Intelligence, family size and sibling age spacing

Abstract

This chapter assesses and synthesizes research findings concerning the effects of child spacing on intelligence, interfamily relations, psychosocial characteristics, and health. It suggests strategic and theoretically significant areas for further investigation and encourages future research with the final goal of increasing our knowledge regarding personality and health. The effects of birth spacing is the least researched of sibling constellation variables, although several research groups have recently added interesting findings of spacing effects on intrafamily relations. The findings on spacing effects are astonishingly consistent. Close spacing is more disadvantageous to perinatal, infant, and childhood health and to longevity of adults. It seems deleterious to intelligence and achievement, to good relations between children and parents, between children and their siblings, and even between the parents themselves, and to emotion and psychological adjustment. With the consistency of findings of negative effects of spacing up to 24 months, and probably to 30 months, the chances seem high that similar effects will again appear, especially for boys but likely for girls too, and especially for verbal ability and morbidity and mortality, but also for many personality variables and psychosocial adjustment.