Stanford marshmallow experiment
The Stanford marshmallow experiment was a study on delayed gratification in 1970 led by psychologist Walter Mischel, a student at Stanford University. In this study, a child was offered a choice between one small but immediate reward, or two small rewards if they waited for a period of time. During this time, the researcher left the child in a room with a single marshmallow for about 15 minutes and then returned. If they did not eat the marshmallow, the reward was either another marshmallow or pretzel stick, depending on the child's preference. 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, and other life measures. A replication attempt with a sample from a more diverse population, over 10 times larger than the original study, showed only half the effect of the original study. The replication suggested that economic background, rather than willpower, explained the other half. The predictive power of the marshmallow test was challenged in a 2020 study. Work done in 2018 and 2024 found that the Marshmallow Test "does not reliably predict adult functioning".
Original Stanford experiment
The first experiment in delayed gratification was conducted by Walter Mischel and Ebbe B. Ebbesen at Stanford University in 1970. The purpose of the study was to understand when the control of delayed gratification, the ability to wait to obtain something that one wants, develops in children. Most of the research conducted during that time was done with delayed rewards in areas such as time perspective and the delay of rewards, resistance to temptation, and psychological disturbances. Not many studies had been conducted in the area of human social behavior. The authors hypothesized that an increased salience of a reward would in turn increase the amount of time children would be able to delay gratification. Since the rewards were presented in front of them, children were reminded of why they were waiting. The attention on the reward was supposed to make them wait longer.The children were led into a room, empty of distractions, where a treat of their choice were placed on a table. The researchers let the children know they could eat the treat, but if they waited 15 minutes without giving in to the temptation, they would be rewarded with a second treat. Mischel and Ebbesen observed, " covered their eyes with their hands, rested their heads on their arms, and found other similar techniques for averting their eyes from the reward objects. Many seemed to try to reduce the frustration of delay of reward by generating their own diversions: they talked to themselves, sang, invented games with their hands and feet, and even tried to fall asleep while waiting – as one successfully did."
Participants
32 children were enrolled as participants in this experiment, including 16 boys and 16 girls. The participants attended the Bing Nursery School of Stanford University. The children ranged in age from three years and six months, to five years and eight months. The median age was four years and six months. Three subjects were disqualified from the experiment because they were unable to understand the instructions and choices given by the experimenters.Detailed procedure
The procedures were conducted by two experimenters. There was an opaque cake tin presented on a table in the experimental room. Under the cake tin, there were five pretzels and two animal cookies. There were two chairs in front of the table; on one chair was an empty cardboard box. Near the chair with the empty cardboard box, there were four battery operated toys on the floor. The experimenter pointed out the four toys before the child could play with the toys. The experimenter asked the child to sit in the chair and then demonstrated each toy briefly, and in a friendly manner said they would play with the toys later on. Then the experimenter placed each toy in the cardboard box and out of sight of the child. The experimenter explained to the child that he needed to leave the room, and if the child ate the pretzel, the experimenter would return to the room. These instructions were repeated until the child seemed to understand them completely. The experimenter left the room and waited for the child to eat the pretzel – they repeated this procedure four times.Then the experimenter returned to the experimental room and opened the cake tin to reveal two sets of rewards : five pretzels and two animal crackers. The experimenter asked the child which of the two they preferred. Once the child chose, the experimenter explained that the child could either continue to wait for the more preferred reward until the experimenter returned, or the child could stop waiting by bringing back the experimenter. If the child stopped waiting then the child would receive the less preferred reward and forgo the more preferred one.
Depending on the condition and the child's choice of preferred reward, the experimenter picked up the cake tin and along with it either nothing, one of the rewards, or both. The experimenter returned either as soon as the child signaled him to do so or after 15 minutes.
Results
The results indicated the exact opposite of what was originally predicted. Instead of the rewards serving as a cue to attend to possible delayed rewards, the rewards themselves served to increase the children's frustration and ultimately decreased the delay of gratification. The results seemed to indicate that not thinking about a reward enhances the ability to delay gratification, rather than focusing attention on the future reward.Stanford marshmallow experiment
Purpose
The following study, conducted by Mischel, Ebbesen, and Zeiss, 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 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 waiting for delayed reward with an external distractor, waiting for delayed reward with an internal distractor, waiting for a delayed reward, external distractor without delay-of-reward waiting contingency, and internal distractor without delay of reward contingency.