Mecanismos cooperativos: adotando estratégias diferentes contra oponentes distintos no dilema do prisioneiro

Abstract

The emergence of cooperation has been widely studied in the context of game theory with populations structured on graphs. Usually the individuals adopt one strategy against all their neighbors. But what does happen if the players adopt simultaneously dierent strategies against each one of their opponents, not just a single one? Here we study this question in the prisoner dilemma scenario structured on dierent graph topologies (ring, square lattice, random graphs and scale-free networks). We show that if an update rule is dened in which the players replace the strategy that furnishes the smallest payo, a punishment response mechanism against defectors without imputing cost to the punishers appears, cooperation dominates and, even if the tendency of defection is huge, cooperation still remains alive. This was established by analytical arguments and numerical simulation. We also derive a mean-eld approximation for a well-mixed population. In another context, we study a repeated public good game where the players can leave the game with a xed probability. We show that if the probability of staying is large enough cooperation thrives