| Abstract: | Analyzed data on cognitive abilities from 3 samples of normal Ss: (1) 195 undergraduates, (2) 215 18–30 yr old newly married couples, and (3) 122 pairs of monozygotic and dizygotic twins (aged 12–38 yrs). Findings reveal a common Sex by Handedness by Reasoning-Ability interaction: For Ss with above-median reasoning ability, spatial scores of left-handed males were reduced but those of left-handed females were raised, relative to their right-handed counterparts; the opposite pattern was found for Ss with below-median reasoning ability. The dependence of handedness effects on reasoning ability level appears to explain some of the inconsistent findings in the literature. Verbal fluency, perceptual speed, and visual memory also showed sex and handedness effects, which often interacted with level of reasoning ability or other cognitive variables. Results strongly suggest that sex and handedness differences in cognitive ability are partly neurological in origin. Variations in the effects of handedness across levels of reasoning ability (or other abilities) may indicate that different trade-offs among structural, and thus cognitive, characteristics will be found in different subsamples: There may be many kinds of normal brain organization. (French abstract) (98 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
