On the Science of Changing Sex

Smarter Than The Average Bear

Posted in Confirming Two Type Taxonomy by Kay Brown on April 6, 2010

“… smarter than the average bear…”  – Yogi Bear, cartoon character

In the scientific literature, there have been occasional references to the general intelligence of transsexuals, several noting that Male-to-Female transsexuals are well above average, others noted just average intelligence.  Bailey in his book, TMWWBQ, remarked observationally, from those that he had seen, that the feminine androphilic type (“Homosexual”: HSTS) seemed to be lower than average.

In personal conversations with “late transitioning” transsexuals, they often remarked, wonderingly, at their observations that the transsexuals that they knew were above average, if not exceedingly above average intelligence.  In one such conversation, one TS made such a remark, while another, obviously extremely intelligent, rejected the idea, saying that that was just wishful thinking, that every “oppressed” group wanted to believe that they were special and superior.

For myself, I have long observed that the average intelligence of the feminine androphilic type was just average, that I knew as many bright kids as dull ones.  But, except for exactly one AGP, who was mildly mentally challenged, the rest of the “late transitioning” transsexuals were above average to exceedingly above average in intelligence and often, accomplishment.  How many top musicians, scientists, engineers, physicians, businesswomen, lawyers, and even politicians, have transitioned in mid-career?  But all of this is still anecdotal.

The Smith paper, studying a group of TS folk from their Netherlands clinic, included IQ scores.  Given that in the Netherlands, transfolk are fully covered by their national medical plan, this clinic is the most likely source of an unbiased sample to determine if there is any IQ effect:

“Non-Homosexual”:  121.7  (n=42)

“Homosexual”:            107.3  (n=39)

The difference between these two groups is an amazingly large effect size, being almost one standard deviation difference.  This alone would support the two type taxonomy.  However, I wondered about the IQ of the “homosexual” group being a half standard deviation above average, which is by definition 100.  Lawrence has already pointed out that the sorting method used by the Smith study was inadequate to separate AGP from the MTF transkid population, as I have already blogged about in BridesHead Revisited.  I wondered if we could mathematically estimate the MTF transkid IQ score if we assume that the IQ of the AGP folk that were accidentally miscategorized as HSTS is the same as the AGP (Non-Homosexual) group already reported.  Another assumption would be that the ratio of miscatergorized AGPs is the same in the “Homosexual” group as that for whom the IQ was included in the above score.

Lawrence recategorized 23 out of 61 of the original Homosexual group as being Non-Homosexual based on their sexual history with women.  So, 23/61 of the 39 = 14.7 people with IQ scores are likely to have been miscategorized as Homosexual.  We won’t worry about quantizing to whole people at each stage, since that will introduce excessive rounding error.  That leaves 39 – 14.7 = 24.3 people for whom we want to find an estimate of their IQ:

( (39*107.3) – (14.7*121.7) )/24.3 = 98.6

Thus, our estimated average IQ for the resorted Homosexual transsexual population is very nearly 100, or average IQ for the non-transsexual population at large. This estimate does not say that this is in fact the case, but it does suggest that this is quite plausible, even probable.  So, assuming for the moment, and I think we can be safe doing so, that the HSTS population has an average IQ, this would suggest that there is no IQ selection pressure acting on the MTF transkid population in their decision to pursue transition and SRS.

However, for the AGP TS population, with an IQ of 121.7, which is one and a half standard deviations above norm, there must be an extremely high IQ selection pressure acting on them.  Looking at the math a bit closer, Smith, et al. reported that the SD=17.2 for the Non-Homosexual population, that means that 90% of the Non-Homosexual Transsexual population has an IQ greater than average.  That is to say, that only the more intelligent of the AGP population transitions and obtains SRS.

As confirmation that we are dealing with two different etiologies, this is powerful evidence.  But we are left searching for a theoretical model to explain why there is such a difference in selection pressures, why do only the more intelligent of the AGP type seek and obtain SRS?

One possible model is that for AGP TS, there is a high socio-economic cost to be paid when one transitions, that losing straight male privilege is weighed against the personal benefits of transition.  IQ score and subsequent socio-economic status are highly correlated.  Thus, it may be that only those AGP transsexuals who feel they can “afford” to lose some of that socio-economic status will pursue transition and SRS.  While for the HSTS population, other factors, unrelated to IQ / socio-economic status are paramount.

Addendum 3/1/2011

The recent Steensma paper with a shared co-author of the above study, published the IQ of a combined group of MTF and FtM teenagers, which at 98.86, essentially agrees with my estimate of 98.6 for the MTF trankids.  This gives added confidence in my estimate and conclusions.

Addendum 3/8/2013

I’m seeing a lot of traffic hitting this page so I believe I need to make it very clear:  TransFolk are not intrinsically more intelligent than non-transfolk, as groups.  What we are seeing is that the less intelligent, less financially successful individuals, simply forgo transition, leaving only the more financially successful, who are likely to be more intelligent as well, to transition.  To make this easier to grasp:  Imagine a middle-aged night janitor who has been secretly cross-dressing for years, who would dearly love to do it full time, to have SRS, etc.  But he would lose his wife, likely lose the respect of his co-workers, and couldn’t afford SRS on his salary, even if he could keep his job… This poor soul may just stick to dreaming about living as woman, and continue being a closet cross-dresser.

References:

Male-to-female transsexual subtypes: Sexual arousal with cross-dressing and physical measurements
Lawrence, A.
http://akikos-planet.cocolog-nifty.com/blog/files/maletofemale_transsexual_subtypes_sexual_arousal_with_crossdressing_and_physical_measurements_319320.pdf

Transsexual subtypes: Clinical and theoretical significance
Yolanda L.S. Smith, Stephanie H.M. van Goozen, A.J. Kuiper, Peggy T. Cohen-Kettenis
http://akikos-planet.cocolog-nifty.com/blog/files/psychiatry_research__transsexual_subtypes_clinical_and_theoretical_significance.pdf

Social mobility and IQ components
C. G. Nicholas Mascie-Taylora, John B. Gibson
Journal of Biosocial Science (1978)
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=1384992

Thomas D. Steensma, Roeline Biemond, Fijgie de Boer and Peggy T. Cohen-Kettenis, “Desisting and persisting gender dysphoria after childhood: A qualitative follow-up study”
http://ccp.sagepub.com/content/early/2011/01/06/1359104510378303

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