Oxytocin sharpens self-other perceptual boundary.

Recent cross-species research has demonstrated that the neurohormone oxytocin plays a key role in social interaction and cognitive processing of others' emotions. Whereas oxytocin has been shown to influence social approach, trust, and bond formation, a potential role of the oxytocinergic system in blurring or enhancing the ability to differentiate between one's self and other's related stimuli is unknown. Thus, we investigated whether oxytocin affects the ability to differentiate between self- and other-related stimuli using a facial morphing procedure. In a placebo-controlled, double-blind study, 44 healthy men received either 24 IU oxytocin or placebo intranasally. After 45 min, we measured participants' ability to differentiate their own identity while viewing a photo of themselves morphing into the photo of an unfamiliar face. Oxytocin administration shortened the latency of self-other differentiation. Additionally, when asked to rate the pleasantness of the unmorphed photos, the oxytocin-treated participants rated their own and the unfamiliar face as comparably pleasant. Oxytocin increases the ability to recognize differences between self and others and increases positive evaluation of others. Our findings are consistent with the hypothesis that impaired oxytocin signaling may be involved in the development and manifestation of human psychopathologies in which self-recognition is altered.