Oxytocin enhances the encoding of positive social memories in humans

Background: In nonhuman mammals, oxytocin has a critical role in social recognition and the development of long-term bonds. There has been limited research evaluating effects of oxytocin on the encoding and recognition of faces in humans. Methods: In a double-blind, randomized, placebo-controlled, between-subject design, we administered oxytocin (24 IU) or a placebo to 69 healthy human male volunteers and then presented 36 happy, angry, or neutral human faces. Participants returned the following day to make "remember," "know," or "new" judgments for a mix of 72 new and previously seen faces. Results: Oxytocin-administered participants were more likely to make remember and know judgments for previously seen happy faces compared with angry and neutral human faces. In contrast, oxytocin did not influence judgments for faces that had not been presented previously. Conclusions: This study shows that the administration of oxytocin to male humans enhances the encoding of positive social information to make it more memorable. Results suggest that oxytocin could enhance social approach, intimacy, and bonding in male humans by strengthening encoding to make the recall of positive social information more likely.