The Illusion of “Neurosex”: Your Brain Is Not “Male” nor “Female”

There’s been an unfortunately increasingly popular tendency among many trans communities to rely on some notion of “brain sex“, “subconscious sex“, etc, to provide justificatory accounts of trans womanhood/manhood. The most obvious manifestation of this historically ignorant & sociologically uninformed way of thinking about trans-liberation is the appeal to “neuroscientific” studies that purportedly demonstrate that transness is intrinsic, “biological”, and in a way that trans people are scientifically their true gender (we are, of course, falling right into a naturalistic fallacy).

While this justificatory account of the production of scientific knowledge may be a fascinating sociology of science question, it’s more immediately a political question. The discourse about “male brains” and “female brains” has underpinned a large host of misogynist bioessentialist thought over the last few centuries, including & especially within the scientific sphere. This has elicited a quite justified* reaction from the host of radical, cultural, materialist, lesbian, queer, scientific and radical (trans)feminists who have given radical accounts of sex-gender based not in illusory biology (aside from cultural feminists), but in the material (re)production of difference.

What are the bases for this purported “neurosex”? There is a small, but growing, literature of sex difference research that is aimed at interrogating the purportedly neurobiological foundation of ‘transsexuality’. It is important to recognize that this burgeoning literature does not originate from a trans-inclusive or feminist perspective, but from a classificatory, pathologizing way of constraining trans subjectivity under the microscope of the scientific interlocutor. The transsexual becomes the subject of the scientist, for her (the subject is nearly always a trans woman) brain is a site for knowledge production. She is not considered as a person to be cared for, but as a subject to be poked, prodded & studied.

The “Science”

The ‘original’ study in the this line of literature purporting to demonstrate that ‘transsexuals’ have ‘female’/’male’ brains was a 1996 study done by Zhou et. al. It looked at the bed nucleus of the stria terminalis of the brain of 6 postmortem ‘male-to-female’ transsexuals in comparison with cis ‘male’ and ‘female’ brains. The way that gender norms have infested scientific knowledge production is quite apparent from the start. Brains are presupposed to be dimorphically (that is ‘having two forms) sexed as “male” or “female” so that the finding that ‘transsexuals’ have ‘male’ or ‘female’ brains is either a justificatory or delegitimatizing account of their true sex-gender. But, as we will see later, it is not obvious, and in fact false, that brains are organized dimorphically.

This initial study has been cited 872 times, including in other literatures like explicitly bioessentialist work such as Lippa’s “Gender, nature and nurture”. It is perhaps the most focused upon within the entire literature, meaning it has been the subject of a number of critiques: the horrific sample size (n=6 for the trans individuals), the comparison group(s), sexuality composition, analyzing brain structure postmortem, whether or not the subjects had taken hormones. To  me, all of these critiques have important points to them, especially situating the sample size of the group within the replication crisis within neuroscience.

Whose Science?

Here we ought to consider the parent field of this series of studies: neuroscience. Neuroscience has received increased attention & funding as a revolutionary “neurocognitive” turn in many sciences (behavioral, psychological, etc). This “turn” has been the subject of a number of criticisms, not least by William Uttal. In his book “The New Phrenology“, he critiqued the notion that we can localize psychological processes to a particular region of the brain. That is, the very  subsets of the whole brain that are being interrogated for their sex differences, may not prove very useful in determining the behavioral consequences of these differences, whatever they may be. This idea that a person’s psychological attributes (emotions, intelligence) can be “located” in a particular region of the brain reminds many of the pseudoscience of phrenology, hence the title. Not only is there a theoretical objection to the knowledge that is asserted to be produced by neuroscientific studies, but there’s an empirical one. Despite the valorization of neuroscience in the media as another “biology” to ground the “nature” of the human body, it has a lower replication rate than psychology; famously affected by the replication crisis. In Uttal’s Reliability in Cognitive Neuroscience: A Meta-Meta Analysis, he analyzes the findings from the field and finds them very wanting in terms of empirical support. Other works critiquing naive neuroscience are Rees & Rose’s The New Brain Sciences, De Vos & Pluth’s Neuroscience and Critique: The Limits of the Neurological Turn, and Satel & Lilienfeld’s Brainwashed.

Scan, Compare, Contradict, Deny and Repeat

Returning back to the ‘transsexual brain studies’, a later set of studies after Zhou et. al have produced mixed findings. Some find that the sexuality composition of the ‘transsexual’ selection produces differing results as to the ‘grouping’ that ‘transsexuals’ fit into (i.e. straight [androphilic] trans women have ‘female’ brains in contrast to lesbian [gynephilic] trans women who have ‘male’ brains). Some find that it is not that ‘transsexuals’ have ‘male‘ or ‘female‘ brains, but brains intermediate between the ‘male’ and ‘female’ groupings. And still others confirm the initial finding that trans women have ‘female’ brains and trans men have ‘male’ brains.

For example, a 2000 study by Krujiver et. al again studied the “bed nucleus of the stria terminalis” and discovered that, in a sample of 42 individuals total, that ‘female-to-male’ transsexuals have a ‘male’ number of neurons while ‘male-to-female transsexuals’ have a ‘female’ number of neurons. They also reported that sexuality & hormone treatment did not affect the results. This cannot be considered a replication as 26 of the patients (most of whom were not trans) came from the original Zhou et. al ’96 study. Just as in the other study, all of the postmortem brains analyzed were medical deaths: they had died from a disease or other medical condition. This makes it difficult to interpret the results, especially in light of the inclusion of a large number of AIDS patients & the complex etiology and effects of these diseases. Indeed, one trans female patient had “cytomegaly of the brain”, along with one of the lowest brain weights in the entire study! It is also unclear as to how the authors made the inference that hormone therapy was irrelevant, as they included only one individual that was not on hormone therapy. This individual also happened to be 84 years old! They reported that they did not find an age interaction in any of the numbers, but this is severely limited by the small sample size & methodological heterogeneity.

To delve into the long list of poorly conducted studies would require too much space in this already lengthy article, so I will save this task for another period. There is, however, a useful review of the heterogeneity among study results here.

The “Female Brain”?

Let’s take a moment to consider what the findings that trans women have ‘a female brain’ means. In these studies, there is a comparison group of ‘normal‘ (i.e. cis) women who the ‘abnormal‘ (i.e. ‘transsexual’) women is compared to. The variability within cis women is elided and collapsed into a single ‘average’ value, an awfully unfruitful way of thinking about differences in brain structure. If we are to call a particular brain “size” of a specific section that of a “female” or “woman”, what of the other cis women who have “male” values? By sexing/gendering quantities, we are introducing quite an interesting site of (re)sexing the body. Not only do the studies collapse variability among cis control groups, but they completely elide any variability among ‘transsexual’ test subjects. It is not obvious that every trans woman will have a ‘female’ brain: this would be very unusual given that not all cis women do. But if a justificatory account of trans womanhood is supposed to emanate from this science, then how does one consider the trans woman with a ‘male’ brain? The typical correction to the  discussion of the cis woman with a ‘male’ brain is to shy away from sexing the brain, but this response is unintelligible and out of reach for the purportedly justificatory narrative, for both cis & trans women.

2019-05-16 10_50_39-Sci-Hub _ A sex difference in the human brain and its relation to transsexuality

This discussion of ‘male’ and ‘female’ brains is awfully reminiscent of the ways that TECFs (trans-exclusionary cultural feminists) and other transphobes have talked about sexual difference: some body part is innately sexed, producing a particular meaning of sex that includes/excludes particular groups. It is not relevant that some individuals that we ought to consider women/men are included/excluded in/out of the wrong category, because there is the presumption that this particular physiological characteristic grounds and defines sex-gender. For the TECF, the intersex body produces a challenge of classification. For trans neuroessentialist, the cis women’s ‘male brain’ is the site of failure. For the traditional conservative bioessentialist, the masculine lesbian defies a particular way of thinking about the sex-gender equivalency. United in their exclusion is the thought that there must be a physiological/physiognomic way of defining a gender-sex that provides justification for a liberatory politics.

But as the discussion of the trans woman with the ‘male brain’ shows, none of these discussions of physiological grounding of sex-gender actually hold up theoretically. The anti-trans cultural feminist has provided a litany of valid objections to the ‘neurosex’ framework, the transfeminist an account of intersex bodies in sexual difference to object to the genital/chromosomal formations of sex-gender, the liberal feminist objects to the conservative account on the questioning of the connection between their theory of ‘sex roles’ and ‘sex’ (this of course may not be a useful distinction after all). If a neuroessentialist account provided meaningful justification for trans womanhood, one ought to see trans women getting their brains tested & compared to ‘female’ values. But we do not see this form of self-validation: scientific knowledge in the form of averages (i.e. the average volume of trans women’s brain structures in comparison to cis women/men) is assumed to apply to all trans women, regardless of what type of ‘bell curve‘ brains are supposed to be distributed on. A trans woman with SD=2 away from the mean is assumed to have just as much of a ‘female’ brain as a trans woman with SD=-2, despite one falling right as ‘hyper-female’ and another as ‘male’ in the original account of ‘brainsex’ (the one formulated by academic institutions).

Do trans women have “female brains” or simply “female ratios”? Often forgotten is that there is an average (as always, the reality of average sex differences exists on a continuum) difference between the size of the brains (and heads) of ‘males’ and ‘females’. On this account, trans women have ‘male’ brains: their average head (and thus brain) size would be firmly within the ‘male’ range, whatever this is supposed to mean. But the cited studies don’t compare total brain volume, but rather the size of particular brain structures corrected for total brain volume. This is supposed to fix the issue about whether sex differences in brain volumes are simply an artifact of total body size. It’s not entirely clear why the neuroessentialist ought to use this ratio standard rather than the ‘total volume’ standard.

The Male Brain is Empty

It must also be questioned what, exactly, a “male” brain is supposed to represent. If, for instance, the finding that trans women have a “female” brain is purportedly not neuroessentialist or reproductive of the gender roles trans people often deconstruct, then it begs the question of what does a ‘male’ brain mean? The typical meaning of ‘male’ brains within scientific spheres is typically within the framework that men & women have different brains, causally related to prenatal hormones & chromosomal differences, which then produces distinct behaviors. If this essentialist formulation of “male” brains is rejected by the trans affirmationist, then it seems there is not much left to a ‘male’ brain. If it is simply a quantitative average, then it is unclear why this would be in any way constitutive of trans women as women & trans men as men any more than the finding women are, on average, shorter than men is constitutive of tall women as ‘men’ and short men as ‘women’. It is interesting to note that the portions of the brain studied by scientists in (in)validating trans gender-sexes are typically the ones involved in the discussion of ‘innate’ gendered preferences: bed nucleus of the stria terminalis INAH3, etc. This review of the “trans brain” literature is filled with claims that sexed behavior is innate, specifically affirming the misogynist “brain organization hypothesis” that has been debunked time and time again.

The Queer Feminist Scientist’s Objection

Even more, the entire concept of a ‘male’ / ‘female’ brain must be questioned on more empirical grounds (rather than the theoretical objection that it provides a basis for pro-trans attitudes). There have been a litany of feminist empirical works seeking to question the mainstream narrative that ‘male’ brains produce ‘male’ behaviors, and ‘female’ brains ‘female’ behaviors. One of the first books (I skip over Ruth Bleier’s important work) attempting to debunk this idea is Anne Fausto-Sterling (whose name one might recognize for producing a book Sexing the Body that is commonly cited & discussed by the very same people trying to push neuroessentialism) and her Myths of Gender. Although the book is partially devoted to disproving the oft-cited ‘greater male variability’ hypothesis that has been revived (in James Damore) and other silly arguments about IQ, innate differences in aggression, it also has an addendum to the second edition discussing sex differences in the brain. She (FS) discusses the aforementioned issue of total brain volume corrected for body size & the illusory corpus callosum. The numerous methodological choices one makes in measuring the body have a profound influence on the results obtained: a point obvious to any scholar of the sociology of science. The particular way that one cuts the corpus callosum will affect the presence or absence of sex differences, the size of the difference, and the qualitative differences one finds. Whether one “scans” the brain with an MRI or “photographs” and “dissects” it with a postmortem analysis is also important. But a point Fausto-Sterling makes earlier in the book, in the chapter on genes, seems most important & most fruitful to me: that brains developed at the interaction of a complex system of genes, cellular environments, biological and social environments. As more & more research has demonstrated, the biological and social are not easily separable, and the ontogeny of found differences, whether or not they meaningful exist, cannot be assumed from the existence of the differences.

Another infamous book on the sex differences in the brain is Cordelia Fine’s Delusions of Gender [apologize for the link]. While her focus is mostly on the connection between purported sex differences in the brain & the behaviors they are supposed to be causally connected to, she does talk about the complex ways that social learning & socialization can manifest themselves literally as biology. In chapters 15 and 16, she discusses the now seemingly obvious finding that behavior, the social world, environmental factors influences development, including of the brain: neuroplasticity. This novel concept is used to help explain sex differences: perhaps it isn’t that sex differences in the brain are determined by one’s genes at birth, but rather by a complex interaction between genes & environment, nature and nurture. Or perhaps, as developmental systems theorists put it, there is no distinction between nature and nurture.

The most recent magnum opus (skipping over Lise Eliot’s Pink Brains, Blue Brains) on “brains” is Gina Rippon’s The Gendered Brain. I have unfortunately been unable to obtain a copy, but she repeats and elaborates on the many arguments formed within Cordelia Fine & other’s books. She argues that brains cannot be gendered dimorphically (or sexed in most cases) because there is more variation within ‘sexes’/’genders’ than between. This is reminiscent of the Lewontin argument against the existence of races on genetic grounds: there is more genetic variability within races than between them. While we may be able to “statistically distinguish” brains based on some overfit machine learning algorithm, how is that supposed to tell us anything about the differences between brains other than that we can create all sorts of hyperpredictive models. That is, statistical abstraction doesn’t inform us about the ontology of sex differences. Most often cited is a 2015 study done by Daphna Joel (who is very trans-affirming: see my post here) that purported to show that brains are not ‘sexed’, they are intersex. In her study, she demonstrated that most brains are not ‘extreme’: they don’t have all of the ‘male’ or ‘female’ characteristics on each side of the ‘dimorphic’ spectrum. Most brains are a heterogeneous composition of differently ‘sexed’ portions: someone may have a ‘male’ amygdala, but a ‘female’ hypothalamus.

Who Benefits

Now we have to return to the issue at hand: whether “neurosex” exists & supports trans narratives. If someone can have parts of their brain that are differently sexed, then how does one “sex” the brain as a whole? Do we privilege specific parts of the brain that we think are most relevant to ‘determining’ sex? That seems like an inevitably social decision that won’t satisfy any critics. I think it has become clear that not only does the neuroessentialist narrative of “trans women have female brains” & “trans men have male brains” not justify a trans-affirming narrative, but that brains aren’t dimorphic enough to even justify classifications of ‘male’ or ‘female’ brains.

Next, we must turn to the consequences of adopting this narrative: how the entire trans community is supposed to fit within it. Obviously, this discussion of ‘male’ brains and ‘female’ brains has already started to adopt an exorsexist conceptualization of gendered difference, privileging binary gender legitimacy over that of nonbinary people. But how are nonbinary people supposed to fit within this “male brain” – “female brain” conceptualization. Some people have suggested we ought to conceive “brainsex” as yet another spectrum. This may seem plausible at first: nonbinary individuals are neither “male” nor “female”, but it immediately raises a few questions. First, what of the nonbinary identities that exist outside the already exorsexist framework of a gender ‘spectrum’ (presuming polarity and opposition)? The myth of nonbinary as “between” male and female has been the subject of numerous critiques for not only being explicitly misrepresentative of nonbinary identity, but exorsexist/transphobic for imposing a particular view of transness onto nonbinary identity. Are agender & bigender people supposed to occupy neither ends of the ‘brainsex’ spectrum or both, respectively? Or are they to be thrown under the bus in a respectability politic in the goal of transsexual legitimacy in the eyes of the broader public & medical establishment? Second, if we are appealing to a spectrum to legitimize transness, then how are we to pick where “male” starts & “nonbinary” begins. If there is a range from -1 to 1, where 1 represents maleness and -1 represents femaleness, then where does femaleness end, nonbinary begin & end & maleness start? Do ‘female brains’ go from -1 to -1/3, nonbinary from -1/3 to 1/3, and ‘male brains’ from 1/3 to 1? This would divide up the spectrum evenly. But then we encounter our earlier objection: given that brains don’t exist in dichotomies, they exist in distributions within groups, there are going to be trans women whose brains are “nonbinary” or “male”, nonbinary people with “male” or “female” brains & trans men with “nonbinary” or “female” brains. Here we have just legitimized a privileged few whose brains were lucky enough to be the “right” size and/or “right” proportions.

Who is “neurosex” serving? Not women, not men, not trans people, not nonbinary people, not feminists nor transfeminists. The only people it “serves” is the academic misogynists, the “sex difference” evolutionary psychologists, the right-wing reactionaries. It’s time for transfeminists to abandon this model.


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