Instability of defection in the prisoner's dilemma under best experienced payoff dynamics

We study population dynamics under which each revising agent tests each action k times, with each trial being against a newly drawn opponent, and chooses the action whose mean payoff was highest during the testing phase. When k=1, defection is globally stable in the prisoner's dilemma. By contrast, when k>1 we show that, if the gains from defection are not too large, there exists a globally stable state in which agents cooperate with probability between 28% and 50%. Next, we characterize stability of strict equilibria in general games. Our results demonstrate that the empirically plausible case of k>1 can yield qualitatively different predictions than the case k=1 commonly studied in the literature.