Abstract
The effects of high, medium and low levels of perinatal complications and family adversity on intelligence quotient (IQ) scores were examined in a large sample of Dunedin children tested every second year in the age group 3-13 years. The aim was to test the hypothesis that favourable environmental circumstances attenuate the effects of perinatal complications on later cognitive ability. The results did not support this hypothesis but rather suggested that perinatal complications and family adversity have independent adverse effects on the development of children's cognitive ability.