Adoption Is a Successful Natural Intervention Enhancing Adopted Children's IQ and School Performance
Is the cognitive development of adopted children different from that of (a) children who have remained in institutional care or in their birth families or (b) their current (environmental) nonadopted siblings or peers? We attempt to answer these questions on the basis of a meta-analysis of 62 studies including 17,767 adopted children. Compared to their nonadopted siblings or peers who stayed behind, adopted children scored substantially higher on IQ tests and they performed much better at school. Compared to their current nonadopted environmental peers or siblings, adopted children showed similar IQ scores but their school performance and language abilities lagged somewhat behind. Most importantly, we found a twofold increase in special-education referrals in adopted children compared to their nonadopted peers. Taken together, the findings document the positive impact of adoption on children's cognitive development and adopted children's remarkably normal cognitive competence but somewhat delayed school performance.