Triadic awareness, or knowledge of the relationships between others, is essential to navigating many complex social interactions. While some animals maintain relationships with former group members post-dispersal, recognizing cross-group relationships between others may be more cognitively challenging than simply recognizing relationships between members of a single group because there is typically much less opportunity to observe interactions between individuals that do not live together. We presented acorn woodpeckers (Melanerpes formicivorus), a highly social species, with playback stimuli consisting of a simulated chorus between two different individuals, a behavior that only occurs naturally between social affiliates. Subjects were expected to respond less rapidly if they perceived the callers as having an affiliative relationship. Females responded more rapidly to a pair of callers that never co-occurred in the same social group, and responded less rapidly to callers that were members of the same social group at the time of the experiment and to callers that last lived in the same group before the subject had hatched. This suggests that female acorn woodpeckers can infer the existence of relationships between conspecifics that live in separate groups by observing them interact after the conspecifics in question no longer live in the same group as each other. This study provides experimental evidence that nonhuman animals may recognize relationships between third parties that no longer live together and emphasizes the potential importance of social knowledge about distant social affiliates.

中文翻译：

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实验证据表明橡子啄木鸟认识到不再共同生活的第三方之间的关系

三元意识或他人之间关系的知识对于驾驭许多复杂的社交互动至关重要。虽然一些动物在分散后仍与以前的群体成员保持着关系，但识别其他群体之间的跨群体关系可能比简单地识别单个群体成员之间的关系更具认知挑战性，因为通常很少有机会观察到不同群体之间的互动在一起生活。我们展示了橡子啄木鸟 (Melanerpes formicivorus)，一种高度社会化的物种，其回放刺激由两个不同个体之间的模拟合唱组成，这种行为仅在社会附属机构之间自然发生。如果他们认为呼叫者具有从属关系，则预计受试者的反应速度会较慢。女性对从未同时出现在同一社会群体中的一对来电者反应更快，而对实验时属于同一社会群体成员的来电者以及最后生活在同一群体中的来电者反应较慢在对象孵化之前。这表明雌性橡子啄木鸟可以通过观察它们在所讨论的同种不再生活在同一组中后的相互作用来推断生活在不同组中的同种之间关系的存在。这项研究提供了实验证据，表明非人类动物可能会识别不再共同生活的第三方之间的关系，并强调了有关远距离社会附属者的社会知识的潜在重要性。