SEX-RELATED DIFFERENCES IN COGNITION - DEVELOPMENT DURING EARLY-CHILDHOOD

Fifty-five right-handed children from right-handed families between 2- and 5-years-of-age were individually administered two batteries of ha nd preference, verbal and spatial measures with a six month interval s eparating administrations. Early between-sex differences in production and comprehension abilities were revealed; Girls outscored boys on me asures of verbal fluency and graphic reproduction of shapes. Boys outs cored girls on a measure of verbal comprehension. Within-sex differenc es between comprehension and production abilities were also apparent. At both administrations, boys scored significantly higher on verbal te sts of knowledge, comprehension and reasoning than on measures requiri ng oral or manual production. Girls showed the reverse pattern. By the second administration, however, the high production/low comprehension pattern was only significant for girls consistently demonstrating hig h degrees of right-hand preference across testing times. Significant b etween-sex differences in these comprehension versus production abilit y patterns ranged between 1/2 to 11/6 standard deviations in magnitude and accounted for 8-10% of the variance in children's ability differe nce scores. These results are interpreted as support for a biological basis of early sex-related cognitive differences and Kimura's (1983) m odel of sex differences in the organization of the left hemisphere.