Summary
A widely cited 2022 brain-scan study by Kurth and colleagues reported that the brains of 24 transgender women, before hormone treatment, fell between those of men and women, though closer to men. This 2026 critique argues the key difference from men only looked real because of lenient statistical choices: testing in one direction only, and not adjusting for making three comparisons. With standard adjustments, the difference from men could easily be chance, though the difference from women still holds. Small groups and one unusual result make it fragile. Sexual orientation, known to relate to brain structure, was never analysed though the data existed. The critique is plausible but uses only published figures, was accepted nine days after it was sent in, and its lead author is a Manhattan Institute fellow on the journal's advisory board.
Key findings
- مطالعهٔ 2022، 24 مرد، 24 زن و 24 زن ترنسجندر را که هنوز هورمون نمی‌گرفتند با مدلی رایانه‌ای مقایسه کرد که مغزها را روی یک مقیاس واحد مرد-زن امتیاز می‌دهد. نتیجه گرفت مغز زنان ترنس از جنس تولدشان به سوی هویت جنسیتی‌شان جابه‌جا شده است.
- مطالعه فقط تفاوت در یک جهت را آزمود. آزمودن هر دو جهت، چنان‌که معمول است، تفاوت کلیدی زنان ترنس در برابر مردان را ضعیف‌تر می‌کند. تعدیل برای اینکه سه مقایسه انجام شد یعنی به‌راحتی می‌تواند تصادفی باشد.
- تفاوت بزرگ‌تر میان زنان ترنس و زنان پس از این تعدیل‌ها همچنان می‌ماند. پس اختلاف دربارهٔ این است که آیا مغز زنان ترنس با مردان فرق دارد، نه اینکه با زنان فرق دارد یا نه.
- با تنها 24 نفر در هر گروه، اندازهٔ هر تفاوت ناپایدار است. یک نتیجهٔ غیرعادی در گروه مردان هرگز با اجرای دوبارهٔ تحلیل بدون آن بررسی نشد.
- آزمونی که مطالعه برای توجیه روش آماری‌اش به کار برد با گروه‌هایی به این کوچکی ضعیف است. منتقدان می‌گویند روش‌هایی که فرضیات کمتری دارند دست‌کم باید گزارش می‌شدند.
- از 24 زن ترنس، 6 نفر به مردان و 18 نفر به زنان جذب بودند. گرایش جنسی با ساختار مغز مرتبط است و نویسندگان اصلی این داده را داشتند اما آن را در نظر نگرفتند.
- هر منتقد بارها داده‌های اصلی را خواست و پاسخی نگرفت، پس نقد به ارقام منتشرشده تکیه دارد. آن‌ها خواستار انتشار داده‌ها و تکرار مطالعه توسط دیگران هستند.
Abstract
Kurth et al. (2022) concluded that the brain anatomy of transgender women is shifted away from their biological sex and toward their gender identity. We evaluate whether the study’s evidence supports this conclusion by focusing on its statistical methods and treatment of sexual orientation in its analyses. The principal finding relies on a very small sample, a weak justification for parametric analyses, one-tailed post hoc tests, no correction for multiple comparisons, and limited robustness testing. The study also did not properly account for sexual orientation as a potential neuroanatomical confound despite having the relevant participant data to do so. These methodological choices consistently bias the results toward smaller p-values and stronger apparent support for the authors’ stated hypothesis. The evidence presented therefore does not justify the study’s headline conclusion.
Conclusion
The analyses presented do not adequately support the paper's headline conclusion that transgender women's brains are shifted toward their gender identity. The evidence used to support that conclusion is weakened by a series of methodological limitations and poor choices, including a small sample size, parametric statistical methods, one-tailed post hoc hypothesis tests without correction for multiple comparisons, and the absence of several robustness analyses. The study also does not address sexual orientation as a potential confound, despite the authors possessing both the neuroanatomical and sexual orientation data needed to evaluate this possibility. These methodological choices and omissions consistently strengthen the perceived support for the authors' stated hypothesis while weakening confidence in the reported findings. Given the paper's unusually broad influence in neuroscience, medicine, journalism, law, and public policy, the methodological issues warrant careful consideration before the study can be cited as evidence supporting the hypothesis, and the authors welcome a response from the original authors and encourage public release of the anonymized participant-level data so that the findings can be independently replicated and evaluated.