Do you stick with your diet or have that dessert? You imagine yourself strutting the beach next summer with a trim bikini body, but that cheesecake is staring you down, just begging to be eaten. YOLO, or not this time?

The delay of gratification is an essential component of successful adulthood. Oftentimes, we have to give up an immediate but smaller reward for a larger reward later. One more nightcap, or time to cap the bottle? Sleep in, or get to the gym before work? Tell the boss what you really think of him, or hold your tongue and keep your job?

The ability to delay gratification develops gradually through childhood into early adulthood. And at any age, some of us are better at it than others. This is true even for preschoolers.

Noted psychologist Walter Mischel and his colleagues developed the marshmallow test to assess youngsters’ abilities to delay gratification. The experimenter seats the child at a table and places a marshmallow in front of him. “You can eat that marshmallow now,” she tells him. “But if you wait until I get back, you can have two marshmallows, not just one.”

The experimenter then leaves the room, but what follows is caught on hidden camera. The next 15 minutes are excruciating for the youngster, but it’s quite entertaining to watch as the child scowls and squirms, pokes and prods, nibbles and gnaws. Many try to wait it out, but few succeed. You can see some examples in the following YouTube clip.

Using this and similar procedures, Mischel and his colleagues have made two important discoveries. The first is that performance on the marshmallow test at age four predicts future life outcomes, such as academic and career success as well as overall health in adulthood.

The other finding has to do with how children succeed at the task. Those who failed tended to focus their attention on the marshmallow—touching it, holding it, tasting it. Apparently, the more they thought about it, the more tempting it became.

Children who passed the marshmallow test did so by distracting themselves. Although they were instructed to remain seated, they would cast their gaze elsewhere in the room, turn around in their seats, or even cover their eyes. By diverting their attention away from the immediate temptation, they were able to wait for the later but larger reward.

The capacity to delay gratification is not only an important milestone in human development, it has long been thought of as a uniquely human ability. But now Georgia State University psychologist Michael Beran has demonstrated that chimpanzees can pass the marshmallow test. And they do this by actively diverting their attention away from the desired reward.

First, Beran and his colleagues trained chimpanzees on a special food dispenser. As long as the chimp didn’t release the food, pellets dropped into the dispenser at regular intervals. Thus, the longer the chimp waited, the more food it got. This is the primate version of the marshmallow test.

Beran then tested the chimps in two conditions. In the first condition, the food dispenser was placed inside the enclosure, and the chimp could release the food at any time. Nearby were items such as magazines, crayons, and drawing paper, which the chimps could use to distract themselves. And that’s just what they did. In this condition, chimps were able to wait up to 20 minutes before releasing the food.

In the second condition, the food dispenser was located just outside the enclosure. So the chimps could watch the dispenser filling with food, but they had to wait for the experimenter to bring it to them. The enclosure contained the same magazines, crayons, and drawing paper as in the first condition.

This situation is somewhat like flipping through magazines in the waiting room of a doctor’s office while listening for your name to be called. The chimps also used the items to distract themselves, but they spent less time with these and more time looking longingly at the food just out of reach.

To Beran and his associates, these results suggest that the chimpanzees have some awareness of their own mental processes. That is, when the chimps knew they could have the food whenever they wanted, they intentionally used items in the enclosure to draw their attention away from the food. The chimps tried to distract themselves in the second condition as well, but they also needed to remain vigilant, since they never knew when the experimenter would make the food dispenser available.

Psychologists refer to an awareness of one’s own mental processes as metacognition. And most behavioral researchers have considered metacognition to be an ability unique to mature humans. Even human children generally lack metacognitive skills, let alone all those adult humans who bumble their way through life blithely unaware of what they’re doing.

We’d like to think there’s a gulf between us intelligent humans and all other animals. Yet research over the last few decades has shown that our primate cousins are much closer to us in mental capacities than we’d previously thought. When it comes to the marshmallow test, an adult chimpanzee can outperform the typical human preschooler.


Beran, M. J. (2015). Chimpanzee cognitive control. Current Directions in Psychological Science, 24, 352-357.

Eigsti, I.-M., Zayas, V., Mischel, W., et al. (2006). Predicting cognitive control from preschool to late adolescence and young adulthood. Psychological Science, 17, 478-484.

David Ludden is the author of The Psychology of Language: An Integrated Approach (SAGE Publications).

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