SUBSTANTIAL GENETIC INFLUENCE ON COGNITIVE-ABILITIES IN TWINS 80 OR MORE YEARS OLD

General and specific cognitive abilities were studied in intact Swedis h same-sex twin pairs 80 or more years old for whom neither twin had m ajor cognitive, sensory, or motor impairment. Resemblance for 110 iden tical twin pairs significantly exceeded resemblance for 130 fraternal same-sex twin pairs for all abilities. Maximum-likelihood model-fittin g estimates of heritability were 62 percent for general cognitive abil ity, 55 percent for verbal ability, 32 percent for spatial ability, 62 percent for speed of processing, and 52 percent for memory, There was also evidence for the significant influence of idiosyncratic experien ce as the environmental component that most determines individual diff erences in cognitive abilities late in life.