We are creatures of habit. Our brains are routine-creating machines that establish patterns so that we can automatically complete simple, repetitive tasks without giving them much thought. This mindless automation allows us to reserve our mental energies for more important tasks; it also helps us to effectively manage the myriad decisions we face each day. But not all habitual behavior is good. Sometimes we pick up habits we’re not proud of, like overeating, procrastinating, smoking, angry outbursts, and alcoholism. The Power of Habit shows us how habits form, how they become ingrained, and how they can be changed so that you can master your habits before they master you.

Eugene Pauly catalyzed a shift in our understanding of habits when he entered UC San Diego’s laboratories in 1993. Eugene suffered from severe memory loss, the cause of which remained a mystery until an ER hospitalization and near-death-inducing fever. A battery of tests revealed that encephalitis had infiltrated his brain and, with surgical precision, devoured his medial temporal lobe, the portion of gray matter that houses thoughts and dreams. To the doctor’s surprise, Eugene recovered from the high fever, but medical personnel warned Eugene’s wife, Beverly, that he might never be the same again. As Beverly cared for Eugene, she discovered the extent to which his memory had been impaired. He had a clear memory of events before 1960, but he was incapable of retaining new short-term memories.

The head scientist overseeing Eugene was Larry Squire. Squire ran tests, conversed with Eugene, and visited the Pauly residence frequently. Squire and Beverly observed that while Eugene could no longer describe how to get to the kitchen from his arm chair or tell you his address or what the house looked like, he somehow knew where to look for the peanuts he would snack on each day. He also took the same walk through the neighborhood every day and always knew how to get back home. How was he able to consistently perform these actions without having any memory of them?

The secret lay with a small, walnut-sized portion of the brain near the spine called the basal ganglia. Unlike the outer portions of the brain that facilitate more complex thought, the basal ganglia serves the more primal function of handling automatic reactions and storing habits. Around the same time that Squire was working with Eugene, researchers at MIT’s Brain and Cognitive Science Department were also making groundbreaking discoveries. Scientists implanted microchips in the brains of rats that monitored their basal ganglia activity as they ran through a simple maze, at the end of which was a piece of chocolate. When first learning the course, the rats’ brains were alive with intense activity, notably in the basal ganglia. As the rats got used to the maze and learned where the chocolate was, their brains became less and less active. The rats got to the chocolate faster and faster and their brains worked less and less. The basal ganglia had stored the information, enabling the rats to speed through the maze to the treat while also conserving their mental energy. This process, know as chunking, is an energy saver that enables rats or people to devote brainpower to other activities. 

The rats were operating on what is called a “habit loop,” which consists of a cue, a routine, and a reward. A cue can be anything from a sound to a sight or smell that triggers a particular action. The routine is the action that is habitually performed in response to the cue. The routine is compulsively performed because there is some sort of reward anticipated. In the case of the rats, the audible click associated with the maze door opening triggered the routine of running through the maze that led to the reward of chocolate.

These discoveries at MIT dovetailed seamlessly with the Eugene Pauly case in San Diego. Even though Eugene’s short-term memory was flawed, his basal ganglia—unbeknownst  to him—was internalizing the routines he followed every day. Such habits are powerful but fragile. Eugene walked the same route everyday, but if there was a detour due to construction, he became completely disoriented. If scientists moved the chocolate to another portion of the maze, the rats’ basal ganglias would fire up again as they sought to establish a new pattern.

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In many people’s estimation—including his own—Claude C. Hopkins was a wizard in the world of advertising. His trick was to convince people that they needed a product, and that they needed to use it daily. He did this by identifying a simple, readily “triggerable” cue and then clearly defining a reward. Using this method, he made goods like Quaker Oats, Goodyear Tires, and Palmolive common household products.

Perhaps Hopkin’s greatest success was Pepsodent, a brand of toothpaste that took off in the 1920s. By making people feel self-conscious about the naturally occurring film that develops on the teeth, he created a cue that could be easily triggered and offered a routine that would lead to the reward of a beautiful smile. Hopkins understood the power of the habit loop. He also understood how to create a craving.

Experiments with Julio the monkey help us better understand how cravings develop and strengthen. When scientists monitored the chimp’s brain signals, they found that, initially, the brain’s pleasure centers would light up the moment the blackberry juice hit his tongue. But after Julio identified the pattern of actions required to get juice (pulling a lever when certain shapes appeared on a monitor), his brain activity spiked in anticipation of receiving his reward. Over time, this expectation had become a craving. When Julio performed the action, but researchers withheld the juice, he would express anger or dejection. Images on the screen cued a routine (pulling the lever), which led to juice. This love of juice became the craving that drove Julio’s habit loop.

Craving is what drives and strengthens a habit loop. When Proctor and Gamble, one of the largest consumer goods companies on the planet, was trying to market a new product called Febreze, they initially thought that bad odors were the obvious cues to exploit in order to sell a sweet-smelling disinfectant spray. But if a woman with nine cats rarely smells the vile feline fumes because she’s become accustomed to them, then what would make her—let alone anyone else—use the product consistently? Eventually they realized that instead of using odor as a cue, a clean house would be a better cue to advertise. If a post-cleaning spritz became the reward for cleaning a room, the product would be a hit. The altered approach was wildly successful. It turns out that no one craves a scentless room, but people do crave a sweet-smelling, clean room.

We have seen how habits form and how cravings drive and strengthen habits, but how do they change? Contrary to the conventional wisdom that advocated a complete lifestyle change as the path to breaking habits, the more effective way to change habits is not a complete overhaul, but the implementation of new routines that deliver a desirable reward.

The Golden Rule of habit change is to alter the routine while keeping the cues and rewards the same. For years, the organization Alcoholics Anonymous received criticism from academic quarters for ignoring the physical and biochemical dimensions of addiction. More recently, however, top universities have begun to recognize that AA methodology aligns neatly with recent discoveries about habit formation and habit change.

Steps four and five of the Twelve Step Program challenge participants to perform a thorough, critical self-examination and acknowledge the nature of their wrongs to themselves, to God, and to another person. Essentially, people identify their triggers. Later steps delve into the reasons why they drink. It is rarely to feel drunk. Typically, people drink to forget, to feel safe, to say the things they are afraid to say otherwise, to find comfort, or companionship. Wilson understood that it is not enough to break old habits—one must create new ones. By identifying the reasons why people drink (reward) and the places and images that trigger the craving (cues), people can insert a new routine to get the same reward when the craving arises. The sponsor element of AA is designed to be the routine replacement by giving people an outlet to talk about their problem with a trusted other, thereby achieving, say, the reward of companionship and comfort that they would otherwise search for at the bottom of a bottle.

This approach to identifying triggers and rewards that drive bad habits is called awareness training. It’s used in habit reversal therapy to help people substitute routines and alter patterns in areas as diverse as obesity, nail biting, depression, smoking, procrastination, and OCD.

We now understand how habits are formed, ingrained, and changed. But instead of attempting to upend all your old routines, a more effective approach is to identify and adjust the routine of keystone habits. Changing a keystone habit is the initial shift that frees up other habits to be refashioned more readily. Changing keystone habits creates a structure in which other changes happen more naturally and a climate in which those habits can become ingrained.

When Paul O’Neill assumed the position of CEO at the struggling Aluminum Company of America (Alcoa) in 1987, people were shocked that the board had picked a bureaucrat from Washington. The shock became horror when his first remarks at the Alcoa gala were about improving workplace safety instead of the vague claptrap that everyone expected of high hopes for improving profit. Company executives figured it was an obsession that would fade in a few weeks, but they were wrong.

There are safer places to work than an aluminum plant, where operating enormous machinery that pours molten metal are daily occupational hazards. Still, O’Neill was committed to the ambitious goal of zero injuries. Alcoa’s injury toll was the cue that spurred the creation of the new routine of sending any injury reports up the chain of command to O’Neill himself within twenty-four hours of the incident. Promotions would only be given to those who cooperated with the new initiative, which ensured managerial cooperation. Anyone who didn’t cooperate would be fired. Workers on the floor were glad about the change because the routine showed that the new CEO cared about all of his employees. Morale improved, as did communication, which led to safer, more streamlined processes. The injury count dropped significantly, which led not only to better press, but ultimately higher rates of productivity. Of course, higher productivity led to substantial company growth.

O’Neill understood what success literature refers to as “small wins.” These small wins do not necessarily follow a predictable linear path, but they accumulate and eventually provide unexpected breakthroughs and improvement. For most of his life, O’Neill had a knack for identifying an organization’s bad habits and recommending routines that would improve the keystone habit. He did this with federal government agencies in D.C. for years and then with Alcoa. By focusing on one keystone habit—worker safety—he created a structure in which other positive habits flourished. 

In the past, willpower was understood as a skill that some had but others did not. But this fails to account for why someone could resist a sugary snack at the beginning of the day but succumb to the temptation later that night. The increasingly popular view is that willpower is a muscle that grows as it is exercised. The moments when you fail to use willpower are likely the result of the muscle being too small or exhausted.

In one experiment, researchers found that, when they placed a bowl of radishes and a bowl of cookies before subjects, the group of subjects whom they asked to eat the radishes but refrain from eating cookies were often unable to complete difficult puzzles that they were given right after the radish feast. They often grew impatient and were sometimes even rude to the researchers who entered the room. By contrast, those who were told to eat the cookies and avoid the radishes happily worked on the puzzles and stuck with it far longer. Eating oven-fresh chocolate chip cookies requires no willpower; so the unused willpower could then be devoted to solving the puzzles.

Another study investigated the role of willpower in hip replacement outpatients. In addition to the standard packet detailing basic do’s and don’ts of the recovery process, the experiment conductor included blank sheets for the patients to write down the daily steps they would take to aid in their recovery process. Those who wrote down intentional, detailed steps recovered two to three times faster than those who did not. The written goals often included strategies for overcoming anticipated inflection points, or junctures where a patient’s willpower might flag or dissipate. The patients who recovered most quickly identified simple cues (specific moments of pain) and strategic routines that would be rewarded with the feeling of accomplishment and recovery.

These studies overturn the conventional wisdom regarding willpower. It’s more like a muscle than a talent or innate skill. Exercise your willpower and it will get stronger.

Andrew Pole is a statistician. Target hired him in 2002 to examine shoppers’ spending habits and discern patterns in the heaps of data from Target rewards cards and credit cards, email addresses, coupons used, and online shopping. In the past, corporations would base their produce arrangements and store layout on broad generalizations in consumer psychology, but within the past twenty years, companies have shifted to intense number crunching and personalized analysis to maintain a competitive edge. Most people would be shocked and unnerved to learn the amount of personal information companies have access to, as well as what mathematicians like Pole can divine from the consumer information they receive.

Perhaps one of Pole’s most challenging assignments was to design an algorithm that would help Target predict whether women are pregnant—even before they’d told anyone. In retail, pregnant women and parents with young children are a veritable goldmine. Parents spend an average of $6,800 on their child before their first birthday, and the baby market in North America brings in a almost forty billion dollars per year.

What is more, researchers find that it generally takes a significant life event—having a baby, for example—to dramatically alter consumer spending habits. Target wanted to identify this demographic before their competitors did.  Once in their fold, these women would likely continue shopping at Target throughout their baby’s childhood. Using information from the online registry that some women had completed (which included the baby’s due date), Pole was able to identify twenty-five products that women tended to buy in a certain sequence. Depending on which products they bought, Pole was able to guess with a high degree of certainty how far into gestation a woman was.

The challenge was how to advertise these pregnancy-related products to pregnant women without seeming invasive and downright creepy. Instead of sending a catalog advertising vitamin supplements, large bottles of unscented lotion, and maternity clothing, they broke up the sequence of relevant items with other items that were completely irrelevant. The solution that Target used is called “sandwiching.” It is the same technique that the music industry utilizes to make new songs feel familiar quickly. The government also uses this tactic to introduce nutrition campaigns. The sandwiching technique is used to manipulate habits by giving the sense of familiarity, a feeling that the human brain craves.

When Rosa Parks was arrested in 1955 for refusing a white man her seat, it struck a more resonant chord than other individual acts of civil disobedience had. Parks was deeply intertwined in the social fabric of Montgomery, Alabama, and her arrest activated social habits that were key to effecting change. Friends rallied around her and spread the word through social clubs and church communities—including the church of a twenty-six-year-old minister named Martin Luther King Jr. King reluctantly agreed to open his church to activists and eventually became part of planning the citywide boycott of the Montgomery bus line on the day of Park’s hearing. The press got wind of the boycott and effectively alerted those members of the black community who had not yet heard about the protest. The commotion galvanized the broader community into action, to the point where it would have meant marring one’s social standing not to participate. As is often the case, peer pressure tends to be more effective among weak ties than strong ties.

Three elements that foster habit change were present in this historic social movement: Rosa’s arrest was the cue that activated the routines of sympathetic friendship (strong ties) and of responding to peer pressure by joining the boycott (weak ties). By harnessing these habits, King and other leaders instilled a habit change by creating a new routine that the crisis of Rosa’s arrest had stirred up.

It was boredom that motivated Angie Bachmann’s first trip to the casino. Her husband worked long hours and all three daughters were now attending school, which meant that she was alone all day for the first time in almost twenty years. At first, her visits to the casino were infrequent and her bets modest, but as she became better at blackjack, she went more often and began placing more ambitious bets. Sometimes she would walk away with thousands, but over the years, she accrued massive amounts of debt. Her gambling became compulsive, and, despite her attempts to curb her habits, she eventually felt powerless to resist the tantalizing personal invitations that the casinos would dangle in front of her, like free concerts and all-inclusive stays at resorts in Las Vegas. The casino eventually sued Bachmann when she couldn’t pay back the hundreds of thousands of dollars she owed. She counter-sued the casino for aggressively exploiting an area of vulnerability.

Around the same time that these lawsuits were going to court, Welsh law enforcement got a call from a brokenhearted man named Brian Thomas. “I think I just killed my wife,” Thomas sobbed. While Thomas and his wife were on vacation at a campground on the coast of Wales, a young man broke into the camper where they were sleeping. When the man began to attack Thomas’s wife, Thomas jumped on him and began to strangle him. Thomas was devastated to discover that the attack had been a dream—the “attacker” he strangled had actually been his wife. He went on to plead guilty to murder.

As the trial proceeded, it came out that Thomas had been a sleepwalker since he was a boy and also suffered from night terrors. The defense maintained that because the crime was an act of “automatism”—performing an unconscious behavior—Thomas should not be held responsible. The defense’s case gained force as neighbors and coworkers testified that Thomas’s marriage was a loving one, and that he had never harmed his wife before, waking or sleeping. Moreover, Thomas was genuinely devastated by the event. “I’ll never forgive myself,” he told the jury. Even the prosecution’s psychiatrists argued that there was no reason to think that Thomas would respond violently to his night terrors. Not only the defense, but eventually the prosecution, advised the jury to return a not-guilty decision. The judge cleared Thomas of charges and even offered some consoling words before the final gavel strike.

Angie Bachmann’s gambling ruined her life and tore her family apart. Brian Thomas’s night terrors led to his wife’s death. Why do we hold Bachmann responsible for her actions, but not Thomas? They both acted out of habits over which they claimed they had no control. Cognizance is perhaps the chief reason that the cases required different verdicts: Bachmann was aware of her destructive habit, whereas Thomas had no reason to suspect that his habit was destructive beforehand and was unaware that he was killing his wife. 

It has been argued in this book that habits are powerful, but they are not destiny. People have faced far more challenging struggles than Bachmann and managed to chart and follow different courses. As you become aware of your habits, you bear responsibility for changing them. Now that you know how habits form, what drives them, and that it is within your power to change them, you are free to choose a different course of action. You can replace the habits that hinder and harm with ones that edify both you and others.