The idea that early experiences disproportionately influence adult beh
aviour has long been a Fixture of mainstream developmental theory. Alt
hough unambiguous empirical support for this view at the human level i
s surprisingly sparse, compelling evidence from animal studies abounds
. Recent studies with rhesus monkeys have demonstrated dramatic short-
and long-term effects of differential early social experiences on bot
h behavioural and physiological functioning. Early social relationship
s with mothers or other caregivers appear to provide especially powerf
ul determinants of behavioural propensities throughout the lifespan.