Smithsonian.com

A four-year-old girl reenacts the marshmallow test (Credit: J. Adam Fenster / University of Rochester)

When I wrote about the marshmallow test several years ago, it seemed so simple:

A child was given a marshmallow and told he could either ring a bell to summon the researcher and get to eat the marshmallow right away or wait a few minutes until the researcher returned, at which time the child would be given two marshmallows. It’s a simple test of self control, but only about a third of kids that age will wait for the second marshmallow. What’s more interesting, though, is that success on that test correlates pretty well with success later in life. The children who can’t wait grow up to have lower S.A.T. scores, higher body mass indexes, problems with drugs and trouble paying attention.

The initial finding hasn’t been overturned, but a new study in the journal Cognition is adding a layer of complexity to the test with the finding that whether the child perceives the researcher as trustworthy matters.

“Our results definitely temper the popular perception that marshmallow-like tasks are very powerful diagnostics for self-control capacity,” Celeste Kidd, a doctoral candidate in brain and cognitive sciences at the University of Rochester and the study’s lead author, said in a statement.

Kidd and her colleagues started their experiment by adding a step before giving their group of 28 three- to five-year-old children the marshmallow test: Similar to the marshmallow test, the children were given an art task, with a researching placing before a child either a well-worn set of crayons or a small sticker. The children were promised a better art supply (new crayons or better stickers) if they waited for the researcher to come back. With half of the children, though, the researcher didn’t follow up on that promise, telling the kid that better supplies were unavailable.

And then the researcher administered the marshmallow test.

Children who had been primed to believe that the researcher was reliable waited an average of 12 minutes before eating the marshmallow, but those in the “unreliable” group waited only three minutes. What’s more, nine out of 14 children in the “reliable” group were able to wait the full 15 minutes for the researcher to return, while only one kid in the unreliable group was able to wait that long.

“Delaying gratification is only the rational choice if the child believes a second marshmallow is likely to be delivered after a reasonably short delay,” Kidd said. Self control isn’t so important, it seems, if you don’t think there’s anything worth controlling yourself for.

Kidd got interested in the test after volunteering at a homeless shelter. “There were lots of kids staying there with their families. Everyone shared one big area, so keeping personal possessions safe was difficult,” Kidd said. “When one child got a toy or treat, there was a real risk of a bigger, faster kid taking it away. I read about these studies and I thought, ‘All of these kids would eat the marshmallow right away.’ “

The study doesn’t invalidate the marshmallow test–willpower is still important–but it does mean that people shouldn’t look at kids who fail the test as being instantly doomed to failure. Instead, parents of kids who appear to lack self control might want to look more closely at why they would eat the marshmallow–is it because they can’t wait or because they can’t trust that the next marshmallow will appear?