Trans brains are in the news again thanks in part to a recent talk from Julie Bakker, an endocrinology researcher at the University of Liège. The work Bakker spoke of includes research that measures brain activity in four groups of young children: trans girls, trans boys, cis girls, and cis boys. The researchers attempted to answer questions like: Do trans girls and boys have brain activity similar to cis girls, cis boys, both, or neither? From the Telegraph to Pink News, the work has been celebrated as confirmation that trans children “show functional brain characteristics that are typical of their desired gender,” according to Bakker.

This research, at first glance, seems to advance the cause of trans acceptance. Bakker told the Telegraph, “We will...be better equipped to support these young people, instead of just sending them to a psychiatrist and hoping that their distress will disappear spontaneously.” To Newsweek, Bakker also touted the diagnostic implications of this work: “The earlier it [being transgender] is detected, the better the outcome of the treatment.” However, these conclusions rest on a reductive and inaccurate understanding of sex differences in the brain, and this framing of research on trans brains trades long-term goals of the trans rights movement for short-term headlines.

The central question of said research — whether a trans person’s brain is more similar to those of their assigned sex, their gender, or neither — is ill-formed. Cis brains must form distinct categories, a “male brain” and “female brain,” in order for such a comparison to be meaningful in the first place — and they don’t.

Though fMRI studies of sex differences have been around for years, the literature on sex differences in brain imaging is likely biased, favoring studies that purport to find sex differences over those that do not. Sean P. David, a physician scientist at Stanford, and several colleagues performed a meta-analysis of 179 papers reporting results on sex differences in brain images. If there are indeed sex differences along multiple measurements, then studies that include more participants should find differences along more measurements than smaller studies. However, David and colleagues found that the number of reported differences did not increase as studies included more participants.

Indeed, not only is the existing literature on sex differences in brain imaging likely biased, but recent work does significant damage to the idea that there are distinct, separate, “male brains” and “female brains” at all. A research group led by Daphna Joel summarizes the findings of their meta-analysis that included brain images from 1,400 participants: “Brains with features that are consistently at one end of the ‘maleness-femaleness’ continuum are rare. Rather, most brains are comprised of unique ‘mosaics’ of features, some more common in females compared with males, some more common in males compared with females, and some common in both females and males.”

So an essential premise of Bakker’s work on trans brains — that there are distinct groups of “male brains” and “female brains” in cis people to which we can compare the brains of trans people — is flawed. Even more important, the interpretation that Bakker’s results are a victory for trans kids actually threatens to undermine the acceptance of trans people generally. We don’t need to validate trans identities via brain matter — we need to take trans people at their word when they express their genders.

Bakker suggests that her work should further the cause of trans acceptance because it shows that adolescent trans brains are similar to the brains of their cis peers of the same gender, regardless of assigned sex. But what of the converse? If Bakker had found that adolescent trans brains were more similar to cis brains of the same assigned sex, or different from either sex, then would the results have suggested that trans identities are less legitimate? If so, researchers in this field are gambling with trans lives. They are conducting research which, according to these interpretations, very well might challenge the validity of trans identities.