1 Title: The Two-Type Taxonomy Is a Useful Approximation for a More Detailed Causal Model
4 Tags: causality, two-type taxonomy
7 A lot of people tend to balk when first hearing about the [two-type taxonomy of male-to-female transsexualism](https://en.wikipedia.org/wiki/Blanchard's_transsexualism_typology). What, one scoffs, you're saying _all_ trans women are exactly one of these two things? It seems at once both too simple and too specific.
9 In some ways, it's a fair complaint! Psychology is _complicated_; every human is their own unique snowflake. But it would be impossible to navigate the world using the "every human is their own unique _maximum-entropy_ snowflake" theory. In order to [compress our observations](https://www.lesswrong.com/posts/mB95aqTSJLNR9YyjH/message-length) of the world we see, we end up distilling our observations into categories, clusters, diagnoses, [taxons](https://lorienpsych.com/2020/10/30/ontology-of-psychiatric-conditions-taxometrics/): no one matches any particular clinical-profile stereotype _exactly_, but [the world makes more sense when you have language for theoretical abstractions](https://astralcodexten.substack.com/p/ontology-of-psychiatric-conditions) like ["comas"](https://slatestarcodex.com/2014/08/11/does-the-glasgow-coma-scale-exist-do-comas/) or "depression" or "borderline personality disorder"—or "autogynephilia".
11 Concepts and theories are good to the extent that they can "pay for" their complexity by making more accurate predictions. How much complexity is worth how much accuracy? Arguably, it depends! General relativity has superceded Newtonian classical mechanics as the ultimate theory of how gravity works, but if you're not dealing with velocities approaching the speed of light, Newton still makes _very good_ predictions: it's pretty reasonable to still talk about Newtonian gravitation being "true" if it makes the math easier on you, and the more complicated math doesn't give appreciably different answers to the problems you're interested in.
13 Moreover, if relativity hasn't been invented yet, it makes sense to stick with Newtonian gravity as the _best_ theory you have _so far_, even if there are a few anomalies [like the precession of Mercury](https://en.wikipedia.org/wiki/Tests_of_general_relativity#Perihelion_precession_of_Mercury) that it struggles to explain.
15 The same general principles of reasoning apply to psychological theories, even though psychology is a much more difficult subject matter and our available theories are correspondingly much poorer and vaguer. There's no way to make precise quantitative predictions about a human's behavior the way we can about the movements of the planets, but we still know _some_ things about humans, which get expressed as high-level generalities that nevertheless admit many exceptions: if you don't have the complicated true theory that would account for everything, then simple theories plus noise are better than _pretending not to have a theory_. As you learn more, you can try to pin down a more complicated theory that explains some of the anomalies that looked like "noise" to the simpler theory.
17 What does this look like for psychological theories? In the crudest form, when we notice a pattern of traits that go together, we give it a name. Sometimes people go through cycles of elevated arousal and hyperactivity, punctuated by pits of depression. After seeing the same distinctive patterns in many such cases, doctors decided to reify it as a diagnosis, ["bipolar disorder"](https://en.wikipedia.org/wiki/Bipolar_disorder).
19 If we notice further patterns _within_ the group of cases that make up a category, we can spit it up into sub-categories: for example, a diagnosis of bipolar I requires a full-blown manic episode, but hypomania and a major depressive episode qualify one for bipolar II.
21 Is the two-type typology of bipolar disorder a good theory? Are bipolar I and bipolar II "really" different conditions, or slightly different presentations of "the same" condition, part of a "bipolar spectrum" along with cyclothymia? In our current state of knowledge, this is debateable, but if our understanding of the etiology of bipolar disorder were to advance, and we were to find evidence that that bipolar I has a different underlying _causal structure_ from bipolar II with decision-relevant consequences, like responding to different treatments, that would support a policy of thinking and talking about them as mostly separate things—even while they have enough in common to both be kinds of "bipolar". The simple high-level category ("bipolar disorder") is a useful approximation in the absence of knowing the sub-category (bipolar I _vs._ II), and the subcategory is a useful approximation in the absence of knowing the patient's detailed case history.
23 With a _sufficiently_ detailed causal story, you could even dispense with the high-level categories altogether and directly talk about the consequences of different neurotransmitter counts or whatever—but lacking that supreme precise knowledge, it's useful to sum over the details into high-level categories, and meaningful to debate whether a one-type or two-type taxonomy is a better statistical fit to the underlying reality whose full details we don't know yet.
27 In the case of male-to-female transsexualism, we notice a pattern where androphilic and non-androphilic trans women seem to be different from each other—not just in their sexuality, but also in their age of dysphoria onset, interests, and personality.
29 [Blanchard](/papers/blanchard-typology_of_mtf_transsexualism.pdf), [Bailey](https://en.wikipedia.org/wiki/The_Man_Who_Would_Be_Queen), and [Lawrence](http://www.annelawrence.com/autogynephilia_&_MtF_typology.html)
31 But many authors have noticed this bimodal clustering of traits under various names, [while disagreeing about the underlying causality](/2021/Feb/you-are-right-and-i-was-wrong-reply-to-tailcalled-on-causality/).
33 [Veale, Clarke, and Lomax](/papers/veale-lomax-clarke-identity_defense_model.pdf) attribute the differences to whether defense mechanisms are used to suppress a gender-variant identity. [Anne Vitale](http://www.avitale.com/developmentalreview.htm) identifies distinct groups (Group One and Group Three), and hypothesizes that the difference is due to degree of prenatal androgenization.
37 Is a two type typology of male-to-female transsexualism a good theory? Is it "really" two different conditions (following Blanchard _et al._), or slightly different presentations of "the same" condition (following Veale _et al._)?
39 At the high level of taxonomy—if I have to choose between a one-type and a two-type theory—then I think the two-type theory is superior. But I also think we can do better and say more about the underlying causal structure that the simple two-types story is approximating, and hopefully explain anomalous cases that look like "noise" to the simple theory.
41 In the language of [causal graphs](https://en.wikipedia.org/wiki/Causal_graph) (where the arrows point from cause to effect), here's what I think is going on:
43 
47 What are the reasons a male-to-female transition might seem like a good idea to someone? _Why_ would a male be interested in undergoing medical interventions to resemble a female and live socially as a woman? I see three prominent reasons, depicted as the parents of the "transition" node in a graph.
49 First and most obviously, femininity: if you happen to be a male with unusually female-typical psychological traits, then [...]
51 Second—second is hard to explain if you're not already familiar with the phenomenon, but basically, [...]
53 [3. cultural/ideological factors]
57 [Okay, but where do the two types come from? The graph is just showing cause-and-effect, but if this were actually a Bayes net, there would be numbers representing a probability distribution, and I claim that the distribution clusters into two types]
59 [The sexual orientation node increases femininity and decreases AGP, so those pathways are anti-correlated; however, the fact that straight AGP men also vary somewhat in their degree of femininity; some accounts have emphasized how masculine (even hypermasculine) AGPs are, but this seems wrong]
61 [People who don't quite seem to fit the coarse taxonomy might still be explained by the graph and a threshold model]
63 [Why do I believe this? All six arrows in the graph are something that I think we have a huge weight of evidence for, either formally, or just looking at the world]
65 [Sexual orientation effect on femininity documented by Lippa and Bailey-Zucker]
67 [femininity->transition would be obvious even if it weren't in th]
69 [ETLE sexual orientation AGP v-structure, and effect of AGP on transition documented by Lawrence]
71 [I don't have a good formal citation on cultural factors, but it seems really obvious if you've been paying attention for the last decade]
73 [quantifying the two-type effect:
74 Lippa 2000 "Gender-Related Traits in [...]"
75 2.70 effect of femininity for gay vs. not-day and 1.07 for "any" vs. "no" attraction to men
76 mean GD score for non-lesbian women as 0.31; mean score for gay men was 0.30!
77 —oh, maybe I want to be using Study 2, which had a better sample of gays
78 GD occupations in study 2
79 gay men are at .48 (.14); straight women at .36 (.13); straight men at .68 (.12)
80 that's d=–1.61 between gay and straight men
81 a gay man only needs to be 1 standard deviation (.48-.36 = 0.12) more feminine than average to be as feminine as a straight women
82 whereas a straight man needs to be (.68-.36 = 0.32) 0.32/0.12=2.67 more feminine than average to be as feminine as a straight woman—that's rarer, but not impossible
85 [okay, my inner Tailcalled is telling me I need to quantitatively model the joint effect of AGP and femininity to see if two types actually emerge]
87 [further implications: as cultural factors increase, the late-onset type becomes more of a "NOS" rather than AGP type]
89 _(Thanks to the immortal [Tailcalled](https://surveyanon.wordpress.com/) for discussion.)_
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