Social bonding success in life impacts on health, survival and fitness. It is proposed that early and later social experience as well as heritable factors determine social bonding abilities in adulthood, although the relative influence of each is unclear. In humans, the resulting uncertainty likely impedes psychological and psychiatric assessment and therapy. One problem hampering progress for human studies is that social bonding success is hard to objectively quantify, particularly in adults. I propose to directly address this problem by determining the key influences on social bonding abilities in chimpanzees, our closest living relative, where social bonding success can be objectively quantified, and variation in underlying hormonal and cognitive mechanisms can be examined.