Our judgments of whether an action is morally wrong depend on who is involved and their relationship to one another. But how, when, and why do social relationships shape such judgments? Here we provide new theory and evidence to address this question. In a pre- registered study of U.S. participants (n = 423, nationally representative for age, race and gender), we show that particular social relationships (like those between romantic partners, housemates, or siblings) are normatively expected to serve distinct cooperative functions – including care, reciprocity, hierarchy, and mating – to different degrees. In a second pre- registered study (n = 1,320) we show that these relationship-specific norms, in turn, influence the severity of moral judgments concerning the wrongness of actions that violate cooperative expectations. These data provide evidence for a unifying theory of relational morality that makes highly precise out-of-sample predictions about specific patterns of moral judgments across relationships. Our findings show how the perceived morality of actions depends not only on the actions themselves, but also on the relational context in which those actions occur.

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