Don´t Speak to Strangers: The Suspicious Strategy Can Help to Improve Cooperation in Spatial Donation Game

This paper studies the evolution of cooperation by using an indirect reciprocity game in complex networks. For an indirect reciprocity game, an individual who helps others at the expense of itself can be recognized as a helpful individual. And this meritorious individual can get help from other individuals with a higher probability in the future. Previous studies show that effectively identifying the meritorious individuals is the key to promote the evolution of cooperation. However, discriminating cooperative from various individuals is a big challenge only with a flat indirect reciprocity model. In this paper we introduce a suspicious strategy and combine it with coalition mechanism to improve the cooperation among self-interested individuals of a complex network. In this method, individuals play against each other in a donation game where they can create coalitions to share information about their reputations, and use suspicious strategy to avoid the exploitation from defectors. With extensive experiments, we ascertain that using our method, the cooperation between individuals in a complex network is promoted.