Evolution of cooperative strategies for iterated prisoner's dilemma on networks

Evolution of cooperative strategies was examined for spatial iterated prisoner's dilemma (IPD) games in many studies. Lattices and networks were frequently used as spatial structures where a single player was assigned to each node. It was demonstrated that spatial structures were beneficial for the evolution of cooperation. In this paper, we examine the effect of the choice of a network structure on the evolution of cooperation in a network-based spatial IPD game. We use a variety of networks. They are different from each other in the network size and the number of edges from each node. Some networks have edges between randomly selected nodes while edges of other networks are only between adjacent nodes. Memory-based lookup tables are used as strategies of players. Computational experiments are performed under two settings with respect to the noise in action selection. One is a noise-free setting where each player always chooses the suggested action by its strategy. The other is a noisy setting where each player chooses a different action from the suggested one with a pre-specified error probability. We examine the effects of the network size, the number of edges, the number of opponents and the addition of randomly specified edges as well as the memory length on the evolution of cooperative strategies.