Abstract：
Direct reciprocity is a mechanism for the evolution of cooperation in repeated social interactions. According to the literature, individuals naturally learn to adopt conditionally cooperative strategies if they have multiple encounters with their partner. Corresponding models have greatly facilitated our understanding of cooperation, yet they often make strong assumptions on how individuals remember and process payoff information. For example, when strategies are updated through social learning, it is commonly assumed that individuals compare their average payoffs. This would require them to compute (or remember) their payoffs against everyone else in the population. To understand how more realistic constraints influence direct reciprocity, we consider the evolution of conditional behaviours when individuals learn based on more recent experiences. Even in the most extreme case that they only take into account their very last interaction, we find that cooperation can still evolve. However, such individuals adopt less generous strategies, and they cooperate less often than in the classical setup with average payoffs. Interestingly, once individuals remember the payoffs of two or three recent interactions, cooperation rates quickly approach the classical limit. These findings contribute to a literature that explores which kind of cognitive capabilities are required for reciprocal cooperation. While our results suggest that some rudimentary form of payoff memory is necessary, it suffices to remember a few interactions.
摘要：
直接互惠是在反复的社会互动中合作演变的机制。根据文献,如果与伴侣多次接触，个人自然会学会采取有条件的合作策略。相应的模式极大地促进了我们对合作的理解,然而，他们经常对个人如何记住和处理回报信息做出强有力的假设。例如,当通过社会学习更新策略时，人们通常认为个人比较他们的平均收益。这将要求他们计算（或记住）他们对人口中其他所有人的收益。要了解更现实的约束如何影响直接互惠，当个人根据最近的经验学习时，我们考虑条件行为的演变。即使在最极端的情况下，他们只考虑了他们最后的互动，我们发现合作仍然可以发展。然而,这些人采取不太慷慨的策略，他们合作的频率比传统的平均收益低。有趣的是,一旦个人记住了最近两三次互动的回报，合作率迅速接近经典极限。这些发现有助于文献探索互惠合作需要哪种认知能力。虽然我们的结果表明，一些基本形式的回报记忆是必要的，记住一些互动就足够了。
