Max Planck Research Group on the Dynamics of Social Behavior, Max Planck Institute for Evolutionary Biology, 24306 Plön, Germany.
School of Data Science and Society, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Proc Biol Sci. 2024 Jun;291(2025):20232493. doi: 10.1098/rspb.2023.2493. Epub 2024 Jun 19.
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.
直接互惠是在重复的社会互动中进化出合作的一种机制。根据文献，个体如果与他们的伙伴多次相遇，自然会学会采用条件合作策略。相应的模型极大地促进了我们对合作的理解，但它们经常对个体如何记忆和处理收益信息做出强烈的假设。例如，当通过社会学习来更新策略时，通常假设个体比较他们的平均收益。这将要求他们计算（或记住）与群体中的每个人的收益。为了了解更现实的限制如何影响直接互惠，我们考虑了当个体基于最近的经验学习时，条件行为的进化。即使在他们只考虑最后一次互动的最极端情况下，我们发现合作仍然可以进化。然而，这样的个体采用的策略不那么慷慨，而且合作的频率比在具有平均收益的经典设置中要低。有趣的是，一旦个体记住了两三个最近的互动的收益，合作率就会迅速接近经典极限。这些发现有助于探索互惠合作需要哪种认知能力的文献。虽然我们的结果表明需要某种基本形式的收益记忆，但记住几次互动就足够了。
