Sex differences in the brain

For a while I’ve been criticizing ideologically-based scientific claims, including the arguments that “evolutionary psychology is bunk” and “there are no differences between male and female brains in either structure or wiring”. These claims are based on ideology because both are palpably ridiculous from what we know about biology or from recently published research, and yet people maintain them because they want the brain to be a blank slate and they want there to be no average differences between men and women in brain structure and function. These wants come from left-wing ideology.

Although these claims are ideological and not scientific, they are based on a well-meaning philosophy: the view that people should be treated fairly and given equal opportunities. But this has engendered the fears that distort the science:  a fear that if we’re not blank slates, but that sexes and different ethnic groups differ genetically—perhaps in part because of evolution—then that would somehow justify misogyny and racism.

I don’t think that follows at all, since equality is a moral stand that is independent of biology. Making equality somehow contingent on biology, whether we be all biologically identical or not, has the unpalatable consequence that your stand on equality is malleable in view of new findings in biology.

In fact, the same people who unjustifiably deny sex differences in brain and behavior also call for medical researchers to take into account sex differences in the body, for the choice and efficacy of different treatments often depend on sex. And so, as I say—in league with Robert King, a psychologist at University College Cork—that yes, there are differences on average between the behavior and the brains of men and women, and no, that should not justify sexism in any way. After all, why should evolution have differentiated sexes from the neck down (a differentiation based in part on sexual selection), but left what’s above the neck the same? Sexual selection, after all, creates sex differences in behavior, and those are mediated through the brain:

Here’s King’s new piece in Psychology Today (click on screenshot):

One of the biggest proponents of the “no brain/behavior differences between men and women” has been the Aussie-British philosopher Cordelia Fine. King wrote a fair but critical review of her latest book, Testosterone Rex, in Quillette.  Fine’s ideological “no difference” view has recently been buttressed by a new book by Gina Rippon that I recently highlighted: (note: I’ve read Fine’s books but haven’t read Rippon’s yet since it’s not available in the US):

The same problems that plagued Fine’s books now appear to resurface in a new book by Gina Rippon that makes the same “no-difference-in-brains” claim: The Gendered Brain: The New Neuroscience that Shatters the Myth of the Female Brain, recently out in the UK and soon to be released in the US under the title Gender and Our Brains: How New Neuroscience Explodes the Myths of the Male and Female Minds. Wikipedia describes Rippon as “professor of cognitive neuroimaging at the Aston Brain Centre, Aston University, Birmingham.”

Rippon’s book got extremely favorable reviews in Nature and The Guardian, with both reviews being almost embarrassing in their complete failure to deal with existing data (see below) and the insupportable claim that every difference between male and female brains and behavior can be ascribed to plasticity, social conditioning, and our “gendered world.” King notes, however, that two researchers (both women) wrote a strong critique of the lame book-review in Nature. I’ll add that Nature doesn’t usually publish rebuttals of book reviews (click on the screenshot):

Much of the review:

We are concerned that Lise Eliot’s review of Gina Rippon’s book The Gendered Brain (Nature 566, 453–454; 2019) undermines the premise that sex is a biological variable with respect to many medical conditions and drug responses (see J. A. Clayton and F. S. Collins Nature 509, 282–283; 2014).

As president-elect and president, respectively, of the Organization for the Study of Sex Differences, we disagree with Eliot’s claim that the brain is “no more gendered than the liver or kidneys or heart”. We also disagree that sex differences in behaviour are due to cultural effects on newborns, not to biological effects. In our view, these are not mutually exclusive. Sex disparities occur in animal models that are not subject to cultural bias.

The brain, like many organs, shows differences attributable to sex, both during health (see, for example, E. Luders et al. J. Neurosci. 29, 14265–14270; 2009) and during disease. Two-thirds of people with Alzheimer’s disease are women; twice as many men as women have Parkinson’s disease (see, for example, L. J. Young and D. W. Pfaff Front. Neuroendocrinol.35, 253–254; 2014). And multiple sclerosis affects three times more women than men, although men with the condition develop neurological disability more quickly (see, for example, R. R. Voskuhl and S. M. Gold Nature Rev. Neurol.8, 255–263; 2012). Sex is a modifier of disease risk and progression.

Finally, King presents a long list of references showing sex-based brain differences; these papers appeared in the January, 2017 special issue of Journal of Neuroscience Research called “An issue whose time has come: Sex/gender influences on nervous system function.”  Click on the screenshot below to see it; I’m not sure if the content is available for free:

And the contents, miniaturized:

This is only a small sample of the relevant literature.