Abstract Hamilton's rule predicts that altruism should depend on costs incurred and benefits provided, but these depend on the relative needs of the donor and recipient. Rewriting Hamilton's rule to account for relative need suggests an amplifying effect of need on relatedness, but not necessarily other relationship qualities. In a reanalysis of three studies of social discounting and a new replication, we find that relative need amplifies the effects of relatedness on giving in two samples of U.S. adults recruited online, but not U.S. undergraduates or Indian adults recruited online. Among U.S. online participants, the effect of genetic kinship was greater when the partner was perceived to be in higher need than when in lower need. In the other samples, relatedness and greater partner need were associated with greater giving, but the effect of relatedness on giving was not significantly amplified by need. Need never amplified the effect of social closeness on giving, although it did diminish the effect of closeness in U.S. undergraduates, likely reflecting a ceiling effect. These results confirm predictions from a modification of Hamilton's rule in a sample of U.S. adults, but raise important questions about why they hold in some samples but not others. They also illustrate the importance of understanding how contextual factors, such as relative need, can moderate the importance of common variables used in evolutionary cost-benefit analyses.

中文翻译：

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需求在决策中的放大作用

摘要 汉密尔顿规则预测利他主义应该取决于所发生的成本和所提供的收益，但这些取决于捐赠者和接受者的相对需求。重写汉密尔顿的规则以解释相对需要表明需要对相关性的放大效应，但不一定是其他关系质量。在对三项社会折扣研究和新复制的重新分析中，我们发现相对需求放大了相关性对在线招聘的两个美国成年人样本的影响，但不是在线招聘的美国本科生或印度成年人。在美国在线参与者中，当伴侣被认为需要较高时，遗传亲属关系的影响比需要较低时更大。在其他样本中，亲缘关系和更大的合作伙伴需求与更大的给予有关，但亲缘关系对给予的影响并未因需要而显着放大。需要从未放大社会亲密度对捐赠的影响，尽管它确实减少了美国本科生亲密度的影响，可能反映了天花板效应。这些结果证实了在美国成年人样本中修改汉密尔顿规则的预测，但提出了一些重要问题，即为什么它们在某些样本中成立，而在其他样本中不成立。它们还说明了理解环境因素（例如相对需求）如何调节演化成本收益分析中使用的常见变量的重要性的重要性。可能反映了天花板效应。这些结果证实了在美国成年人样本中修改汉密尔顿规则的预测，但提出了一些重要问题，即为什么它们在某些样本中成立，而在其他样本中不成立。它们还说明了理解上下文因素（例如相对需求）如何调节演化成本收益分析中使用的常见变量的重要性的重要性。可能反映了天花板效应。这些结果证实了在美国成年人样本中修改汉密尔顿规则的预测，但提出了一些重要问题，即为什么它们在某些样本中成立，而在其他样本中不成立。它们还说明了理解上下文因素（例如相对需求）如何调节演化成本收益分析中使用的常见变量的重要性的重要性。