The Power of Habit: Prologue Summary & Analysis

In a research study about habit change, Lisa Allen was “the scientists’ favorite participant.” For almost two decades, she smoked, drank, was obese, amassed thousands of dollars in debt, and struggled to keep a job. But in just a few months, she totally changed. She stopped smoking and drinking, shed 60 pounds, started running marathons, got a stable job and paid off her debt, and even went to grad school and purchased a house. She then joined the scientists’ study, which focused on how people can successfully correct their own destructive habits in a short period of time.

Lisa Allen told the scientists that she decided to quit smoking a few months after a sudden and devastating divorce. After the divorce, she went on vacation to Cairo, but on her first morning there, she woke up exhausted and disoriented in her pitch-black hotel room and accidentally lit a pen on fire, thinking it was a cigarette. She then kicked over and shattered a water jug. Feeling desperate and out of control, she decided that “she needed a goal in her life.” She decided that she would return to Egypt in a year and do a trek in the desert. Over the next six months, Allen worked to improve her life. She started jogging instead of smoking. She changed her diet and sleep schedule, then started saving money and planning for her future.

In the laboratory, brain scans clearly showed the change in Allen’s habits. The neurological patterns associated with her old habits were still there, but she had also created new patterns for her new habits, and these were much more active. Like everyone else in the scientists’ study, Allen started by changing a single “keystone habit.” (For her, it was smoking.) This taught her how to reprogram her other habits. Her brain scans showed that, when she was hungry, areas of her brain associated with food cravings still lit up. But after her habit change, areas responsible for self-discipline and inhibition also lit up. Allen’s brain scans helped scientists understand how decisions turn into habits over time.

Charles Duhigg (the author) asks the reader about their habits: what do they do first thing in the morning? What did they eat for lunch? What did they do when they got home from work? William James famously wrote that “all our life, so far as it has definite form, is but a mass of habits.” In other words, most of people’s choices aren’t well-reasoned decisions—they’re habits. Over time, people’s habits deeply shape how they live and who they become.

This book is about scientists and marketers’ research into how habits work and change. The first section focuses on how individuals form and change habits. The second section is about the habits of companies and organizations. And the third section is about the social implications of habits. Duhigg’s central thesis is that understanding how habits work makes it possible to change them. To write this book, he reviewed hundreds of studies and interviewed hundreds of scientists and businesspeople.

Duhigg’s interest in habits started when, as a reporter in Baghdad, he realized that the U.S. military is essentially just a huge habit-formation machine. It depends on teaching soldiers routines for how to think, act, shoot, and follow orders. In Iraq, the U.S. military also used habits to try and create peace. For instance, one army officer noticed that riots usually broke out after a crowd built up in a public plaza for several hours. He asked a small city’s mayor to ban food vendors in public plazas, and it worked: instead of staying all day and rioting, the next crowd of protestors got hungry and dispersed instead.

The army officer Duhigg interviewed explained that his entire military career was about forming habits. Having built his entire life around controlling his habits, he learned that they could change entire organizations and societies. Moreover, he was confident that everyone is capable of such change. Now, Duhigg points out, scientists know more about habits than ever before. Transforming these habits isn’t always simple, but it’s definitely possible—and science can show how.