Abstract

: Indirect reciprocity is a cooperation mechanism based on the idea that prosocial behavior can help individuals accrue a good reputation in the eyes of third parties who can in turn behave cooperatively towards them. Previous work has investigated the conditions under which moral systems of indirect reciprocity—here defined as combinations of a strategy or action rule specifying how to behave towards second parties and an assessment rule specifying how to judge third parties—can be stable and sustain cooperation when reputations can be either "good" or "bad", actions are binary, and social interactions take the form of a simple donation game. We extend this influential framework to a broader set of cooperative dilemmas (including general binary-action prisoner's dilemmas, snowdrift games, and stag hunts) and to a broader set of assessment rules that consider the two actions and the two reputations of a pair of players when updating their reputations. While this extension implies an important increase in the dimensionality of the space of games used to model social interactions and in the number of possible assessment rules, it also enables us to identify the key features of successful moral systems across cooperative dilemmas. Moral consistency is the fundamental ingredient; it requires that the combination of action and assessment rule is non-hypocritical in the sense of only judging as "good" those individuals who behave exactly like oneself. We find that consistent discriminator strategies are evolutionarily stable and maximally cooperative across diverse social environments, particularly if they also show contrition, which means that they prescribe unconditional cooperation when their own reputation is "bad". Our results unify previous research on indirect reciprocity under a single organizing principle and suggest that simple moral principles can sustain cooperation across social environments with different degrees of payoff interdependence.

Reference

Jorge Peña, “Contrition and moral consistency sustain reputation-based cooperation across cooperative dilemmas”, IAST Lunch Seminar, Toulouse: IAST, June 20, 2025, 12:45–13:45, room Auditorium 4 (First floor - TSE Building).