A registered replication study on oxytocin and trust

In an influential paper, Kosfeld et al. (2005) showed that intranasal administration of oxytocin (OT) increases the transfers made by investors in the trust game-suggesting that OT increases trust in strangers. Subsequent studies investigating the role of OT in the trust game found inconclusive effects on the trusting behaviour of investors but these studies deviated from the Kosfeld et al. study in an important way-they did not implement minimal social contact (MSC) between the investors and the trustees in the trust game. Here, we performed a large double-blind and placebo-controlled replication study of the effects of OT on trusting behaviour that yields a power of more than 95% and implements an MSC condition as well as a no-social-contact (NoC) condition. We find no effect of OT on trusting behaviour in the MSC condition. Exploratory post hoc analyses suggest that OT may increase trust in individuals with a low disposition to trust in the NoC condition, but this finding requires confirmation in future research. PROTOCOL REGISTRATION: The stage 1 protocol for this Registered Report was accepted in principle on 19 October 2018. The protocol, as accepted by the journal, can be found at https://doi.org/10.6084/m9.figshare.11980368.