The effects of time-varying rewards on the evolution of cooperation

Understanding how cooperative behavior emerges within a population of autonomous individuals has been the focus of a great deal of research in biology, economics and more recently in the multi-agent systems domain. However, there are still many open questions. In this paper, we address some of these questions by investigating the effects of time-varying, non-symmetric rewards on the evolution of cooperation in the spatial Prisoner's dilemma game. The rationale behind this approach is based on the notion that the associated payoffs from pursuing certain strategies do vary among members of real-world populations. In our model, agents with limited cognitive capacity play the game with their local neighbours. In addition to its game playing strategy, each agent has additional attributes that can be used to control the number of rounds of the game the agent actually participates in, as well as the magnitude of any rewards that it receives. Numerical simulations show that dynamic updates to payoff values induce a change in equilibrium cooperation levels. This suggests that heterogeneous payoff values and social diversity within a cost-benefit context are important factors in the promotion of cooperation in the spatial Prisoner's dilemma game. © Springer-Verlag 2009.