How did cooperative behavior prevail in human evolution? Researchers from the universities of Zurich, Lausanne and Konstanz have challenged two prevailing explanations – repeated interaction on the one hand or group competition on the other. Instead, both mechanisms contribute synergistically to promoting effective cooperation.

One of the great unsolved mysteries of human evolution is how social, cooperative behaviors could have evolved. In a world where the materially successful individuals reproduce, and others slowly perish, what causes the establishment of an attitude that prioritizes the benefit of society over the individual?

The prevailing theory suggests that this is due to repeated interactions. Over generations, humans learned that cooperative behavior is productive in the long run. People cooperate because they expect to interact with the same individuals in the future. Therefore, those who behave antisocially suffer reputational damage and are punished by others for uncooperative behavior, indicating that uncooperative behavior does not pay off in the long run.

Exchange experience in Papua New Guinea

However, there is strong empirical evidence that people behave cooperatively even in informal and anonymous interactions where there is no risk of reputational damage. How can this be explained? Behavioral economists from the universities of Zurich, Lausanne and Konstanz addressed this question by conducting an experiment among indigenous people in Papua New Guinea.

In a set-up resembling a trust game, pairs of individuals had to exchange money with each other and decide whether they wanted to act selfishly and uncooperatively or instead to act socially and cooperatively. Collaborative (see box). Conclusion: When paired with an anonymous member of their own community, participants exchanged significantly more. In pairing with members of other communities, however, little was transferred.

The prevailing paradigm was challenged.

In a comprehensive theoretical analysis linked to the experiment, the researchers show that the prevailing theory of repeated interaction alone cannot explain the evolution of human cooperation, because repeated interactions enable the evolution of cooperation only when An individual’s ability to reduce cooperation should be arbitrarily limited. Without such discretionary restrictions, cooperation is lost.

This is because, even in frequent interactions, there is always an incentive to gain an advantage from the partner by cooperating a little less. Over time, this leads to a breakdown in cooperation. “This is perhaps the most provocative result of our study, because it completely contradicts the mainstream,” says corresponding author Ernst Fehr of the University of Zurich.

Collaborative groups compete with each other.

Another common thesis about how cooperation can evolve is also short-lived: the idea that groups with many team-based members fare better than competition — and that general cooperation expands as less cooperative groups disappear. However, theoretical analysis suggests that transfers between groups of cooperative and noncooperative individuals weaken cooperative groups. Additionally, there is competition between cooperative groups, which undermines overall cooperation in the population.

A combined, “super-additive” approach is key.

So how can one explain the apparent fact that people often behave very cooperatively even in one-on-one conversations? The authors show that this can be explained by the simultaneous interaction of both mechanisms. They found that two well-known mechanisms, “repetitive interaction” and “group competition,” interact synergistically and lead to a form of highly additive cooperation.

First author Charles Efferson of the University of Lausanne summarized the study’s findings this way: “Repeated interactions create an incentive for cooperation within the group. However, this is a critical condition. Group competition, on the other hand, has a stabilizing effect on it. It strengthens cooperation between the group on the one hand and promotes non-cooperative behavior towards outsiders on the other.” Thus, social motives seem to have evolved under the combined influence of both mechanisms throughout human history.

Experience in Papua New Guinea

Each participant was given five monetary units in the local currency, equivalent to half a day’s wages. They were then divided into pairs and had a one-time interaction between people, an anonymous sequential exchange. Person 1 is asked to decide how much of five monetary units he wants to give to Person 2, knowing that the amount will be doubled and given to Person 2. This decision was announced to person 2. Person 2 can now decide how much they have. Five monetary units he would like to give to person 1. This amount was also doubled. This leads to a situation in which the mutual transfer of monetary units (= cooperation) is beneficial to both parties. However, if person 2 acted selfishly and transferred nothing to person 1, and if person 1 expected this and acted selfishly, he would also transfer nothing to person 2.