Across cultures and time, societies have relied upon cooperation to flourish. Cooperation has an Achilles' heel that can perturb such flourishing, though: individuals’ temptations to free ride on others’ cooperation. How is cooperation maintained when individuals have incentives to cheat? Across disciplines, researchers have suggested that cooperation is made possible by third party punishment (TPP) – that is, observers’ punishment of non-cooperators. TPP has its own free riding problem, though; it is costly in itself, and people could be tempted to allow others to incur the costs of punishing cheaters.In addition, evidence has shown that punishers but are sometimes disliked and avoided, perhaps because of uncertainty about their motives. Due to these costs, the evolutionary origins of TPP are mysterious, as are the incentives for engaging in TPP in contemporary society.We argue that moral emotions may provide a solution to the costliness and ambiguity of monetary punishment because emotions convey different motives and behavioral intentions. By solving the problem of the ambiguity of a punisher’s motives and intentions, the expression of moral emotions might contribute to the stability of human cooperation. We used behavioral economic games, the third party punishment game followed by a trust game, to find out whether the expression of emotion enhances reputation. Results supported our hypothesis: third parties who expressed anger or disgust after seeing an individual act selfishly by not sharing money, were subsequently entrusted with more money than third parties who didn't express anything, or third parties who financially punished the selfish individual by taking money away from them. Furthermore, third parties who expressed anger or disgust at the same time as financially punishing were subsequently trusted more than third parties who only financially punished. These findings show that the expression of moral emotions can enhance the reputation of people who engage in third party punishment, providing a potential solution to the puzzle of third party punishment, and thereby helping to enable the evolution of human cooperation.
Findings have implications for societally relevant issues. Expressions of outrage increasingly influence social and political events.Outrage can shape and enforce social norms, mobilize groups of activists, and shape political events. The research reveals how the expression of emotions underlying outrage – disgust and anger – can be used by individuals to gain reputation benefits, helping to explain why expressions of outrage have become increasingly prevalent. These insights could also be of great value to institutions and government agencies who seek to discourage certain behaviors: doing so by using emotion expressions, instead of, or as well as, costly punishments could be more beneficial in many circumstances.
