Oxytocin and vasopressin, made in the pituitary gland, turn out to be multi-purpose hormones, not just for giving milk and water balance. They are central in promoting social bonding behavior in rats and monkey, and now apparently also in humans. . Giving people a nasal spray of oxytocin raises their trust, as tested in a game devised by Kosfeld et al. They show that the effect of oxytocin on trust is not due to a general increase in the readiness to bear risks. Rather, it specifically affects an individual's willingness to accept social risks arising through interpersonal interactions. The results concur with animal research suggesting an essential role for oxytocin as a biological basis of prosocial approach behavior.
Oxytocin levels normally rise during physical interaction of children and their mothers. Seth Pollack has shown that this rise is not observed in children that have been neglected in Eastern European orphanages and then adopted by parents in the United States. These children have difficultly forming social relationships, even after being adopted into loving families, apparently because the oxytocin system has not developed to give a positive feeling about social interactions.