A sniff of trust: meta-analysis of the effects of intranasal oxytocin administration on face recognition, trust to in-group, and trust to out-group.

The neuropeptide oxytocin has a popular reputation of being the 'love' hormone. Here we test meta-analytically whether experiments with intranasal administration of oxytocin provide support for the proposed effects of oxytocin. Three psychological effects were subjected to meta-analysis: facial emotion recognition (13 effect sizes, N=408), in-group trust (8 effect sizes, N=317), and out-group trust (10 effect sizes; N=505). We found that intranasal oxytocin administration enhances the recognition of facial expressions of emotions, and that it elevates the level of in-group trust. The hypothesis that out-group trust is significantly decreased in the oxytocin condition was not supported. It is concluded that a sniff of oxytocin can change emotion perception and behavior in trusting relationships.