Do experimental subjects favor their friends?

Ideally we would like subjects of experiments to be perfect strangers so that the situation they face at the lab is not just a part of a long run interaction. Unfortunately, it is not easy to reach those conditions and experimenters try to mitigate any effects coming form these out-of- the-lab relationships by, for instance, randomly matching subjects. However, even if this type of procedure is used, there is a positive probability that a subject faces a friend or an acquaintance. We find evidence that social proximity among subjects is irrelevant for experiments’ results in dictator games. Thus, although ideal conditions are not met, relations among subjects are not contaminating the experiments’ results.