Spatial prisoner´s dilemma with stochastic reaction strategies

We extend the spatial game proposed by Nowak in 1992. In Nowak´s original model, agents can only choose two strategies: AllC(unconditional cooperation) and AllD(unconditional defection). In our model, agents are allowed to adopt stochastic reaction strategies, and can learn from neighbors´ according to payoff differences. Only the lattice network was considered in Nowak´s model, while both homogenous(lattice, small-world) and non-homogenous(scale-free) networks are investigated in our paper. On the lattice networks, we found that the evolving process of the population´s strategies is quite similar to that in the replicator dynamics model [13]. On the small-world networks, we investigated the effect of randomness of the topology to the evolving result, and found that a more clustering topology tends to sustain a more cooperative world. On the scale-free networks, we investigate how the hub nodes´ initial states affect the evolving result.