The influence of oxytocin and vasopressin on men's judgments of social dominance and trustworthiness: An fMRI study of neutral faces

Cues signaling trust and dominance are crucial for social life. Previous studies on the effects of oxytocin (OT) nasal sprays on trustworthiness evaluations have been inconsistent and its influence on dominance is unknown. Vasopressin (AVP) may also influence social cue perception, but even fewer investigations have evaluated this possibility. We evaluated the effects of intranasal OT and AVP compared to placebo control during three double blinded functional magnetic resonance imaging sessions. Twenty males received a pseudo-randomized order of nasal spray conditions and rated the trustworthiness and dominance of neutral faces. OT increased facial dominance ratings compared to placebo. Neuroimaging results revealed an inverse relationship between brain activation and face ratings for OT compared to placebo in regions involved in processing emotional expressions. Specifically, the right superior temporal gyrus was attenuated as ratings increased and the left precuneus selectively diminished with increasing dominance ratings. Additionally, OT increased functional connectivity between frontoparietal regions and the right amygdala for faces rated as highly dominant, but OT increased connectivity between the fusiform gyros, hippocampus, and bilateral ventral tegmental area (VTA) for faces perceived as highly trustworthy. Overall, OT increased the perception of dominance but did not influence trustworthiness judgments. However, we observed regional neural effects for OT that differed between judgments of trustworthiness and dominance. AVP attenuated left temporoparietal junction activity as face ratings increased, a result consistent with AVP influencing mentalization. AVP also led to increased left amygdala and right VTA connectivity with the putamen, which is consistent with cue-driven, habitual responses.