I think I’ve been looking for something like https://www.researchgate.net/profile/Nick_Haslam/publication/341912127_Dimensions_over_categories_a_meta-analysis_of_taxometric_research/links/5edee8c9a6fdcc476890a131/Dimensions-over-categories-a-meta-analysis-of-taxometric-research.pdf my entire life. Now that I’ve found it, I’m confused and angry.

This is a meta-analysis of “taxometrics”, the study of figuring out which things are distinct bimodal groups and which things are are just a dimensional variation along a spectrum or a normal distribution or something. It looks at a lot of personality variables, but focuses on psychiatric disease. It finds that most psychiatric conditions are probably just dimensional spectrum variation, which matches my impression.

But it does find a few things it says hint at maybe being real honest-to-goodness objective categories. It can’t prove any of them, and all of them are sort of ambiguous, but it thinks this might be true of autism, pedophilia, intermittent explosive disorder, alcohol/nicotine/gambling addiction, and biological sex.

I will give them pedophilia - pedophiles really do seem to be a separate group who work very differently from everyone else. Everything else on there is utterly bizarre.

Take intermittent explosive disorder. I thought everyone agreed it was the fakest of fake psychiatric conditions - just a fancy word for people who are often very angry. Yet this study suggests it’s one of the only ones that gets its own taxon - a completely real, utterly separate from the rest of the population stamp of approval.

And what about autism? Just when everybody finally accepted that autism existed on a spectrum, this study claims it’s one of the only psychiatric disorders that *doesn’t*! You’re either autistic or non-autistic, end of story, no shades of gray, and autism is supposedly one of the only things that works like that!

Alcoholism, nicotine addiction, and gambling addiction, same story! I think maybe the explanation here is that this isn’t measuring *tendency toward* alcohol addiction, it’s measuring whether you’re actually addicted to alcohol right now. And there are lots of teetotalers and other people who are definitely not addicted to alcohol, so maybe it’s easier to make categories out of this? Smoking is probably an even easier one - you’re either a nonsmoker or a smoker, that’s a real difference. I guess gambling and stuff work the same way.

The biological sex finding is bizarre for the opposite reason. I don’t mean to wade into any kind of weird political weeds when I say that should just be clearly bimodal, end of story, no ambiguity. I agree intersex people exist and so on, but the question isn’t whether there’s some overlap or ambiguity, the question is whether there’s anything *other* than overlap or ambiguity - that is, whether there’s any tendency at all for things to be other than uniform. I think even the most fervent queer theorist should admit this is obviously true in the case of biological sex. And yet this study cannot do more than say it detects signs this might be true, same as gambling addiction or something.

(there are only two genders: addicted to gambling, and not addicted to gambling.)



Equally annoying is what’s *not* on here. Most of the stuff I’ve read speculating about this sort of thing has always said that if there’s one really real binary-division psychiatric disorder out there, it’s schizophrenia. This meta-analysis utterly fails to find evidence for that.

At some point I am going to look at the individual studies and see whether they’re completely flawed - garbage in, garbage out. Until then, I am just going to sit around being confused and angry.

