cooperative behavior

New twist on marshmallow test shows power of a promise

cooperative behavior, Human behavior, Marshmallow Test, psychology, Science, sociology / Shannon Garcia / May 15, 2025

There have also been several studies examining the effects of social interdependence and similar social contexts on children’s ability to delay gratification, using variations of the marshmallow test paradigm. For instance, in 2020, a team of German researchers adapted the classic experimental setup using Oreos and vanilla cookies with German and Kenyan schoolchildren, respectively. If both children waited to eat their treat, they received a second cookie as a reward; if one did not wait, neither child received a second cookie. They found that the kids were more likely to delay gratification when they depended on each other, compared to the standard marshmallow test.

An online paradigm

Rebecca Koomen, a psychologist now at the University of Manchester, co-authored the 2020 study as well as this latest one, which sought to build on those findings. Koomen et al. structured their experiments similarly, this time recruiting 66 UK children, ages 5 to 6, as subjects. They focused on how promising a partner not to eat a favorite treat could inspire sufficient trust to delay gratification, compared to the social risk of one or both partners breaking that promise. Any parent could tell you that children of this age are really big on the importance of promises, and science largely concurs; a promise has been shown to enhance interdependent cooperation in this age group.

Koomen and her Manchester colleagues added an extra twist: They conducted their version of the marshmallow test online to test the effectiveness compared to lab-based versions of the experiment. (Prior results from similar online studies have been mixed.) “Given face-to-face testing restrictions during the COVID pandemic, this, to our knowledge, represents the first cooperative marshmallow study to be conducted online, thereby adding to the growing body of literature concerning the validity of remote testing methods,” they wrote.

The type of treat was chosen by each child’s parents, ensuring it was a favorite: chocolate, candy, biscuits, and marshmallows, mostly, although three kids loved potato chips, fruit, and nuts, respectively. Parents were asked to set up the experiment in a quiet room with minimal potential distractions, outfitted with a webcam to monitor the experiment. Each child was shown a video of a “confederate child” who either clearly promised not to eat the treat or more ambiguously suggested they might succumb and eat their treat. (The confederate child refrained from eating the treat in both conditions, although the participant child did not know that.)

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Ants vs. humans: Solving the piano-mover puzzle

Who is better at maneuvering a large load through a maze, ants or humans?

The piano-mover puzzle involves trying to transport an oddly shaped load across a constricted environment with various obstructions. It’s one of several variations on classic computational motion-planning problems, a key element in numerous robotics applications. But what would happen if you pitted human beings against ants in a competition to solve the piano-mover puzzle?

According to a paper published in the Proceedings of the National Academy of Sciences, humans have superior cognitive abilities and, hence, would be expected to outperform the ants. However, depriving people of verbal or nonverbal communication can level the playing field, with ants performing better in some trials. And while ants improved their cognitive performance when acting collectively as a group, the same did not hold true for humans.

Co-author Ofer Feinerman of the Weizmann Institute of Science and colleagues saw an opportunity to use the piano-mover puzzle to shed light on group decision-making, as well as the question of whether it is better to cooperate as a group or maintain individuality. “It allows us to compare problem-solving skills and performances across group sizes and down to a single individual and also enables a comparison of collective problem-solving across species,” the authors wrote.

They decided to compare the performances of ants and humans because both species are social and can cooperate while transporting loads larger than themselves. In essence, “people stand out for individual cognitive abilities while ants excel in cooperation,” the authors wrote.

Feinerman et al. used crazy ants (Paratrechina longicornis) for their experiments, along with the human volunteers. They designed a physical version of the piano-movers puzzle involving a large t-shaped load that had to be maneuvered across a rectangular area divided into three chambers, connected via narrow slits. The load started in the first chamber on the left, and the ant and human subjects had to figure out how to transport it through the second chamber and into the third.