In the late 1960s, psychologist Walter Mischel and other researchers at Stanford famously showed that individual differences among preschool-age children in the ability to delay gratification correlated strongly with success in later life. Longer wait times as a child were linked years later to higher SAT scores, less substance abuse, and parental reports of better social skills.
Because of the surprising correlation, the landmark “marshmallow studies”—children were presented with the choice of eating one marshmallow immediately or holding out for two later—have been cited as evidence that qualities such as self-control or emotional intelligence may be more important to navigating life successfully than more traditional measures of intelligence, such as IQ.
Now a new Rochester study indicates that being able to delay gratification is influenced as much by the environment as by innate ability. Children who experienced reliable interactions immediately before the marshmallow task waited on average four times longer—12 versus 3 minutes—than youngsters in similar but unreliable situations.
“Our results definitely temper the popular perception that marshmallow-like tasks are very powerful diagnostics for self-control capacity,” says Celeste Kidd, a doctoral candidate in brain and cognitive sciences and lead author of the study published online in the journal Cognition.
“Being able to delay gratification—in this case to wait 15 difficult minutes to earn a second marshmallow—not only reflects a child’s capacity for self-control, it also reflects their belief about the practicality of waiting,” says Kidd. “Delaying gratification is only the rational choice if the child believes a second marshmallow is likely to be delivered after a reasonably short delay.”
The findings provide an important reminder about the complexity of human behavior, adds coauthor Richard Aslin, the William R. Kenan Professor of Brain and Cognitive Sciences. “This study is an example of both nature and nurture playing a role,” he says. “We know that to some extent, temperament is clearly inherited because infants differ in their behaviors from birth. But this experiment provides robust evidence that young children’s actions are also based on rational decisions about their environment.”
In his original experiment, Mischel set out to understand why some people can postpone gratification while others give in. As he continued to track the children in the 1980s, he found that the preschoolers who waited to earn a second treat seemed to be more socially competent and to achieve more scholastically, with average SAT scores more than 200 points higher. “Based on these findings,” Kidd and Aslin write in their paper, “the marshmallow task was argued to be a powerful diagnostic tool for predicting personal well-being and later life achievement”—a yardstick by which to measure self-control as an enduring and inherent personal trait.
For the new study, the Rochester team wanted to explore more closely whether the social environment of preschoolers influences why some are able to resist the marshmallow while others succumb to licking, nibbling, and eventually swallowing the sugary treat. The researchers assigned 28 three- to five-year-olds to two contrasting environments: unreliable and reliable. The study results were so strong that a larger sample group wasn’t required to ensure statistical accuracy. In both groups the children were given a “create-your-own-cup” kit and asked to decorate a blank paper that would be inserted into a cup.
In the unreliable condition, the children were provided a container of used crayons and told that if they could wait, the researcher would return shortly with a bigger and better set of new art supplies for their project. After two-and-a-half minutes, the researcher returned, apologizing that there were no other art supplies after all.
Next a quarter-inch sticker was placed on the table, and the children were told that if they could wait, the researcher would return with a large selection of better stickers to use. After the same wait, the researcher again returned empty handed.
The reliable group experienced the same set up, but the researcher returned with the promised materials: first with a rotating tray full of art supplies and the next time with five to seven large stickers.
The marshmallow task followed, with the explanation that the child could have “one marshmallow right now. Or—if you can wait for me to get more marshmallows from the other room—you can have two marshmallows to eat instead.” The researcher removed the art supplies and placed a single marshmallow in a small dessert dish directly in front of the child.
Kids danced in their seats, sang, and took pretend naps. Several took a bite from the bottom of the marshmallow then placed it back in the dessert cup so it looked untouched.
“We had one little boy who grabbed the marshmallow immediately, and we thought he was going to eat it,” recalls Kidd. But he sat on it. “Instead of covering his eyes, he covered the marshmallow.”
Children who experienced unreliable interactions with an experimenter waited for a mean time of three minutes and two seconds on the marshmallow task, while youngsters who experienced reliable interactions held out for 12 minutes and 2 seconds. Only one of the 14 children in the unreliable group waited the full 15 minutes, compared to nine children in the reliable condition.
“I was astounded that the effect was so large,” says Aslin. “I thought that we might get a difference of maybe a minute or so. You don’t see effects like this very often.”
In prior research, children’s wait time averaged between 5.71 and 6.08 minutes, the authors report. By comparison, manipulating the environment doubled wait times in the reliable condition and halved the time in the unreliable scenario.
The robust environmental effect provides strong evidence that the wait times reflect the children’s rational decision making about the probability of reward, the authors conclude. The results are consistent with other research showing that children are sensitive to uncertainty in future rewards.
So does that mean that if little ones gobble up dessert without waiting, parents should worry that they have failed to be role models of reliability?
“Children do monitor the behavior of parents and adults, but it’s unlikely that they’re keeping detailed records of every single action,” says Aslin. “It’s the overall sense of a parent’s reliability or unreliability that’s going to get through, not every single action.”
Adds Kidd: “Don’t do the marshmallow test on your kitchen table and conclude something about your child. It especially would not work with a parent, because your child has all sorts of strong expectations about what a person who loves them very much is likely to do.”