This questionnaire study sheds light on the psychological component of kin selecting tendencies predicted by Hamilton's (1964b) inclusive fitness theory of discriminatory altruistic behavior based on genetic similarity. Participants rated donations of assistance aiding survival
and material wealth as more rational and ethical when these actions were performed for closer relatives. Participants also felt a greater obligation to perform these acts for a close relation. A comparison condition where assistance was unlikely to affect survival or reproductive success did
not exhibit these tendencies.