Human altruism is a widespread phenomenon that has puzzled evolutionary biologists since Darwin. Economic games illustrate human altruism by demonstrating that behavior deviates from economic predictions of selfish utility maximization. A game that most plainly demonstrates this altruistic tendency is the Dictator Game. We hypothesized that human pro-social behavior is to some extent hardwired and that two likely candidate genes that may contribute to individual differences in altruistic behavior are the arginine vasopressin receptor (AVPR1a) and the oxytocin receptor (OXTR).

Genes that in some mammals such as the vole have been shown to have a profound impact on affiliative behaviors. Multiple studies have shown how the two closely related neuropeptides facilitate social communication, and cognition across mammals; in the current investigation, we demonstrate that AVPR1a and OXTR polymorphisms predict pro-social allocation of funds in two economic games that measure altruistic and pro-social behavior, the Dictator Game and Social Value Orientations (SVO). 203 college students participated in both a one-time online version of the Dictator game and SVO. Subjects and their parents were also genotyped for the AVPR1a and OXTR. Using a family-based method, we observed preferential transmission of individual alleles for the Dictator game and the SVO.