interested in the science of habits eight years ago, as a newspaper

reporter in Baghdad. The U.S. military, it occurred to me as I watched it in action, is one
of the biggest habit-formation experiments in history.prl.4 Basic training teaches soldiers
carefully designed habits for how to shoot, think, and communicate under re. On the
battle eld, every command that’s issued draws on behaviors practiced to the point of
automation. The entire organization relies on endlessly rehearsed routines for building
bases, setting strategic priorities, and deciding how to respond to attacks. In those early
days of the war, when the insurgency was spreading and death tolls were mounting,
commanders were looking for habits they could instill among soldiers and Iraqis that
might create a durable peace.
I had been in Iraq for about two months when I heard about an o cer conducting an
impromptu habit modi cation program in Kufa, a small city ninety miles south of the
capital. He was an army major who had analyzed videotapes of recent riots and had
identi ed a pattern: Violence was usually preceded by a crowd of Iraqis gathering in a
bottle and all hell would break loose.
grew in size. Some people started chanting angry slogans. Iraqi police, sensing trouble,
radioed the base and asked U.S. troops to stand by. At dusk, the crowd started getting
restless and hungry. People looked for the kebab sellers normally lling the plaza, but
P.M ., everyone was gone.
When I visited the base near Kufa, I talked to the major. You wouldn’t necessarily
think about a crowd’s dynamics in terms of habits, he told me. But he had spent his
entire career getting drilled in the psychology of habit formation.
At boot camp, he had absorbed habits for loading his weapon, falling asleep in a war
zone, maintaining focus amid the chaos of battle, and making decisions while exhausted
and overwhelmed. He had attended classes that taught him habits for saving money,
exercising each day, and communicating with bunkmates. As he moved up the ranks, he
learned the importance of organizational habits in ensuring that subordinates could
make decisions without constantly asking permission, and how the right routines made
it easier to work alongside people he normally couldn’t stand. And now, as an
impromptu nation builder, he was seeing how crowds and cultures abided by many of
the same rules. In some sense, he said, a community was a giant collection of habits
occurring among thousands of people that, depending on how they’re in uenced, could
result in violence or peace. In addition to removing the food vendors, he had launched
dozens of di erent experiments in Kufa to in uence residents’ habits. There hadn’t been
a riot since he arrived.
major told me. “It’s changed everything about how I see the world. You want to fall

triggers to make it a routine. I drill my kids on this stu . My wife and I write out habit
plans for our marriage. This is all we talk about in command meetings. Not one person
in Kufa would have told me that we could in uence crowds by taking away the kebab
stands, but once you see everything as a bunch of habits, it’s like someone gave you a
flashlight and a crowbar and you can get to work.”
The major was a small man from Georgia. He was perpetually spitting either
sun ower seeds or chewing tobacco into a cup. He told me that prior to entering the
military, his best career option had been repairing telephone lines, or, possibly,
becoming a methamphetamine entrepreneur, a path some of his high school peers had
chosen to less success. Now, he oversaw eight hundred troops in one of the most
sophisticated fighting organizations on earth.
“I’m telling you, if a hick like me can learn this stu , anyone can. I tell my soldiers all
the time, there’s nothing you can’t do if you get the habits right.”
ways we couldn’t have imagined fty years ago. We now know why habits emerge, how
parts and rebuild them to our speci cations. We understand how to make people eat
less, exercise more, work more e ciently, and live healthier lives. Transforming a habit
isn’t necessarily easy or quick. It isn’t always simple.
But it is possible. And now we understand how.

How Habits Work

shade over six feet tall, and neatly dressed in a blue button-down shirt.1.1 His thick white
hair would have inspired envy at any ftieth high school reunion. Arthritis caused him
to limp slightly as he paced the laboratory’s hallways, and he held his wife’s hand,
About a year earlier, Eugene Pauly, or “E.P.” as he would come to be known in
medical literature, had been at home in Playa del Rey, preparing for dinner, when his
wife mentioned that their son, Michael, was coming over.
“Who’s Michael?” Eugene asked.1.2
“Your child,” said his wife, Beverly. “You know, the one we raised?”
Eugene looked at her blankly. “Who is that?” he asked.
The next day, Eugene started vomiting and writhing with stomach cramps. Within
twenty-four hours, his dehydration was so pronounced that a panicked Beverly took him
to the emergency room. His temperature started rising, hitting 105 degrees as he
sweated a yellow halo of perspiration onto the hospital’s sheets. He became delirious,
then violent, yelling and pushing when nurses tried to insert an IV into his arm. Only
after sedation was a physician able to slide a long needle between two vertebra in the
small of his back and extract a few drops of cerebrospinal fluid.
The doctor performing the procedure sensed trouble immediately. The uid
surrounding the brain and spinal nerves is a barrier against infection and injury. In
healthy individuals, it is clear and quick owing, moving with an almost silky rush
through a needle. The sample from Eugene’s spine was cloudy and dripped out
sluggishly, as if lled with microscopic grit.1.3 When the results came back from the
laboratory, Eugene’s physicians learned why he was ill: He was su ering from viral
fever blisters, and mild infections on the skin. In rare cases, however, the virus can
make its way into the brain, in icting catastrophic damage as it chews through the
delicate folds of tissue where our thoughts, dreams—and according to some, souls—
Eugene’s doctors told Beverly there was nothing they could do to counter the damage

already done, but a large dose of antiviral drugs might prevent it from spreading.
Eugene slipped into a coma and for ten days was close to death. Gradually, as the drugs
fought the disease, his fever receded and the virus disappeared. When he nally awoke,
he was weak and disoriented and couldn’t swallow properly. He couldn’t form sentences
and would sometimes gasp, as if he had momentarily forgotten how to breathe. But he
was alive.
Eventually, Eugene was well enough for a battery of tests. The doctors were amazed
to nd that his body—including his nervous system—appeared largely unscathed. He
could move his limbs and was responsive to noise and light. Scans of his head, though,
revealed ominous shadows near the center of his brain. The virus had destroyed an oval
of tissue close to where his cranium and spinal column met. “He might not be the person
you remember,” one doctor warned Beverly. “You need to be ready if your husband is
Eugene was moved to a di erent wing of the hospital. Within a week, he was
swallowing easily. Another week, and he started talking normally, asking for Jell-O and
salt, ipping through television channels and complaining about boring soap operas. By
the time he was discharged to a rehabilitation center ve weeks later, Eugene was
walking down hallways and o ering nurses unsolicited advice about their weekend
“I don’t think I’ve ever seen anyone come back like this,” a doctor told Beverly. “I
don’t want to raise your hopes, but this is amazing.”
Beverly, however, remained concerned. In the rehab hospital it became clear that the
disease had changed her husband in unsettling ways. Eugene couldn’t remember which
day of the week it was, for instance, or the names of his doctors and nurses, no matter
how many times they introduced themselves. “Why do they keep asking me all these
questions?” he asked Beverly one day after a physician left his room. When he nally
returned home, things got even stranger. Eugene didn’t seem to remember their friends.
He had trouble following conversations. Some mornings, he would get out of bed, walk
into the kitchen, cook himself bacon and eggs, then climb back under the covers and
turn on the radio. Forty minutes later, he would do the same thing: get up, cook bacon
and eggs, climb back into bed, and fiddle with the radio. Then he would do it again.
Alarmed, Beverly reached out to specialists, including a researcher at the University of
California, San Diego, who specialized in memory loss. Which is how, on a sunny fall
day, Beverly and Eugene found themselves in a nondescript building on the university’s
campus, holding hands as they walked slowly down a hallway. They were shown into a
small exam room. Eugene began chatting with a young woman who was using a
“Having been in electronics over the years, I’m amazed at all this,” he said, gesturing
at the machine she was typing on. “When I was younger, that thing would have been in
a couple of six-foot racks and taken up this whole room.”
The woman continued pecking at the keyboard. Eugene chuckled.
“That is incredible,” he said. “All those printed circuits and diodes and triodes. When I
was in electronics, there would have been a couple of six-foot racks holding that thing.”

A scientist entered the room and introduced himself. He asked Eugene how old he
“Oh, let’s see, fifty-nine or sixty?” Eugene replied. He was seventy-one years old.
The scientist started typing on the computer. Eugene smiled and pointed at it. “That is
really something,” he said. “You know, when I was in electronics there would have been
a couple of six-foot racks holding that thing!”
The scientist was fty-two-year-old Larry Squire, a professor who had spent the past
three decades studying the neuroanatomy of memory. His specialty was exploring how
the brain stores events. His work with Eugene, however, would soon open a new world
to him and hundreds of other researchers who have reshaped our understanding of how
habits function. Squire’s studies would show that even someone who can’t remember his
own age or almost anything else can develop habits that seem inconceivably complex—
until you realize that everyone relies on similar neurological processes every day. His
and others’ research would help reveal the subconscious mechanisms that impact the
countless choices that seem as if they’re the products of well-reasoned thought, but
actually are influenced by urges most of us barely recognize or understand.
By the time Squire met Eugene, he had already been studying images of his brain for
weeks. The scans indicated that almost all the damage within Eugene’s skull was limited
to a ve-centimeter area near the center of his head. The virus had almost entirely
destroyed his medial temporal lobe, a sliver of cells which scientists suspected was
responsible for all sorts of cognitive tasks such as recall of the past and the regulation of
some emotions. The completeness of the destruction didn’t surprise Squire—viral
encephalitis consumes tissue with a ruthless, almost surgical, precision. What shocked
him was how familiar the images seemed.
Thirty years earlier, as a PhD student at MIT, Squire had worked alongside a group
studying a man known as “H.M.,” one of the most famous patients in medical history.
When H.M.—his real name was Henry Molaison, but scientists shrouded his identity
throughout his life—was seven years old, he was hit by a bicycle and landed hard on his
head.1.4, 1.5, 1.6 Soon afterward, he developed seizures and started blacking out. At
sixteen, he had his rst grand mal seizure, the kind that a ects the entire brain; soon, he
was losing consciousness up to ten times a day.
By the time he turned twenty-seven, H.M. was desperate. Anticonvulsive drugs hadn’t
helped. He was smart, but couldn’t hold a job.1.7 He still lived with his parents. H.M.
wanted a normal existence. So he sought help from a physician whose tolerance for
experimentation outweighed his fear of malpractice. Studies had suggested that an area
of the brain called the hippocampus might play a role in seizures. When the doctor
proposed cutting into H.M.’s head, lifting up the front portion of his brain, and, with a
small straw, sucking out the hippocampus and some surrounding tissue from the interior
of his skull, H.M.1.8, 1.9 gave his consent.
The surgery occurred in 1953, and as H.M. healed, his seizures slowed. Almost
immediately, however, it became clear that his brain had been radically altered. H.M.
knew his name and that his mother was from Ireland. He could remember the 1929
stock market crash and news reports about the invasion of Normandy. But almost

everything that came afterward—all the memories, experiences, and struggles from
most of the decade before his surgery—had been erased. When a doctor began testing
H.M.’s memory by showing him playing cards and lists of numbers, he discovered that
H.M. couldn’t retain any new information for more than twenty seconds or so.
From the day of his surgery until his death in 2008, every person H.M. met, every
song he heard, every room he entered, was a completely fresh experience. His brain was
frozen in time. Each day, he was befuddled by the fact that someone could change the
television channel by pointing a black rectangle of plastic at the screen. He introduced
himself to his doctors and nurses over and over, dozens of times each day.1.10
“I loved learning about H.M., because memory seemed like such a tangible, exciting
way to study the brain,” Squire told me. “I grew up in Ohio, and I can remember, in rst
grade, my teacher handing everyone crayons, and I started mixing all the colors
together to see if it would make black. Why have I kept that memory, but I can’t
remember what my teacher looked like? Why does my brain decide that one memory is
more important than another?”
When Squire received the images of Eugene’s brain, he marveled at how similar it
seemed to H.M.’s. There were empty, walnut-sized chunks in the middle of both their
heads. Eugene’s memory—just like H.M.’s—had been removed.
As Squire began examining Eugene, though, he saw that this patient was di erent
from H.M. in some profound ways. Whereas almost everyone knew within minutes of
meeting H.M. that something was amiss, Eugene could carry on conversations and
perform tasks that wouldn’t alert a casual observer that anything was wrong. The
e ects of H.M.’s surgery had been so debilitating that he was institutionalized for the
remainder of his life. Eugene, on the other hand, lived at home with his wife. H.M.
couldn’t really carry on conversations. Eugene, in contrast, had an amazing knack for
guiding almost any discussion to a topic he was comfortable talking about at length,
such as satellites—he had worked as a technician for an aerospace company—or the
Squire started his exam of Eugene by asking him about his youth. Eugene talked about
the town where he had grown up in central California, his time in the merchant
marines, a trip he had taken to Australia as a young man. He could remember most of
the events in his life that had occurred prior to about 1960. When Squire asked about
later decades, Eugene politely changed the topic and said he had trouble recollecting
some recent events.
Squire conducted a few intelligence tests and found that Eugene’s intellect was still
sharp for a man who couldn’t remember the last three decades. What’s more, Eugene
still had all the habits he had formed in his youth, so whenever Squire gave him a cup of
water or complimented him on a particularly detailed answer, Eugene would thank him
and o er a compliment in return. Whenever someone entered the room, Eugene would
introduce himself and ask about their day.
But when Squire asked Eugene to memorize a string of numbers or describe the
hallway outside the laboratory’s door, the doctor found his patient couldn’t retain any
new information for more than a minute or so. When someone showed Eugene photos of

his grandchildren, he had no idea who they were. When Squire asked if he remembered
getting sick, Eugene said he had no recollection of his illness or the hospital stay. In
fact, Eugene almost never recalled that he was su ering from amnesia. His mental
image of himself didn’t include memory loss, and since he couldn’t remember the injury,
he couldn’t conceive of anything being wrong.
In the months after meeting Eugene, Squire conducted experiments that tested the
limits of his memory. By then, Eugene and Beverly had moved from Playa del Rey to
San Diego to be closer to their daughter, and Squire often visited their home for his
exams. One day, Squire asked Eugene to sketch a layout of his house. Eugene couldn’t
door to the bathroom. A few minutes later, the toilet ushed, the faucet ran, and
At the time, no one wondered how a man who couldn’t draw a map of his home was
able to nd the bathroom without hesitation. But that question, and others like it, would
eventually lead to a trail of discoveries that has transformed our understanding of
habits’ power.1.11 It would help spark a scienti c revolution that today involves
hundreds of researchers who are learning, for the rst time, to understand all the habits
that influence our lives.
As Eugene sat at the table, he looked at Squire’s laptop.
“That’s amazing,” he said, gesturing at the computer. “You know, when I was in
In the rst few weeks after they moved into their new house, Beverly tried to take
Eugene outside each day. The doctors had told her that it was important for him to get
exercise, and if Eugene was inside too long he drove Beverly crazy, asking her the same
questions over and over in an endless loop. So each morning and afternoon, she took
him on a walk around the block, always together and always along the same route.
The doctors had warned Beverly that she would need to monitor Eugene constantly. If
he ever got lost, they said, he would never be able to nd his way home. But one
morning, while she was getting dressed, Eugene slipped out the front door. He had a
tendency to wander from room to room, so it took her a while to notice he was gone.
When she did, she became frantic. She ran outside and scanned the street. She couldn’t
see him. She went to the neighbors’ house and pounded on the windows. Their homes
looked similar—maybe Eugene had become confused and had gone inside? She ran to
the door and rang the bell until someone answered. Eugene wasn’t there. She sprinted
back to the street, running up the block, screaming Eugene’s name. She was crying.
What if he had wandered into tra c? How would he tell anyone where he lived? She

had been outside for fteen minutes already, looking everywhere. She ran home to call
the police.
When she burst through the door, she found Eugene in the living room, sitting in front
of the television watching the History Channel. Her tears confused him. He didn’t
remember leaving, he said, didn’t know where he’d been, and couldn’t understand why
she was so upset. Then Beverly saw a pile of pinecones on the table, like the ones she’d
seen in a neighbor’s yard down the street. She came closer and looked at Eugene’s
hands. His ngers were sticky with sap. That’s when she realized that Eugene had gone
for a walk by himself. He had wandered down the street and collected some souvenirs.
And he had found his way home.
Soon, Eugene was going for walks every morning. Beverly tried to stop him, but it
was pointless.
“Even if I told him to stay inside, he wouldn’t remember a few minutes later,” she told
me. “I followed him a few times to make sure he wouldn’t get lost, but he always came
back.” Sometimes he would return with pinecones or rocks. Once he came back with a
wallet; another time with a puppy. He never remembered where they came from.
When Squire and his assistants heard about these walks, they started to suspect that
something was happening inside Eugene’s head that didn’t have anything to do with his
conscious memory. They designed an experiment. One of Squire’s assistants visited the
house one day and asked Eugene to draw a map of the block where he lived. He couldn’t
do it. How about where his house was located on the street, she asked. He doodled a bit,
then forgot the assignment. She asked him to point out which doorway led to the
kitchen. Eugene looked around the room. He didn’t know, he said. She asked Eugene
what he would do if he were hungry. He stood up, walked into the kitchen, opened a
cabinet, and took down a jar of nuts.
Later that week, a visitor joined Eugene on his daily stroll. They walked for about
fteen minutes through the perpetual spring of Southern California, the scent of
bougainvillea heavy in the air. Eugene didn’t say much, but he always led the way and
seemed to know where he was going. He never asked for directions. As they rounded the
corner near his house, the visitor asked Eugene where he lived. “I don’t know, exactly,”
he said. Then he walked up his sidewalk, opened his front door, went into the living
room, and turned on the television.
It was clear to Squire that Eugene was absorbing new information. But where inside
his brain was that information residing? How could someone nd a jar of nuts when he
couldn’t say where the kitchen was located? Or nd his way home when he had no idea
which house was his? How, Squire wondered, were new patterns forming inside
Eugene’s damaged brain?
Within the building that houses the Brain and Cognitive Sciences department of the
Massachusetts Institute of Technology are laboratories that contain what, to the casual

observer, look like dollhouse versions of surgical theaters. There are tiny scalpels, small
drills, and miniature saws less than a quarter inch wide attached to robotic arms. Even
the operating tables are tiny, as if prepared for child-sized surgeons. The rooms are
always kept at a chilly sixty degrees because a slight nip in the air steadies researchers’
ngers during delicate procedures. Inside these laboratories, neurologists cut into the
skulls of anesthetized rats, implanting tiny sensors that can record the smallest changes
inside their brains. When the rats wake, they hardly seem to notice that there are now
dozens of microscopic wires arrayed, like neurological spider webs, inside their heads.
These laboratories have become the epicenter for a quiet revolution in the science of
habit formation, and the experiments unfolding here explain how Eugene—as well as
you, me, and everyone else—developed the behaviors necessary to make it through each
day. The rats in these labs have illuminated the complexity that occurs inside our heads
whenever we do something as mundane as brush our teeth or back the car out of the
driveway. And for Squire, these laboratories helped explain how Eugene managed to
learn new habits.
When the MIT researchers started working on habits in the 1990s—at about the same
time that Eugene came down with his fever—they were curious about a nub of
neurological tissue known as the basal ganglia. If you picture the human brain as an
onion, composed of layer upon layer of cells, then the outside layers—those closest to
the scalp—are generally the most recent additions from an evolutionary perspective.
When you dream up a new invention or laugh at a friend’s joke, it’s the outside parts of
your brain at work. That’s where the most complex thinking occurs.
Deeper inside the brain and closer to the brain stem—where the brain meets the
spinal column—are older, more primitive structures. They control our automatic
behaviors, such as breathing and swallowing, or the startle response we feel when
someone leaps out from behind a bush. Toward the center of the skull is a golf ball–sized
lump of tissue that is similar to what you might nd inside the head of a sh, reptile, or
mammal.1.12 This is the basal ganglia, an oval of cells that, for years, scientists didn’t
understand very well, except for suspicions that it played a role in diseases such as
Parkinson’s.1.13, 1.14
In the early 1990s, the MIT researchers began wondering if the basal ganglia might be
integral to habits as well. They noticed that animals with injured basal ganglia suddenly
developed problems with tasks such as learning how to run through mazes or
remembering how to open food containers.1.15 They decided to experiment by
employing new micro-technologies that allowed them to observe, in minute detail, what
was occurring within the heads of rats as they performed dozens of routines. In surgery,
each rat had what looked like a small joystick and dozens of tiny wires inserted into its
skull. Afterward, the animal was placed into a T-shaped maze with chocolate at one

The maze was structured so that each rat was positioned behind a partition that
opened when a loud click sounded.1.16 Initially, when a rat heard the click and saw the
partition disappear, it would usually wander up and down the center aisle, sni ng in
corners and scratching at walls. It appeared to smell the chocolate, but couldn’t gure
out how to nd it. When it reached the top of the T, it often turned to the right, away
from the chocolate, and then wandered left, sometimes pausing for no obvious reason.
Eventually, most animals discovered the reward. But there was no discernible pattern in
their meanderings. It seemed as if each rat was taking a leisurely, unthinking stroll.
The probes in the rats’ heads, however, told a di erent story. While each animal
wandered through the maze, its brain—and in particular, its basal ganglia—worked
furiously. Each time a rat sni ed the air or scratched a wall, its brain exploded with
activity, as if analyzing each new scent, sight, and sound. The rat was processing
information the entire time it meandered.
The scientists repeated their experiment, again and again, watching how each rat’s
brain activity changed as it moved through the same route hundreds of times. A series of
shifts slowly emerged. The rats stopped sni ng corners and making wrong turns.
Instead, they zipped through the maze faster and faster. And within their brains,
something unexpected occurred: As each rat learned how to navigate the maze, its
started thinking less and less.
It was as if the rst few times a rat explored the maze, its brain had to work at full
To see this capacity in action, consider this graph, which shows activity within a rat’s

skull as it encounters the maze for the rst time.1.17 Initially, the brain is working hard
the entire time:

After a week, once the route is familiar and the scurrying has become a habit, the rat’s
brain settles down as it runs through the maze:

This process—in which the brain converts a sequence of actions into an automatic
routine—is known as “chunking,” and it’s at the root of how habits form.1.18 There are
dozens—if not hundreds—of behavioral chunks that we rely on every day. Some are
mouth. Some, such as getting dressed or making the kids’ lunch, are a little more
Others are so complicated that it’s remarkable a small bit of tissue that evolved
millions of years ago can turn them into habits at all. Take the act of backing your car
out of the driveway. When you rst learned to drive, the driveway required a major

dose of concentration, and for good reason: It involves opening the garage, unlocking
the car door, adjusting the seat, inserting the key in the ignition, turning it clockwise,
moving the rearview and side mirrors and checking for obstacles, putting your foot on
mentally estimating the distance between the garage and the street while keeping the
wheels aligned and monitoring for oncoming tra c, calculating how re ected images in
the mirrors translate into actual distances between the bumper, the garbage cans, and
the hedges, all while applying slight pressure to the gas pedal and brake, and, most
likely, telling your passenger to please stop fiddling with the radio.
Nowadays, however, you do all of that every time you pull onto the street with hardly
any thought. The routine occurs by habit.
because habits allow our minds to ramp down more often. This e ort-saving instinct is a
huge advantage. An e cient brain requires less room, which makes for a smaller head,
e cient brain also allows us to stop thinking constantly about basic behaviors, such as
irrigation systems, and, eventually, airplanes and video games.
But conserving mental e ort is tricky, because if our brains power down at the wrong
bushes or a speeding car as we pull onto the street. So our basal ganglia have devised a
clever system to determine when to let habits take over. It’s something that happens
whenever a chunk of behavior starts or ends.
To see how it works, look closely at the graph of the rat’s neurological habit again.
Notice that brain activity spikes at the beginning of the maze, when the rat hears the
click before the partition starts moving, and again at the end, when it nds the

Those spikes are the brain’s way of determining when to cede control to a habit, and
which habit to use. From behind a partition, for instance, it’s di cult for a rat to know
if it’s inside a familiar maze or an unfamiliar cupboard with a cat lurking outside. To
deal with this uncertainty, the brain spends a lot of e ort at the beginning of a habit
looking for something—a cue—that o ers a hint as to which pattern to use. From
behind a partition, if a rat hears a click, it knows to use the maze habit. If it hears a
meow, it chooses a di erent pattern. And at the end of the activity, when the reward
appears, the brain shakes itself awake and makes sure everything unfolded as expected.


anticipation and craving emerges. Eventually, whether in a chilly MIT laboratory or
your driveway, a habit is born.1.19

Habits aren’t destiny. As the next two chapters explain, habits can be ignored, changed,
deliberately fight a habit—unless you nd new routines—the pattern will unfold
However, simply understanding how habits work—learning the structure of the habit
loop—makes them easier to control. Once you break a habit into its components, you
can fiddle with the gears.
Ann Graybiel, a scientist at MIT who oversaw many of the basal ganglia experiments,
told me. “Then one day, we’ll put the reward in the old place, and put in the rat, and,
by golly, the old habit will reemerge right away. Habits never really disappear. They’re
that your brain can’t tell the di erence between bad and good habits, and so if you have
the doughnuts becomes as automatic as any other habit.
daily life. People whose basal ganglia are damaged by injury or disease often become
mentally paralyzed. They have trouble performing basic activities, such as opening a
door or deciding what to eat. They lose the ability to ignore insigni cant details—one
study, for example, found that patients with basal ganglia injuries couldn’t recognize
facial expressions, including fear and disgust, because they were perpetually uncertain
about which part of the face to focus on. Without our basal ganglia, we lose access to
the hundreds of habits we rely on every day. Did you pause this morning to decide
whether to tie your left or right shoe rst? Did you have trouble guring out if you
should brush your teeth before or after you showered?
Of course not. Those decisions are habitual, e ortless. As long as your basal ganglia is
intact and the cues remain constant, the behaviors will occur unthinkingly. (Though
when you go on vacation, you may get dressed in di erent ways or brush your teeth at
a different point in your morning routine without noticing it.)
At the same time, however, the brain’s dependence on automatic routines can be
dangerous. Habits are often as much a curse as a benefit.
Take Eugene, for instance. Habits gave him his life back after he lost his memory.

Then they took everything away again.

As Larry Squire, the memory specialist, spent more and more time with Eugene, he
became convinced his patient was somehow learning new behaviors. Images of Eugene’s
brain showed that his basal ganglia had escaped injury from the viral encephalitis. Was
it possible, the scientist wondered, that Eugene, even with severe brain damage, could
still use the cue-routine-reward loop? Could this ancient neurological process explain
how Eugene was able to walk around the block and find the jar of nuts in the kitchen?
To test if Eugene was forming new habits, Squire devised an experiment. He took
sixteen di erent objects—bits of plastic and brightly colored pieces of toys—and glued
them to cardboard rectangles. He then divided them into eight pairs: choice A and choice
B. In each pairing, one piece of cardboard, chosen at random, had a sticker placed on
the bottom that read “correct.”1.21
Eugene was seated at a table, given a pair of objects, and asked to choose one. Next,
he was told to turn over his choice to see if there was a “correct” sticker underneath.
This is a common way to measure memory. Since there are only sixteen objects, and
they are always presented in the same eight pairings, most people can memorize which
item is “correct” after a few rounds. Monkeys can memorize all the “correct” items after
eight to ten days.
Eugene couldn’t remember any of the “correct” items, no matter how many times he
did the test. He repeated the experiment twice a week for months, looking at forty
pairings each day.
“Do you know why you are here today?” a researcher asked at the beginning of one
session a few weeks into the experiment.
“I don’t think so,” Eugene said.
“I’m going to show you some objects. Do you know why?”
“Am I supposed to describe them to you, or tell you what they are used for?” Eugene
couldn’t recollect the previous sessions at all.
But as the weeks passed, Eugene’s performance improved. After twenty-eight days of
training, Eugene was choosing the “correct” object 85 percent of the time. At thirty-six
days, he was right 95 percent of the time. After one test, Eugene looked at the
researcher, bewildered by his success.
“How am I doing this?” he asked her.
“Tell me what is going on in your head,” the researcher said. “Do you say to yourself,
‘I remember seeing that one’?”
“No,” Eugene said. “It’s here somehow or another”—he pointed to his head—“and the
hand goes for it.”
To Squire, however, it made perfect sense. Eugene was exposed to a cue: a pair of
objects always presented in the same combination. There was a routine: He would
choose one object and look to see if there was a sticker underneath, even if he had no

idea why he felt compelled to turn the cardboard over. Then there was a reward: the
satisfaction he received after nding a sticker proclaiming “correct.” Eventually, a habit
loop emerged.


To make sure this pattern was, in fact, a habit, Squire conducted one more
experiment. He took all sixteen items and put them in front of Eugene at the same time.
He asked him to put all the “correct” objects into one pile.
Eugene had no idea where to begin. “Gosh sakes, how to remember this?” he asked.
He reached for one object and started to turn it over. The experimenter stopped him.
No, she explained. The task was to put the items in piles. Why was he trying to turn
them over?
“That’s just a habit, I think,” he said.
He couldn’t do it. The objects, when presented outside of the context of the habit loop,
made no sense to him.
Here was the proof Squire was looking for. The experiments demonstrated that
Eugene had the ability to form new habits, even when they involved tasks or objects he
couldn’t remember for more than a few seconds. This explained how Eugene managed to
go for a walk every morning. The cues—certain trees on corners or the placement of
particular mailboxes—were consistent every time he went outside, so though he couldn’t
recognize his house, his habits always guided him back to his front door. It also
explained why Eugene would eat breakfast three or four times a day, even if he wasn’t
hungry. As long as the right cues were present—such as his radio or the morning light
through his windows—he automatically followed the script dictated by his basal ganglia.
What’s more, there were dozens of other habits in Eugene’s life that no one noticed
until they started looking for them. Eugene’s daughter, for instance, would often stop by
his house to say hello. She would talk to her father in the living room for a bit, then go
into the kitchen to visit with her mother, and then leave, waving good-bye on her way
out the door. Eugene, who had forgotten their earlier conversation by the time she left,
would get angry—why was she leaving without chatting?—and then forget why he was
upset. But the emotional habit had already started, and so his anger would persist, red
hot and beyond his understanding, until it burned itself out.
“Sometimes he would bang the table or curse, and if you asked him why, he’d say ‘I
don’t know, but I’m mad!’ ” Beverly told me. He would kick his chair, or snap at

whoever came into the room. Then, a few minutes later, he would smile and talk about
the weather. “It was like, once it started, he had to finish the frustration,” she said.
Squire’s new experiment also showed something else: that habits are surprisingly
delicate. If Eugene’s cues changed the slightest bit, his habits fell apart. The few times he
walked around the block, for instance, and something was di erent—the city was doing
street repairs or a windstorm had blown branches all over the sidewalk—Eugene would
get lost, no matter how close he was to home, until a kind neighbor showed him the way
to his door. If his daughter stopped to chat with him for ten seconds before she walked
out, his anger habit never emerged.
Squire’s experiments with Eugene revolutionized the scienti c community’s
understanding of how the brain works by proving, once and for all, that it’s possible to
learn and make unconscious choices without remembering anything about the lesson or
decision making.1.22 Eugene showed that habits, as much as memory and reason, are at
habits, but once they are lodged within our brains they in uence how we act—often
without our realization.
Since Squire’s rst paper on Eugene’s habits was published, the science of habit
formation has exploded into a major eld of study. Researchers at Duke, Harvard,
UCLA, Yale, USC, Princeton, the University of Pennsylvania, and at schools in the
United Kingdom, Germany, and the Netherlands, as well as corporate scientists working
for Procter & Gamble, Microsoft, Google, and hundreds of other companies are focused
on understanding the neurology and psychology of habits, their strengths and
weaknesses, and why they emerge and how they can be changed.
sensations, to emotional payo s, such as the feelings of pride that accompany praise or
And in almost every experiment, researchers have seen echoes of Squire’s discoveries
with Eugene: Habits are powerful, but delicate. They can emerge outside our
but can be reshaped by ddling with their parts. They shape our lives far more than we
exclusion of all else, including common sense.
In one set of experiments, for example, researchers a liated with the National
Institute on Alcohol Abuse and Alcoholism trained mice to press levers in response to
certain cues until the behavior became a habit. The mice were always rewarded with
food. Then, the scientists poisoned the food so that it made the animals violently ill, or
electri ed the oor, so that when the mice walked toward their reward they received a

shock. The mice knew the food and cage were dangerous—when they were o ered the
poisoned pellets in a bowl or saw the electri ed oor panels, they stayed away. When
they saw their old cues, however, they unthinkingly pressed the lever and ate the food,
or they walked across the oor, even as they vomited or jumped from the electricity.
The habit was so ingrained the mice couldn’t stop themselves.1.23
It’s not hard to nd an analog in the human world. Consider fast food, for instance. It
makes sense—when the kids are starving and you’re driving home after a long day—to
stop, just this once, at McDonald’s or Burger King. The meals are inexpensive. It tastes
so good. After all, one dose of processed meat, salty fries, and sugary soda poses a
relatively small health risk, right? It’s not like you do it all the time.
But habits emerge without our permission. Studies indicate that families usually don’t
intend to eat fast food on a regular basis. What happens is that a once a month pattern
families gradually increased their fast food consumption, they found a series of cues and
rewards that most customers never knew were in uencing their behaviors. 1.24 They
discovered the habit loop.
Every McDonald’s, for instance, looks the same—the company deliberately tries to
standardize stores’ architecture and what employees say to customers, so everything is a
consistent cue to trigger eating routines. The foods at some chains are speci cally
engineered to deliver immediate rewards—the fries, for instance, are designed to begin
disintegrating the moment they hit your tongue, in order to deliver a hit of salt and
grease as fast as possible, causing your pleasure centers to light up and your brain to
lock in the pattern. All the better for tightening the habit loop.1.25
However, even these habits are delicate. When a fast food restaurant closes down, the
families that previously ate there will often start having dinner at home, rather than
seek out an alternative location. Even small shifts can end the pattern. But since we
control them. By learning to observe the cues and rewards, though, we can change the
By 2000, seven years after Eugene’s illness, his life had achieved a kind of equilibrium.
He went for a walk every morning. He ate what he wanted, sometimes ve or six times
a day. His wife knew that as long as the television was tuned to the History Channel,
Eugene would settle into his plush chair and watch it regardless of whether it was airing
reruns or new programs. He couldn’t tell the difference.
As he got older, however, Eugene’s habits started impacting his life in negative ways.
He was sedentary, sometimes watching television for hours at a time because he never
grew bored with the shows. His physicians became worried about his heart. The doctors

told Beverly to keep him on a strict diet of healthy foods. She tried, but it was di cult to
in uence how frequently he ate or what he consumed. He never recalled her
admonitions. Even if the refrigerator was stocked with fruits and vegetables, Eugene
would root around until he found the bacon and eggs. That was his routine. And as
Eugene aged and his bones became more brittle, the doctors said he needed to be more
careful walking around. In his mind, however, Eugene was twenty years younger. He
never remembered to step carefully.
“All my life I was fascinated by memory,” Squire told me. “Then I met E.P., and saw
how rich life can be even if you can’t remember it. The brain has this amazing ability to
find happiness even when the memories of it are gone.
“It’s hard to turn that off, though, which ultimately worked against him.”
Beverly tried to use her understanding of habits to help Eugene avoid problems as he
aged. She discovered that she could short-circuit some of his worst patterns by inserting
new cues. If she didn’t keep bacon in the fridge, Eugene wouldn’t eat multiple,
unhealthy breakfasts. When she put a salad next to his chair, he would sometimes pick
at it, and as the meal became a habit, he stopped searching the kitchen for treats. His
diet gradually improved.
Despite these e orts, however, Eugene’s health still declined. One spring day, Eugene
was watching television when he suddenly shouted. Beverly ran in and saw him
clutching his chest. She called an ambulance. At the hospital, they diagnosed a minor
heart attack. By then the pain had passed and Eugene was ghting to get o his gurney.
That night, he kept pulling o the monitors attached to his chest so he could roll over
and sleep. Alarms would blare and nurses would rush in. They tried to get him to quit
ddling with the sensors by taping the leads in place and telling him they would use
restraints if he continued fussing. Nothing worked. He forgot the threats as soon as they
were issued.
Then his daughter told a nurse to try complimenting him on his willingness to sit still,
and to repeat the compliment, over and over, each time she saw him. “We wanted to,
you know, get his pride involved,” his daughter, Carol Rayes, told me. “We’d say, ‘Oh,
Dad, you’re really doing something important for science by keeping these doodads in
place.’ ” The nurses started to dote on him. He loved it. After a couple of days, he did
whatever they asked. Eugene returned home a week later.
Then, in the fall of 2008, while walking through his living room, Eugene tripped on a
ledge near the replace, fell, and broke his hip. At the hospital, Squire and his team
worried that he would have panic attacks because he wouldn’t know where he was. So
they left notes by his bedside explaining what had happened and posted photos of his
children on the walls. His wife and kids came every day.
Eugene, however, never grew worried. He never asked why he was in the hospital.
“He seemed at peace with all the uncertainty by that point,” said Squire. “It had been
fteen years since he had lost his memory. It was as if part of his brain knew there were
some things he would never understand and was okay with that.”
Beverly came to the hospital every day. “I spent a long time talking to him,” she said.
“I told him that I loved him, and about our kids and what a good life we had. I pointed

to the pictures and talked about how much he was adored. We were married for
seven years, and forty-two of those were a real, normal marriage. Sometimes it was
hard, because I wanted my old husband back so much. But at least I knew he was
A few weeks later, his daughter came to visit. “What’s the plan?” Eugene asked when
she arrived. She took him outside in a wheelchair, onto the hospital’s lawn. “It’s a
beautiful day,” Eugene said. “Pretty nice weather, huh?” She told him about her kids and
they played with a dog. She thought he might be able to come home soon. The sun was
going down. She started to get ready to take him inside.
Eugene looked at her.
“I’m lucky to have a daughter like you,” he said. She was caught o -guard. She
couldn’t remember the last time he had said something so sweet.
“I’m lucky that you’re my dad,” she told him.
“Gosh, it’s a beautiful day,” he said. “What do you think about the weather?”
That night, at one o’clock in the morning, Beverly’s phone rang. The doctor said
Eugene had su ered a massive heart attack and the sta had done everything possible,
but hadn’t been able to revive him. He was gone. After his death, he would be celebrated
by researchers, the images of his brain studied in hundreds of labs and medical schools.
“I know he would have been really proud to know how much he contributed to
science,” Beverly told me. “He told me once, pretty soon after we got married, that he
wanted to do something important with his life, something that mattered. And he did.
He just never remembered any of it.”


How to Create New Habits

One day in the early 1900s, a prominent American executive named Claude C. Hopkins
was approached by an old friend with a new business idea. The friend had discovered an
amazing product, he explained, that he was convinced would be a hit. It was a
toothpaste, a minty, frothy concoction he called “Pepsodent.” There were some dicey
investors involved—one of them had a string of busted land deals; another, it was
rumored, was connected to the mob—but this venture, the friend promised, was going to
be huge. If, that is, Hopkins would consent to help design a national promotional
Hopkins, at the time, was at the top of a booming industry that had hardly existed a
few decades earlier: advertising. Hopkins was the man who had convinced Americans to
while neglecting to mention that every other company used the exact same method. He
had seduced millions of women into purchasing Palmolive soap by proclaiming that
Cleopatra had washed with it, despite the sputtering protests of outraged historians. He
had made Pu ed Wheat famous by saying that it was “shot from guns” until the grains
pu ed “to eight times normal size.” He had turned dozens of previously unknown
and beans—into household names. And in the process, he had made himself so rich that
difficulties of spending so much money.
Claude Hopkins was best known for a series of rules he coined explaining how to
create new habits among consumers. These rules would transform industries and
eventually became conventional wisdom among marketers, educational reformers,
public health professionals, politicians, and CEOs. Even today, Hopkins’s rules in uence
everything from how we buy cleaning supplies to the tools governments use for
eradicating disease. They are fundamental to creating any new routine.
However, when his old friend approached Hopkins about Pepsodent, the ad man
expressed only mild interest. It was no secret that the health of Americans’ teeth was in
steep decline. As the nation had become wealthier, people had started buying larger
amounts of sugary, processed foods.2.2 When the government started drafting men for
World War I, so many recruits had rotting teeth that o cials said poor dental hygiene

was a national security risk.
Yet as Hopkins knew, selling toothpaste was nancial suicide. There was already an
army of door-to-door salesmen hawking dubious tooth powders and elixirs, most of them
going broke.
The problem was that hardly anyone bought toothpaste because, despite the nation’s
dental problems, hardly anyone brushed their teeth.2.3
So Hopkins gave his friend’s proposal a bit of thought, and then declined. He’d stick
with soaps and cereals, he said. “I did not see a way to educate the laity in technical
tooth-paste theories,” Hopkins explained in his autobiography. The friend, however, was
persistent. He came back again and again, appealing to Hopkins’s considerable ego
until, eventually, the ad man gave in.
“I nally agreed to undertake the campaign if he gave me a six months’ option on a
block of stock,” Hopkins wrote. The friend agreed.
It would be the wisest financial decision of Hopkins’s life.
Within ve years of that partnership, Hopkins turned Pepsodent into one of the bestknown products on earth and, in the process, helped create a toothbrushing habit that
moved across America with startling speed. Soon, everyone from Shirley Temple to
Clark Gable was bragging about their “Pepsodent smile.”2.4 By 1930, Pepsodent was sold
in China, South Africa, Brazil, Germany, and almost anywhere else Hopkins could buy
ads.2.5 A decade after the rst Pepsodent campaign, pollsters found that toothbrushing
had become a ritual for more than half the American population.2.6 Hopkins had helped
establish toothbrushing as a daily activity.
The secret to his success, Hopkins would later boast, was that he had found a certain
kind of cue and reward that fueled a particular habit. It’s an alchemy so powerful that
even today the basic principles are still used video game designers, food companies,
hospitals, and millions of salesmen around the world. Eugene Pauly taught us about the
habit loop, but it was Claude Hopkins that showed how new habits can be cultivated
and grown.
So what, exactly, did Hopkins do?
He created a craving. And that craving, it turns out, is what makes cues and rewards
work. That craving is what powers the habit loop.
Throughout his career, one of Claude Hopkins’s signature tactics was to nd simple
symptoms’ rst appearance. Soon, people were devouring oatmeal at daybreak and
would have it, often happened at least once a day.

which I afterward called ‘the lm.’ That gave me an appealing idea. I resolved to
advertise this toothpaste as a creator of beauty. To deal with that cloudy film.”
In focusing on tooth lm, Hopkins was ignoring the fact that this same lm has
always covered people’s teeth and hadn’t seemed to bother anyone. The lm is a
often you brush.2.7 People had never paid much attention to it, and there was little
reason why they should: You can get rid of the lm by eating an apple, running your
nger over your teeth, brushing, or vigorously swirling liquid around your mouth.
Toothpaste didn’t do anything to help remove the lm. In fact, one of the leading dental
That didn’t stop Hopkins from exploiting his discovery. Here, he decided, was a cue
“Just run your tongue across your teeth,” read one. “You’ll feel a lm—that’s what
woman have dingy film on her teeth? Pepsodent removes the film!”2.9
The brilliance of these appeals was that they relied upon a cue—tooth lm—that was
when they did, they were likely to feel a lm. Hopkins had found a cue that was simple,
people to comply automatically.
Moreover, the reward, as Hopkins envisioned it, was even more enticing. Who, after
all, doesn’t want to be more beautiful? Who doesn’t want a prettier smile? Particularly
when all it takes is a quick brush with Pepsodent?


After the campaign launched, a quiet week passed. Then two. In the third week,
demand exploded. There were so many orders for Pepsodent that the company couldn’t
keep up. In three years, the product went international, and Hopkins was crafting ads
in Spanish, German, and Chinese. Within a decade, Pepsodent was one of the top-selling

goods in the world, and remained America’s best-selling toothpaste for more than thirty
years.2.10, 2.11
number had jumped to 65 percent.2.12 By the end of World War II, the military
downgraded concerns about recruits’ teeth because so many soldiers were brushing
every day.
First, find a simple and obvious cue.
Second, clearly define the rewards.
If you get those elements right, Hopkins promised, it was like magic. Look at
Pepsodent: He had identi ed a cue—tooth lm—and a reward—beautiful teeth—that
had persuaded millions to start a daily ritual. Even today, Hopkins’s rules are a staple of
marketing textbooks and the foundation of millions of ad campaigns.
without people realizing how closely they are hewing to Hopkins’s formula. Studies of
people who have successfully started new exercise routines, for instance, show they are
more likely to stick with a workout plan if they choose a speci c cue, such as running as
soon as they get home from work, and a clear reward, such as a beer or an evening of
guilt-free television.2.13 Research on dieting says creating new food habits requires a
predetermined cue—such as planning menus in advance—and simple rewards for
dieters when they stick to their intentions.2.14
science,” Hopkins wrote. “Advertising, once a gamble, has thus become, under able
direction, one of the safest of business ventures.”
It’s quite a boast. However, it turns out that Hopkins’s two rules aren’t enough.
There’s also a third rule that must be satis ed to create a habit—a rule so subtle that
Hopkins himself relied on it without knowing it existed. It explains everything from why
it’s so hard to ignore a box of doughnuts to how a morning jog can become a nearly
effortless routine.
woman who owned nine cats, when one of them nally said what everyone was
“If we get red, what exactly happens?” she asked. “Do security guards show up and

stared at her.
It was 1996, and the group at the table was nding out, despite Claude Hopkins’s
assertions, how utterly unscienti c the process of selling something could become. They
all worked for one of the largest consumer goods rms on earth, the company behind
their marketing campaigns. The rm was incredibly good at guring out how to sell
two laundry loads in America.2.15 Its revenues topped $35 billion per year.2.16
how to get people to buy it.
“Did you quit smoking?” she asked him.
years. This seemed like some kind of reverse psychology trickery.
When the chemist explained his ndings to P&G’s executives, they were ecstatic. For
viable product. They spent millions perfecting the formula, nally producing a colorless,

with a background in math and psychology, to lead the marketing team.2.17 Stimson was
Before joining P&G, he had spent ve years on Wall Street building mathematical
fabric softener and Downy dryer sheets. But Febreze was di erent. It was a chance to
cart that had never been there before. All Stimson needed to do was gure out how to
make Febreze into a habit, and the product would y o the shelves. How tough could
that be?
Phoenix, Salt Lake City, and Boise. They ew in and handed out samples, and then
visited hundreds of households. Their rst big breakthrough came when they visited a
when they were caught.
“I’m single, and I’d like to nd someone to have kids with,” the ranger told Stimson
“When I’m on a date, I’ll get a whi of something that smells like skunk and I’ll start
him home and he wants to leave?
She looked at him. She was crying.

anymore. The skunk is gone.”
product is so important.”
Stimson sni ed the air inside her living room. He couldn’t smell anything. We’re going
to make a fortune with this stuff, he thought.
lled business school textbooks. They wanted to keep the ads simple: Find an obvious
cue and clearly define the reward.
They designed two television commercials. The rst showed a woman talking about
woman worrying about her dog, Sophie, who always sits on the couch.2.18 “Sophie will
animals.2.19 The reward: a house that doesn’t smell like a kennel.
they would spend their bonuses.
Shelves were lled with Febreze bottles that had never been touched. They started
visiting housewives who had received free samples.
you want it back?”
Febreze was a dud.
equivalent of Siberia.

everything around,” he said. “At the very least, let’s ask the PhDs to gure out what’s
elsewhere who were supposed experts in consumer psychology. The division’s president
agreed to give the product a little more time.
interviews.2.20 Their rst inkling of why Febreze was failing came when they visited a
“What do you do about the cat smell?” a scientist asked the woman.
“It’s usually not a problem,” she said.
“How often do you notice a smell?”
“Oh, about once a month,” the woman replied.
The researchers looked at one another.
“Do you smell it now?” a scientist asked.
“No,” she said.
that should have reminded them the living room needed a spritz.
Stimson’s team went back to headquarters and gathered in the windowless conference
what happens if you get red. Stimson put his head in his hands. If he couldn’t sell
most need it don’t appreciate the reward?
The laboratory belonging to Wolfram Schultz, a professor of neuroscience at the
University of Cambridge, is not a pretty place. His desk has been alternately described

by colleagues as a black hole where documents are lost forever and a petri dish where
organisms can grow, undisturbed and in wild proliferation, for years. When Schultz
needs to clean something, which is uncommon, he doesn’t use sprays or cleansers. He
wets a paper towel and wipes hard. If his clothes smell like smoke or cat hair, he doesn’t
notice. Or care.
However, the experiments that Schultz has conducted over the past twenty years have
revolutionized our understanding of how cues, rewards, and habits interact. He has
explained why some cues and rewards have more power than others, and has provided a
scienti c road map that explains why Pepsodent was a hit, how some dieters and
exercise bu s manage to change their habits so quickly, and—in the end—what it took
to make Febreze sell.
In the 1980s, Schultz was part of a group of scientists studying the brains of monkeys
as they learned to perform certain tasks, such as pulling on levers or opening clasps.
Their goal was to figure out which parts of the brain were responsible for new actions.
“One day, I noticed this thing that is interesting to me,” Schultz told me. He was born
in Germany and now, when he speaks English, sounds a bit like Arnold Schwarzenegger
if the Terminator were a member of the Royal Society. “A few of the monkeys we
watched loved apple juice, and the other monkeys loved grape juice, and so I began to
wonder, what is going on inside those little monkey heads? Why do di erent rewards
affect the brain in different ways?”
Schultz began a series of experiments to decipher how rewards work on a
neurochemical level. As technology progressed, he gained access, in the 1990s, to
devices similar to those used by the researchers at MIT. Rather than rats, however,
Schultz was interested in monkeys like Julio, an eight-pound macaque with hazel eyes
who had a very thin electrode inserted into his brain that allowed Schultz to observe
neuronal activity as it occurred.2.21
One day, Schultz positioned Julio on a chair in a dimly lit room and turned on a
computer monitor. Julio’s job was to touch a lever whenever colored shapes—small
yellow spirals, red squiggles, blue lines—appeared on the screen. If Julio touched the
lever when a shape appeared, a drop of blackberry juice would run down a tube
hanging from the ceiling and onto the monkey’s lips.
Julio liked blackberry juice.
At rst, Julio was only mildly interested in what was happening on the screen. He
spent most of his time trying to squirm out of the chair. But once the rst dose of juice
arrived, Julio became very focused on the monitor. As the monkey came to understand,
through dozens of repetitions, that the shapes on the screen were a cue for a routine
screen with a laserlike intensity. He didn’t squirm. When a yellow squiggle appeared, he
went for the lever. When a blue line ashed, he pounced. And when the juice arrived,
Julio would lick his lips contentedly.


As Schultz monitored the activity within Julio’s brain, he saw a pattern emerge.
Whenever Julio received his reward, his brain activity would spike in a manner that
suggested he was experiencing happiness.2.22 A transcript of that neurological activity
shows what it looks like when a monkey’s brain says, in essence, “I got a reward!”
Schultz took Julio through the same experiment again and again, recording the
neurological response each time. Whenever Julio received his juice, the “I got a reward!”
pattern appeared on the computer attached to the probe in the monkey’s head.
Gradually, from a neurological perspective, Julio’s behavior became a habit.


What was most interesting to Schultz, however, was how things changed as the
experiment proceeded. As the monkey became more and more practiced at the behavior
—as the habit became stronger and stronger—Julio’s brain began anticipating the
blackberry juice. Schultz’s probes started recording the “I got a reward!” pattern the
instant Julio saw the shapes on the screen, before the juice arrived:


In other words, the shapes on the monitor had become a cue not just for pulling a
lever, but also for a pleasure response inside the monkey’s brain. Julio started expecting
his reward as soon as he saw the yellow spirals and red squiggles.
Then Schultz adjusted the experiment. Previously, Julio had received juice as soon as
down until it was only half as sweet.
When the juice didn’t arrive or was late or diluted, Julio would get angry and make
unhappy noises, or become mopey. And within Julio’s brain, Schultz watched a new
neurological pattern associated with desire and frustration erupted inside his skull.
Researchers in other labs have found similar patterns. Other monkeys were trained to
anticipate juice whenever they saw a shape on a screen. Then, researchers tried to
distract them. They opened the lab’s door, so the monkeys could go outside and play
with their friends. They put food in a corner, so the monkeys could eat if they
abandoned the experiment.
For those monkeys who hadn’t developed a strong habit, the distractions worked.
They slid out of their chairs, left the room, and never looked back. They hadn’t learned
to crave the juice. However, once a monkey had developed a habit—once its brain
anticipated the reward—the distractions held no allure. The animal would sit there,
watching the monitor and pressing the lever, over and over again, regardless of the
offer of food or the opportunity to go outside. The anticipation and sense of craving was
so overwhelming that the monkeys stayed glued to their screens, the same way a
gambler will play slots long after he’s lost his winnings.2.23
This explains why habits are so powerful: They create neurological cravings. Most of
the time, these cravings emerge so gradually that we’re not really aware they exist, so
we’re often blind to their in uence. But as we associate cues with certain rewards, a
subconscious craving emerges in our brains that starts the habit loop spinning. One

researcher at Cornell, for instance, found how powerfully food and scent cravings can
a ect behavior when he noticed how Cinnabon stores were positioned inside shopping
malls. Most food sellers locate their kiosks in food courts, but Cinnabon tries to locate
their stores away from other food stalls.2.24 Why? Because Cinnabon executives want the
smell of cinnamon rolls to waft down hallways and around corners uninterrupted, so
that shoppers will start subconsciously craving a roll. By the time a consumer turns a
corner and sees the Cinnabon store, that craving is a roaring monster inside his head
and he’ll reach, unthinkingly, for his wallet. The habit loop is spinning because a sense
of craving has emerged.2.25
and automatically want a sugary treat,” Schultz told me. “But once our brain learns that
doughnut, we’ll feel disappointed.”
To understand this process, consider how Julio’s habit emerged. First, he saw a shape
on the screen:

Over time, Julio learned that the appearance of the shape meant it was time to
execute a routine. So he touched the lever:

As a result, Julio received a drop of blackberry juice.

That’s basic learning. The habit only emerges once Julio begins craving the juice when
he sees the cue. Once that craving exists, Julio will act automatically. He’ll follow the


reward, and then cultivating a craving that drives the loop.2.26 Take, for instance,
smoking. When a smoker sees a cue—say, a pack of Marlboros—her brain starts
anticipating a hit of nicotine. Just the sight of cigarettes is enough for the brain to crave
a nicotine rush. If it doesn’t arrive, the craving grows until the smoker reaches,
unthinkingly, for a Marlboro.

Or take email. When a computer chimes or a smartphone vibrates with a new
message, the brain starts anticipating the momentary distraction that opening an email
provides. That expectation, if unsatis ed, can build until a meeting is lled with antsy
executives checking their buzzing BlackBerrys under the table, even if they know it’s
probably only their latest fantasy football results. (On the other hand, if someone
disables the buzzing—and, thus, removes the cue—people can work for hours without
thinking to check their in-boxes.)

Scientists have studied the brains of alcoholics, smokers, and overea