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

The Marshmallow Experiment


The Stanford marshmallow experiment was a psychological study conducted in the late 1960s to early 1970s, in which children were placed in a room with some tasty snack, such as a marshmallow, and told that if they could wait for a short while before eating it then they will get an extra snack as a reward. Follow-up studies on the experiment found that children’s ability to exercise self-control in this situation, by waiting before eating the snack, was correlated with a large range of positive outcomes later in life, such as academic success and physical health.

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

However, later studies criticized the Stanford marshmallow experiment for various issues with its methodology. Furthermore, the results of a large replication study cast doubt on the predictive abilities of the marshmallow test, especially when controlling for relevant background factors such as family background and home environment.

Nevertheless, despite these criticisms, the Stanford marshmallow experiment remains of interest, due to the notable influence it had on psychological research of self-control and on people’s perception of the topic.

As such, in the following article you will learn more about the Stanford marshmallow experiment and about 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, a 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 without eating the snack, and if not, then by seeing how long it took before they ate the snack or called the researcher back into the room.

Even though the experiment was short and 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 researcher associated with the Stanford marshmallow experiment is psychologist Walter Mischel, who, together with his colleagues, published the initial studies on the experiment in 1970 and 1972, as well as the later follow-up studies. Two other notable researchers associated with this experiment are Ebbe B. Ebbesen, who was involved with the initial studies, and Yuichi Shoda, who was involved with the follow-up studies.


Other studies using the marshmallow test

Several studies used the marshmallow test in order to examine the factors that affect children’s performance on it.

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. Furthermore, similar results regarding the influence of social trust were also found in delayed-gratification tests conducted on adults.

In addition, one study found that children delayed gratification for longer if they believed that members of their ingroup, which is the social group that they identify as being a part of, also waited, while members of their outgroup did not, compared to if they believed that the opposite was true.

Finally, another study compared children’s performance on the marshmallow test when it came to three birth cohorts, from the late 1960s, 1980s, and 2000s, and found that, contrary to people’s expectations, children’s ability to delay gratification has been increasing over time, a finding that has been replicated in other studies.


Other research on the importance of self-control

“People who have better control of their attention, emotions, and actions are better off almost any way you look at it.

They are happier and healthier. Their relationships are more satisfying and last longer. They make more money and go further in their careers. They are better able to manage stress, deal with conflict, and overcome adversity. They even live longer.

When pit against other virtues, willpower comes out on top. Self-control is a better predictor of academic success than intelligence… a stronger determinant of effective leadership than charisma…. and more important for marital bliss than empathy…”

— Kelly McGonigal in “The Willpower Instinct: How Self-Control Works, Why It Matters, and What You Can Do to Get More of It

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

For example, one study found that childhood self-control predicts employment rates at adulthood, with individuals who are low in self-control being more likely to be unemployed.

Similarly, another study found that self-control at childhood predicts factors such as financial status, physical health, substance dependence, and criminal offending at adulthood, with higher levels of self-control leading to better outcomes. This remained the case even when the researchers controlled for background factors such as intelligence and familial socioeconomic status, though these factors did play a crucial role in children’s development. A later study replicated these findings, though its results emphasized, to a greater degree, the role that relevant background factors play in children’s development.

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

For example, 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.

Similarly, 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”.

Overall, these studies, together with other studies on the topic, demonstrate that self-control measured both during childhood as well as at later stages of life, is associated with a range of positive outcomes, which suggests that it’s an important ability to have.


Related concepts and terms

The marshmallow experiment focused on people’s ability to delay gratification, a facet of self-control that’s sometimes referred to as “patience”. However, the experiment has been found to be a good predictor of self-control in general, meaning that it can be used to predict people’s ability to exercise control in other ways, such as by bringing themselves to do something that they feel anxious about.

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

A notable, related concept in psychology 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.

Note: the term ‘willpower’ is sometimes used in place of the term ‘self-control’, though it’s also possible to view willpower as something that people use while they’re exercising self-control.


Criticism and replications of the Stanford marshmallow experiment

Though the Stanford marshmallow experiment gained much positive attention in the research community and the press, it has also been heavily criticized by various groups. The main criticisms of the Stanford marshmallow experiment include the following:

  • The initial sample for the experiment was highly selective, as it consisted of children from the Stanford University community.
  • The samples used in the longitudinal studies on the experiment were small and even more selective than the initial sample, since they contained only the children examined in the original experiment that the researchers were able to reach later.
  • The analyses of the data didn’t always account for potential confounding factors, such as family socioeconomic status and general cognitive abilities.

In light of these criticisms, a large replication study was conducted to assess the validity of the findings from the Stanford marshmallow experiment. This replication examined how well preschooler’s ability to delay gratification on the marshmallow test predicted a variety of 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 some 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, such as family background, home environment, and early cognitive ability.

Furthermore, the researchers found that most of the achievement boost 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 utilize relevant 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, more than a decade later, at a task requiring cognitive control. 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.

Moreover, a follow-up study on the original sample from the Stanford marshmallow experiment found that there is no significant relationship between people’s delay of gratification at preschool age and their economic outcomes in their late 40s. Nevertheless, the study did find that there is an association between more comprehensive measures of self-regulation at later ages and people’s economic outcomes in their 40s.

Finally, however, it’s important to note that some of the research criticizing the Stanford marshmallow experiment has also been criticized in itself. For example, the main replication on the topic has been criticized for various reasons, as evident, for instance, in a paper on the topic, which argues that “many of the variables in their models should not have been included as confounds because they likely captured factors that measure fundamental processes supporting delay of gratification”.

Overall, the criticisms and replications of the Stanford marshmallow experiment 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 during childhood as well as when measured during adulthood. This suggests that the main issues with the marshmallow experiment are its methodology, which is simple and appealing, but not sufficiently robust.


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 potential temptations). These strategies help us exercise self-control, and successfully delay gratification.

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


Lessons from the marshmallow experiment on exercising self-control

Though the marshmallow test is primarily known for illustrating the importance of self-control, it also provides several insights into how people can learn to better exercise their self-control.

For example, one of the original studies on the Stanford marshmallow experiment describes several factors that affected the children’s ability to exercise self-control during the test:

  • Children who were told to distract themselves by playing with a toy or by 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 of the test generally struggled to delay gratification.

Furthermore, the studies on the topic also demonstrate how the children coped with temptation, even when they weren’t instructed how to do so by the researchers. 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, in order to help yourself exercise self-control in the face of temptation, you want to avoid obsessing about the potential reward that you’re tempted by or fixating on the difficulty of resisting it. 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 taking part in unrelated positive experiences, such as reading a book, playing a game, or talking to 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. As the main book on the topic states:

“…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

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 book written about the marshmallow test 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 conducted in the late 1960s to early 1970s, in which children were placed in a room with some tasty snack, such as a marshmallow, and told that if they could wait for a short while before eating it then they will get an extra snack as a reward.
  • Follow-up studies on the experiment found that children’s ability to exercise self-control in this situation, by waiting before eating the snack, was correlated with a large range of positive outcomes later in life, such as academic success and physical health.
  • The validity of the marshmallow experiment has been questioned by a number of studies, but also supported by related research on the topic, and overall, it appears that while the marshmallow test is flawed in some ways, self-control nevertheless plays an important role in people’s development.
  • The researchers who conducted the Stanford marshmallow experiment suggested that the ability to delay gratification depends primarily on the ability to engage our cool, rational cognitive system, in order to inhibit our hot, impulsive system.
  • Therefore, to improve your ability to exercise self-control, you can focus on using relevant cool strategies, such as distracting yourself from tempting rewards, in order to inhibit hot behaviors, such as 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, which was written by the primary researcher involved with the study: “The Marshmallow Test: Why Self-Control Is the Engine of Success“.