The Stanford Marshmallow Experiment: How Self-Control Affects Your Success in Life

The Marshmallow Experiment


The Stanford marshmallow experiment was a psychological study originally conducted in the late 1960’s to early 1970’s, in which children were placed in a room with some tasty snack (e.g. a marshmallow), and told that if they could wait for a short while before eating it then they will get another one as a reward. Follow-up studies on the topic then showed that the children’s ability to exercise self-control in this situation and delay gratification by waiting before eating the snack, is correlated with a large range of positive outcomes later in life.

This experiment received much attention in the media, and was used to emphasize the importance of self-control, a concept which was supported by other studies on the topic.

However, later studies also criticized the Stanford marshmallow experiment itself for various issues with its methodology and underlying concepts. Furthermore, a large replication study found smaller effect sizes than were found in the original study, especially when controlling for relevant background factors such as family background and the home environment, and other replications also cast doubts on the validity of this experiment.

Nevertheless, despite these criticisms, the Stanford marshmallow experiment is worth learning about, due to the major influence it has on psychological research and popular perception of this topic, and due to the general importance that self-control has on people’s life, as well the related advice that if offers on understanding and improving your own self-control.

As such, in the following article you will learn more about the Stanford marshmallow experiment and related research on the importance of self-control, see the main criticisms of this study, and learn how you can use a few simple techniques in order to strengthen your own self-control when necessary.


The procedure and results of the Stanford marshmallow experiment

The initial data collection for the Stanford marshmallow experiment took place between 1968 and 1972, using toddlers and preschoolers around the age of 4, who attended Stanford University’s Bing Nursery School.

The main procedure for the experiment was as follows:

  • First, the child was taken into a room and allowed to pick a snack that they would like to eat, such as a marshmallow, a pretzel, or a cookie.
  • Then, the child was then told that the researcher has to leave the room for a few minutes, and that if they could wait until the researcher came back without eating the snack, then they would get another snack of their choice as a reward.

The children’s ability to delay gratification was measured by seeing whether they were able to wait until the researcher returned, and if not, then by seeing how long it took before they ate the snack or called the researcher back.

Even though the experiment was simple, the researchers found that the children’s performance on this test at an early age predicted their long-term success in various ways. Specifically, kids who were able to wait longer before eating the snack were:

Note: the main research associated with the Stanford marshmallow experiment is psychologist Walter Mischel, who together with his colleagues, published the first two studies on the experiment, in 1970 and 1972, and who was involved in the follow-up studies on the initial sample. Also, note that this experiment and the related studies are sometimes referred to by similar names, such as the Stanford marshmallow test.


Other research on the importance of self-control

Other research on the topic of self-control, which used different methods than the Stanford marshmallow experiment, supports the idea that self-control is associated with a range of positive outcomes in life.

For example, one study found that self-control at childhood predicts factors such as financial status, physical health, substance dependence, and criminal offending outcomes at a later age, with higher levels of self-control leading to better outcomes. This remained the case even when controlling for background factors such as intelligence and familial socioeconomic status, though these factors do play a crucial role in children’s development and odds of success. A later study replicated these findings, though it emphasized, to a greater degree, the role that relevant background factors play in children’s development.

Similarly, another study found that childhood self-control is able to predict people’s outcomes in life, with individuals who are low in self-control being more likely to be unemployed as adults.

Furthermore, research on self-control found that this factor also plays an important role in predicting people’s success when measured during adulthood.

For example, a study conducted on university students showed that higher levels of self-control are correlated with “a higher grade point average, better adjustment (fewer reports of psychopathology, higher self-esteem), less binge eating and alcohol abuse, better relationships and interpersonal skills, secure attachment, and more optimal emotional responses”.

Similarly, a study conducted on people participating in a weight-loss program found that higher levels of self-control were associated with increased weight loss during the program, as a result of eating less and exercising more.

Overall, these studies, together with other studies on the topic, demonstrate that self-control measured both during childhood as well as at later of stages of life, is associated with a range of positive outcomes.


Related concepts and terms

The marshmallow experiment focuses on people’s ability to delay gratification, which is one aspect of self-control, and has been found to be a good predictor of self-control in general.

n some cases, people use the term ‘patience’ to refer to self-control as it was investigated in this study, and research on the topic sometimes uses the term ‘willpower’ in place of self-control.

The trait of self-control in general is crucial to people’s ability to self-regulate their behavior in pursuit of their goals, an ability which is also affected by people’s executive functions, which are the cognitive processes and abilities, such as task-switching and behavioral inhibition.

In addition, a related concept is conscientiousness, which is the trait of being disciplined, achievement-oriented, organized, and focused, since this trait is one of the strongest predictors of people’s ability to delay gratification.


Criticism and replications of the Stanford marshmallow experiment

The main criticisms of the Stanford marshmallow experiment include the following:

  • The initial sample for the experiment is based on a selective sample, composed of children from the Stanford university community.
  • The samples used in the longitudinal studies on the experiment were based on small and even more selective sample of the children from the original study.
  • The analyses of the data didn’t always account for potential confounding factors, such as family socioeconomic status and general cognitive abilities.

A large replication study was therefore conducted in order to assess the validity of the findings from the Stanford marshmallow experiment, by examining the associated between preschooler’s ability to delay gratification with academic and behavioral outcomes at age 15.

The researchers considered their study to be “a conceptual, rather than traditional, replication of Mischel and Shoda’s seminal work”, since there were several notable differences between their replication and the original work on the topic. These differences included a larger sample, a focus on children born to mothers who had not completed college, and the use of a modified version of the original marshmallow experiment.

The replication did find that the ability to delay gratification at the age of 4 predicted increased achievement at the age of 15. However, the effect size of this association was only half as big as in the original studies, and was reduced by two thirds when the researchers controlled for relevant factors, including family background, home environment, and early cognitive ability.

Furthermore, the researchers found that most of the achievement boost coming from the early ability to delay gratification came from the ability to wait for only 20 seconds. This calls into question the hypothesis proposed by the original researchers, that the relationship between the ability to delay gratification and later academic achievement is driven primarily by the ability to generate useful metacognitive strategies, since such strategies are unlikely to have played a significant role in children’s ability to wait only 20 seconds.

The findings of this replication were supported by another replication, which found that the ability to delay gratification at age 4.5 did not predict children’s academic achievement at age 15, once relevant background variables were controlled for.

In addition, a different replication of the original study, which followed the original protocol more closely but used a smaller sample, found that the ability to delay gratification at the age of 4 did not predict children’s performance at a go/no-go task requiring cognitive control, where participants are expected to press a button wherever a target (go) stimulus appears, but abstain from reacting when a non-target (no-go) appears. However, the children’s ability to direct their attention away from the rewarding stimuli was associated with increased efficiency at the task, in terms of being able to perform it at greater speed without reduced accuracy.

Overall, the criticisms of the Stanford marshmallow effect and its replications cast doubt on its validity. Nevertheless, given the large body of supporting evidence on the topic, research suggests that self-control does play an important role when it comes to success in life, both when measured on children as well as on adults, and the main issues seem to be the procedure of the marshmallow experiment, which is simple and appealing, but not sufficiently robust.

Note: the research criticizing the Stanford marshmallow experiment has also been criticized. For example, the main replication on the topic has been criticized in a paper which argues that the analyses in the replication “may have removed the very relationship of interest by controlling for fundamental processes supporting delay of gratification that indeed are likely targets of interventions”.


Variations of the Stanford marshmallow experiment

Several studies used the marshmallow experiment in order to measure factors beyond the effects of the ability to delay gratification on later success in life.

For example, studies found that trust plays a significant role in children’s decision to wait on the marshmallow task. This was the case both when it came to specific trust in the person conducting the experiment, who promised the reward to the children if they could wait, as well as when it came to children’s generalized trust in unfamiliar people. Similar results on the importance of social trust were also found later in similar delayed-gratification tasks conducted on adults.

Another study found that children delayed gratification for longer if they believed that their in-group, which is the social group that they identify as being a part of, waited, and their out-group did not, compared to if they believed that the opposite was true.

Finally, another study compared children’s performance on the marshmallow test between children in three birth cohorts in the late 1960s, 1980s, and 2000s, and found that, contrary to people’s intuition, children’s ability to delay gratification increased over time, rather than decreased.


The cognitive mechanisms of self-control

Based on the findings of the Stanford marshmallow experiment, researchers suggest that we engage two cognitive systems when faced with a situation that requires self-control:

  • Hot system. The hot system is our impulsive, emotional system. “Hot” behaviors, which rely on this system, include things such as fixating on rewards (e.g. imagining what a marshmallow will taste like). These behaviors undermine our self-control, and make it more difficult for us to resist temptation.
  • Cool system. The cool system is our rational, emotionally-neutral system. “Cool” strategies, which rely on this system, include things such as successful self-distraction (e.g. playing a game which is unrelated to the rewards). These strategies help us exercise self-control, and successfully delay gratification.

Based on these mechanisms, we can say that our self-control depends on our ability to inhibit the occurrence of “hot” thoughts behaviors, by utilizing “cool” strategies.


Lessons from the marshmallow experiment on improving your self-control

“…the ability to delay immediate gratification for the sake of future consequences is an acquirable cognitive skill.”

— Walter Mischel in “The Marshmallow Test: Why Self-Control Is the Engine of Success

Based on the cognitive mechanisms of self-control that were outlined in the previous section, and on the results of the various marshmallow experiments, several effective techniques for improving your self-control have been identified. Specifically, one of the original studies on the topic showed that techniques affected the children’s ability to delay gratification:

  • Children who were told to distract themselves by playing with a toy or by just thinking about playing with one were able to delay gratification for longer.
  • Children who were told to think about “fun things” were able to wait for significantly longer than those who were told to think “sad thoughts”.
  • Children who were told to spend their time thinking about the rewards themselves generally struggled to delay gratification.

As the first study on the topic states:

“One of the most striking delay strategies used by some subjects was exceedingly simple and effective. These children seemed to facilitate their waiting by converting the aversive waiting situation into a more pleasant nonwaiting one. They devised elaborate self-distraction techniques through which they spent their time psychologically doing something (almost anything) other than waiting.

Instead of focusing prolonged attention on the objects for which they were waiting, they avoided looking at them. Some children 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 child successfully did…

These observations, while obviously inconclusive, suggest that diverting one’s attention away from the delayed reward (while maintaining behavior directed toward its ultimate attainment) may be a key step in bridging temporal delay of reward. That is, learning not to think about what one is awaiting may enhance delay of gratification, much more than does ideating about the outcomes.”

This means that you want to avoid obsessing about the rewards, or fixating on the difficulty of resisting the temptation to enjoy them. Instead, as soon as you recognize yourself starting to fall into one of these negative thought patterns, you need to mentally “exit” it as quickly as possible.

You can do this by distracting yourself, and by engaging in unrelated positive experiences, which is a way of engaging your “cool”, rational cognitive system in order to inhibit your “hot”, impulsive system. This can be anything from playing a game to reading a book, to talking with a friend. The more positive the experience, and the more it can distract you from the potential reward, the more it will help you exercise restraint and self-control.

This may sound difficult to accomplish, but studies show that self-control training can be beneficial in the long term, and that you can strengthen your self-control through the regular practice of small acts of self-control. This is important, since it means that doing something such as reducing your snacking behavior can later help you exercise self-control in unrelated areas, such as pushing yourself at the gym, or fighting against your procrastination tendencies when it comes to doing work.

Note: the main book on the topic discusses other techniques that you can use to improve your self-control, such as increasing your connection to your future self and creating if-then implementation plans.


Summary and conclusions

  • The Stanford marshmallow experiment was a psychological study originally conducted in the late 1960’s to early 1970’s, in which children were placed in a room with some tasty snack (e.g. a marshmallow), and told that if they could wait for a short while before eating it then they will get another one as a reward.
  • Follow-up studies on the topic then showed that the children’s ability to exercise self-control in this situation and delay gratification by waiting before eating the snack, is correlated with a large range of positive outcomes later in life.
  • The validity of the marshmallow experiment has been questioned by a number of later studies, but also supported by related research on the topic, which overall suggests that self-control plays an important role in people’s development.
  • The researchers who conducted the experiment suggest that the ability to delay gratification is affected primarily by the ability to engage our “cool”, rational cognitive system in order to inhibit your “hot”, impulsive system.
  • To improve your own self-control by using “cool” strategies, such as distracting yourself from tempting rewards, and by inhibiting “hot” behaviors, such as not obsessing about the difficulty of resisting a certain temptation.


If you found this concept interesting and you want to learn more about it, read the main book on the topic, written by the researcher who conducted the original study: “The Marshmallow Test: Why Self-Control Is the Engine of Success“.