A number of studies suggest that oxytocin (a peptide hormone) plays a key role in social behaviour and social understanding. In studies of typical individuals, increases in oxytocin appears to be correlated with increases in trust and in emotion recognition ability. In animal studies it also seems to be associated with social interest. Oxytocin is released during childbirth and lactation and is thought to facilitate the social relationship of attachment between mother and infant. It is also released in response to touch and during sexual relationships suggesting it plays a role in intimate emotional relationships.


http://www.autismresearchcentre.com/project_14_oxytocin