Costly Signaling and Cooperation

We propose an explanation of cooperation among unrelated members of a social group, in which providing group benefits evolves because it constitutes an honest signal of the member's quality as a mate, coalition partner or competitor, and therefore results in advantageous alliances for those signalling in this manner. Our model is framed as an {\itn}-player game that involves no repeated or assortative interactions, and assumes a payoff structure that would conform to an {\n}-player public goods game in which non-cooperation would be a dominant strategy if there were no signaling benefits. We show that honest signaling of underlying quality by providing a public good to group members can be evolutionarily stable. We also show that this behavior is capable of proliferating in a population in which it is initially rare. Our model applies to a range of cooperative interactions, including providing individually consumable resources, participating in group raiding or defense, and punishing free-riding or other violations of social norms. Our signaling model is distinctive in applying to group rather than dyadic interactions and in determining endogenously the fraction of the group that signals high quality in equilibrium.