Oxytocin improves "mind-reading" in humans

The ability to infer the internal state of another person to adapt one's own behavior is a cornerstone of all human social interactions. Humans have to infer internal states from external cues such as facial expressions in order to make sense of or predict another person's behavior, an ability that is referred to as "mind-reading" (Siegal and Varley 2002; Stone et al 1998). In particular, individuals with autism have distinct difficulties in interpreting social cues such as facial expressions, leading to severe social impairment (Hill and Frith 2003). The neurohypophyseal peptide oxytocin is well known for its physiological functions in labor and lactation. In addition, oxytocin receptors are distributed in various brain areas (Landgraf and Neumann 2004) that are associated with social behavior, including reproductive and parenting behaviors, affiliation and attachment, social memory, and reactivity to social stress in nonhuman mammals (Carter 1998; Ferguson et al 2000; Young and Wang 2004). Neuropeptides have been shown to cross the blood-brain barrier after intranasal administration (Born et al 2002), with several studies reporting direct effects on human behavior (Heinrichs et al 2003, 2004; Kosfeld et al 2005). In particular, oxytocin appears to reduce responses to social stress and to increase trust in social interaction (Heinrichs et al 2003; Kosfeld et al 2005). Because mind-reading is an essential basis of human social interaction and oxytocin has been shown to modulate social approach behavior, we hypothesized that oxytocin might also promote mind-reading in humans. Specifically, oxytocin was expected to improve performance in a task testing the ability to infer the affective mental state of others from subtle facial cues.