Modeling the Evolution of Third-Party Punishment

Our recent paper on the evolution of third-party punishment behavior was published in Proceedings for The Royal Society B. Here is a link to the paper. It subsequently attracted considerable media coverage, including a press release at the University of Maryland and a magazine article in The Atlantic Cities. To quote UMD’s press release, the paper investigates the following question through an evolutionary game-theoretic lens:

Unlike police and courts that mete out official punishments, third-party punishment is informal, based on an individual’s decision to right a perceived wrong. In some cultures, third-party punishment, when used responsibly, is a useful tool to enforce social norms. Why does it evolve in some places but not others?

This research was done in collaboration with my PhD advisors Dana Nau from UMD’s Department of Computer Science, and Michele Gelfand from UMD’s Department of Psychology.Below is a video animation of a small example of the evolutionary game model, where nodes represent different individuals with different strategies. The animation shows how Responsible Punishers take over a population under social network conditions of high “strength of ties”. Left panel shows punishment strategies (R=Responsible, N=Non-Punisher, A=Antisocial, S=Spiteful). Right panel shows cooperation strategies (C=Cooperative, D=Defective, O=Opportunistic).