Parochial altruism (PA), or ingroup favoritism paired with outgroup hostility, is sometimes treated as a synonym for human intergroup relations. However, empirical data suggest that PA is highly variable—across individuals, across situations, and across groups. Here, we review theory and data on PA to explore the candidate sources for this variability. Along the way, we unpack assumptions (e.g., what constitutes a group?), identify precursors to PA behavior (e.g., context and internal states), and review evidence for the pairing of ingroup favoritism with outgroup hostility. We discuss phenomena with measurable impact on downstream behavior, including resource access and cultural institutions, but also flag how researcher expectations and methodological design impact reported variability in PA. We close by making recommendations for how researchers can reduce noise in the study of PA by checking assumptions and being deliberate in research design; this is key, as the PA literature is part of sensitive public discourse.

狭隘利他主义（PA），即内群体偏爱与外群体敌意相结合，有时被视为人类群体间关系的同义词。然而，经验数据表明，PA 在不同个体、不同情况和不同群体之间存在很大差异。在这里，我们回顾了 PA 的理论和数据，以探索这种变异性的候选来源。在此过程中，我们解开假设（例如，群体由什么组成？），识别 PA 行为的前兆（例如，背景和内部状态），并审查内群体偏爱与外群体敌意配对的证据。我们讨论了对下游行为具有可衡量影响的现象，包括资源获取和文化机构，但也指出了研究人员的期望和方法设计如何影响报告 PA 的变异性。最后，我们就研究人员如何通过检查假设和深思熟虑的研究设计来减少 PA 研究中的噪音提出建议；这是关键，因为公共事务文献是敏感公共话语的一部分。