 The connection between ESSs and stable states under an evolutionary dynamical model is weakened further if we do not model the dynamics using a continuous population model. For example, suppose we use a local interaction model in which each individual plays the prisoner’s dilemma with his or her neighbors. Nowak and May (1992, 1993), using a spatial model in which local interactions occur between individuals occupying neighboring nodes on a square lattice, show that stable population states for the prisoner’s dilemma depend upon the specific form of the payoff matrix.  [4]  (What is interesting about this finding is that, in all cases, it remains true that Defect strictly dominates Cooperate, so the fundamental underlying strategic problem described by the game has not changed.)