Effects of compassion on the evolution of cooperation in spatial social dilemmas.

Cooperation plays an essential role in the evolution of social species, chief among all in humans. In this paper, we study the effects of compassion on the evolution of cooperation in spatial social dilemmas by introducing a payoff redistribution mechanism. In particular, a player whose payoff is larger than the average in its neighborhood will share some it with its comparatively poor neighbors. We find that such a simple redistribution mechanism, which we interpret as a form of compassion, significantly promotes the evolution of cooperation. While traditional network reciprocity already supports the formation of compact cooperative clusters, an in-depth analysis of payoff transfer events between players reveals an enhanced form of this phenomenon through the reinforcement of payoffs of cooperators that reside along the borders of such clusters. This significantly enhances the resilience of cooperative clusters, who are in turn able to survive even at adverse conditions where traditional network reciprocity alone would long fail. We show that the observed positive effects of compassion on the evolution of cooperation are robust to changes of the interaction network and to changes in the type of the governing social dilemma.