On the Science of Changing Sex

Love is love and not fade away… ♫♫

Posted in Confirming Two Type Taxonomy by Kay Brown on March 14, 2010

Many transfolk make the claim that data supporting Blanchard’s hypothesis has not been replicated.  Already I’ve shown how it had been replicated by both the Leavitt&Burger study and the Smith Study, which was further refined by Lawrence when she showed that the statistical signal strength is increased when one carefully sorts by sexual history.  Now, a recent paper has been added to the list: Nuttbrock, et. al.  This study is important because it was conducted in such a way as to “cast a wider and looser net” and has the largest sample size of any study (N=571).

First, the conclusion, so as not to lose my reader’s attention:  The Nuttbrock paper confirms, absolutely confirms, the Freund/Blanchard two type taxonomy for Male-To-Female (MTF) transsexuals, one that is exclusively androphilic and one that is autogynephilic. There can be no doubt now.

In analyzing the data of each paper, to compare the results, we must bear in mind both the similarities and the differences between each of the study’s sort method, as each will result in different signal strength’s for the same underlying populations.

Blanchard (N=163) sorted by using a two dimensional survey instrument that measured the level of androphilia and gynephilia on separate axis.  He then used a software program to find latent clusters in the two dimensional data.  Looking at the data, as I’ve already explored, we note that there was a tight cluster of exclusively androphilic individuals that yeilded a strong signal of a low number of autogynephilic individuals.  Also, Blanchard used another survey instrument, to measure autogynephila, which captured “dreamers”, individuals whose autogynephilia did not include erotic cross-dressing, as well as those who were classically erotic cross-dressers.

Leavitt and Berger used only Blanchard’s androphilia scale to find those who self-reported a strong erotic interest in men.  Thus, it did not separate out those who would have scored high on gynephilia as well.  However, as I showed in an earlier post, Leavitt&Berger did ask the all important question about sexual history, so I was able to demonstrate that the more a given group of transsexuals had had a sexual history of attraction to women (gynephilia), the more that group reported erotic cross-dressing.

The Smith study (N=111) used no other criteria to sort other than to ask, post-transition, whether the subject was exclusively attracted to men or not.  This binary sort did not separate out those who had had a sexual history of attraction to women.

Lawrence took the Smith study data set and further sorted out those who self-reported being androphilic but had a sexual history of being attracted to women, as being non-homosexual.

Nuttbrock, et al.  followed the Smith example and used self-report, but with Blanchard’s original four categories, sorting into exclusively androphilic, bisexual, exclusively gynephilic, and asexual.  I must emphasize, this was self-reported sexual identity, not actual sexual history.  Interestingly, the study, which was funded to explore risk factors for sexually transmitted diseases, did in fact study, in great depth, sexual history, but did not use that as a sort method (as was done in Lawrence).  Another important difference between the Nuttbrock study and the others is that while all of the other subjects were from a gender reassignment clinic seeking somatic feminization, those in the Nuttbrock study were obtained through advertisements and direct contact, in the community at large.  This means that potentially, an important personality type may have been missed, as it has been remarked that asexual transsexuals are typically schizotypal (fancy word for non-social, shy, loner).  It also means that many of the subjects are not strongly motivated toward somatic feminization, instead simply identifying as “transgender” or “gender-queer”.  Indeed, 28% of the subjects are not even taking feminizing hormones.  These differences may change the absolute numbers in some fashion, however, we still expect to see a similar statistical effect if the two type taxonomy is correct, and indeed, the data clearly shows just that.  The percentage of subjects reporting erotic cross-dressing  (and other expressions of autogynephilia, in Blanchard’s study) for each type in each study is shown below here:

“Type”     Nuttbrock  Smith    Lawrence    L&B    “Avoidant”  Blanchard

HSTS                    23%       31%        15%            36%          7%              15%

Non-HSTS         73%       63%        60%          N/A         N/A           ~75%

Given that Nuttbrock and Smith are using similar self-reported sexuality, we would expect that these two studies would have both similar sorting efficiency and thus similar signal strengths, and we do.  In fact, Nuttbrock’s is stronger, but not by much.  Although not provided, I would predict that if we had access to the Nutbrock data set, we could resort it in the same fashion that Lawrence did with the Smith data set, and that Leavitt and Berger accidentally did for the “avoidant” group, and get a similarly increased signal strength.

It is important when reviewing the above data, that as in all sociological studies of taxa, because we have not yet found a perfect instrument by which to sort the taxa, and do not have a perfect instrument to detect autogynephilia, we are only able to statistically tease out the two types.  After all, we are asking people to be self-reflective, honest, and accurate, about something that is very personal and as yet poorly understood.  But about the existence of the two types, there is no doubt.

Thus, Blanchard’s taxonomy is very much alive and well… and won’t be fading away.

Please read additional entries and analysis:

Profiles in Courage

Scientific Sodoku

Time Will Tell

Scientific Sodoku II


A Further Assessment of Blanchard’s Typology of Homosexual versus Non-Homosexual or Autogynephilic Gender Dysphoria, Nuttbrock, et al. Archives of Sexual Behavior

Typology of male-to-female transsexualism, Archives of Sexual Behavior
Blanchard, R.,

Transsexual subtypes: Clinical and theoretical significance
Yolanda L.S. Smith, Stephanie H.M. van Goozen, A.J. Kuiper, Peggy T. Cohen-Kettenis

Clinical Patterns Among Male Transsexual Candidates with Erotic Interest in Males
Frank Leavitt, Ph.D., Jack C. Berger, M.D.

Male-to-female transsexual subtypes: Sexual arousal with cross-dressing and physical measurements
Lawrence, A.


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