Coevolution of discrete, mixed, and continuous strategy systems boosts in the spatial prisoner's dilemma and chicken games

A coevolutionary model by which both the strategy system and strategy value itself are allowed to adapt is established in the framework of spatial 2 × 2 games. Agents decide to update their behaviors in accordance with a discrete strategy (with a binary strategy set comprising only either cooperation (C) or defection (D)), mixed strategy, or continuous strategy. Because of the evolutionary advantage of the mixed strategy, which allows relatively high cooperators to offer defection to their defective neighbors to avoid exploitation by them, we found that the mixed strategy diffuses to the entire society in most of the dilemma region, and uses robust cooperation to increase the agents' typical payoffs.