Daniela Glätzle-Rützler

Third-party punishment increases cooperation in children through (misaligned) expectations and conditional cooperation

Significance Cooperation among humans depends upon the willingness of others to take costly action to enforce the social norm to cooperate. Such behavior is often coined third-party punishment. Here we show that third-party punishment is already effective as means to increase cooperation in children. Most importantly, we identify why this is the case. First, children expect (mistakenly) third parties to punish quite often and therefore they become more cooperative. Second, the presence of third parties lets children become (rightfully) more optimistic about the cooperation levels of the interaction partner in a simple prisoner’s dilemma game. As a reaction to more optimistic expectations, children cooperate more themselves. The experiment has been run with about 1,100 children aged 7 to 11 y. The human ability to establish cooperation, even in large groups of genetically unrelated strangers, depends upon the enforcement of cooperation norms. Third-party punishment is one important factor to explain high levels of cooperation among humans, although it is still somewhat disputed whether other animal species also use this mechanism for promoting cooperation. We study the effectiveness of third-party punishment to increase children’s cooperative behavior in a large-scale cooperation game. Based on an experiment with 1,120 children, aged 7 to 11 y, we find that the threat of third-party punishment more than doubles cooperation rates, despite the fact that children are rarely willing to execute costly punishment. We can show that the higher cooperation levels with third-party punishment are driven by two components. First, cooperation is a rational (expected payoff-maximizing) response to incorrect beliefs about the punishment behavior of third parties. Second, cooperation is a conditionally cooperative reaction to correct beliefs that third party punishment will increase a partner’s level of cooperation.