"A basically unisex brain"?

From Neurosexism: the myth that men and women have different brains by Lise Eliot.

A chaotic book review. Both the book and the reviewer apparently are determined to find that the there is no difference between the male and the female brain. I know a small amount about this field but not nearly enough to hold firm views. However, there is enough wrong with the review and, if the reviewer presents the argument accurately, with the book, that there is reason to disbelieve either source as good evidence.

Is there a difference between the male and the female brain? How would we know?

Can biologists tell the difference? Not just probabilistically, but determinatively? Males are bigger than females therefore, on average, male brains are going to be larger than female brains. But the distribution curves between male and female sizes have a large degree of overlap so one could not distinguish a brain as being male or female simply by size.

The interesting corollary question, not asked in the review or, apparently, in the book, is whether there are any animals in which it is possible to identify physiologically or chemically a male from a female brain in a deterministic fashion? If it is not possible at all, then it makes it improbable that we would expect to find material physiological or chemical brain difference in humans. But if it occurs to some degree or a large degree in other animals, particularly in social mammals, then it would make it increasingly probable that we would expect to see sex differences in human brains as well. Is the fact that this elementary question is unasked the dog that didn't bark?

Is there any architectural difference between male and female brains that would allow a deterministic answer? I do not, a priori, know. I have read dozens, if not hundreds of articles on the topic over the years. Evidence is always scattered and contradictory. I don't have a firm recollection whether biologists can identify male and female brains by structure.

And structure isn't the only issue. We do know that males and female brains exist in a different chemical environment from one another. It is part of the sex differentiation that occurs in fetus development. Does that leave any tell-tale finger-prints which would absolutely differentiate between a male and female brain? I don't know.

Then there is brain socialization - are there activities, especially given that we are such social animals, which leave a mark on brain development that are forensically deterministic?

The counter-evidence offered is not reassuring that the reviewer or researcher is making a neutral argument:

Yet, as The Gendered Brain reveals, conclusive findings about sex-linked brain differences have failed to materialize. Beyond the “missing five ounces” of female brain — gloated about since the nineteenth century — modern neuroscientists have identified no decisive, category-defining differences between the brains of men and women. In women’s brains, language-processing is not spread any more evenly across the hemispheres than it is in men’s, as a small 1995 Nature study proclaimed but a large 2008 meta-analysis disproved (B. A. Shaywitz et al. Nature 373, 607–609 (1995) and I. E. Sommer et al. Brain Res. 1206, 76–88; 2008). Brain size increases with body size, and certain features, such as the ratio of grey to white matter or the cross-sectional area of a nerve tract called the corpus callosum, scale slightly non-linearly with brain size. But these are differences in degree, not kind. As Rippon notes, they are also seen when we compare small-headed men to large-headed women, and have no relationship to differences in hobbies or take-home pay.

The 1995 study was small. Fair point. Almost certainly not a reliable source. But to refute that study is to present a replication with opposite findings or to conduct the same study again with a sufficient sample size to be valid. If the large study produces opposite results to the small study, then that serves as a refutation.

A meta-analysis is not nearly the beast-slayer as it is presented. Meta-analysis studies are hard to conduct well. They have their own issues which have to be addressed. But comparing a flawed study (too small a study size) with a different type of study (meta-analysis) is something of a non sequitur. A meta-study on its own, because of the design challenges, rarely refutes specific studies. They might suggest but rarely refute.

In addition, I have a hard time squaring these two sentences in conjunction with one another:

Brain size increases with body size, and certain features, such as the ratio of grey to white matter or the cross-sectional area of a nerve tract called the corpus callosum, scale slightly non-linearly with brain size.

and

But these are differences in degree, not kind.

But non-linear changes can have outsized impacts. Linearity would make male and female brains identical regardless of size. Non-linearity is a different kettle of fish.

The review begins to get confusing - due to the researcher or reviewer is unclear. Eliot notes:

Rippon’s central message is that “a gendered world will produce a gendered brain”.

So wait - does that mean that there are differences in brain anatomy between males and females? The statement suggests that there are such differences and that Rippon is subscribing that difference to the socialization process.

That paragraph ends with a tell that we are dealing with a researcher and a reviewer who are both dwelling in an ideological argument and not a scientific argument.

She [Rippon] ends in 2017, with Google engineer James Damore blogging to co-workers about “biological causes” for the dearth of women in tech and leadership roles.

Damore was making a much more sophisticated argument than suggested and the fact that it is being boiled down to a misleading characterization as "biological causes" suggests people who are wanting to deal with straw man arguments rather than the actual arguments made.

At this point, the review is deep into gender studies/victimhood culture studies territory. It becomes hard to sustain a neutral view of what is being argued because it calls on so many disputable priors as to make it meaningless. If the conclusion is entirely dependent on acceptance of the priors, we are not dealing with an argument but a falsely constructed tautology. Increasingly the focus has shifted from neural anatomy to sociological discussion and treating the sociological discussion as if it were settled science. These are topics which are still being researched, are hotly disputed, in a field with only rudimentary basics of the scientific method. A field where the majority of longstanding but unexamined findings have been overturned as a consequence of the replication crisis.

Part 4 brings us into the twenty-first century, although not to any happy ending. It focuses on women in science and technology, and how the gendered world — including the professionalization of science and a masculine stereotype of “brilliance” — has impeded their entry into, and advancement across, this high-status realm. Talented women are regarded as “workhorses”, men as “feral geniuses”, a distinction that children internalize by the age of six, according to research by Lin Bian, Sarah-Jane Leslie and Andrei Cimpian (L. Bian et al. Am. Psychol. 73, 1139–1153; 2018). And all of this factors into the brain-building cycle of differential expectations, self-confidence and risk-taking that drives boys and girls down different trajectories of career and success.

If you go to the linked article bearing so much probative weight, you find the sort of motivated research, small sample size, negligible effect sizes, non-treatment of confounding variables and over-expansive conclusions which so sully the field already. We are deep in sociological and ideological studies of victimhood and neurological differences between male and female brains are a distant issue.

The muddledness of the review continues right to the concluding paragraph.

Whatever the subtitle, the book accomplishes its goal of debunking the concept of a gendered brain. The brain is no more gendered than the liver or kidneys or heart. Towards the end, Rippon flirts with the implications of this finding for the growing number of people transitioning or living between current binary gender categories. But for now, she concludes, most of us remain strapped in the “biosocial straitjackets” that divert a basically unisex brain down one culturally gendered pathway or another.

"A basically unisex brain"? Basically? Is it unisex or not? Males and females have "basically" the same body type but their minor differences are pretty gloriously material. Chimps and humans "basically" have the same genetic makeup (a 1.3% genetic difference). That 1.3% difference makes all the difference. So don't give me this "basically unisex brain" guff.

I am open to believing either argument (that brains are structurally and chemically identical or that they differ in numerous but individually insignificant ways) - open in the sense I can make plausible arguments with selected data for both positions. I am looking for evidence that tilts the argument one way or another and all I get is a muddled motivated word salad. Both from the reviewer and from the researcher.

UPDATE: A rebuttal of this book's premise from someone in the field.