AI 中文总结
研究发现基于突变和成对比较的简单进化过程，可在囚徒困境等四种社会困境中驱动直接互惠达到最大收益，记忆-2策略能实现这一目标，记忆-1策略则易在雪堆博弈中被Hold-trap击败。
AI 中文摘要
直接互惠是一种基于相同个体间重复互动的合作进化机制，它能帮助自然选择偏向合作者而非背叛者，但合作是否盛行取决于进化动态的细节。我们描述了简单的进化过程，其具备惊人的能力，能在我们研究的所有社会困境中驱动直接互惠达到最大收益。该基本过程基于突变和成对比较：突变会在策略空间边界附近采样策略，成对比较包含选择强度参数。对于大种群规模、中等至高突变率以及中等至强选择强度的情况，我们发现该过程会使策略群落达到囚徒困境、雪堆博弈、猎鹿博弈和和谐博弈中的最大收益；若玩家可使用记忆-2策略，这四种博弈的最大收益均能一致实现。记忆-1策略有能力解决这四种社会困境，但通常会在雪堆博弈中被“Hold-trap”（陷阱策略）击败。
英文摘要
Direct reciprocity is a mechanism for evolution of cooperation based on repeated interactions between the same individuals. Direct reciprocity can help natural selection to favor cooperators over defectors, but whether or not cooperation prevails depends on the details of the evolutionary dynamics. We describe simple processes of evolution that have the astonishing ability of driving direct reciprocity to maximum payoff in all social dilemmas which we study. The basic process is based on mutation and pairwise comparison. Mutation samples strategies near the boundary of the strategy space. Pairwise comparison includes a parameter for intensity of selection. For large population sizes, intermediate to high mutation rates and intermediate to strong intensities of selection, we find that the process leads to communities of strategies that reach maximum payoff in Prisoner's Dilemma, Snowdrift, Stag Hunt and Harmony games. Maximum payoff in all four games is consistently achieved if players have access to memory-2 strategies. Memory-1 strategies have the capacity to resolve all four social dilemmas, but they are usually defeated by a ``Hold-trap'' in Snowdrift games.
