A landmark study in the late 1960s and early 1970s used marshmallows and cookies to assess the ability of preschool children to delay gratification. If they held off on the temptation to eat a treat, they were rewarded with more treats later. Some of the children resisted, others didn't.
A newly published follow-up revisits some of the same children, now adults, revealing that these differences remain: Those better at delaying gratification as children remained so as adults; likewise, those who wanted their cookie right away as children were more likely to seek instant gratification as adults. Furthermore, brain imaging showed key differences between the two groups in two areas: the prefrontal cortex and the ventral striatum. The findings are published in the Aug. 29 edition of the Proceedings of the National Academy of Sciences.
"This is the first time we have located the specific brain areas related to delayed gratification. This could have major implications in the treatment of obesity and addictions," says lead author Dr. B.J. Casey, director of the Sackler Institute for Developmental Psychobiology at Weill Cornell Medical College and the Sackler Professor of Developmental Psychobiology.
In the current study, Dr. Casey and her co-investigators recruited 59 adults who participated as young children in the original study and represented either extreme of the delayed-gratification spectrum -- high delayers and low delayers. Because marshmallows and cookies can be less rewarding to adults, the researchers substituted two tests. In the first, participants looked at a screen displaying a series of faces and were asked to signal only when a face of one gender was shown. This "cool" test revealed no significant differences between the two groups. A second, "hot" test used emotional cues such as a happy or frightened face. These results were much more varied and revealed that aptitude for delayed gratification was consistent from childhood into adulthood.
"In this test, a happy face took the place of the marshmallow. The positive social cue interfered with the low delayer's ability to suppress his or her actions," explains Dr. Casey.
The second test was then repeated while the participant's brain was scanned using functional magnetic resonance imaging (fMRI). The results showed that the brain's prefrontal cortex was more active for high delayers and the ventral striatum -- an area linked to addictions -- was more active in low delayers.
The original marshmallows and cookies study was led by Dr. Walter Mischel, a co-author of the current study and the Niven Professor of Humane Letters at Columbia University.