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 hand preference, verbal and spatial measures with a six month interval separating administrations. Early between-sex differences in production and comprehension abilities were revealed; Girls outscored boys on measures of verbal fluency and graphic reproduction of shapes. Boys outscored girls on a measure of verbal comprehension. Within-sex differences between comprehension and production abilities were also apparent. At both administrations, boys scored significantly higher on verbal tests of knowledge, comprehension and reasoning than on measures requiring 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 high degrees of right-hand preference across testing times. Significant between-sex differences in these comprehension versus production ability patterns ranged between 1/2 to 11/6 standard deviations in magnitude and accounted for 8-10% of the variance in children's ability difference scores. These results are interpreted as support for a biological basis of early sex-related cognitive differences and Kimura's (1983) model of sex differences in the organization of the left hemisphere.