Purpose The following study, conducted by Mischel, Ebbesen, and
Zeiss (1972), is generally recognized as the Stanford marshmallow experiment due to its use of marshmallows as a preferred reward item. Building on information obtained in previous research regarding self-control, Mischel
et al hypothesized that any activity that distracts a participant from the reward they are anticipating will increase the time of delay gratification. It was expected that overt activities, internal cognitions, and fantasies would help in this self-distraction. Through such distraction it was also hypothesized that the subject would be able to take the frustrative nature of the situation and convert it into one psychologically less aversive. To test their expectations, the researchers contrived three settings under which to test participants; an overt activity, a covert activity, or no activity at all. They predicted that under the overt and covert activities that delay of gratification should increase, while under the no activity setting it would decrease. To assess the children's ability to understand the instructions they were given, the experiment asked them three comprehension questions; "Can you tell me, which do you get to eat if you wait for me to come back by myself?", "But if you want to, how can you make me come back?", and "If you ring the bell and bring me back, then which do you get?" Three distinct experiments were conducted under multiple differing conditions.
Experiment 1 Participants The participants consisted of 50 children (25 boys and 25 girls) from the Bing Nursery School at Stanford University. They ranged in age from 3 years 6 months to 5 years 6 months. The median age was 4 years 6 months. Six subjects were eliminated because they failed to comprehend the instructions given by the experimenters.
Whitney Tilson, later a hedge fund manager, philanthropist, author, and Democratic political activist, was a participant in the study.
Procedures The procedures were conducted by one male and one female experimenter. During the test conditions the male experimenter conducted his session with 3 male and 2 female participants, while the female experimenter conducted her session with 3 female and 2 male participants. The small room where the tests were conducted contained a table equipped with a barrier between the experimenter and the child. On the table, behind the small barrier, was a slinky toy along with an opaque cake tin that held a small marshmallow and pretzel stick. Next to the table equipped with the barrier there was another table that contained a box of battery- and hand-operated toys, which were visible to the child. Against one wall of the small room there was a chair, another table, and a desk bell. In experiment 1, the children were tested under the conditions of (1) waiting for delayed reward with an external distractor (toy), (2) waiting for delayed reward with an internal distractor (ideation), (3) waiting for a delayed reward (no distractor), (4) external distractor (toy) without delay-of-reward waiting contingency, and (5) internal distractor (ideation) without delay of reward contingency.
Experiment 2 Participants The participants consisted of 32 children from the Bing Nursery School of Stanford University. They ranged in age from 3 years 9 months to 5 years 3 months. The mean age was 4 years and 9 months. Six of the subjects were eliminated from the study because they failed to comprehend the instructions or because they ate one of the reward objects while waiting for the experimenter.
Procedures Experiment 2 focused on how the substantive content of cognitions can affect subsequent delay behavior. The conditions in Experiment 2 were the same as in Experiment 1, with the exception that after the three comprehension questions were asked of the children the experimenter suggested ideas to think about while they were waiting. These suggestions are referred to as "think food rewards" instructions in the study. They were intended to induce in the subject various types of ideation during the delay-of-gratification period.
Experiment 3 Participants The participants consisted of 16 children (11 boys and 5 girls). They ranged in age from 3 years 5 months to 5 years 6 months. The mean age was 4 years 6 months.
Procedures In experiment 3 all of the conditions and procedures were the same as in experiment 1 and experiment 2, except that the reward items were not visible to the children while they waited. In the previous experiments both of the reward objects were directly available to the children while they waited in the delay period. To achieve this change in condition the children were told that the food items needed to be kept fresh. The marshmallow and pretzel stick were then placed under the opaque cake tin and put under the table out of sight of the child. In this experiment the same "think food rewards" were given to the children as in experiment 2.
Overall results The three separate experiments demonstrate a number of significant findings. The effective delay of gratification depends heavily on the cognitive avoidance or suppression of the reward objects while waiting for them to be delivered. Additionally, when the children thought about the absent rewards, it was just as difficult to delay gratification as when the reward items were directly in front of them. Conversely, when the children in the experiment waited for the reward and it was not visibly present, they were able to wait longer and attain the preferred reward. The Stanford marshmallow experiment is important because it demonstrated that effective delay is not achieved by merely thinking about something other than what we want, but rather, it depends on suppressive and avoidance mechanisms that reduce frustration. The frustration of waiting for a desired reward is demonstrated nicely by the authors when describing the behavior of the children. "They made up quiet songs ... hid their head in their arms, pounded the floor with their feet, fiddled playfully and teasingly with the signal bell, verbalized the contingency ... prayed to the ceiling, and so on. In one dramatically effective self-distraction technique, after obviously experiencing much agitation, a little girl rested her head, sat limply, relaxed herself, and proceeded to fall sound asleep." ==Follow-up studies==