Family environment and the malleability of cognitive ability: A Swedish national home-reared and adopted-away cosibling control study.
Cognitive ability strongly aggregates in families, and prior twin and adoption studies have suggested that this is the result of both genetic and environmental factors. In this study, we used a powerful design-home-reared and adopted-away cosibling controls-to investigate the role of the rearing environment in cognitive ability. We identified, from a complete national Swedish sample of male-male s