Enhanced cooperation in prisoner's dilemma with aspiration

We develop an aspiration-based dynamic model which leads to enhanced cooperation in the Prisoner's Dilemma game played by the continuous population of agents. The main idea is to limit the aggregate information available to the agents. The model - a system of three nonlinear differential equations - describes the evolution of the aspiration levels of players who use different strategies, and the evolution of the mean frequency of the cooperative strategy in the system of players. The stationary (partial) cooperation level is calculated explicitly. We demonstrate that, contrary to the similar model with only one global aspiration level, the stationary cooperation level can be greater than half. (C) 2009 Elsevier Ltd. All rights reserved.