Is there G beyond g? (Is there genetic influence on specific cognitive abilities independent of genetic influence on general cognitive ability?)

Both general and specific cognitive abilities show genetic influence, but are these the same genetic effects? Multivariate genetic analyses are beginning to build the case that there are genetic effects on specific cognitive abilities independent of genetic effects (G) on general cognitive ability ( g). This article investigates this issue using a simple model that tests whether significant genetic influence on specific cognitive abilities remains after genetic effects for g are partialed out. Data for 13 cognitive tests from the Swedish Adoption/ Twin Study of Aging (SATSA) were employed. The adoption/twin design includes identical twins separated at an early age and reared apart (46 pairs), matched identical twins reared together (67 pairs), fraternal twins reared apart (100 pairs), and fraternal twins reared together (89 pairs); average age was 65.6 years. Although much genetic influence can be explained by genetic effects on g, 12 of 13 tests showed significant genetic influence independent of genetic influence on general cognitive ability.