On Tue, 31 Oct 2000, Stephen Black wrote:
>
> Aside from the speculative application to alleged differences in
> the way the sexes think, a debate has been raging concerning
> corpus callosal differences between men and women. Kolb and
> Whishaw (3rd ed. 1990, and there's probably a newer edition it
> would be of interest to consult) summarize the debate. They say
> (p. 386) that the main claim is that the posterior part of the CC
> (the splenium) is larger in females than in males, and of a
> different shape. K & W comment that this has not been confirmed
> by either postmortem exam or MRI scans. The scorecard (before
> 1990) was five replications, six failures.
>
> I did a quick PubMed search and came up with plenty of studies.
> Of two of the most recent, one says "myth", the other says
> "true". BTW, one difference I haven't checked recently which
> probably holds up is that us lefties have larger CCs than
> brain-deficient right-handers. Makes me proud to be sinister.
>
> -Stephen
>
> It has been claimed that the human corpus callosum shows sex
> differences, and in particular that the splenium (the posterior
> portion) is larger in women than in men. Data collected before
> 1910 from cadavers indicate 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 difference in the size or shape
> of the splenium of the corpus callosum, whether or not an
> appropriate adjustment is made for brain size using analysis of
> covariance or linear regression. It is argued that a simple ratio
> of corpus callosum size to whole brain size is not an appropriate
> way to analyse the data and can create a false impression of a
> sex difference in the corpus callosum. The recent studies, most
> of which used magnetic resonance imaging (MRI), confirm the
> earlier findings of larger average brain size and overall corpus
> callosum size for males. The widespread belief that women have a
> larger splenium than men and consequently think differently is
> untenable. Causes of and means to avoid such a false impression
> in future research are discussed.
>
I saw a video clip where Marion Diamond found differences in the
CC between male and female rats.
Michael Sylvester,PhD
Daytona Beach,Florida
