The role of oxytocin in promoting social attachment in humans has recently received increased attention. A study in healthy men participating in a laboratory-based economic trust game showed that intranasal administration of oxytocin increased trust, and suggested involvement of the amygdala116. Imaging studies have demonstrated that mutual cooperation induces activation in reward circuitry regions, which are modulated by oxytocin and vasopressin117. Conversely, oxytocin reduced amygdala activation in response to fear-inducing visual stimuli and reduced connectivity between the amygdala and brainstem areas that mediate autonomic and behavioural fear responses118. Oxytocin thus seems to facilitate social attachment by enhancing the reward value of social stimuli and reducing potential fear responses119. In laboratory animals, central release of oxytocin and vasopressin regulates anxiety and social behaviour120. In rodent species, oxytocin and vasopressin increase social recognition, pair bonding and affiliation121.
