Oxytocin may be partly responsible for that wiring: http://www.pnas.org/content/108/4/1262 http://www.pnas.org/content/108/4/1262 My limited review of the res

Oxytocin may be partly responsible for that wiring: http://www.pnas.org/content/108/4/1262 http://www.pnas.org/content/108/4/1262 My limited review of the research suggests that humans tit-for-tat trackers of betrayal and reciprocated trust. Oxytocin seems to add more weight to these memories in social interactions versus rational thought. The formation of outgroups may be the natural outcome of events that trigger the release of oxytocin.