One Of Psychology's Most Famous Experiments May Be Greatly Exaggerated


Stephen Luntz

Stephen has a science degree with a major in physics, an arts degree with majors in English Literature and History and Philosophy of Science and a Graduate Diploma in Science Communication.

Freelance Writer

This happy child apparently passed the marshmallow test, getting a second treat, but it doesn't mean her life is on track. Nikolai Kazakov/Shutterstock

Fifty years ago Stanford Professor Walter Mischel conducted a test that later became one of the most famous experiments in psychology. A Google search on the “marshmallow test” brings up more than 5 million hits. However, science depends on replication, and a new study has found that this simple test of children's ability to delay gratification may not be as powerful a predictor of their outcomes in life as claimed.

Part of the appeal of the marshmallow test is its simplicity. All you need is a 3-6-year-old child with a sweet tooth and two marshmallows. The test involves a researcher putting a marshmallow in front of the child and telling them that if the treat is still there when the researcher returns, they can have two marshmallows instead of one. The adult then leaves the room for approximately 15 minutes, videoing the child to see how long they can last without eating the treat.


Mischel conducted follow-up studies decades later. He found those children who were able to practice delayed gratification at an early age, holding off taking what they wanted in order to get the larger reward later, subsequently did better on a range of life measures. Notably, they were less likely to use harmful drugs and more likely to get high grades and graduate from school and university. Curiously, for such an influential study, conclusions from the follow-ups were based on groups as small as 34, all of whom had parents at one of America's most prestigious universities.

When Dr Tyler W. Watts of New York University repeated the study using a more diverse group of 918 children, he found the marshmallow test's predictive power is real, but much weaker than Mischel's data suggested. Moreover, the effect disappeared after Watts controlled for family and environmental factors.

Given the test's cult fanbase and use as a metaphor for adults' ability to delay gratification, the publication of Watts' findings in Psychological Science will no doubt put noses out of joint. However, in the light of programs inspired by Mischel's work, designed to increase children's capacity to delay gratification, it's important we use the best information available to us.

"Our findings suggest that an intervention that alters a child's ability to delay, but fails to change more general cognitive and behavioral capacities, will probably have very small effects on later outcomes," Watts said in a statement


Instead, Watts thinks we need to “target the broader cognitive and behavioral abilities related to gratification delay” if we want to improve children's capacity to achieve their goals as they grow up.

For those wondering how the test works for children who don't like marshmallows; despite the name, both Mischel and Watts allowed each child to choose their favorite from three sorts of treats.


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  • marshmallow test,

  • delayed gratification,

  • research replication