CROSS-SEQUENTIAL ANALYSIS OF GENETIC INFLUENCES ON COGNITIVE-ABILITY IN THE SWEDISH ADOPTION TWIN STUDY OF AGING

Cross-sequential methods of analysis were applied to cognitive data fr om the Swedish Adoption/Twin Study of Aging. Thirteen measures of cogn itive ability assessing four major domains (verbal, spatial, memory, a nd perceptual speed) were collected at two times of measurement separa ted by a three-year interval. Data were available from 41 pairs of mon ozygotic twins reared apart (MZA), 54 pairs of monozygotic twins reare d together (MZT), 86 pairs of dizygotic twins reared apart (DZA), and 73 pairs of dizygotic twins reared together (DZT) ranging in age from 41 to 84 years. Cross-sectional differences and longitudinal changes i n total variance and sources of variance were examined. With a few exc eptions, both cross-sectional and longitudinal stability were found fo r rotal variance. In addition, few cross-sectional differences and lon gitudinal changes were found for genetic and environmental components of variance.