“Scans show that transgender people’s brains match the sex they identify with.”

Many transgender activists attempt to validate the transgender identity by relying on the outdated and unscientific notion of “brain sex.” This often includes arguments about trans-identified males having “female brains” and vice versa. But as Lise Eliot’s work has shown, the very idea of distinct male and female brains is unsupported by the data, and it’s unclear how meaningful a neurological model of transgender identity can be without them. Of course, our understanding of the brain is limited in general, and new discoveries are always possible. But even if a direct neurological correlate to transgender identity was discovered, it would merely explain a person’s self-conception, as opposed to justifying or validating it. Identifying why someone holds a particular belief can often be very helpful, but the truth or falsehood of that belief is always another question.

Consider, as analogy, a disorder like anorexia. Brain scans can indeed find unique markers that indicate someone is suffering from anorexia – although, as with gender identity, it’s unclear whether these markers are the cause of the person’s perceptions or merely a result of them. But either way, ask yourself: Even if anorexia did have a neurological base, does that mean the anorexic person’s feelings about themselves must be true? Of course not! A person’s neurobiology might explain why they perceive themselves as overweight, even when they aren’t, but it doesn’t give us any reason to validate those perceptions. The same is true of transgender identity and its possible neurological correlates; just because a particular feature in the brain may cause a male person to consider themselves female doesn’t, by itself, give any support to the claim that they are female.

The notion of identifiable “brain sex” also has worrisome implications for transgender activists themselves. If womanhood or manhood really is a result of a particular neurological structure, then it should be possible, at least in theory, to determine someone’s “true gender” with a brain scan. Would transgender activists accept that sort of objective test? How would they handle someone who claimed to be transgender, but nonetheless had a “male brain” to go with his male body? The assertion of an objective biological basis for transgender identity necessarily conflicts with an emphasis on self-identification, and transgender activists should stop using obviously inconsistent arguments to make a point.