Photograph by Adrian Nakic / Getty.

Walter Mischel had a terrible time quitting smoking. He had started young, and, even as his acumen and self-knowledge grew, he just couldn’t stop. His habit continued through his years as a graduate student, at Ohio State, and into the beginning of his teaching career, as a psychologist at Harvard and then at Stanford, in the nineteen-fifties and sixties. “I was a three-packs-a-day smoker, supplemented by a pipe,” Mischel told me recently. “And, when the pipe ran out, it was supplemented by a cigar.” After the first Surgeon General’s report on the dangers of tobacco came out, in 1964, Mischel realized that his smoking could very well kill him. And yet his attempts to quit failed spectacularly. He’d stop, and then, like so many people who try to break the habit, he’d start again. He justified his continued puffing as part of his professorial image.

Mischel’s story isn’t surprising—nicotine is addictive, and quitting is difficult—except for one thing: Mischel is the creator of the marshmallow test, one of the most famous experiments in the history of psychology, which is often cited as evidence of the importance of self-control. In the original test, which was administered at the Bing Nursery School, at Stanford, in the nineteen-sixties, Mischel’s team would present a child with a treat (marshmallows were just one option) and tell her that she could either eat the one treat immediately or wait alone in the room for several minutes until the researcher returned, at which point she could have two treats. The promised treats were always visible and the child knew that all she had to do to stop the agonizing wait was ring a bell to call the experimenter back—although in that case, she wouldn’t get the second treat. The longer a child delayed gratification, Mischel found—that is, the longer she was able to wait—the better she would fare later in life at numerous measures of what we now call executive function. She would perform better academically, earn more money, and be healthier and happier. She would also be more likely to avoid a number of negative outcomes, including jail time, obesity, and drug use.

Mischel has travelled around the world to study delayed gratification in various cultural and socioeconomic contexts. The principles from the marshmallow test seemed to hold universally. But, even as he was learning just how important self-control is to success in life, he couldn’t keep himself from smoking. He told himself that he was perfectly in control, that smoking kept him calm, balanced, and focussed. He convinced himself that all of those negative repercussions he had learned about had nothing to do with him.

It was not until one day in the late nineteen-sixties, when he saw a man with metastasized lung cancer in the halls of Stanford’s medical school—chest exposed, head shaved, little green “x” marks all over his body, marking the points where radiation would go—that Mischel realized he was fooling himself. Finally, something clicked. From then on, each time he wanted a cigarette (approximately every three minutes, by his count) he would create a picture in his mind of the man in the hallway. As he described it to me, “I changed the objective value of the cigarette. It went from something I craved to something disgusting.” He hasn’t had a smoke since.

Mischel, who is now eighty-four years old, has just published his first popular book, “The Marshmallow Test: Mastering Self-Control.” It is part memoir, part scientific analysis, and part self-help guide. In the book, he describes the original impetus for the marshmallow study. At the time, his daughters, Judith, Rebecca, and Linda, were three, four, and five years old, respectively. “I began to see this fascinating phenomenon where they morphed from being highly impulsive, immediate creatures who couldn’t delay anything,” he told me. “There were these amazingly rapid changes—everything around them was the same, but something inside them had changed. I realized I didn’t have a clue what was going on in their heads.” He wondered what was it that had enabled them to go from deciding that they wanted to wait to actually being able to do so. He found the answer among their classmates at the Bing preschool.

Mischel followed the kids in the original Bing sample for five decades, tracking how the ability to exercise self-control at an early age was correlated with various life outcomes as the children grew into adolescents and adults. (More recently, he also studied brain scans of that original cohort to examine how the ability to delay gratification is related to neural structures.) In all this work, Mischel has consistently found that the crucial factor in delaying gratification is the ability to change your perception of the object or action you want to resist. Trying to avoid the tasty treat in front of your nose? Put a frame around it in your mind, as if it were a picture or photograph, to make the temptation less immediate. One boy in Mischel’s test was initially unable to wait, but, with careful instruction, eventually learned to hold out. When Mischel asked him what had changed, the boy replied, “You can’t eat a picture.” Mischel used a different kind of picturing when he quit smoking—he replaced his pleasurable associations with cigarettes with the image of the man in the hospital.

The key, it turns out, is learning to mentally “cool” what Mischel calls the “hot” aspects of your environment: the things that pull you away from your goal. Cooling can be accomplished by putting the object at an imaginary distance (a photograph isn’t a treat), or by re-framing it (picturing marshmallows as clouds not candy). Focussing on a completely unrelated experience can also work, as can any technique that successfully switches your attention.

Mischel’s research has repeatedly shown that, while some people are naturally better at cooling than others, both children and adults can learn mental distancing techniques to strengthen their self-control. Indeed, in the years since the original Bing study, Mischel and his colleagues have started multiple school initiatives to teach delay techniques to children and adolescents, especially to those in high-stress environments. They have also worked as consultants on children’s TV shows, including “Sesame Street,” on which Cookie Monster has undergone a self-control transformation in the last few years.

Mischel believes that the skills which enable us to delay gratification are the same skills that allow us to make other good choices despite temptations to do otherwise. “We’ve found a way to really improve human choice and freedom,” he told me. “If we have the skills to allow us to make discriminations about when we do or don’t do something, when we do or don’t drink something, and when we do and when we don’t wait for something, we are no longer victims of our desires.” As Roy Baumeister, a professor of psychology at Florida State University who studies willpower, put it, self-control is like a muscle: the more you use it, the stronger it gets. Avoiding something tempting once will help you develop the ability to resist other temptations in the future.

In the nineteen-eighties, Mischel was diagnosed with celiac disease. This time around, he found it much easier to “quit” his favorite snacks than he had found it to quit smoking. “It was a eureka moment that showed me what happens when there is an automatic internal transformation,” he recalled. “It’s a sudden change where the things I’ve adored all my life—Viennese pastries, pasta Alfredo—have been mentally transformed into poison.”