We investigate the effects of spatial structure and mobility on the evolution of cooperation. We consider a finite fixed size population of mobile cooperators and free-riders. Cooperators provide benefits to all individuals in their vicinity at a cost to themselves, whereas free-riders do not provide any benefits and incur no cost. Individuals occupy positions in a 1-dimensional lattice and are allowed to move to try to maximize their payoff. Our model allows simultaneous interactions among multiple individuals as all individuals in a neighborhood compete for the same limited resource. We create an exact stochastic simulation of this Markov process and find that smaller neighborhood size, lower mobility and shorter migration range promote the fixation of cooperators in the population. On the other hand, sufficiently large migration range coupled with high mobility rate may result in breakdown of cooperation.

evolution of cooperation, spatial structure, mobility, stochastic simulation.