How to Change

Katy Milkman, a behavioral scientist and professor at the Wharton School of the University of Pennsylvania, argues that the most effective path to behavior change is not a one-size-fits-all approach but a tailored strategy that identifies the specific internal obstacle preventing progress and deploys a targeted technique to overcome it. As a graduate engineering student, Milkman became captivated by this problem after encountering research showing that an estimated 40 percent of premature deaths result from changeable personal behaviors. The book, structured around a series of common obstacles, presents scientifically tested interventions for each one.

Milkman opens with tennis player Andre Agassi, whose career was in steep decline by early 1994. Over dinner at a Miami restaurant, Agassi met Brad Gilbert, a less gifted but far more strategic player who had reached number four in the world. Gilbert diagnosed Agassi's core problem: He tried to hit a winner on every shot, a perfectionist habit inherited from his father, an Olympic boxer who always sought the knockout blow. Gilbert advised Agassi to exploit each opponent's specific weaknesses instead. Agassi adopted this approach and, months later, won the 1994 U.S. Open as an unseeded player, meaning he entered the tournament without a top ranking or seeded bracket placement. Milkman uses this transformation as the book's central analogy: Just as Gilbert taught Agassi to study his opponent, people seeking change must identify the particular internal adversary standing in their way, whether it is forgetfulness, impulsivity, laziness, or self-doubt.

The first chapter introduces the "fresh start effect," the finding that people are more motivated to pursue change at moments that feel like new beginnings. Milkman and her doctoral student Hengchen Dai analyze multiple data sets and find that people consistently pursue goals more often in January, at the start of a new week, after holidays, and after birthdays. Surveys confirm that such dates make people feel distanced from past failures. However, Dai's analysis of Major League Baseball data reveals a caveat: Cross-league trades, which reset a player's season statistics and thus create an artificial fresh start, help struggling players improve but harm those who were already performing well. Fresh starts can disrupt good habits as easily as they break bad ones. In a field experiment, framing a future retirement savings start date as a fresh start proves 20 to 30 percent more effective than pointing to an arbitrary date.

The second chapter tackles present bias, the universal tendency to favor instant gratification over larger long-term rewards. Rather than relying on willpower, which research shows people consistently overestimate, Milkman argues for making beneficial behaviors enjoyable. She introduces "temptation bundling," a strategy she devised as a graduate student: She allowed herself to enjoy page-turning audiobooks only while exercising, simultaneously addressing her gym avoidance and her tendency to procrastinate. In a controlled experiment at the University of Pennsylvania, participants given access to tempting audiobooks only at the gym exercised 55 percent more than a control group. Milkman also discusses gamification, the practice of adding game-like rewards, competition, or points to non-game activities. Economist Jana Gallus's experiment awarding symbolic accolades to new Wikipedia editors increased their continued participation by 20 percent the following month. However, gamification fails when imposed on unwilling participants; it works only when people voluntarily embrace it.

The third chapter addresses procrastination through "commitment devices," self-imposed constraints that lock people into wise choices. Green Bank in the Philippines offered customers savings accounts that forbade withdrawals until a self-chosen date or balance was reached. Despite skepticism, 28 percent of offered customers opened such accounts, and they saved 80 percent more over the following year than a control group. Milkman also discusses "soft commitments" such as public pledges: When doctors at Los Angeles clinics signed and displayed pledges not to prescribe unnecessary antibiotics, inappropriate prescriptions dropped by roughly a third. The mechanism is cognitive dissonance, the discomfort of acting contrary to one's stated commitments. Milkman distinguishes between "sophisticates," who recognize their self-control limitations and adopt such tools, and "naïfs," who overestimate their willpower and reject them.

The fourth chapter identifies forgetting as a surprisingly common cause of follow-through failure. Research by Hermann Ebbinghaus, a 19th-century German psychologist, showed that humans forget nearly half of newly learned information within 20 minutes. Milkman presents NYU psychologist Peter Gollwitzer's research on cue-based plans that link a specific action to a specific trigger ("When ___ happens, I'll do ___"). Students who formed such plans for holiday break goals achieved a 62 percent success rate, compared to 22 percent for those who did not. Milkman adapts the approach for flu shot mailings, adding a prompt for recipients to write down when they plan to get vaccinated, which increases vaccinations by 13 percent. Psychologist Angela Duckworth, a frequent collaborator of Milkman's, argues that cue-based planning is the single most important behavioral science insight for goal achievement because it forces people to break large goals into concrete steps.

The fifth chapter reframes laziness as a feature that can be harnessed through wise defaults and habit engineering. After an IT consultant changed a software default at Penn Medicine so that prescriptions were automatically sent as generics, the generic prescription rate jumped overnight from 75 to 98 percent. For repeated decisions where defaults cannot help, Milkman turns to habits. An experiment she conducts with economist John Beshears at Google yields a surprising finding: Employees rewarded for exercising on a flexible schedule develop stickier gym habits than those rewarded for exercising at a fixed time. Rigid exercisers skip the gym entirely when unable to go at their usual time, while flexible exercisers learn to work out under varying conditions. Milkman concludes that the stickiest habits form when people practice good decisions across a range of circumstances.

The sixth chapter addresses self-doubt. Milkman's doctoral student Lauren Eskreis-Winkler discovers that most people struggling with goals already know what would help; the barrier is not ignorance but a lack of confidence. Eskreis-Winkler proposes a counterintuitive solution: asking struggling people to give advice to others rather than receive it. In a study with nearly 2,000 high school students, those assigned to advise younger peers on study strategies earned higher grades. Being asked for advice signals capability, and people feel compelled to follow their own counsel. Milkman also explores how expectations shape outcomes: Psychologist Alia Crum informed half of a group of hotel housekeepers that their daily work met recommended exercise levels, and four weeks later this group lost weight and saw blood pressure reductions despite no change in routine. To address setbacks, Wharton colleague Marissa Sharif's strategy of allowing "emergency" skips proves effective: Participants given a demanding goal with two emergency passes achieved it at more than double the rate of those given an equivalent goal without the emergency framing.

The seventh chapter examines conformity. UC Davis economist Scott Carrell analyzes data from the U.S. Air Force Academy, where cadets were randomly assigned to squadrons of 30 students, and finds that peers' academic quality substantially affects individual grades. Milkman introduces the "copy and paste" strategy of deliberately imitating successful peers' methods, noting that research confirms people exercise more when encouraged to find and replicate strategies from peers they know than when given tips from anonymous sources. However, positive social norms can backfire. When the Air Force Academy grouped the lowest and highest performers together, grades declined for two consecutive years: Without middle performers to bridge the gap, the groups polarized. Milkman's own research finds that telling low-saving employees that most colleagues save depresses sign-up rates, likely because those already behind feel they can never catch up. Social influence works best when peer achievements feel attainable rather than hopelessly out of reach.

The concluding chapter argues that lasting behavior change requires treating internal obstacles as chronic conditions demanding ongoing management. Milkman and Duckworth disagree about their massive experiment testing more than 50 interventions at gym chain 24 Hour Fitness: Many boost attendance during the four-week program, but almost none produce lasting effects. Economist and physician Kevin Volpp reframes the problem: Doctors do not prescribe insulin for a month and expect diabetes to be cured. A study of home-energy reports reinforces this point: Households that received social-comparison messages for two years conserved energy even after the reports stopped, but their savings decayed by 10 to 20 percent annually without continued messaging. Milkman concludes that the internal obstacles to change are enduring features of human nature, and when repeated attempts at a specific goal fail, the broader objective can often be pursued through alternative paths and a fresh start with a better-tailored approach.