Incentivising the social discounting task impacts the measurement of altruism in a student population. Incentivised subjects are more altruistic at close social distances, especially subjects who are less altruistic, thus providing evidence of reciprocal altruism. There is also some evidence of hypothetical bias among more altruistically inclined subjects. Making payments real also influences the subject's choice of recipient. Paid subjects select more geographically distant, but psychologically closer subjects, because of prospects for increased anonymity and enforced reciprocity, respectively. Further research is required to verify the robustness of these results, in the laboratory and especially in the field.
Human Sciences Research Council (Sat,) studied this question.