就学前児童がマシュマロを前にして「15分待ったら2個目をあげる」と言われて待つことができたかどうかが、その児童の成長後の成功に強く相関している、という1990年の実験
しかし2018年現在、家庭環境などの要因をコントロールすると相関は小さくなる https://journals.sagepub.com/doi/abs/10.1177/0956797618761661
We replicated and extended Shoda, Mischel, and Peake’s (1990) famous marshmallow study, which showed strong bivariate correlations between a child’s ability to delay gratification just before entering school and both adolescent achievement and socioemotional behaviors. Concentrating on children whose mothers had not completed college, we found that an additional minute waited at age 4 predicted a gain of approximately one tenth of a standard deviation in achievement at age 15. But this bivariate correlation was only half the size of those reported in the original studies and was reduced by two thirds in the presence of controls for family background, early cognitive ability, and the home environment. Most of the variation in adolescent achievement came from being able to wait at least 20 s. Associations between delay time and measures of behavioral outcomes at age 15 were much smaller and rarely statistically significant.