Post-encoding administration of oxytocin selectively enhances memory consolidation of male faces in females
Oxytocin plays a critical role in modulating social cognition and enhancing human memory for faces. However, it remains unclear which stage of memory oxytocin affects to enhance face memory. Our study explored oxytocin's potential to selectively enhance the consolidation of social memories, specifically human faces, and whether this effect varies between genders. In two preregistered, randomized, double-blind, placebo-controlled trials with heterosexual participants (total N=294, comprising 149 males and 145 females), we explored how oxytocin affects memory consolidation. We administered oxytocin immediately after encoding (i.e., Study1) and 30 minutes before retrieval in a parallel study (i.e., Study2). This design allowed us to confirm that oxytocin's effects were indeed due to consolidation rather than retrieval. We found that administering oxytocin post-encoding, but not before-retrieval, significantly improved female participants' ability to recognize male faces 24 hours later, with no similar enhancement observed in males recognizing opposite-gender faces. Together with our analyses of social placebo effects and approachability rating during encoding, we concluded that oxytocin enhanced consolidation of long-term social memories in humans. Our results not only advance the understanding of the neurobiological mechanisms underlying social memory consolidation but also highlight oxytocin as a pharmacological tool for selectively enhancing human memory consolidation.