A Quantitative Genetic Analysis of Cognitive Abilities during the Second Half of the Life Span

Abstract

Little is known about the importance of genetic effects on individual differences in cognitive abilities late in life. We present the first report from the Swedish Adoption/Twin Study of Aging (SATSA) for cognitive data, including general cognitive ability and 13 tests of specific cognitive abilities. The adoption/twin design consists of identical twins separated at an early age and reared apart (46 pairs), identical twins reared together (67 pairs), fraternal twins reared apart (100 pairs), and fraternal twins reared together (89 pairs); average age was 65 years. Heritability of general cognitive ability in these twins was much higher (about 80%) than estimates typically found earlier in life (about 50%). Consistent with the literature, heritabilities of specific cognitive abilities were lower than the heritability of general cognitive ability but nonetheless substantial. Average heritabilities for verbal, spatial, perceptual speed, and memory tests were, respectively, 58%, 46%, 58%, and 38%.