+[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.
+
+[Serano 2020]
+
+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._)?
+
+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.