Psych prof puts new wrinkle in marshmallow test

Marshmallow Test

For decades, a psychological experiment known as the marshmallow test has captured the public’s imagination as a marker of self-control and a predicator of future success. In the test, a researcher presents a child with a marshmallow and leaves him or her alone for a few minutes. If the child can resist eating the marshmallow until the researcher returns, he or she can have two marshmallows instead of one.

Hidden cameras show that some kids wait patiently for the second treat, while others twist themselves into knots resisting temptation, only to eventually cave in and gobble up the sole marshmallow.

This test of delayed gratification has been found to be better correlated with scholastic performance than traditional IQ tests, but a new study shows that waiting for a bit and then giving up can actually be a rational decision. 

Joseph Kable, an assistant professor in the Department of Psychology, studies how people make value-based decisions, especially when they require valuing something in the present with something else in the future. When trying to replicate the marshmallow test in his own research, he found that a key fact had been glossed over in both popular and academic discussions: The participants don’t know how long it will be before the researcher returns.

“The kids’ responses seem illogical—if you decided to wait in the first place, why wouldn’t you wait the whole way through?” Kable says. ”Stopping in the middle seems self-defeating, but when you exert self-control in the real world, you don't know when it’s going to pay off.”

In addition to analyzing data from earlier marshmallow test studies, Kable and post-doc Joseph McGuire conducted their own survey-based research to see how people estimate the lengths of waiting times in different situations.

The researchers asked participants to imagine themselves in a variety of scenarios, such as watching a movie, practicing the piano, or trying to lose weight. Participants were told the amount of time they had been at the activity, and were asked to respond how long they thought it would be until they reached their goal or the end.

“Our intuition is that when we are waiting for something, the longer we wait, the closer and closer we get to that thing, which is what we see when we ask people about familiar things, like how long a movie will last,” Kable says. “But what we’ve found is that if you don’t know anything about when the outcome will occur, the longer you wait, the more you think you’re getting farther and farther away from that outcome.”

While the marshmallow test remains a good predictor of who is better or worse at delaying gratification, Kable’s research suggests that the mechanism behind that ability needs to be reinterpreted. It may give some hope to the impatient.  

“This is exciting to us because it suggests a way to get people to persist to the end,” Kable says. “You need to give them experiences that provide them with the right kinds of expectations.”

Originally published on March 14, 2013