The paper by James Andreoni and John H. Miller examines rational cooperation in the finitely repeated prisoner's dilemma through experimental evidence. The authors test the sequential equilibrium reputation hypothesis, which suggests that cooperation can be maintained if players believe there is a small chance their opponent might be altruistic. They manipulate subjects' beliefs about their opponents' types and compare the results with a control group playing single-shot games. The findings support the hypothesis, showing that subjects are willing to build reputations for altruism and that a significant fraction of the population appears to be altruistic. The study also suggests that cooperation can be sustained even without the possibility of reputation building, indicating that altruism may play a crucial role in maintaining cooperation. The results are consistent with the idea that a stable set of cooperative players can emerge in the population, even if they are not all altruists.The paper by James Andreoni and John H. Miller examines rational cooperation in the finitely repeated prisoner's dilemma through experimental evidence. The authors test the sequential equilibrium reputation hypothesis, which suggests that cooperation can be maintained if players believe there is a small chance their opponent might be altruistic. They manipulate subjects' beliefs about their opponents' types and compare the results with a control group playing single-shot games. The findings support the hypothesis, showing that subjects are willing to build reputations for altruism and that a significant fraction of the population appears to be altruistic. The study also suggests that cooperation can be sustained even without the possibility of reputation building, indicating that altruism may play a crucial role in maintaining cooperation. The results are consistent with the idea that a stable set of cooperative players can emerge in the population, even if they are not all altruists.