Critique of a major "brain sex" study published

UtopiaPlanitia · 2026-10-10T16:30:41+00:00

Came across a new paper published recently that I thought would be of interest to FWR: [[https://x.com/SwipeWright/status/2102028205183910006 https://x.com/SwipeWright/status/2102028205183910006?]] *^NEW^*^: Our critique of a major "brain sex" study is now published.^ ^_[[https://x.com/AdamRochussen @AdamRochussen]] [[https://x.com/NeuroSGS @NeuroSGS]]_ and I evaluate a central premise of gender activism and medicine: that trans-identifying people have brains that are shifted away from their sex and toward their "gender identity."^ ^The "brain sex" concept is so central because it purports to provide an empirical scientific basis for the notion that a child can be "born in the wrong body" and would therefore benefit from body-altering medical procedures to align their body with their mind/brain.^ ^The problem is that this concept is pure pseudoscience and propped up by deeply flawed methods and badly misinterpreted data.^ ^One of the most prominent studies is Kurth et al. (2022), published in the Journal of Clinical Medicine, which claimed that the brains of transgender women are shifted away from their sex and toward their "gender identity." The paper became one of the journal’s most accessed articles and has been cited in major media outlets, scientific papers, legal arguments, and policy discussions involving pediatric gender medicine and sports.^ ^We point out that the paper's headline conclusion rests on a series of serious methodological problems.^ ^Each group contained only 24 participants. The authors used poorly justified parametric methods, one-tailed post hoc tests, made no correction for multiple comparisons, and omitted important robustness checks. Once accounted for, the main finding is no longer statistically significant.^ ^An even more glaring failure of the study was that it failed to account for sexual orientation, despite its known association with neuroanatomical variation and despite the authors having the relevant participant data needed to examine it!^ ^We each repeatedly requested the anonymized participant-level data from the paper's lead author so we could independently evaluate the findings.^ ^We received no response.^ ^The evidence simply does not justify the sweeping "brain sex" conclusion for which this study has become famous.^ ^Our full critique in _Theory Society_ is open access. Read it at the link below, and please cite it and share it whenever you encounter the false claim that trans people have brains that more closely resemble the sex they identify than their own sex.^ [[https://link.springer.com/article/10.1007/s11186-026-09747-2 https://link.springer.com/article/10.1007/s11186-026-09747-2]]

Original poster

UtopiaPlanitia · Today 17:24

Ta muchly for the link @AlexaAdventuress

OP posts:

AlexaAdventuress · Today 17:05

Here's the study about taxi drivers and their hippocampi that was mentioned earlier:
https://www.pnas.org/doi/10.1073/pnas.070039597
Here's one about musicians too:
doi: 10.1523/JNEUROSCI.23-27-09240.2003

In the same way, if you spend several years in your bedroom reading trans Reddit and ingesting hormones you've bought off a dodgy website, your brain might look a bit different. But I don't think anybody's done that study. Or maybe they have . . .

Maybe that's what Kurth et al. have done.

Original poster

UtopiaPlanitia · Today 16:26

Additional tweet from one of the OP critique's authors:

https://x.com/NeuroSGS/status/2111817726511436121?s=20

Finding neurological differences in transgender people does NOT establish that there is some innate “gender identity” that we all possess.

Look at depression. We could hypothetically identify specific changes in neural circuitry associated with depression, but this doesn’t mean we’ve identified some dedicated “depression circuit” that everyone possesses. Instead, these differences may reflect alterations in systems involved in a wide range of other functions.

Why should we interpret neurological differences in transgender populations any differently?

Even if we identified consistent neurological differences, these could reflect variation in neural systems involved in numerous other functions, rather than evidence of a dedicated “gender identity” mechanism that everyone possesses.

Finding neural correlates of a phenomenon does not establish that it represents a distinct, universal psychological characteristic.

OP posts:

AniahJeremiah · 16/10/2026 21:35

We already have studies on males with more female typical brain patterns they are called gays, yet most don't go around identifying as women hmmm

I think Ray Blanchard was correct in identifying the two types of TIM

BinturongsSmellOfPopcorn · 16/10/2026 19:33

UtopiaPlanitia · 16/10/2026 16:14

That analysis also makes good points about the thinking behind the methodology of the scan studies:

But lumping androphilic and non-androphilic transwomen together is not only a mistake, but given our current understanding based on previous brain sex research, which as Guillamon showed that only the androphilic type had female shifted phenotypes, guarantees that the whole will show a shift toward female phenotype for the whole subject group; which is likely the desired result of this current study, depending upon the ratio of androphilic to non-androphilic subjects, as the paper details.....

...One might excuse this failure to examine the two types separately based upon the argument that the were already so few transsexual subjects and thus less likely to be statistically powered enough. But this is NOT a valid excuse. One could have done the analysis both ways. But I strongly suspect that would have defeated the ideological aim of the authors, as it would have demonstrated what those earlier studies also showed, that only the androphilic group had a female shifted phenotype. Instead, by lumping them together, one could give the false impression that MTF transsexuals as a whole show such a shift, if slight....

...When I realized that they had lumped the two types together, I made a silent bet with myself, predicting that there would be a bimodal distribution, two “humps” in the data, indicative of two types, taxa, being lumped together. Sure enough, the violin plot of the transwomen shows exactly that!

Show quote history

It would also be interesting to have separate plots for the gay and straight men in the 'men' group, as a comparator for the ones in the 'trans' group.

LoremIpsumCici · 16/10/2026 16:45

Demonstrating that a transgender group differs from same-sex controls

This is weak in the rebuttal because the TW group does not differ from same sex controls. They all fit within the normal range for their sex. The visual difference is just due to the small sample size.

LoremIpsumCici · 16/10/2026 16:43

Memoryhole · 14/10/2026 07:56

The key point of that graph is that even with subjects taking cross sex hormones, and the fact they didn’t control for sexuality, all the trans subjects fitted within the distribution of the ordinary male subjects. Even the outliers. It superficially looks impressive. But it isn’t.

and there is a fuck if big overlap between ordinary male and female brains which explains why you can’t correctly sex people from their brains anything like as well as from their gonads.

My reaction to the graph as well.

Original poster

UtopiaPlanitia · 16/10/2026 16:14

WildRubyAmber · 16/10/2026 15:57

https://sillyolme.wordpress.com/2022/10/30/gaming-transsexual-brain-sex-research/

That analysis also makes good points about the thinking behind the methodology of the scan studies:

But lumping androphilic and non-androphilic transwomen together is not only a mistake, but given our current understanding based on previous brain sex research, which as Guillamon showed that only the androphilic type had female shifted phenotypes, guarantees that the whole will show a shift toward female phenotype for the whole subject group; which is likely the desired result of this current study, depending upon the ratio of androphilic to non-androphilic subjects, as the paper details.....

...One might excuse this failure to examine the two types separately based upon the argument that the were already so few transsexual subjects and thus less likely to be statistically powered enough. But this is NOT a valid excuse. One could have done the analysis both ways. But I strongly suspect that would have defeated the ideological aim of the authors, as it would have demonstrated what those earlier studies also showed, that only the androphilic group had a female shifted phenotype. Instead, by lumping them together, one could give the false impression that MTF transsexuals as a whole show such a shift, if slight....

...When I realized that they had lumped the two types together, I made a silent bet with myself, predicting that there would be a bimodal distribution, two “humps” in the data, indicative of two types, taxa, being lumped together. Sure enough, the violin plot of the transwomen shows exactly that!

OP posts:

WildRubyAmber · 16/10/2026 15:57

https://sillyolme.wordpress.com/2022/10/30/gaming-transsexual-brain-sex-research/

Gaming Transsexual Brain Sex Research

Another study done by Luders research group on MTF transsexual brains comparing them to control men and women shows a shift toward female brain phenotype. I’m sure this will be picked up by m…

https://sillyolme.wordpress.com/2022/10/30/gaming-transsexual-brain-sex-research/

WildRubyAmber · 16/10/2026 15:54

This is interesting too:

https://x.com/NeuroSGS/status/2103510575040929885

We all (authors of the rebuttal) contacted Kurth and all the co-authors on multiple occasions to get access to their participant-level data (which they stated on their paper they would give), to no response. They also declined an offer to respond to our criticisms.

The only time I had an email back from Kurth (3 years ago at this point), he agreed that sexual orientation confounded his data.

This is all rather telling…

Sammy (@NeuroSGS) on X

We all (authors of the rebuttal) contacted Kurth and all the co-authors on multiple occasions to get access to their participant-level data (which they stated on their paper they would give), to no response. They also declined an offer to respond to ou...

https://x.com/NeuroSGS/status/2103510575040929885

Original poster

UtopiaPlanitia · 16/10/2026 15:07

This neuroscientist has a pinned thread on TwiX that might be of interest as well:

https://x.com/NeuroSGS/status/1551155044267032577?s=20

My pinned thread of threads, primarily containing citations and explanations about neurological/ psychological sex differences, sexuality, gender dysphoria, and other academic research interests of mine

OP posts:

Original poster

UtopiaPlanitia · 16/10/2026 15:04

One of the critique's authors has further clarified on TwiX (in response to various TIMs telling him that the brain scans show that TIMs don't have male brains):

https://x.com/NeuroSGS/status/2109716400684101704?s=20

Normative sex differences are not even particularly well-characterised in the human brain in the first place. While univariate differences definitely exist (small in size and usually sporadic), sex differences are much better understood as multivariate and probabilistic. Individual anatomical features overlap substantially between sexes, yet their combined distributions and covariance structures can produce considerable group separation without requiring consistently sex-biased neuroanatomical landmarks.

Knowing this, the transgender neuroimaging literature has substantial methodological limitations.

Studies frequently use inconsistent male–female reference groups, with inadequate control for sexual orientation and/or “gender-affirming” hormone exposure. Both variables can independently influence anatomical measures, potentially producing apparent cross-sex shifts that cannot necessarily be attributed to “gender identity” or its developmental origins.

Other studies are insufficiently designed to distinguish competing hypotheses, while some employ flawed and questionable statistical approaches, inadequate brain-size correction, small samples and underpowered analyses, increasing the risk of unstable or misleading findings.

Independent replication is also limited, with reported cross-sex patterns varying considerably across studies, brain regions, imaging modalities and analytical methods.

Demonstrating that a transgender group differs from same-sex controls does NOT establish that its members resemble the opposite sex, nor does a shift in selected regions establish a coherent, multivariate pattern of cross-sex neuroanatomical organisation.

The existence of brain scans is not in dispute. What remains unestablished is whether the reported differences represent a reliable, generalisable cross-sex phenotype rather than alternative biological or methodological explanations.

OP posts:

Memoryhole · 15/10/2026 22:23

Helleofabore · 15/10/2026 06:43

Yes. When it is pointed out to those who link it as a gotcha, they try to make the point that the the grouping is closer to the female range. But then, I and others point out the lack of control for sexual orientation and how that has in the past shown impact to the readings.

there is then the taxi driver study which I cannot find which I remember reading showed that the London cabbies had scans that showed a particular grouping. Because people who have similar interests and people who have similar occupation often do. So if people who have similar interests /occupations have similar results on their scans, of course these male people with transgender identities are potentially going to loosely group. But always within the overall male range.

I think that activists and those desperate for a biological marker for those with a transgender identity are going to find over the coming years that there really is none. Which makes sense because as we have seen from a long term poster who frequently name changes but claims to have a doctorate level qualification in a related field to gender identity (make of that claim what you will), the only thing they can give as an explanation of what gender identity is, is a claim about someone understanding that they are the opposite sex to their body’s sex category. Or another similar existential / philosophical theory type wording as that has changed slightly over the years.

But that explanation never stands up to any analysis. Because those people cannot possibly know what the fuck they are feeling. They cannot. It is impossible for them to know.

There is a great clip of Germaine Greer on a discussion panel where she explaina this to activists on the panel. She said, of course it is impossible ‘to know’ what being the opposite sex ‘feels’ like.

But it is another link I cannot find unfortunately.

Show quote history

This might be the taxi driver study? Linked to changes in the hippocampus.

https://pubmed.ncbi.nlm.nih.gov/17024677/

Original poster

UtopiaPlanitia · 15/10/2026 18:31

harderthanIexpected · 15/10/2026 17:40

The graph looks even less persuasive when you correct the blatant and shameless use of suggestive colour coding in the original...

Edited

You make such a good, and an obvious, point and I'm miffed with myself that I didn't that colour coding until you pointed it out. Thank you 👍

OP posts:

harderthanIexpected · 15/10/2026 17:42

Image didn't attach to my last post

Critique of a major "brain sex" study published

harderthanIexpected · 15/10/2026 17:40

The graph looks even less persuasive when you correct the blatant and shameless use of suggestive colour coding in the original...

Helleofabore · 15/10/2026 17:15

UtopiaPlanitia · 15/10/2026 16:00

Thing is, even if there ever was such a thing as an accurate brain scan that could locate this 'feeling of having a female brain in a male body', there's no way TRAs would allow it be used as a means to accurately diagnose men in order to allow them to receive cross-sex hormones etc. TRAs would refuse to take it or decry it as medicalisation.

Show quote history

Yep.

I am sure most of us remember the outcry when it was even suggested that there was a biological marker found, and that magical announcement we all were going to tune into, got cancelled... just like that. Never to be heard mentioned again...

Memoryhole · 15/10/2026 16:27

Helleofabore · 15/10/2026 06:43

Yes. When it is pointed out to those who link it as a gotcha, they try to make the point that the the grouping is closer to the female range. But then, I and others point out the lack of control for sexual orientation and how that has in the past shown impact to the readings.

there is then the taxi driver study which I cannot find which I remember reading showed that the London cabbies had scans that showed a particular grouping. Because people who have similar interests and people who have similar occupation often do. So if people who have similar interests /occupations have similar results on their scans, of course these male people with transgender identities are potentially going to loosely group. But always within the overall male range.

I think that activists and those desperate for a biological marker for those with a transgender identity are going to find over the coming years that there really is none. Which makes sense because as we have seen from a long term poster who frequently name changes but claims to have a doctorate level qualification in a related field to gender identity (make of that claim what you will), the only thing they can give as an explanation of what gender identity is, is a claim about someone understanding that they are the opposite sex to their body’s sex category. Or another similar existential / philosophical theory type wording as that has changed slightly over the years.

But that explanation never stands up to any analysis. Because those people cannot possibly know what the fuck they are feeling. They cannot. It is impossible for them to know.

There is a great clip of Germaine Greer on a discussion panel where she explaina this to activists on the panel. She said, of course it is impossible ‘to know’ what being the opposite sex ‘feels’ like.

But it is another link I cannot find unfortunately.

Show quote history

Yes, totally this.

and the ‘look our grouping is closer to that of natal women’ is such a pile of horse shit as you could skim off the bottom set of natal male responders and say ‘look, these men are women too’.

Original poster

UtopiaPlanitia · 15/10/2026 16:00

Helleofabore · 15/10/2026 06:43

Yes. When it is pointed out to those who link it as a gotcha, they try to make the point that the the grouping is closer to the female range. But then, I and others point out the lack of control for sexual orientation and how that has in the past shown impact to the readings.

there is then the taxi driver study which I cannot find which I remember reading showed that the London cabbies had scans that showed a particular grouping. Because people who have similar interests and people who have similar occupation often do. So if people who have similar interests /occupations have similar results on their scans, of course these male people with transgender identities are potentially going to loosely group. But always within the overall male range.

I think that activists and those desperate for a biological marker for those with a transgender identity are going to find over the coming years that there really is none. Which makes sense because as we have seen from a long term poster who frequently name changes but claims to have a doctorate level qualification in a related field to gender identity (make of that claim what you will), the only thing they can give as an explanation of what gender identity is, is a claim about someone understanding that they are the opposite sex to their body’s sex category. Or another similar existential / philosophical theory type wording as that has changed slightly over the years.

But that explanation never stands up to any analysis. Because those people cannot possibly know what the fuck they are feeling. They cannot. It is impossible for them to know.

There is a great clip of Germaine Greer on a discussion panel where she explaina this to activists on the panel. She said, of course it is impossible ‘to know’ what being the opposite sex ‘feels’ like.

But it is another link I cannot find unfortunately.

Show quote history

Thing is, even if there ever was such a thing as an accurate brain scan that could locate this 'feeling of having a female brain in a male body', there's no way TRAs would allow it be used as a means to accurately diagnose men in order to allow them to receive cross-sex hormones etc. TRAs would refuse to take it or decry it as medicalisation.

OP posts:

Helleofabore · 15/10/2026 06:43

Memoryhole · 14/10/2026 07:56

The key point of that graph is that even with subjects taking cross sex hormones, and the fact they didn’t control for sexuality, all the trans subjects fitted within the distribution of the ordinary male subjects. Even the outliers. It superficially looks impressive. But it isn’t.

and there is a fuck if big overlap between ordinary male and female brains which explains why you can’t correctly sex people from their brains anything like as well as from their gonads.

Yes. When it is pointed out to those who link it as a gotcha, they try to make the point that the the grouping is closer to the female range. But then, I and others point out the lack of control for sexual orientation and how that has in the past shown impact to the readings.

there is then the taxi driver study which I cannot find which I remember reading showed that the London cabbies had scans that showed a particular grouping. Because people who have similar interests and people who have similar occupation often do. So if people who have similar interests /occupations have similar results on their scans, of course these male people with transgender identities are potentially going to loosely group. But always within the overall male range.

I think that activists and those desperate for a biological marker for those with a transgender identity are going to find over the coming years that there really is none. Which makes sense because as we have seen from a long term poster who frequently name changes but claims to have a doctorate level qualification in a related field to gender identity (make of that claim what you will), the only thing they can give as an explanation of what gender identity is, is a claim about someone understanding that they are the opposite sex to their body’s sex category. Or another similar existential / philosophical theory type wording as that has changed slightly over the years.

But that explanation never stands up to any analysis. Because those people cannot possibly know what the fuck they are feeling. They cannot. It is impossible for them to know.

There is a great clip of Germaine Greer on a discussion panel where she explaina this to activists on the panel. She said, of course it is impossible ‘to know’ what being the opposite sex ‘feels’ like.

But it is another link I cannot find unfortunately.

DramaAndBullshit · 14/10/2026 19:12

Luckydog7 · 13/10/2026 18:49

I'm baffled why 'brain sex' even matters. We segregate single sex spaces by body type aka sex not on your brain because of known differences of behaviour between those two groups.

If there was a study that shown that all's transwomen's BEHAVIOUR eg crime and offending rates was identical or better then the sex they desired to be you might have an actual argument.

It seems however that this 'apparent' brain difference doesn't actually translate to visible behaviour difference towards the female, in fact it seems to be the opposite with an increase in sex crimes in the transwoman inmate population at least.

It doesn’t matter, because it’s nonsense. But it’s been used as ‘evidence’ to support transitioning. That’s why critique of studies like this are important.

Awkwardisfunny · 14/10/2026 18:53

fanOfBen · 14/10/2026 10:07

These any good to you? (I do not do style, sorry if obviously not.) https://share.google/7W9Oxth4T0aiswPew

Sorry no haha not blue (enough if at all) and I do want a chic / fashionable mid heel - like I could wear them to work or for cocktails 😆 (so nothing you'd wear to ride horses or to fit in with cowboys) x

solerolover · 14/10/2026 17:59

Great post, OP! It definitely mirrors the critiques of the study that many of the wonderful, intelligent posters have discussed on FWR, I find myself learning so much from then.

And anyway, even if the studies did show that trans-identified men have "lady brains," what the hell does that have to do with women again? Female people still exist as a discrete sex class. The physical, social and historical consequences of being female still exist and always will. Whatever luxury belief a man has about himself, has nothing to do with the material, biological reality of the female half of the planet.

BinturongsSmellOfPopcorn · 14/10/2026 17:19

Wrong quote, but I'm sure you can work it out.

BinturongsSmellOfPopcorn · 14/10/2026 17:15

UtopiaPlanitia · 14/10/2026 15:57

Yup, I have to admit the shapes in the graph did make me laugh a little when I first saw them 😈

Show quote history

Hmm. Bit rude.

I can understand if they perhaps have an auto filter on 'sex'. And just about understand if the weekend team couldn't deal (although that's fairly shoddy in itself). But the lack of explanation or apology is very poor.