Oxytocin and cooperative behavior in social dilemmas: The moderating role of explicit incentives, social cues and individual differences

The neuropeptide Oxytocin (OT), implicated in mammalian social behavior, may affect cooperation through its anxiolytic and affiliative properties. The current study experimentally investigates how OT interacts with three well-studied determinants of cooperative behavior in social dilemmas: extrinsic incentives, social cues, and individual differences. Participants received OT or a placebo following a double blind procedure and played two economic games with randomly determined partners: a Coordination Game (with strong extrinsic incentives to cooperate (CG)) and a Prisoner’s Dilemma (with weak extrinsic incentives (PD)). Social cues were present when participants had the chance to meet their partners in advance, and absent when the interactions were anonymous. A first prediction, that OT enhances cooperation when social cues are present, was confirmed by the data. This appeared to be more pronounced when participants played a CG. In contrast, in a PD we predicted that OT’s influence on cooperation would depend on the subject’s intrinsic willingness to cooperate, as assessed by means of his/her Social Value Orientation and Machiavellianism. The data indicate that for prosocials, OT and social cues appear to be substitutes, with either one being sufficient to overcome fear of betrayal and elicit cooperation. For proselfs, OT and social cues appear to be complements: their concurrence is essential to overcome greediness in situations with weak cooperative incentives. Machiavellists cooperated very little overall, and the combination of OT and social cues, in contrast to proselfs, actually reduced machiavellists’ willingness to cooperate.