Pick two people off the street at random, put them in a brain
scanner, and look at the thickness of their corpus callosums –
that’s the massive bundle of nerve fibres that connects the two
halves of the brain. In all likelihood, you’ll find it’s much
thicker in one person than the other. Indeed, some people can
have up to three times as many nerve fibres in their corpus
callosum compared with the next person. According to Bruce
Morton and Stein Rafto, psychologists used to think callosum
thickness was largely explained by gender and left or right
handedness. For example, one theory had it that men have a
thinner connection between their hemispheres, thus causing them
to have more specialised brains suitable for maths and the like.
But literally hundreds of papers have now been published on the
topic and the results have been completely inconsistent – some
showing men have thinner hemispheric connectivity, others
showing the opposite. Morton and Rafto think these inconsistent
findings are due to the fact callo