Shifting normative beliefs: On why groups behave more antisocially than individuals

A growing body of research shows that people tend to act more antisocially in groups than alone. However, little is known about why having “partners in crime” has such an effect. We run an experiment using sender–receiver games in which we elicit subjects’ normative and empirical beliefs to shed light on potential driving factors of this phenomenon. We find that the involvement of an additional sender makes the antisocial actions of senders more normatively acceptable to all parties, including receivers. By contrast, empirical beliefs are unaffected by the additional sender, suggesting that antisocial behavior increases in groups because antisocial actions become more acceptable and not because acceptable behavior is expected less often. We identify a necessary condition for this effect: the additional sender has to actively participate in the decision-making.