Asymmetry differs between men and momen. Girl’s brains don’t develop the right side specificity for nonverbal processes as early as boys do. Girls’ brains thus retain plasticity, or the ability to change, for longer than boys’ brains do. This is supported by the greater ability to transfer language abilities to the right hemisphere after damage to the left side of the brain. This extended plasticity also may account for less incidences of disorders related to left-hemisphere dysfunction, e.g. autism.

Female brains seem to have a lesser degree of specialisation than males, which many have attributed to the larger corpus callosum in females, connecting the two hemispheres. There also seems generally to be less initial development of the brain into two specialised halves in females. Tests on different cognitive abilities consistently show that females are better at verbal fluency, perceptual speed and mathematical calculations, whilst males are better at mathematical reasoning, spatial relationships and target directed motor tasks. These differences are unlikely to be related to any kind of social conditioning, and more likely to reflect physical differences between the brains of men and women.

Simon Baron-Cohen, Chair of Psychology at Cambridge University