Does gender leave a physical imprint on the brain, beyond biological sex? Researchers at Stellenbosch University (South Africa) have detected in the general population an “inverted” pattern in the white matter of men who identify with more feminine role traits. It is the first time this phenomenon, similar to the one described in studies with transgender people, has been observed outside the clinical setting.
For years, neuroscience has found that the brain of transgender people tends to move away from the sex assigned at birth and towards that of their gender identity. The question left open was whether that shift was exclusive to gender dysphoria or whether it responded to a broader mechanism present across the whole population.
To find out, the Stellenbosch team studied 88 healthy adults —46 men and 42 women— who underwent strict screening to rule out mental illness, medical conditions, head trauma or substance use. Each participant’s “gender role” was measured with the Bem inventory, which places each person on a continuum between typically masculine and typically feminine traits. A diffusion tensor imaging MRI scan then allowed the researchers to trace the white matter tracts, the “cables” that connect the different regions of the brain.
The most striking result appeared when the two variables were crossed. In men, the more feminine their gender role, the lower the fractional anisotropy —an indicator of white matter integrity— in several brain tracts: the trunk of the corpus callosum, the uncinate fasciculus, the superior longitudinal fasciculus and the cingulum, among others. In women, by contrast, that effect did not appear.
“Inverted” is the word the authors use to describe it: those men showed a brain microstructure that deviated from the typical pattern of their sex and resembled the female one. The direction is the same as the one revealed by studies with transgender people, but now observed in healthy individuals with no diagnosis.
The researchers call for caution. It is a cross-sectional study, with a modest sample, that describes an association and does not prove causation: it is not known whether gender role “shapes” the brain, whether the opposite happens, or whether both depend on a third factor —genes, hormones or life experiences. What it does add is one more piece to the idea that gender identity and gender role have a measurable neurobiological correlate that is not reduced to sex.
Source: Sex versus Gender Role Endorsement Associations With White Matter Microstructure in South African Adults: A Diffusion Tensor Imaging Study. Luckhoff HK, Smit R, Phahladira L, Kilian S, Emsley R, Asmal L. Brain and Behavior 2026;16(4):e71340. DOI: 10.1002/brb3.71340.
Publication reference: Brain and Behavior.
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