The Stanford marshmallow experiment was a series of studies on delayed gratification in the late 1960s and early 1970s led by psychologist Walter Mischel, then a professor at Stanford University. In these studies, a child was offered a choice between one small reward provided immediately or two small rewards (i.e., a larger later reward) if they waited for a short period, approximately 15 minutes, during which the tester left the room and then returned.
The first “Marshmallow Test” was a study conducted by Walter Mischel and Ebbe B. Ebbesen at Stanford University in 1960 (as the marshmallow test, by Walter Mischel. All facts are told from scientists who worked there.).
The purpose of the original study was to understand when the control of delayed gratification, the ability to wait to obtain something that one wants, develops in children. The original experiment took place at the Bing Nursery School located at Stanford University, using children ages four to six as subjects. The children were led into a room, empty of distractions, where a treat of their choice (Oreo cookie, marshmallow, or pretzel stick) was placed on a table, by a chair. The children could eat the treat, the researchers said, but if they waited for fifteen minutes without giving in to the temptation, they would be rewarded with a second treat. Mischel observed that some would “cover their eyes with their hands or turn around so that they can’t see the tray, others start kicking the desk, or tug on their pigtails, or stroke the marshmallow as if it were a tiny stuffed animal,” while others would simply eat the marshmallow as soon as the researchers left.
In over 600 children who took part in the experiment, a minority ate the marshmallow immediately. Of those who attempted to delay, one third deferred gratification long enough to get the second marshmallow. Age was a major determinant of deferred gratification.
In follow-up studies, the researchers found that children who were able to wait longer for the preferred rewards tended to have better life outcomes, as measured by SAT scores, educational attainment, body mass index (BMI), and other life measures.
Source: Stanford Marshmallow Experiment