What a New Marshmallow Test Teaches Us About Cooperation

Imagine you’re getting ready for a dinner party tonight. You’ve been busy baking a pie all afternoon, and, when the timer finally chimes, you excitedly open the oven to discover a heavenly aroma wafting out. You briefly consider what would happen if you just took a piece now while it’s still warm—it would be so delicious with some ice cream. Then, you think about how good it will feel to arrive later at the dinner party with your pie, and how happy it will make your friends, especially after they’ve worked all afternoon on their dishes, too. So, you wait. Congratulations—you’ve just delayed gratification for cooperative ends.

Exercising delay of gratification is an important aspect of human cooperation. Often, when we engage with others toward some collective goal, we are required to resist immediate temptations for ourselves in order to achieve a more long-term outcome that benefits everyone.

Consider environmental sustainability as another example. If we all want to live in a clean and healthy world, we all have to reduce our ecological footprints, using fewer resources today so we can collectively avoid environmental degradation. This requires delaying the comfort, convenience, or financial gains of using resources immediately.

Often, when we engage with others toward some collective goal, we are required to resist immediate temptations for ourselves in order to achieve a more long-term outcome that benefits everyone.

Scientists have studied delay of gratification in children for decades, in part because it’s considered to be a skill that predicts a range of life outcomes. Studies with children have sought to understand, for example, how delay of gratification in childhood may relate to academic achievement and physical health later in life.

The classic delay of gratification experiment involves giving a child a treat of some sort, traditionally a marshmallow. The experimenter then leaves the room, explaining that if the child has not yet eaten her marshmallow when the experimenter returns, she will receive a second marshmallow.

While these experiments have explored the development of delay of gratification from many perspectives, until recently this skill was hardly examined in a cooperative context. This is surprising, given how important delay of gratification is for our social lives, particularly contexts in which we rely on others and others rely on us—that is, when we are interdependent.

In a recent study, we wanted to find out how a cooperative context would affect kids’ tendencies to delay gratification in a marshmallow test. Specifically, we wanted to know whether kids would be more or less likely to delay gratification when they relied on one another compared to the standard marshmallow test in which their waiting choices affect themselves alone.

We wanted to know whether kids would be more or less likely to delay gratification when they relied on one another compared to the standard marshmallow test in which their waiting choices affect themselves alone.

We had two competing predictions: On the one hand, children might be more willing to delay gratification when they rely on one another for a second treat. This would be in line with theories proposing that cooperation elicits a sense of commitment or obligation towards our social partners. On the other hand, children might be less likely to delay gratification when they are interdependent. This is because being dependent on others is inherently risky and involves the possibility that one’s own efforts might not be rewarded (just imagine arriving at the potluck dinner with your delicious pie only to find that the other guest didn’t bother to prepare anything).

To test this, we ran a traditional marshmallow test, but we added a twist. We tested kids’ performance when participating alone, as they do in the traditional test, and compared this with a modified version of the test in which two children, interdependent with one another, both had to delay gratification in order to be rewarded with a second treat. In this new cooperative test, if one partner chose to eat the treat without waiting, neither partner would get a second treat. We paired young children who were between the ages of 5 and 6 years old, and who lived in Leipzig, Germany, and Nanyuki, Kenya.

Our study sample included both German and Kenyan children to allow us to look at how culture might affect delay of gratification in this new context. This is an important consideration because a notable criticism of the empirical social sciences is that many data sets only look at behavior in WEIRD cultures—that is, in populations that are Western, educated, industrialized, rich, and democratic. In order to develop a broader understanding of human behavioral variation, it’s important to look at how behaviors develop across distinct cultures.

In our experiment, pairs first played with a balloon together to help them feel comfortable in the testing environment. Then, an experimenter separated them into two different rooms where they each sat at a small table with a cookie on it. Because we ran the study in two different cultures, we used culture-appropriate cookies so that kids in each location would be familiar with their cookie. It’s important to know what you’re waiting for, after all!

In Germany, kids got one Oreo cookie and in Kenya, they got a locally produced vanilla sugar biscuit. The experimenter then explained to each child one by one that the cookie was theirs to eat and that she, the experimenter, had to leave the room briefly (10 minutes, unbeknownst to the kids). She also said that both children would get a second cookie if—and only if—they both refrained from eating their cookie while the experimenter was away. She explained that neither the child nor their partner would get a second cookie, however, if either one of them ate their cookie before the experimenter returned.

Half of all the pairs tested were given these interdependent rules. The other half received the same rules as the traditional marshmallow test, in which each child’s outcome was dependent on his or her behavior alone. This way, we were able to compare how children’s delay of gratification was affected by being in a cooperative context as opposed to a nonsocial context.

We found that the 5- and 6-year-old pairs in our study were more likely to wait to eat their cookie when they were interdependent than when they were independent.

We found that the 5- and 6-year-old pairs in our study were more likely to wait to eat their cookie when they were interdependent than when they were independent. This was the same across both cultures (Germany and Kenya). In other words, kids were more likely to wait to eat their treat when they were mutually dependent with a partner to earn a second treat than when their patience served them alone, like in the independent task. This is rather remarkable when you consider that the effort it took to wait was often not rewarded because a partner chose not to wait; interdependence involves uncertainty and yet kids were more willing to exercise patience despite the added risk.

Interestingly, in both versions of the test children in Kenya were more likely to wait to eat their cookie than were kids in Germany. A similar pattern was found in a previous study comparing marshmallow-test performance between kids in Germany and in Cameroon, with Cameroonian kids generally being more likely to wait. Although it’s hard to say exactly why this might be, it could be the result of different socialization in the two cultures. Specifically, parents in the Kikuyu ethnic group in Kenya, from which all of our study sample were members, tend to prioritize obedience and self-regulatory skills more than parents in Germany tend to. This could have given the Kenyan children a waiting advantage over the German kids. Despite these differences though, the effect of interdependence held across both cultures, suggesting that, potentially, growing up in any human culture might facilitate the emergence of the cooperative motivations we observed.

The effect of interdependence held across both cultures, suggesting that, potentially, growing up in any human culture might facilitate the emergence of the cooperative motivations we observed.

These findings indicate that, already from the age of 5, children are psychologically equipped to respond to social interdependence in ways that facilitate cooperation. The fact that children in two highly distinct cultures displayed the same behavior is evidence that this developmental trajectory may not be unique to children’s cultural upbringing, but may instead be something we all share—perhaps not surprising when you consider how vitally important cooperation has been, and continues to be, for our species.

Taking these findings out of the laboratory and into the real world, we can speculate that perhaps reminding children of their interdependence with classmates can help promote delay of gratification. Taking it one step further, perhaps it’s possible to remind adults the world over of our interdependence, in order to promote resource sustainability and a whole host of other cooperative behaviors dependent upon delay of gratification, not least of which: more shared pies!