The late 1960s ‘Marshmallow study’ is perhaps one of the most famous social-science experiments of recent times.
As part of the test, a number of children (who were just about to enter school) had a marshmallow placed in front of them and given two choices:
- Get one marshmallow immediately.
- Get two marshmallows if they wait for a short period – typically around 15 minutes.
Through follow-up studies in the 1990s, the researchers found that children who waited for the two marshmallows have a significantly higher success rate in life. They had better academic results, were in better physical condition, had a higher income, lower divorce rates, and overall better lives.
However, a new study published at the end of May, now places the entire theory in question.
Published by New York University’s Tyler Watts and the University of California’s Irvine’s Greg Duncan and Hoanan Quan, it focused on the fact that the original marshmallow test completed in the 1960s included fewer than 90 children—all enrolled in a preschool at the prestigious Stanford campus.
Instead the researchers ‘tweaked’ the experiment to focus on more than 900 children that were also more representative of current society, including race, education, and income levels – including a number of mothers who did not have a university education.
They also allowed the children to choose their own treats (allowing for chocolates instead of marshmallows for example) to ensure that the tests were not influenced by the children’s personal traits.
With these new considerations taken into account the study found that, while there were still some benefits for the children who were able to hold out for the second marshmallow, they were nowhere near as pronounced as those found in the original study, and had largely disappeared by age 15.
“Concentrating on children whose mothers had not completed college, we found that an additional minute waited at age 4 predicted a gain of approximately one tenth of a standard deviation in achievement at age 15,” Watts said.
“But this bivariate correlation was only half the size of those reported in the original studies and was reduced by two thirds in the presence of controls for family background, early cognitive ability, and the home environment. Most of the variation in adolescent achievement came from being able to wait at least 20 seconds.”
“Associations between delay time and measures of behavioral outcomes at age 15 were much smaller and rarely statistically significant.”