Cooperation and Endogenous Identity

We consider individual identity as abstract common social kinship, and model it as the fuzzy degree of membership to sets of individuals. We connect identity to propensity of cooperation as modeled by a Prisoners' Dilemma game played in pairs of individuals in a mixed population of cooperators and defectors. Unlike in standard evolutionary game theory, individuals are identified with set dependant strategies; their fuzzy identity is adjusted in reaction to success/insuccess as measured by relative payoff.