Observations on Cooperation
研究随机匹配囚徒困境中，玩家观察对手少量过往行为时，少量承诺型个体的存在如何破坏已有合作机制，并提出一种新策略组合来维持合作。
We study environments in which agents are randomly matched to play a\nPrisoner's Dilemma, and each player observes a few of the partner's past\nactions against previous opponents. We depart from the existing related\nliterature by allowing a small fraction of the population to be commitment\ntypes. The presence of committed agents destabilizes previously proposed\nmechanisms for sustaining cooperation. We present a novel intuitive combination\nof strategies that sustains cooperation in various environments. Moreover, we\nshow that under an additional assumption of stationarity, this combination of\nstrategies is essentially the unique mechanism to support full cooperation, and\nit is robust to various perturbations. Finally, we extend the results to a\nsetup in which agents also observe actions played by past opponents against the\ncurrent partner, and we characterize which observation structure is optimal for\nsustaining cooperation.\n