Emotional closeness as a mediator of the effect of genetic relatedness on altruism

Inclusive fitness theory has been used to explain the over-all pattern of altruistic behavior. However, this theory does not ad-dress the proximal causes of altruism. The purpose of the present study was to increase the understanding of altruism by testing a model that includes both ultimate and proximate causes. In particular, emo-tional closeness was tested as a mediator of the effect of genetic relat-edness on altruistic behavior. This was accomplished by having college students choose which of their family members they would most likely provide with life-saving assistance. As expected, results showed that emotional closeness is an important proximal cause of al-truism that partially mediates the effect of genetic relatedness on will-ingness to act altruistically. Inclusive fitness theory (Hamilton, 1964) posits that social behav-iors such as altruism—assisting other individuals at some cost and without the expectation of a reward—have evolved because they in-crease the prevalence of the actor’s genes. Research findings on altru-ism have been consistent with this proposition. Specifically, altruis