The Stanford marshmallow experiment refers to studies of deferred gratification that were performed in the 1960s and 1970s by Walter Mischel, an American psychologist specializing in personality theory and social psychology.

In the experiments, a child was offered a choice between one immediate small reward and two small rewards if the child successfully waited for fifteen minutes. The purpose of the study was to understand at what age children developed the ability to wait in order to obtain something they wanted (deferred gratification).

Follow-up studies on the same children who had participated in the experiments showed a correlation between the results of the marshmallow test and the success of the children later in life (1).

The first follow-up study, performed in 1988, showed that the children who had delayed gratification longer in the experiment were described 10 years later by their parents and adolescents as being significantly more competent than their peers.

A second follow-up study, performed in 1990, showed that a child’s ability to delay gratification correlated with higher SAT scores.

In 2011, a third study, using neuroimaging techniques, was conducted on the original participants when they reached mid-life. The results showed that those who were able to defer their gratification differed anatomically from those who were unable to defer gratification, seen in the prefrontal cortex and the ventral striatum of the brain.

Source:

(1) Shoda, Yuichi; Mischel, Walter; Peake, Philip K. (1990). “Predicting Adolescent Cognitive and Self-Regulatory Competencies from Preschool Delay of Gratification: Identifying Diagnostic Conditions“. Developmental Psychology 26 (6): 978–986.