Relatives Versus Neighbors- An Experiment Studying Spontaneous Social Exchange

Social institutions regulating group conduct have been regarded as necessaryfor human cooperation to transcend family bonds. However, manystudies in economics and biology indicate that reciprocity based on repeatedinteraction suffices to establish cooperation with non-kin. We shedlight on the issue by a voluntary social exchange experiment where related(via mutual shareholding) players coexist with unrelated ones. Systematicallyvarying the degree of shared interests and the length of the timehorizon, we provide evidence that repeated interactions play a crucial rolein human cooperation, although humans remain attentive to relatedness.