The idea that early experiences disproportionately influence adult behaviour has long been a fixture of mainstream developmental theory. Although unambiguous empirical support for this view at teh human level is surprisingly spares, 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 both behavioural and physiological functioning Early social relatioships with mothers or other caregaivers appear to provide especially powerful determinants of behavioural propensities throughout the lifespan.