Heritability of IQ rises with age

A meta-analysis of 11,500 twin/sibling pairs shows genetic factors explain more variance in cognitive ability as children grow. Novel genetic influences dominate very early, but after about age 8 the same genetic effects get amplified, driving increasing heritability into adolescence. — This clarifies why nature–nurture estimates shift over childhood and cautions against reading early low heritability as proof that environment alone explains cognitive outcomes.