Social attachment and aversion in human moral cognition.

Modern neuroscience is beginning to substantiate Darwin's notion that the roots of human morality lie in social instincts, present in several species. The role of primitive motivational-emotional systems in human morality still remains under-recognized, however. Based on recent experimental evidence and classic neuroanatomical data, we here portray a view of how "ancient" limbic-neurohumoral systems of social attachment and aversion are crucially involved in human moral behaviors, including altruism, empathic concern and aggression. Rather than being a mere evolutionary remnant of our ancestors, such limbic-neurohumoral systems are tightly integrated with cortical mechanisms to enable complex moral sentiments and values, which powerfully influence our choices in socio-cultural settings. Exploring the underlying mechanisms of human social attachment and aversion will provide new insights and foster novel experimental paradigms for the study of moral cognition and behavior.