Reciprocity evolves more readily in competitive than cooperative socio-ecologies.

Tracking what others did and matching other's expected actions is seen across a range of biological systems. As reciprocal matching rewards and reinforces cooperators and punishes and discourages non-cooperators, reciprocal matching can help communal living. The strength of reciprocity as a social strategy also comes from its success in protecting the individual against the risk of exploitation by punishing defectors. Although often overlooked, this feature carries a strong weight when exploitation risk is high. Here, we use evolutionary agent-based simulations to examine how reciprocal matching evolves across competitive socio-ecologies with a high risk of exploitation and cooperative socio-ecologies with a lower risk of exploitation. Results show that reciprocal matching as a social strategy for communal living evolves more readily in more competitive socio-ecologies where the risk of exploitation is high. Results also hold in standard Prisoner's Dilemmas with its equilibrium in single strategies (i.e. unconditional non-cooperation), for specific forms of reciprocity (i.e. tit-for-tat) and the likelihood of repeated interactions. Because reciprocal matching requires some capacity for social perception and memory, these findings suggest that such capacities for social cognition likewise serve to protect against exploitation and evolved in more competitive socio-ecologies as well.