ABSTRACT
Sex differences in language have been known and speculated about for a long time, largely because they are among the most obvious of the cognitive differences. Girls tend to start talking before boys, by an average of about one month, and have higher verbal fluency, larger vocabularies, and better verbal memory. They’re better readers and spellers, and the incidence of developmental dyslexia and other disorders such as stuttering is considerably lower in females than in males. In general the speech of girls is more clearly enunciated than the speech of boys. Females produce, on average, longer sentences than males, and make fewer errors. There’s some evidence for greater cerebral asymmetry in the male brain, with women having more interhemispheric connections, with parts of the corpus callosum – the tract of nerve fibres that connects the two hemispheres of the brain – being significantly large in women (Baron-Cohen, 2003; Kolb & Whishaw, 2003). These findings are supported by autopsy studies and brain imaging, and also by the effects of brain damage: damage to one hemisphere has more pronounced effects on language (for damage to the left hemisphere) and motor and spatial skills (for damage to the right) for women. Somehow the lower degree of lateralisation might lead to a slight processing advantage, probably because females are better able to use both hemispheres, at least partly, and here two is better than one. Some of the developmental differences might also reflect the faster maturation of girls – and this difference in maturation rate might in turn be linked to the greater degree of lateralisation in boys, because the more slowly a person matures, the greater the time available for the development of a more pronounced cerebral asymmetry (Kolb & Whishaw, 2003). It should be said that not everyone agrees with these conclusions. In a meta-analysis – an analysis of many analyses – of brain imaging of lateralisation effects on language tasks, Sommer et al. (2004) found no significant difference in lateralisation on language tasks between women and men, and concluded that it is unlikely that differences in lateralisation in language play a large role in cognitive sex differences.
