Data from: Asymmetry in pay-off predicts how familiar individuals respond to one another

Familiarity influences individual decision-making in many vertebrate species. Here, we propose that familiarity modulates behaviour to different extents depending on the social context of the interaction. Specifically, the more that one player stands to gain relative to the other, the less important familiarity will be in influencing their responses to one another. We test this prediction using pairs of male guppies (Poecilia reticulata) in three competitive scenarios of increasing asymmetry in outcome to the two players: schooling under potential threat (similar outcomes), competing for a defensible food source (some asymmetry) and competing for a receptive female (strongly asymmetrical outcomes). Males show a graded response as asymmetry increases, with familiarity producing marked behavioural differences under potential threat, minor changes when competing for food, but none at all in competition for mating opportunities. This suggests that mutualistic benefits can arise as a by-product of selfish behaviour, supporting the role of pseudo-reciprocity in the evolution of cooperation.熟悉度对众多脊椎动物的个体决策过程具有显著调控作用。本研究提出，熟悉度会依据互动的社会情境，以差异化程度调控个体行为。具体而言，相较于交互另一方，某一参与者的预期收益越高，熟悉度在调节双方互动反应时的重要性就越低。我们以成对的雄性孔雀鱼（Poecilia reticulata）为实验对象，在三种随双方收益不对称程度逐步升高的竞争情境中检验上述预测：潜在威胁下的集群行为（双方收益相近）、争夺可防御食物源（存在一定程度收益不对称）以及争夺发情雌性个体（收益不对称程度极强）。雄性孔雀鱼的响应随收益不对称程度提升呈现分级特征：在潜在威胁情境中，熟悉度会引发显著的行为差异；在争夺食物时仅产生轻微的行为变化；而在交配竞争中则无任何影响。该结果表明，互利收益可作为自私行为的副产品得以产生，这为伪互惠（pseudo-reciprocity）在合作演化中的作用提供了实证支持。