Forty years after succumbing to a mouth-watering marshmallow as a child, middle-aged adults still have a hard time resisting temptation, a new study finds. The results, published online August 29 in the Proceedings of the National Academy of Sciences, suggest that willpower is stable over a person’s lifetime.
“I’m impressed,” says psychologist and neuroscientist Bernd Figner of Columbia University, who wasn’t involved in the experiments. “It really is a unique study.”
The experiment began in the late 1960s at Stanford University’s Bing Nursery School, where more than 500 4-year-olds were given the dreaded “marshmallow test.” The preschoolers sat in a room with only a sweet, gooey marshmallow to keep them company. A child could eat the single marshmallow, or hold out for 15 minutes to get two. Some kids couldn’t resist and gobbled the treat quickly, while others held out and doubled their reward.
Study coauthor B.J. Casey of Weill Cornell Medical College in New York City and her colleagues wanted to know whether the holdouts displayed the same kind of willpower 40 years later.
Fifty-nine of the original subjects — now in their mid-forties — came back for additional tests. This time around, researchers tested willpower in a different way: Instead of a marshmallow, the researchers used feel-good pictures of smiling faces. “We’ve learned throughout life that smiling faces are good things,” Casey says.
Participants were asked to press a button whenever they saw a particular face. The targets flashed frequently, and people grew accustomed to mashing the button quickly. But every so often, a smiling face they were meant to ignore came into the mix, forcing the participant to squelch the desire to push the button.
People who let the marshmallow get the better of them as children had a harder time curbing their impulse to push the button than the adults who held out against the marshmallow as kids, the team found. “The fact that years later, you see these differences, it’s just beyond belief, almost,” Casey says.
Brain scans of 26 participants revealed that activity in part of the brain’s frontal lobe — a region known to be important for exerting control — was associated with temptation resistance. And a brain region called the ventral striatum—thought to be important for processing desires and rewards — was linked to the inability to resist.
Finding that these particular brain regions are important for resisting temptation isn’t surprising, Figner says: “It very nicely converges with what we already know.”
Although willpower seems to be relatively stable in this group, it’s possible that particular strategies can change people’s abilities to delay gratification. Casey and colleagues are currently conducting tests with people whose willpower changed across the years.