The ability to postpone or inhibit a desired response or behaviour. The importance of delayed gratification for understanding individual differences in child development came to prominence as a consequence of the famous Stanford marshmallow experiment carried in 1960s by Walter Mischel in a preschool on the university campus. He told four-year children that they could have two marshmallows if they waited for his return from an errand, then left one marshmallow on a table. Some children eat it within a few seconds of the experimenter leaving, while others waited up 20 minutes for his return. The children were seen again at 18 years of age. The third of the children who showed impulsivity in taking the marshmallow scored on average 524 and 528 on the verbal and math components of the Scholastic Aptitude Test (SAT), while those who demonstrated delayed gratification knowing they would receive two instead of one marshmallows scored 610 and 652, respectively, a remarkable overall difference of 210 points. Thus, one observation that distinguished between impulsive children and those who engaged in inhibitory control in order to achieve a reward predicted academic performance on a standardised academic test some 14 years later. Others have pointed out that this difference is larger than that between children from families with graduate degrees as against those with parents who failed to complete high school, and as large as the average difference between economically advantaged and disadvantaged children.
See Impulsivity, Inhibitory control, Scholastic Aptitude Test (SAT)