SEX-DIFFERENCES IN THE HUMAN CORPUS-CALLOSUM - MYTH OR REALITY

It has been claimed that the human corpus callosum shows sex differenc es, and in particular that the splenium (the posterior portion) is lar ger in women than in men. Data collected before 1910 from cadavers ind icate that, on average, males have larger brains than females and that the average size of their corpus callosum is larger. A meta-analysis of 49 studies published since 1980 reveals no significant sex differen ce in the size or shape of the splenium of the corpus callosum, whethe r or not an appropriate adjustment is made for brain size using analys is of covariance or linear regression. It is argued that a simple rati o of corpus callosum size to whole brain size is not an appropriate wa y to analyse the data and can create a false impression of a sex diffe rence in the corpus callosum. The recent studies, most of which used m agnetic resonance imaging (MRI), confirm the earlier findings of large r average brain size and overall corpus callosum size for males. The w idespread belief that women have a larger splenium than men and conseq uently think differently is untenable. Causes of and means to avoid su ch a false impression in future research are discussed. (C) 1997 Elsev ier Science Ltd.