Early in The Gendered Brain, cognitive neuroscientist Gina Rippon describes one of the myriad brain studies heralded as ‘finally’ explaining the difference between men and women. It was a magnetic resonance imaging (MRI) analysis of 21 men and 27 women by researchers at the University of California, Irvine (R. J. Haier et al. NeuroImage 25, 320–327; 2005). Tiny by today’s standards, this brief communication nonetheless went on quite a publicity tour, from newspapers and blogs to television, books and, eventually, teacher education and corporate leadership conferences.

I woke one morning in 2010 to see an especially bad extrapolation of this study on the Early Show, a programme on US television network CBS. The presenter, Harry Smith, gushed as medical correspondent Jennifer Ashton declared that men have “six-and-a-half times more grey matter” than women, whereas women have “ten times as much white matter” as men. Next came the obvious quips about men’s talent at mathematics and women’s uncanny ability to multitask. Never mind that these differences would demand that women’s heads were about 50% larger, or that the Irvine team didn’t even compare brain volumes, but investigated a correlation between IQ and measures of grey or white matter.
Neurosexism

The history of sex-difference research is rife with innumeracy, misinterpretation, publication bias, weak statistical power, inadequate controls and worse. Rippon, a leading voice against the bad neuroscience of sex differences, uncovers so many examples in this ambitious book that she uses a whack-a-mole metaphor to evoke the eternal cycle. A brain study purports to discover a difference between men and women; it is publicized as, ‘At last, the truth!’, taunting political correctness; other researchers expose some hyped extrapolation or fatal design flaw; and, with luck, the faulty claim fades away — until the next post hoc analysis produces another ‘Aha!’ moment and the cycle repeats. As Rippon shows, this hunt for brain differences “has been vigorously pursued down the ages with all the techniques that science could muster”. And it has exploded in the past three decades, since MRI research joined the fray.