Social norms, Emotions and cooperation in groups

International audienceA large body of literature in experimental economics is concerned by cooperative behavior in a public good context. Several factors are considered important for sustaining cooperative behavior. These are, among others, the net gain from cooperation, privacy of decision, social disapproval or the existence of a punishment mechanism. We discuss the impact of these features on cooperation in the framework of a single model. More specifically, we consider that individuals support some emotional costs deviating from the cooperative behavior. A game theoretical framework enables us to identify a polymorphic equilibrium in which cooperators and defectors coexist. Players with high emotional costs cooperate while those with low emotional costs defect. The equilibrium with cooperative behavior depends on the distribution of emotional cost in the society. We show how the attractiveness of the group, the gain from cooperation or the distribution of emotional cost affects the equilibrium probability of cooperation. More generally we introduce the notion of emotional game which is a Bayesian game with individual types given by emotional costs where the utility function of an individual depends on the deviation from a prescribed action (an implicit norm)