Selective influences of oxytocin on the evaluative processing of social stimuli

The neuropeptide oxytocin has been implicated in a wide range of social processes, such as pair bonding, affiliation, and social judgments that may contribute to normal adjustment and psychiatric states. The present experimental study sought to elucidate potential underlying mechanisms by which oxytocin may impact social processes by examining the effects of intranasal oxytocin on basic evaluative processes. Subjects rated slide stimuli from the International Affective Picture System, varying across multiple categories (pleasant, neutral, unpleasant) and social content. Separate ratings for arousal and for the positive and negative components of valence were obtained in the context of a bivariate evaluative space model. Oxytocin did not have an independent significant effect on positivity or negativity ratings, but instead oxytocin treatment altered the interaction between these component processes for social, relative to non-social stimuli regardless of valence conditions. Specifically, oxytocin, relative to vehicle, significantly decreased arousal ratings to threatening human stimuli without altering ratings of threatening animal stimuli. These results indicate that oxytocin may exert its effects through dynamic alterations in the partially separable neural substrates mediating arousal as well as positive and negative evaluations of social stimuli.