@NeuroSGS
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Neuroscientist (PhD). Research interests include sex differences, dementia, sleep/circadian rhythms, and neuroimmunology.
Joined March 2009
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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:
Sammy retweeted
It's going to be the work of many years to debunk all the zombie genderist "studies". But this is a good one to knock down
🚨NEW: Our critique of a major "brain sex" study is now published.
@AdamRochussen, @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.
🔗link.springer.com/article/10…
Everybody knows the famous Kurth et al., 2022 study (cited below) about “brain-sex” in transgender women being shifted to their “gender identity”.
Colin Wright (@SwipeWright), Adam Rochussen (@AdamRochussen), and myself wrote a post-publication peer-review discussing the methodological and statistical issues with this famous paper.
It’s now been published!
Read below! 💪🏼
This video highlights a huge issue with using science to justify political ideology.
It all sounds very convincing to the average person. I mean, why wouldn’t you trust “the science” when it “repeatedly” demonstrates that transgender individuals have brains of the opposite sex? Why would anyone deny this supposed “scientific fact”?
The problem is, people often don’t actually look at the studies critically. They see the “media-grabbing” headline finding and repeat it.
Many researchers and academics interested in this debate (myself included) have repeatedly pointed out (screaming & shouting) that much of this literature is based on small samples, confounded designs, questionable analyses and findings that often fail to replicate.
But that nuance gets completely lost.
A difference in one brain region becomes an “opposite-sex brain”. A shift towards the opposite-sex average becomes “brain sex”. An association becomes an explanation...
And before you know it, these claims are being used to justify real-world policy, whether that’s trans people’s inclusion in sport, or arguments around cross-sex hormonal “treatments”.
This is what happens when people blindly “follow the science” when they 1) don’t fully understand the studies, 2) can’t critically analyse them, and 3) take the conclusions at face value.
Science should absolutely inform these debates. But that also means actually interrogating the science, and not attack people when they highlight clear issues with the underlying data.
What did they actually test? How big was the sample? What were the confounders? Did they test the interaction? Has it replicated? And does the evidence actually support the claim being made?
Because “a study found X” and “science has established X” are not the same thing.
This is a dangerous game to play…
This video highlights a huge issue with using science to justify political ideology.
It all sounds very convincing to the average person. I mean, why wouldn’t you trust “the science” when it “repeatedly” demonstrates that transgender individuals have brains of the opposite sex? Why would anyone deny this supposed “scientific fact”?
The problem is, people often don’t actually look at the studies critically. They see the “media-grabbing” headline finding and repeat it.
Many researchers and academics interested in this debate (myself included) have repeatedly pointed out (screaming & shouting) that much of this literature is based on small samples, confounded designs, questionable analyses and findings that often fail to replicate.
But that nuance gets completely lost.
A difference in one brain region becomes an “opposite-sex brain”. A shift towards the opposite-sex average becomes “brain sex”. An association becomes an explanation...
And before you know it, these claims are being used to justify real-world policy, whether that’s trans people’s inclusion in sport, or arguments around cross-sex hormonal “treatments”.
This is what happens when people blindly “follow the science” when they 1) don’t fully understand the studies, 2) can’t critically analyse them, and 3) take the conclusions at face value.
Science should absolutely inform these debates. But that also means actually interrogating the science, and not attack people when they highlight clear issues with the underlying data.
What did they actually test? How big was the sample? What were the confounders? Did they test the interaction? Has it replicated? And does the evidence actually support the claim being made?
Because “a study found X” and “science has established X” are not the same thing.
This is a dangerous game to play…
Here’s an example of exactly what I mean.
The first study mentioned in the video (Kurth et al., 2022) is clearly being used to justify policy. Except, when you actually look critically at the study, the data don’t support the authors’ own conclusions.
We (@SwipeWright, @AdamRochussen, and myself) explain why in our new commentary 👇
link.springer.com/article/10…
Seems like a good opportunity to leave this here ☺️
link.springer.com/article/10…
Here is a great study on the human brain that shows how a trans woman’s brain is more aligned with a female brain. They took samples of C1S men & women, as well as trans women before any affirming care or hormones. For those that deny science I expect you to find a way to dismiss this and carry on with your transphobia, this isn’t for you. This is for those that actually want to learn more about who we are and why we are. So then can understand.
I do wish they also included trans men as I believe the results would show the same as trans women (just opposite obvi).
#trans #transhealth #loveislove Trans Women are Women
pmc.ncbi.nlm.nih.gov/article…
Sammy retweeted
Clinical proponents of the transgender brain theory never say that young patients should undergo brain scans as part of diagnosis.
The theory seems intended purely for lay consumption and reassurance of parents (& maybe clinicians).
New peer reviewed article on the science👇
🚨NEW: Our critique of a major "brain sex" study is now published.
@AdamRochussen, @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.
🔗link.springer.com/article/10…
Our commentary:
link.springer.com/article/10…
Sammy retweeted
🚨NEW: Our critique of a major "brain sex" study is now published.
@AdamRochussen, @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.
🔗link.springer.com/article/10…
Read our commentary here!! 💪🏼💪🏼
🚨NEW: Our critique of a major "brain sex" study is now published.
@AdamRochussen, @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.
🔗link.springer.com/article/10…
Sammy retweeted
25 years after our original study showing there are on-average sex differences in the mind, we publish the first replication, confirming this theguardian.com/science/2026…
Important work from @SwipeWright, @NeuroSGS, and @AdamRochussen dismantling the “brain sex” myth and the junk science used to prop it up. ⬇️
🚨NEW: Our critique of a major "brain sex" study is now published.
@AdamRochussen, @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.
🔗link.springer.com/article/10…
It’s kind of amusing that many of these studies you cite are contradictory.
A huge citation dump is NOT evidence the literature is conclusive, replicable, or convincing…
If we have to go through these studies one by one to make you all realise the issues with this literature, then so be it!
Here is a comprehensive list of every study ever done on the brain-sex anomalies in transgender individuals (at least what AI could find). That's the neat thing about science, it doesn't live or die by a single study, I look forward to your breakdown of every single one of these, have fun.
Zhou JN, Hofman MA, Gooren LJ, Swaab DF. Nature. 1995.
Kruijver FPM, Zhou JN, Pool CW, Hofman MA, Gooren LJ, Swaab DF. J Clin Endocrinol Metab. 2000.
Garcia-Falgueras A, Swaab DF. Brain. 2008.
Taziaux M, Swaab DF, Bakker J. J Clin Endocrinol Metab. 2012.
Garcia-Falgueras A, Ligtenberg L, Kruijver FP, Swaab DF. Brain Res. 2011.
Yokota Y, Kawamura Y, Kameya Y. Neurosci Res. 2005.
Hulshoff Pol HE, Cohen-Kettenis PT, Van Haren NEM, et al. Eur J Endocrinol. 2006.
Luders E, Sánchez FJ, Gaser C, et al. NeuroImage. 2009.
Luders E, Sánchez FJ, Tosun D, et al. J Psychiatr Res. 2012.
Savic I, Arver S. Cereb Cortex. 2011.
Rametti G, Carrillo B, Gómez-Gil E, et al. J Psychiatr Res. 2011a.
Rametti G, Carrillo B, Gómez-Gil E, et al. Psychoneuroendocrinology. 2011b.
Rametti G, Carrillo B, Gómez-Gil E, et al. Psychoneuroendocrinology. 2012.
Santarnecchi E, Vatti G, Déttore D, Rossi A. J Sex Med. 2012.
Simon L, Kozák LR, Simon V, et al. PLoS One. 2013.
Zubiaurre-Elorza L, Junque C, Gómez-Gil E, et al. Cereb Cortex. 2013.
Zubiaurre-Elorza L, Junque C, Gómez-Gil E, Guillamon A. J Sex Med. 2014.
Hahn A, Kranz GS, Küblböck M, et al. J Neurosci. 2015.
Hoekzema E, Schagen SEE, Kreukels BPC, et al. Psychoneuroendocrinology. 2015.
Manzouri A, Kosidou K, Savic I. Cereb Cortex. 2017.
Manzouri A, Savic I. Sci Rep. 2018.
Manzouri A, Savic I. Cereb Cortex. 2019.
Kranz GS, Hahn A, Kaufmann U, et al. J Neurosci. 2014.
Kranz GS, Hahn A, Kaufmann U, et al. Hum Brain Mapp. 2014.
Kranz GS, Seiger R, Kaufmann U, et al. Psychoneuroendocrinology. 2015.
Kranz GS, Seiger R, Kaufmann U, et al. NeuroImage. 2017.
Seiger R, Hahn A, Hummer A, et al. Psychoneuroendocrinology. 2016.
Seiger R, Hahn A, Hummer A, et al. NeuroImage. 2016.
Mueller SC, De Cuypere G, T’Sjoen G. J Sex Med. 2017.
Mueller SC, Guillamon A, Zubiaurre-Elorza L, et al. J Sex Med. 2021.
Khorashad BS, Khazai B, Talaei A, et al. Psychoneuroendocrinology. 2020.
Skorska MN, Chavez S, Devenyi GA, et al. Cereb Cortex. 2021.
Skorska MN, Chavez S, Devenyi GA, et al. Hum Brain Mapp. 2023.
Burke SM, Cohen-Kettenis PT, Veltman DJ, et al. Front Endocrinol. 2014.
Burke SM, Kreukels BPC, Cohen-Kettenis PT, et al. J Psychiatry Neurosci. 2016.
Burke SM, Manzouri AH, Dhejne C, et al. Cereb Cortex. 2018.
Beking T, Burke SM, Geuze RH, et al. Psychoneuroendocrinology. 2020.
Gizewski ER, Krause E, Schlamann M, et al. J Sex Med. 2009.
Berglund H, Lindström P, Dhejne-Helmy C, Savic I. Cereb Cortex. 2008.
Nawata H, Ogomori K, Tanaka M, et al. Psychiatry Clin Neurosci. 2010.
Ku HL, Lin CS, Chao HT, et al. World J Biol Psychiatry. 2013.
Lin CS, Ku HL, Chao HT, et al. World J Biol Psychiatry. 2014.
Junger J, Habel U, Bröhr S, et al. Soc Cogn Affect Neurosci. 2014.
Clemens B, Junger J, Pauly K, et al. J Sex Med. 2017.
Feusner JD, Lidström A, Moody TD, et al. Brain Imaging Behav. 2017.
Nota NM, Kreukels BPC, den Heijer M, et al. Psychoneuroendocrinology. 2017.
Spies M, Hahn A, Kranz GS, et al. J Psychiatr Res. 2016.
Soleman RS, Schagen SEE, Veltman DJ, et al. Psychoneuroendocrinology. 2013.
Soleman RS, Staphorsius AS, Cohen-Kettenis PT, et al. Psychoneuroendocrinology. 2016.
Schöning S, Engelien A, Bauer C, et al. J Sex Med. 2010.
Smith ES, Junger J, Derntl B, Habel U. J Sex Med. 2015.
Guillamon A, Junque C, Gómez-Gil E. Arch Sex Behav. 2016.
Kreukels BPC, Guillamon A. Int Rev Psychiatry. 2016.
Frigerio A, Ballerini L, Valdés Hernández M. Arch Sex Behav. 2021.
Flint C, Förster K, Koser SA, et al. Neuropsychopharmacology. 2020.
Baldinger-Melich P, Urquijo Castro MF, Seiger R, et al. Cereb Cortex. 2020.
Kilpatrick LA, Holmberg M, Manzouri A, Savic I. Cereb Cortex. 2019.
Uribe C, Junque C, Gómez-Gil E, et al. NeuroImage Clin. 2020.
Starcevic A, Dakovic M, Radojicic Z, et al. Medicina. 2020.
Wang Y, Khorashad BS, Feusner JD, et al. Cereb Cortex. 2021.
Majid DSA, Burke SM, Manzouri A, et al. Psychoneuroendocrinology. 2020.
Clemens B, Derntl B, Smith E, et al. NeuroImage. 2020.
Nouwen A, et al. related adolescent structural papers overlapping Hoekzema/Burke cohorts.
Spizzirri G, Duran FLS, Chaim-Avancini TM, et al. Sci Rep. 2018.
Luders E, Gaser C, Narr KL, Toga AW. related sex-classifier work preceding 2022.
Holmes D, et al. various small VBM replications of putamen/thalamus.
Simon L, et al. follow-up functional connectivity.
Hahn A, Kranz GS, Sladky R, et al. Hum Brain Mapp. 2016.
Kranz GS, Seiger R, Henning A, et al. Psychoneuroendocrinology. 2018.
Seiger R, Hahn A, Kranz GS, et al. J Psychiatry Neurosci. 2015.
Lanzenberger R, Kranz GS, Haeusler D, et al. related PET serotonin/dopamine papers in MtF.
Hahn A, Haeusler D, Kranz GS, et al. related PET.
Staphorsius AS, Kreukels BPC, Cohen-Kettenis PT, et al. Psychoneuroendocrinology. 2015.
Cohen-Kettenis PT, van Goozen SHM, Doorn CD, Gooren LJG. early related behavioral/brain papers.
Bakker J, et al. adolescent pheromone fMRI (Liège/Amsterdam).
Skorska MN, Chavez S, VanderLaan DP, et al. additional youth T1-relaxometry.
Mueller SC, Wierckx K, Jackson K, T’Sjoen G. Psychoneuroendocrinology. 2016.
Nota NM, Burke SM, den Heijer M, et al. related rs-fMRI.
Feusner JD, Dervisic J, Moody T, et al. own-body perception fMRI.
Kilpatrick LA, et al. additional Savic-group CTh/SA papers.
Manzouri A, Savic I. own-body network papers 2017–2019.
Savic I, Garcia-Falgueras A, Swaab DF. Prog Brain Res. 2010.
Swaab DF, Garcia-Falgueras A. Funct Neurol. 2009.
Swaab DF. various handbook chapters summarizing the postmortem series.
Kruijver FPM. PhD thesis, University of Amsterdam. 2004.
Fernández R, Esteva I, Gómez-Gil E, et al. related genetics plus occasional MRI.
Altinay M, Anand A. related mood/connectivity.
Fisher AD, Ristori J, Morelli G, Maggi M. reviews citing the imaging set.
Nguyen HB, Loughead J, Lipner E, et al. Biol Psychiatry. 2019.
Turban JL, et al. not primary imaging.
Hembree WC, et al. Endocrine Society guideline citing the above.
Taziaux M, et al. kisspeptin/NKB infundibular nucleus follow-ups.
Bao AM, Swaab DF. related reviews of the postmortem collection.
Garcia-Falgueras A, Swaab DF. additional INAH papers.
Chung WCJ, De Vries GJ, Swaab DF. BSTc developmental timing paper (non-trans sample, often cited with the series).
Zhou JN, Hofman MA, Gooren LJ, Swaab DF. Nature. 1995. (BSTc volume)
Kruijver FPM et al. JCEM. 2000. (BSTc neuron number)
Garcia-Falgueras A, Swaab DF. Brain. 2008. (INAH-3)
Taziaux M, Swaab DF, Bakker J. JCEM. 2012. (NKB)
Mueller SC et al. J Sex Med. 2021. (ENIGMA n=803)
Hoekzema E et al. Psychoneuroendocrinology. 2015.
Savic I, Arver S. Cereb Cortex. 2011.
Luders E et al. NeuroImage. 2009.
Zubiaurre-Elorza L et al. Cereb Cortex. 2013.
Rametti G et al. J Psychiatr Res. 2011; Psychoneuroendocrinology. 2011; 2012.
Hahn A et al. J Neurosci. 2015.
Kranz GS et al. J Neurosci. 2014; Hum Brain Mapp. 2014.
Manzouri A, Savic I. Cereb Cortex. 2017; 2019.
Flint C et al. Neuropsychopharmacology. 2020.
Skorska MN et al. Cereb Cortex. 2021.
Khorashad BS et al. Psychoneuroendocrinology. 2020.
Burke SM et al. Front Endocrinol. 2014; J Psychiatry Neurosci. 2016.
Gizewski ER et al. J Sex Med. 2009.
Berglund H et al. Cereb Cortex. 2008.
Clemens B et al. J Sex Med. 2017.
Feusner JD et al. Brain Imaging Behav. 2017.
Nota NM et al. Psychoneuroendocrinology. 2017.
Uribe C et al. NeuroImage Clin. 2020.
Wang Y et al. Cereb Cortex. 2021.
Spizzirri G et al. Sci Rep. 2018.
Baldinger-Melich P et al. Cereb Cortex. 2020.
Kilpatrick LA et al. Cereb Cortex. 2019.
Seiger R et al. Psychoneuroendocrinology. 2016.
Kranz GS, Seiger R et al. later Vienna PET/MRI series.
Staphorsius AS et al. Psychoneuroendocrinology. 2015.
Soleman RS et al. Psychoneuroendocrinology. 2013; 2016.
Junger J et al. Soc Cogn Affect Neurosci. 2014.
Ku HL et al. World J Biol Psychiatry. 2013.
Lin CS et al. World J Biol Psychiatry. 2014.
Nawata H et al. Psychiatry Clin Neurosci. 2010.
Simon L et al. PLoS One. 2013.
Santarnecchi E et al. J Sex Med. 2012.
Yokota Y et al. Neurosci Res. 2005.
Hulshoff Pol HE et al. Eur J Endocrinol. 2006.
Zubiaurre-Elorza L et al. J Sex Med. 2014.
Luders E et al. J Psychiatr Res. 2012.
Frigerio A et al. Arch Sex Behav. 2021.
Guillamon A et al. Arch Sex Behav. 2016.
Kreukels BPC, Guillamon A. Int Rev Psychiatry. 2016.
Smith ES et al. J Sex Med. 2015.
Sammy retweeted
Reproducibility is an important component of science, though not all journals require authors to provide their data.
We wanted to reanalyze the data of this influential "brain sex" paper with more rigorous statistical methods. The paper said to "contact the corresponding author" to obtain the transgender data.
We did. Several times over multiple months.
They never responded.
The authors were also invited to respond to our critique.
Again, silence.
Is this the behavior of scholars who care about the truth? Or is this more like the behavior you'd expect from people who are trying to hide from it?
Real scientists welcome criticism and be prepared to defend their ideas, or change their minds when presented with compelling arguments and evidence. They don't ghost their critics, especially in the academic literature.
The authors of the study we critiqued have an open invitation to respond to our paper. That invitation has no expiration date.
We hope to hear from them.
🚨NEW: Our critique of a major "brain sex" study is now published.
@AdamRochussen, @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.
🔗link.springer.com/article/10…
Sammy retweeted
Cremieux asks in his tweet below (with lots of great references) whether testosterone "radically increases risk-taking, aggravation, the propensity to commit violent acts, and so on." I'm glad he's explaining that testosterone's effects are not so clear cut! But I wish he'd given more consideration to the question of whether male-typical levels of testosterone increase the propensity for such behaviors in males. The answer to that question is "yes."
Cremieux is right that there is no clear evidence that male testosterone levels (within the normal T range) predict levels of sexual or aggressive behavior. It's great to get more eyes on that, and to bust the many myths. But the explanations for differences in behavior within a sex are quite different from those concerning differences between the sexes.
Cremieux primarily relies on research that addresses questions like: does a man's T level predict the intensity of his sex drive or the frequency of his violent behavior? The answer, generally, is no. (And he's right that a bigger body, more muscles or deeper voice, which are potentially associated with higher T at critical developmental stages, do impact behavior indirectly, but not in a clear way.)
But he then uses this “within sex” research to answer questions about the source of the gap between the sexes — in aggression, in sex drive, whatever. But answers to questions about how T predicts behavior in one sex do not address questions about the role of testosterone in explaining differences in behavior between the sexes. Such questions—e.g. why are males more violent than females— require different kinds of evidence, answering questions like what T does across development, why it does it, what happens when you manipulate it in other animals, and what do “natural experiments” in humans tell us? It's about the evolution of sexually differentiated reproductive strategies and the hormonal mechanisms that coordinate body and behavior in each sex.
An evolutionary perspective would have improved Cremieux's perspective. He tweeted that "the [sex] gap in violent behavior is far too large to be explained by testosterone levels." But the size of the sex difference is part of the point: 90-95% of all murders are committed by males, pretty much everywhere in the world. (The size of the gap is driven by differences in male behavior, which tends to respond to cultural incentives.) This pattern is not caused by small differences in T level; it is about large and impactful differences between the sexes in testosterone over a lifetime, that exist for a reason.
On average, a human male is exposed to T levels that are about 10-20 times higher than in females. Across development, male brains and bodies go through "critical periods" in early life (in the womb and shortly after birth) and adolescence, during which the brain and body are particularly sensitive to T's actions, which have permanent effects. So even if T is low in adulthood, it has already permanently affected reproductively relevant behaviors.
Evidence suggests that "sex-typical behavior" (with wide variation!) in male animals (including humans) is elicited once T passes something like a relatively low but male-typical threshold T level, at different phases of life. Above that, what seems to matter more is age, health, history, the ecological environment, and social cues and norms. In humans, these can include things like religion; socioeconomic status; availability of fertile females; disease; threats to resources, mates or children; community values; standards of masculinity; and the law.
Higher lifetime T in males (and not necessarily current T) is why many animals show similar sex differences in aggression, including higher rates of rough play. This is true even in humans, in which boys play rougher than girls around the world, even though little boys don't have higher T than girls. The male preference for rough play has been clearly shown to be driven by higher T, specifically in the womb and/or shortly after birth in male animals. Such play is part of a male reproductive strategy, motivating young males to practice status-competition and cooperation skills they will need in adulthood. In girls, those with unusually high T levels in the womb also tend to prefer rougher play.
Testosterone has these effects in males because of evolutionary pressures: males produce sperm rather than eggs, and thus have evolved reproductive strategies that differ from those of females. On average, males have a higher potential rate of reproduction and invest less in parenting, and generally (not always) compete more intensely for mates. Testosterone is the biological mechanism that coordinates the production of sperm with the other physical and behavioral attributes that help males get sperm to egg, given the species and environment.
Again, environment matters tremendously, but it is not the source of the sex differences in basic reproductive behaviors.
You can read more about testosterone and behavior in my book T: The Story of Testosterone, the Hormone that Dominates and Divides us.
My latest article debunks an incredibly prevalent and powerful myth:
That testosterone makes people angry.
Link: cremieux.xyz/p/testosterone-…
Sammy retweeted
🚨NEW: Our critique of a major "brain sex" study is now published.
@AdamRochussen, @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.
🔗link.springer.com/article/10…
Sammy retweeted
Thanks for all your work putting this together, Colin!
It would be impossible to publish formal critiques for all the terrible science out there, but the remarkable influence of this one makes doing so more than justified and long overdue 🫡
Read our commentary here!! 💪🏼💪🏼
🚨NEW: Our critique of a major "brain sex" study is now published.
@AdamRochussen, @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.
🔗link.springer.com/article/10…
Everybody knows the famous Kurth et al., 2022 study (cited below) about “brain-sex” in transgender women being shifted to their “gender identity”.
Colin Wright (@SwipeWright), Adam Rochussen (@AdamRochussen), and myself wrote a post-publication peer-review discussing the methodological and statistical issues with this famous paper.
It’s now been published!
Read below! 💪🏼
Our commentary:
link.springer.com/article/10…
Kurth et al., 2022 original paper:
pmc.ncbi.nlm.nih.gov/article…