The Power of Habit

Why habits matter

Charles Duhigg, a reporter at The New York Times, argues that a large share of what we do each day is habit, not conscious choice. He cites a Duke University estimate that habits account for about 40 percent of daily actions. Habits run our mornings, our eating, our spending and much of our work. They also run companies and, in a looser sense, whole communities.

The book opens with Lisa Allen, a woman who smoked, drank, was in debt and could not hold a job. Within a few years, she quit smoking, ran a marathon and started a career. Scientists who scanned her brain found that new patterns had overridden the old ones. The old urges were still there, but new habits were stronger. Her change started with one decision: to quit smoking so she could trek across the Egyptian desert. That one shift set off others.

The book has three parts: the habits of individuals, the habits of successful organizations and the habits of societies.

The habit loop

Duhigg's central model is the habit loop. Every habit has three parts:

• Cue: a trigger that tells the brain to go into automatic mode.
• Routine: the behavior itself, which can be physical, mental or emotional.
• Reward: the result that tells the brain the loop is worth remembering.

He shows how scientists found this loop. Researchers at MIT put rats in a T-shaped maze with chocolate at one end. At first, the rats' brains were very active the whole time. As the rats learned the route, brain activity dropped. It rose at the start (the cue, a click and a partition sliding open) and at the end (the reward), but stayed low in the middle. The brain had turned the route into an automatic sequence. Scientists call this chunking, and it happens in a region called the basal ganglia.

The case of Eugene Pauly supports the point. Viral encephalitis destroyed parts of his brain that form new memories. He could not remember a new address or draw a map of his home. Yet he learned to take a daily walk around the block and come back to the right house. His basal ganglia were intact, so he could still form habits without any conscious memory of them.

The key lesson: once a habit forms, the brain stops fully taking part in the decision. That is why habits save effort and why bad ones are so hard to stop.

Cravings complete the picture. Cue, routine and reward are not enough. Duhigg argues that a habit grows strong when the brain starts to crave the reward as soon as it sees the cue.

His main example is Claude Hopkins, an advertiser in the early 1900s who helped make Pepsodent toothpaste a hit. Hopkins told people to run their tongue across their teeth and feel a film. That film became the cue. Brushing became the routine. The reward was clean-feeling teeth, helped by ingredients such as mint oil that left a cool, tingling feeling. People began to crave that tingle. If it was missing, their mouths felt unclean.

Duhigg contrasts this with Febreze, a Procter & Gamble product that first failed. The company marketed it as a way to remove bad smells. But people who live with a smell stop noticing it, so there was no cue. Sales rose only after P&G repositioned Febreze as a finishing touch after cleaning, a small reward at the end of an existing routine. It also added more scent so the reward was noticeable.

Duhigg also describes Wolfram Schultz, a neuroscientist who studied a monkey named Julio. Julio got juice after seeing a shape on a screen. Over time, his brain showed a reward response when the shape appeared, before the juice arrived. When the juice was late or missing, his brain showed a pattern linked to frustration. The anticipation had become a craving.

The golden rule of habit change

You cannot easily erase a habit. Duhigg's Golden Rule of Habit Change is: keep the old cue, deliver the old reward, but insert a new routine.

His examples:

• Tony Dungy, as a football coach, did not give his players more plays. He taught them to respond to the same cues (the formation of the other team) with simpler, automatic routines. His teams performed well until high-pressure moments, when players fell back on old habits.
• Alcoholics Anonymous works, Duhigg argues, partly because it gives people a new routine (meetings, a sponsor, talking) for the same cues and rewards that drinking served, such as relief, escape or company.
• Habit reversal training helped a woman Duhigg calls Mandy stop biting her nails. She learned to notice the tension that came before biting, then to do something else, like put her hands in her pockets, that gave a similar physical relief.

Duhigg adds that habit change often needs belief. Dungy's team and many AA members could keep new habits under stress only once they believed change was possible. Belief often grows inside a group.

Keystone habits and willpower

The second part looks at organizations. Duhigg introduces keystone habits: habits that, when changed, start a chain reaction that changes other habits.

His main example is Paul O'Neill, who became CEO of Alcoa in 1987. At his first meeting with investors, O'Neill spoke only about worker safety. Investors were confused. But to make the plants safer, Alcoa had to fix how work was done, how information moved and how managers reported problems. Those changes improved quality and efficiency. Profits grew a lot during his time as CEO.

Other keystone habits in the book include family dinners and regular exercise, which tend to link with other good outcomes. Keystone habits often work through small wins: early successes that make people believe larger changes are possible. Duhigg describes how Michael Phelps's coach, Bob Bowman, gave him routines such as mentally "watching the videotape" of a perfect race before he slept and when he woke.

Duhigg then turns to willpower. He describes research led by Roy Baumeister, in which people who resisted cookies and ate radishes gave up sooner on a hard puzzle. The idea is that willpower works like a muscle that tires. Duhigg argues that companies can help by turning willpower into a habit. Starbucks trains staff with plans for hard moments, such as the LATTE method for an angry customer: Listen, Acknowledge, Take action, Thank, and Explain. When the cue (an upset customer) appears, the worker follows the plan instead of relying on self-control.

Crisis, truces and companies that shape habits

Duhigg explains that organizations run on routines that work as truces between groups with competing interests, an idea from economists Richard Nelson and Sidney Winter. These truces keep the peace but can be dangerous.

At Rhode Island Hospital, the culture let surgeons dominate nurses. That truce contributed to serious surgical errors, including operations on the wrong side of a patient's head. In London, the 1987 King's Cross fire killed 31 people partly because each department in the Underground protected its own turf, and no one owned the risk of fire. Duhigg argues that a crisis can open the door to new habits, because it makes people willing to change. Good leaders sometimes use a crisis, or let it feel larger, to reset bad routines.

Duhigg also shows that companies study habits to sell more. He tells how Target analysts, including statistician Andrew Pole, built a model that guessed when a shopper was likely pregnant from what she bought, such as unscented lotion and certain supplements. New parents form new shopping habits, so Target wanted to reach them early. When customers felt uneasy about this, Target mixed baby ads in with unrelated items so the ads felt less targeted.

The lesson is that new things succeed when they come wrapped in something familiar. Duhigg describes how the song "Hey Ya!" by OutKast at first made radio listeners change the station. Programmers began to play it between familiar hits, and listeners came to like it. Something similar happened during World War II, when the U.S. government worked to get families to eat organ meats by presenting them in familiar dishes.

Habits of societies and free will

The third part looks at social habits. Duhigg retells the Montgomery bus boycott after the arrest of Rosa Parks. He argues the movement grew because of social habits. Parks had strong ties across many groups in Montgomery, so her friends rallied. Then weak ties (acquaintances, a concept from sociologist Mark Granovetter) spread the word through churches and clubs. Finally, new habits and a shared identity kept people walking for over a year.

He compares this with Saddleback Church, where pastor Rick Warren built a large congregation through small groups that gave members new weekly habits.

The final chapter asks whether we are responsible for our habits. Duhigg compares Angie Bachmann, who lost her family fortune to gambling while casinos fed her habit, with Brian Thomas, who killed his wife while in a sleep-terror state and was not held responsible. Duhigg argues that Bachmann knew her habit and had the power to change it, while Thomas did not. Once we know how a habit works, we have a responsibility to change it.

An appendix gives a four-step plan: identify the routine, experiment with rewards, isolate the cue and have a plan. Duhigg uses his own habit of buying a cookie each afternoon. He tests rewards and finds he really wants a break to chat with colleagues. Most cues, he says, fall into five groups: location, time, emotional state, other people and the action just before the habit.

What the critics say

Some researchers say the habit loop is a useful simplification but not the full science. Studies of habit formation stress context and repetition more than craving. The willpower research Duhigg cites, often called ego depletion, has had trouble replicating in large studies since the book came out. The stories are vivid, but some cases, such as the Alcoa turnaround and AA, have more than one explanation, so readers should treat them as illustrations rather than proof.

Who should read it

Read it if you want to understand why you keep doing things you mean to stop, or if you lead a team and want to change how it works. It suits readers who like narrative nonfiction and want a simple model they can test on their own habits.