Using tags to evolve trust and cooperation between groups

Tags [2] are externally visible markers that are determined by an individual's genes. We study a simple model of interactions between large groups of boundedly rational players playing the prisoner's dilemma [1], who are allowed to see one another's tags prior to choosing an action, but may not choose their opponent. Since tags are genetically determined, they are correlated with the behavior of the tagged individual, and possessing a similar tag implies similar behavior. Our tag model exploits this correlation so as to enable beneficial interactions between groups of players. Computer simulations show that with the tag mechanism in place, cooperation between different groups of players can become common.