On the Science of Changing Sex

An Issue Whose Time Has Come:

Posted in Brain Sex by Kay Brown on August 12, 2017

jnr23934-toc-0001-mSex/Gender Influences on Nervous System Function

The recent spring issue of the Journal of Neuroscience Research was wholely dedicated to papers on sexual dimorphism of the brain.  Of course, many will debate that there is in fact any influence of sex, much less gender (identity), on nervous system function.  I’ve written about this before, how the politics can lead some to make the charge of “neurosexism”, deserved or not.

Larry Cahill, the editor remarked about it thus,

” “Be careful, it’s the third rail.” I received this strong advice to steer clear of studying sex differences from a senior colleague around the year 2000 when my research into brain mechanisms of emotional memory began drawing me into the issue of sex differences—or better yet, sex influences—on brain function. And in a way, he was right. For the vast majority of his long and distinguished neuroscience career, exploring sex influences was indeed a terrific way for a brain scientist not studying reproductive functions to lose credibility at best, and at worst, become a pariah in the eyes of the neuroscience mainstream.  …  Fortunately, times are changing. The past 15 to 20 years in particular witnessed an explosion of research (despite the prevailing biases against the topic) documenting sex influences at all levels of brain function. So overpowering is the wave of research that the standard ways of dismissing sex influences (e.g., “They are all small and unreliable,” “They are all due to circulating hormones,” “They are all due to human culture,” and “They don’t exist on the molecular level”) have all been swept away, at least for those cognizant of the research.”

This is an exciting development and this issue is full of great information.  The best thing about it?  It is NOT behind a paywall.  The entire issue is free to read.  And read it you must if you are to remain at the cutting edge of sex influences on the nervous system.

The papers discuss a wide range of topics including the neurology of people with Disorders of Sexual Development (i.e. “intersex”) to the rather dry and esoteric.  I’ve been enjoying reading them and will likely be referencing them in future.

Further Reading:

Essay on the effects of HRT on Transsexual’s Brains and the politics of Brain Sex

“Two minds – The cognitive differences between men and women” By Bruce Goldman


Journal of Neuroscience Research
An Issue Whose Time Has Come: Sex/Gender Influences on Nervous System Function
January/February 2017, Volume 95, Issue 1-2
Version of Record online: 7 NOV 2016 | DOI: 10.1002/jnr.23934

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Because Boys Must Be Boys…

Posted in Brain Sex, Editorial by Kay Brown on July 5, 2017

Teenage-brain…Its a Fact of Human Nature, and Girls Must Grow Up to Be Mothers!

Over the years that I’ve been writing this blog, I’ve deliberately avoided using the popular term “gender non-conforming”, using the term “gender atypical” instead.  It may have struck some of my readers as odd and idiosyncratic, given that so many others use the “GNC” term.  But, I have done so for several important reasons, some based on science, some on political-philosophical grounds.

The scientific reasons are easier to explain.  There is no “standard” to which behavior should “conform”.  There is only behavior, period.  However, if we look at, study in depth as scientists, a species we can say that there are behaviors that are far more commonly performed by them than other behaviors seen in other species.  These we can label as “typical” for that species.  If we see a behavior in a given individual of a species that is uncommon for that species, we may label it “atypical”; but we would never label it “non-conforming” since we can’t really say what standard that a given species should “conform” to.  Behaviors are selected by evolution depending upon whether they increase the reproductive ‘fitness’ of the individuals exhibiting them.  The same logic applies to sexes within a given species.  We may observe sexually dimorphic behaviors in a given species.  That is, we will label a behavior sexually dimorphic if we see that it is much more commonly performed in one sex than the other.  If we see an individual performing such a behavior that is uncommon in that given sex, we may label it “atypical” for that sex; but to label it “non-conforming”?  That’s smacks of invoking an outside agency which has the authority to define a standard for such behavior that the theory of natural selection does not provide.  Just as with non-human species, humans do not stand outside of nature.  There is no agency that defines for our species a standard by which to judge whether a given behavior does or does not “conform”.

The political reasons include my personal objection to the very notion that there should be such a “standard”.  But even deeper, is my objection to the post-modernist idea that there are no intrinsic sexually dimorphic behaviors in humans, that there are only socially constructed roles.  This notion would state that since all differences in behavior observed between the human sexes are socially constructed and maintained, there must be a socially defined standard to which we can conform or not.  Another idea that I object to is that of a divinely ordained standard that we must conform to, which has the same effect.  Thus, both of these ideas reduce any behavior that is seen in an individual that is uncommon in that person’s sex to an act of “gender non-conformity” either by accident or by will… but never by nature.  I find both the notion that we stand outside of nature to be scientifically preposterous and philosophically offensive.   Further, those who seek humane treatment for gender atypical individuals will find that they must contend with those who hold these ideas often falling back on unquestioned prejudices, the nature of which is determined by which value system through which they view such gender atypical individuals, post-modernist or religious.

Before going into details about the nature of the prejudices and what we must contend, let’s explore how we know that human beings do have sexually dimorphic behaviors that have both neural correlates and developmental pathways leading to them.  It’s important to differentiate between behaviors that are demonstrably sexually dimorphic because of neural correlates and those that are merely cultural role enactments and false gender stereotypes.  Thus, for purposes of this essay, I differentiate between a strong social construction hypothesis which says that all differences in behavior are purely from culture and a weak social construction hypothesis that says that some behaviors and gender roles are socially constructed around truly sexually dimorphic behaviors and gender role limitations built around cultural prejudice and false stereotypes.  It is the strong social construction hypothesis that I will show is not supported by the evidence.

In other pages of this blog, I’ve made reference to the single most sexually dimorphic behavior in humans: androphilia (sexual attraction to adult males).  In female humans, it is extremely common to be attracted to men.  Approximately 98% of women are attracted to men while only approximately 5-10% of men were attracted to men.  One could object to this being a ‘natural’ phenomena and say that social expectations have defined this.  But it would not fit the evidence that has been amassing that sexual orientation is neither “chosen” nor “taught”.  Further, why should humans be unique in the world?  Most mammalian species are sexually dimorphic in their sexual attractions.  (No, I’m not denying that same sex behavior occurs in non-human species… only saying it is not as common as other sex attraction.)  But, this isn’t the end of the story.

Sexual orientation in adults is presaged by gendered behavior as young children.  That is to say, that humans have sexually dimorphic behaviors as young children and that sexual orientation is highly correlated with those behaviors.  Children that grow up to be homosexual evince notable gender atypicality.  The key behaviors that are noted to be gender atypical in boys are avoidance of rough and tumble play, avoidance of physical aggression, preference for female playmates and play style, etc.  But here is where we start to see the issue of having to contend with those prejudices.  Some cultures attach serious negative stigma to gender atypicality while others do not.  Most of my readers will likely live in cultures that do and will recognize the ugly recriminations in the song, “Boys Will Be Boys”; “You bloody sissy, who said you could cry?” down to the call to an authority defining the standard to which a child must conform, “Doctor, Doctor, tell me where did we go wrong?”.

But we in our enlightened age know that the parents did nothing wrong… (yes, you may take that to be sarcasm).

In other essays on this blog, I’ve explored some of the science that shows that sexual orientation is correlated with childhood gender atypicality, the Fraternal Birth Order Effect, etc.  I’ve discussed possible etiological hypothesis.  I have in the past written about the disappointment with using the 2D:4D digit ratios as a means of exploring the possible effect of varying androgens as being correlated with sexual orientation.  But now, I want to share a really amazing bit of evidence that shows that perinatal exposure to androgens is likely to be responsible for masculinizing the human brain and its absence affecting early childhood gender atypicality, as Vicky Pasterski puts it,

By now, the majority of scientists studying the topic likely agree that homosexuality is definitely not a choice and probably not due to socioenvironmental factors. At the same time, there appear to be no physical indicators of disrupted fetal sexual differentiation in homosexual men that would fit with the basic premise of the hormone theory of sex development. However, it is possible that alterations in the androgen surge that occurs in the early postnatal period, also called mini-puberty, could have effects that are not immediately or physically obvious. Based on the finding that penile growth in the first three months of life correlates with a concomitant surge in serum testosterone levels considered the possibility that penile growth may act as a proxy for neonatal androgen exposure and that change measurements may be related to later neurobehavioral outcomes. In a longitudinal study of 81 typically developing boys, we found that the strength of the early postnatal androgen surge, from birth to approximately three months of age, predicted masculine behavior at 4 years old. By controlling for effects of prenatal androgen exposure using measurements of penile length and anogenital distance (AGD; sexually dimorphic and roughly twice as long in males compared to females) at birth, we showed that penile growth in the first three months of life, but not thereafter, accounted for significant variance in later sex-typed behavior. In the overall regression analysis, which controlled for various factors, penile length at birth was not related to sex-typed behavior. This suggests that disruption to male mini-puberty could have implications for future sex-related outcomes that are masked by a typical appearance at birth. Further, this provides support for the hypothesis that early (postnatal) hormone exposure influences aspects of sex-typed development in men, in a similar fashion to prenatal hormone exposure that is presumed to affect women.

1-s2-0-s0018506x15000033-gr1_lrgIn Pasterski’s research, she divided the boys into three groups (tertiles) based on their gendered behavior from the Pre-School Activities Inventory and mapped against the growth rate of their genitals in the first months after birth, which has been shown to correlate with androgen exposure.  (Though to be complete, it may also correlate with androgen receptor sensitivity, but for my purposes, that would have the same epistemic value.)  The results are dramatic, we see with no ambiguity that the rate of growth of genitalia is positively correlated with gender typical behavior.   That also means that the inverse is true.  Gender atypical behavior is inversely correlated with perinatal genital growth.

Had the strong social construction hypothesis of all gendered behavior been true, there would have been no correlation.  We can reject this hypothesis.  At best, we have a weak social construction hypothesis of gender roles around very real sexually dimorphic differences.  Those that lampoon this conclusion by calling it “Lady Brain” theory are just plain wrong.

It has been previously noted that gender atypically behaving children have differences in facial “attractiveness”.  This fits well with the above research as male children who have not had this intense “mini-puberty” would likely remain neotenous and thus feminine in appearance.  This likely also extends past adolescence to explain the rather dramatic differences in passability between androphilic transwomen and gynephilic transwomen.  Being gender atypical in brain organization, it would naturally lead to later androphilia, gender atypical motor skills (feminine walk and hand gestures), and gender atypical vocal production (feminine or “gay lisp”).

Given the religious (or related social views of gender) prejudice, one can easily see how children who exhibit these gender atypical behaviors are placed under tremendous pressure to “conform” to gender behavior standards that tend to skew to the gender typical, or even an exageration of typical behavior.  Children who meet this standard are prized and praised above other children.  That is to say, extreme gender typicality is valorized as well as held as the gender normitive standard and granted privilege over children who fail to meet this standard.

Here I opine, perhaps even hypothesize, that this pressure to conform to normative gender role standards has distorted what would be the natural course of development of gender atypical children and has led to the creation of the artificial gender normative role of Western Gay and Lesbian culture, especially the “Straight Looking / Straight Acting” Gay male standard to which otherwise gender atypical male children are required to adhere.  To the non-gay community members, the benefit of artificial standard was originally to force gay people to remain deep in the closet.  As the Western Gay Liberation movement gained ground, those who had tacitly accepted this standard began to subtly and not so subtly enforce it.

One would, at first glance, believe that those who hold the strong social construction hypothesis as true would then have no qualms about accepting gender atypical children and adults without reservation as breaking stereotypes.  But, as we can easily discern, they often do not, as demonstrated by the minority movement within the gay and lesbian (mostly lesbian) communities of being “gender critical”.  They philosophically approve of people being gender atypical… but only to a very specified point, accepting the gender normative roles that were established during the early Gay Liberation Movement.  The moment that an individual steps past that point, there will be those who will denounce them as hewing to the very stereotypes that they break, but in the opposite gendered sense, denying that underlying sexually dimorphic behavior as valid.  In some cases, public denouncements of the very existence of gender atypical males have been made (e.g. Jean O’Leary’s public denouncement of Silvia Rivera, early androphilic transactivist, as “mocking women” at the 1970 Stonewall commemoriation for wearing feminine clothing).  On the internet today, this same gender role proscription is made where androphilic transwomen are chastised in the ugliest terms, “just because you’re a gay man doesn’t mean that you can be excused for objectifying women (by looking and acting like one).”  Thus, we see that gender role policing based on accepting gender normative standards exists even in the modern LGB communities.

Further Reading:

Essay on motor movement in gender atypical males.

Essay on vocal production in gender atypical people.

Essay on passability differences between gynephilic vs. androphilic transsexuals.


Pasterski, V., “Fetal Androgens and Human Sexual Orientation: Searching for the Elusive Link”, (2017) Archives of Sexual Behavior

Pasterski, V., et al., “Postnatal penile growth concurrent with mini-puberty predicts later sex-typed play behavior: Evidence for neurobehavioral effects of the postnatal androgen surge in typically developing boys”, (2015) Hormones and Behavior

Song Reference:

Boys Will Be Boys
(Leon Rosselson)

Boys will be boys, it’s a fact of human nature
And girls will grow up to be mothers

Look at little Peter, isn’t he a terror?
Shooting all the neighbors with his cowboy gun
Screaming like a jet plane, always throwing something
I just can’t control him. Trouble – he’s the one.

Ah but boys will be boys, it’s a fact of human nature
And girls will grow up to be mothers

Look at little Janie, Doesn’t she look pretty?
Playing with her dolly, proper little mum
Never getting dirty, never being naughty
Don’t punch your sister Peter, now look at what you’ve done

Ah but boys will be boys, it’s a fact of human nature
And girls will grow up to be mothers

What’s come over Janie, Janie’s turning nasty
Left hook to the body, right hook in the eye
Vicious little hussy, now Peter’s started bawling
What a bloody sissy, who said you could cry?

Because boys must be boys, it’s a fact of human nature
And girls must grow up to be mothers

Now things are topsy turvy. Janie wants a football
Peter just seems happy pushing prams along
Makes you feel so guilty. Kids are such a worry
Doctor, doctor, tell me, where did we go wrong?

Because boys must be boys, it’s a fact of human nature
And girls must grow up to be mothers

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Mars and Venus in Conjunction…

Posted in Brain Sex by Kay Brown on March 30, 2017

Teenage-brainOr, Yes, We CAN Tell Men and Women Apart By Their Personalities

In my last post, we looked at the idea that though the brain is comprised of many areas that individually are only mildly sexually dimorphic the pattern of which adds up to a very sexually dimorphic brain mosaic.  It reminded me of an earlier study in which they found that personality traits were also only mildly sexually dimorphic when examined individually, but the overall personality, the matrix of traits, was also very sexually dimorphic.  That is to say, that men and women, on average, do have different personalities, but no one trait is all that different.

Given that brains and minds are intimately linked, that minds are the function of brains, the fact that both brain mosaic and personality are both individually only mildly sexually dimorphic, but collectively very dimorphic should not surprise us.

The idea that men and women have different personalities has been widely accepted for millenia, but recently has been seriously questioned by feminists and some social scientists and psychologists, most notably Prof. Janet S. Hyde.  But even she, in propounding the “Gender Similarity Hypothesis” did find obviously sexually dimorphic behaviors in humans, as Guidice, et Al remarked,

“Specifically, Hyde found consistently “large” (d between .66 and .99) or “very large” (d≥1.00) sex differences in only some motor behaviors and some aspects of sexuality; “moderate” differences (d between .35 and .65) in aggression”

“…some aspects of sexuality…” Yeah!  Duh!  As in sexual orientation, the single largest sexually dimorphic difference between men and women, also motor behaviors that are highly correlated with sexual orientation.  Finally, aggression; yes, men are more aggressive than women by nature.  But what of the more subtle areas of personality?

In this study, the authors chose to use a very well established personality inventory, the 16PF which underlie the more well known Big Five factor personality inventory.

First, we need to discuss the matter of looking at individual aspects of personality as single variables then averaging this difference between the sexes as the authors pointed out,

“The problem with this approach is that it fails to provide an accurate estimate of overall sex differences; in fact, average effect sizes grossly underestimate the true extent to which the sexes differ. When two groups differ on more than one variable, many comparatively small differences may add up to a large overall effect; in addition, the pattern of correlations between variables can substantially affect the end result. As a simple illustrative example, consider two fictional towns, Lowtown and Hightown. The distance between the two towns can be measured on three (orthogonal) dimensions: longitude, latitude, and altitude. Hightown is 3,000 feet higher than Lowtown, and they are located 3 miles apart in the north-south direction and 3 miles apart in the east-west direction. What is the overall distance between Hightown and Lowtown? The average of the three measures is 2.2 miles, but it is easy to see that this is the wrong answer. The actual distance is the Euclidean distance, i.e., 4.3 miles – almost twice the “average” value. The same reasoning applies to between-group differences in multidimensional constructs such as personality. When groups differ along many variables at once, the overall between-group difference is not accurately represented by the average of univariate effect sizes; in order to properly aggregate differences across variables while keeping correlation patterns into account, it is necessary to compute a multivariate effect size. The Mahalanobis distance D is the natural metric for such comparisons. Mahalanobis’ D is the multivariate generalization of Cohen’s d, and has the same substantive meaning. Specifically, D represents the standardized difference between two groups along the discriminant axis; for example, D = 1.00 means that the two group centroids are one standard deviation apart on the discriminant axis.”

f1-largeIn the figure here, we can see that we have two very distinct population when looking at two variables at once, but can hardly be differentiated using one at a time.  Using Mahalonobis’ D allows us to see the real difference in personalities of men and women taking into account the global pattern of  multiple personality traits, rather than one at a time.  From this the authors found,

“We found a global effect size D = 2.71, corresponding to an overlap of only 10% between the male and female distributions. Even excluding the factor showing the largest univariate ES, the global effect size was D = 1.71 (24% overlap). These are extremely large differences by psychological standards.  The idea that there are only minor differences between the personality profiles of males and females should be rejected as based on inadequate methodology.”

‘Gee willikers Mr. Wilson’… that 10% overlap sounds awfully familiar – Oh yeah, that’s similar to that found for the global pattern of the sexually dimorphic mosaic of the brain.  And just as I suggested that this might represent the effect of the non-heterosexual population, I again hypothesize that we might see a larger effect size if all known LGBT folk were excluded from the study subjects.  If so, that would further support my hypothesis that humans don’t have sexually dimorphic brains so much as having androphilic vs. gynephilic ones.

Further Reading:

Essay on Sexually Dimorphic Brain Mosaic

Essay on Sexually Dimorphic Motor Behaviors


Guidice, et Al, “The Distance Between Mars and Venus: Measuring Global Sex Differences In Personality”

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Pink and Blue…

Posted in Brain Sex by Kay Brown on February 26, 2017

Teenage-brain… Brains

Or, Yes, We Now CAN Tell The Sex of a Person By Imaging Their Brain

Before recent developments in neuroimaging, I would have said that there was no way that we could determine the sex / gender of a person looking only at their brain.  In fact, I DID say exactly that.  But now, I don’t believe that that is an accurate statement, at least not wholely accurate, because a recent paper/letter has shown that with increased resolution and computer power we can determine the sex of a person that a particular brain resides in just from an analysis of the 3D image of their brains to 93% accuracy.  The mere fact that this can be done shows that the human brain is in fact highly sexually dimorphic, because if we were to simply guess, we would only be right 50% of the time.

The number, 93%, sounded suspiciously familiar to me.  That’s about the number of people who are not LGBT in the population.  Given that we also know that LGB people are likely to have sexually dimorphic features that as a population, are shifted towards that of the opposite sex, I’m proposing an hypothesis and a prediction.  If this analysis were redone excluding all known LGBT people, that the mathematical regression would result in greater predictive strength.  It would not reach 100% because there would still be those who due to social desirability bias would fail to disclose their sexual orientation and thus still be included in the heterosexual study group.  Increasing the accuracy in that instance will add evidence to a quip that I have made before, that humans don’t have male and female brains so much as androphilic and gynephilic brains.

There’s an important point that is missed by people with discussing the issue of whether the human brain is sexually dimorphic or not; The size and shape of any specific feature of the brain is to an extent only a very crude estimate of the number of neurons and the connection density of that region.  It does not tell us the functional differences, if any, that that difference represents.  As Cordelia Fine has pointed out, these differences, though they clearly exist, does not tell us what, if any, the differences may be in men’s and women’s minds.  Only additional research will help us determine these.

But still, anyone who still says that it is not possible to determine the sex of a human brain hasn’t been keeping up with the science.

f1-large(Addendum 3/4/2017:  I did a bit of calculation and found much to my amazement, that to “guess” the sex of the brain to 93% accuracy means that the effect size (Cohen’s d) would, if it were a single dimorphic feature, be a whopping 3.0 !!!!  That’s an over the top value.  Thus, as we get better imaging tools to see the fine details, we are learning that the human brain, in terms of multivariate statistics of multiple measurements at all points of the brain, is in fact extremely sexually dimorphic.  The problem is that no one area is all that dimorphic, but in aggregate, they are quite dimorphic.  That is to say, if one area is slightly dimorphic, giving a small statistical clue as to the sex of the individual, and a second area is also slightly dimorphic, giving a small clue as the sex of the individual, the two can be used together to give a medium sized clue to increase the accuracy… and with many many areas, each additively pointing towards one sex or the other, the accuracy gets quite good.)

Further Reading:

Book Review: Delusions of Gender by Cordelia Fine


Chekrouda, et al., “Patterns in the human brain mosaic discriminate
males from females”  http://www.pnas.org/content/113/14/E1968.full.pdf

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Posted in Brain Sex, Confirming Two Type Taxonomy, Female-to-Male by Kay Brown on July 2, 2016

critical-thinkingA new review paper has just been published on the current status of brain structure research in transsexuality.  Interestingly, it was submitted to the Archives of Sexual Behavior two full years ago.  This suggests that it went through a rather thorough peer review.  For myself, the first thing I do when reading a review paper is to see that the reference list is comprehensive to ensure that the authors aren’t cherry-picking.  In this case, they are not.  The paper looks to be very complete and scientifically honest.  You may wish to read it yourself, as it is not behind a paywall, thankfully.

The paper is written rather densely, with a great deal of information and discussion; so much in fact, that I will likely be writing several essays covering a number of topics from it.  At the high level, my regular readers will not be surprised at the primary conclusions drawn from the review, as I had already written about a fair number of the brain research papers.  The authors offer this chief conclusion at the end of the paper,

“The review of the available data seems to support two existing hypotheses: (1) a brain-restricted intersexuality in homosexual MtFs and FtMs and (2) Blanchard’s insight on the existence of two brain phenotypes that differentiate “homosexual” and “nonhomosexual” MtFs”

The review of all of the available brain structure research fully supports the Two Type Taxonomy.  In light of this, the authors recommend that future researchers take care to distinguish between the two types, lamenting that some studies in the review had not made this distinction, and further, that it is important that the control groups also be concordant with sexual orientation,

“The study of mixed samples implicitly assumes that transsexuals are a homogeneous group. This is far from the truth with respect to the onset of GD and sexual orientation.  …  These observations signify that control groups in studies of the transsexual brain must be homogeneous in regards to sexual orientation.”

The authors did find separate studies of androphilic “homosexual” MTFs and non-gender dysphoric gay men that used the same methods, such that a tentative comparison could be made,

“The only study on the CTh [cortical thickness] of homosexual persons that do not present gender dysphoria is by the Savic group (Abé et al.). If we compare this study with that of Zubiaurre-Elorza et al. on the CTh of homosexual MtFs, we see both studies report sex differences showing an F > M pattern in similar structures of the right hemisphere. But there is only one region, the pars triangularis, in which homosexuals and homosexual MtFs both present differences. However, these changes are in opposite directions. The pars triangularis of homosexual MtFs is thicker than in heterosexual male controls, while for homosexuals it is thinner than in heterosexual males. Thus, it seems that for transsexuals this region is feminized but demasculinized [i.e.: “different that straight men, but not in the heterosexual female direction” – K. Brown] in homosexual individuals. Interestingly, in both studies, the affected pars triangularis is in the right hemisphere. Nevertheless, confirming Blanchard’s prediction still needs a specifically designed comparison of homosexual MtF, homosexual male, and heterosexual male and female people.”

This is interesting, that there is a difference between gay men and androphilic transwomen?  But the right hemisphere pars triangularis of all things?  For left hemisphere dominant people, this region of the brain is believed to be involved in the understanding and production of prosody, emotionally nuanced speech modulation.  We know this because individuals who have serious lesions in this area have trouble with prosody.

For more information, read the Wikipedia page on prosody.

Before anyone gets too excited about the possible implications for a neurological marker for androphilic transsexuality that differentiates them from gay men, we need to note that the brain exhibits neuroplasticity.  That is to say, that like a muscle, exercise of particular skills causes the brain to increase in volume and neuron number in those regions used to supply that skill.  If this is about language and more particularly, about language production that imparts an emotional / sexual identity / gender identity through one’s voice, the difference in this part of the brain may be caused by experience and practice.

For more information, read my essays on feminine speech production and on voice recognition.

On the other hand, it just might represent a real difference.  We need more studies.


Guillamon, A et al., “A Review of the Status of Brain Structure Research in Transsexualism” Arch Sex Behav (2016). doi:10.1007/s10508-016-0768-5

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Ripe Cherries…

Posted in Brain Sex, Science Criticism by Kay Brown on January 16, 2016

phrenology… or How the Science of Changing Sex is Distorted by the Transsexual Community
Funny how I have been carefully writing about the science regarding transsexuality and transgender sexuality and trying to be very careful about NOT cherry picking or distorting the evidence by either misstating or omitting key points?  Well… now I seem to have competition at The TransScience Project.  Of course, it appears that they are cherry picking or leaving out key data points.  For instance, lets examine an essay written by Sarah Lewis on “The Brain And Gender Dysphoria”:

“The first study of its kind was conducted by Zhou et al (1995). The study found sex a-typical differences in the stria terminalis of the brain stem when studying transgender subjects. A follow up study by Kruijver et al (2000) confirmed the findings and provided greater insight. The central subdivision of the bed nucleus of the stria terminalis (BSTc) is sexually dimorphic. On average, the BSTc is twice as large in men as in women and contains twice the number of somatostatin neurons. These numbers do not appear to be influenced by sexual orientation or hormone replacement therapy – and both were controlled for by Zhou and Kruijver. A paper by Chung et al (2000) studied how the volume of the BSTc varied with age in both male and female subjects. They found that the dimorphism was only prevalent in adulthood. Suggesting that the differences found by Zhou and Kruijver are not a cause of gender dysphoria but rather a result.”

Ummm… “not a cause but rather a result.”  Yes… and not quite.  No, the BSTc was influenced by exogenous hormones as a result of treating gender dyshoria, not because of gender dysphoria.  Gotta hand it to her, Lewis did a great slight of hand trick there huh?  It almost sounded like the BSTc was related to gender dysphoria… but it’s not.  Ms. Lewis failed to explain that taking hormones causes changes in the brain toward the target sex.  Not quite saying a falsehood… just letting an unwary reader be mislead.  Which is what she continues to do in the paper:

“In Luders et al. (2009), 24 trans-women who hadn’t started hormone-replacement therapy were studied via MRI. While regional grey matter concentrations were more similar to men than women, there was a significantly larger volume of grey matter in the right Putamen compared to men. As with many earlier studies, they concluded that gender dysphoria is associated with a distinct cerebral pattern.  In contrast, Savic et al (2011) did not find any sex a-typical differences in the Putaman, or other investigated areas of the brain. They did however find differences between their trans-women group and both the male and female controls.”

She didn’t mention that this research, both studies, included only non-exclusively  androphilic (i.e. primarily gynephilic) transwomen.  In fact, throughout her essay, she fails to make this distinction, which allows data that supports Blanchard’s prediction that exclusively androphilic (transkid) MTF transwomen would show shifts toward a feminized brain, but the non-exclusively androphilic would not, though they would show non-sexually dimorphic differences from both men and women, to be falsely interpreted to suggest that evidence for brain feminization in MTF transkids to apply universally.  Actually, in this case the larger volume of grey matter in the right putamen was larger than men AND women, suggestive of a non-sexually-dimorphic brain marker for autogynephilic transwomen, exactly as predicted, as explained in my essay, “And the Beat Goes On”.

Had she compared the Savic (2011) paper to the Simon (2013) paper, especially if she had quoted Simon, she might have had a far different interpretation, as I did in my earlier essay, “Shades of Grey matter”

In that paper, Simon pointed out that their study used the same methods, but found quite different results, and noted that it was because of the issue of the two types of transwomen.  Looking at only androphilic MTF transwomen, they did find that they were similar to female controls and not to male controls.  But that would not have suited Lewis to have pointed that out.  In fact, Lewis failed to note that studies which did find sexually dimorphic shifts, were conducted on exclusively androphilic transwomen,

“Two studies by Rametti et al (2011) looked at white matter differences in both trans-men and trans-women.

In their study of trans-men they found that control males have significantly higher fractional anisotropy values (FA is a measure often used in diffusion imaging where it is thought to reflect fiber density, axonal diameter, and myelination in white matter) than control females “in the medial and posterior parts of the right superior longitudinal fasciculus (SLF), the forceps minor, and the corticospinal tract”.

Compared to control females in the study, trans-men “showed higher FA values in posterior part of the right SLF, the forceps minor and corticospinal tract. Compared to control males, trans-men showed only lower FA values in the corticospinal tract.”

The study concluded that there was evidence for an inherent difference in the brain structure of trans-men.

In their study of trans-women they found that trans-women “differed from both male and female controls bilaterally in the superior longitudinal fasciculus, the right anterior cingulum, the right forceps minor, and the right corticospinal tract.” The nature of these differences suggests that some fasciculi do not complete the masculinization process in trans-women during brain development.”

However, I did point out that this only applies to exclusively androphilic transkids in my essay, “Seeing the world in grey and white”.

Lewis is not a very critical reader of the scientific literature… especially if it suits her thesis.  In fact, she accepted at face value one paper, that purported to have shown that MTF transwomen (all non-androphilic, btw) responded to human male pheromones the same as control females.  (Which is strange, because if they did respond like straight women, why aren’t they attracted to men?)  Problem?  Ummmm… nothing…. except that there’s no such thing as human pheromones!!  I pointed that out in my essay, “False (Scent) Trail”.

And speaking (er… writing) of not being critical,

“Garcia-Falgueras and Swaab (2008) investigated the hypothalamic uncinate nucleus, which is composed of two subnuclei, namely interstitial nucleus of the anterior hypothalamus (INAH) 3 and 4. They showed for the first time that INAH3 volume and number of neurons of trans-women is similar to that of control females. The study also included analysis of a single trans-man who also had a INAH3 volume and number of neurons within the male control range.”

As I pointed out in my essay, “The Incredible Shrinking Brain”, this too was easily shown to be an effect of hormone therapy, just like Swaab’s earlier report about the BSTc, in fact, these were the same subjects who had been on HRT for years, sigh…  Had she read my essay, would Lewis have included my analysis?

She concludes with one paper which suggests a difference between control men and MTF transwomen with respect to the ability to mentally rotate images.  Looking at the subject’s ages, average 37, we can see that they are likely mostly non-androphilic.  This paper looks interesting, but is this really a sexually dimorphic difference?  Or a difference in IQ?  The transwomen were about IQ 107-109 and the control men, who performed better, were about IQ 123 (a significant difference at one standard deviation).  Me?  I’m going with IQ.

This isn’t the only example of cherry picking I’ve commented upon, as I wrote in an earlier essay, “Gender Allusions”.

So, we see that when looking at the scientific evidence and how it is presented, by and within, the transcommunity clearly wants to believe, and leave others with the impression, that it supports the notion that all transwomen have feminized brains and that there is only one kind of transwomen.  Sadly for them, neither is true.

Further Reading:

Essays on Brain Sex

Cherry Picking at Scientific American {Author uses only papers w/ exclusively androphilic subjects.}


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Brain Power…

Posted in Brain Sex, Confirming Two Type Taxonomy by Kay Brown on December 28, 2015


…I would while away the hours, confir’in with the flowers…. if I only had a brain…”  — Scarecrow, in the Wizard of Oz musical film.

After years of trying to explain the differences between the two types and the statistical evidence for the two type taxonomy of MTF transwomen, I’m now posting what should be the final clincher; solid biomedical laboratory evidence, “proof” even.

Decades ago, as I was researching our collective history and science (the two often go hand in hand), I came across a reference to studies that showed that gay men had feminized brains while MTF transsexuals did not.  SAY WHAT!?!?

Turns out, the study referenced made the false assumption that all MTF transsexuals are the same and had only included gynephilic older transitioners.  Other studies, being aware of, and accounting for the differences between the two MTF transsexual types found something quite interesting, as for example, from the Dörner (1983) abstract:

“In male rats, androgen deficiency during a critical period of sexual brain differentiation was shown to give rise to a predominantly female-differentiated brain. Such animals displayed “homosexual behaviour”, i.e., they were sexually attracted preferentially to partners of the same sex. In addition, they exhibited a sex-specific evocability of a positive oestrogen feedback effect. A positive oestrogen feedback effect on LH secretion was also induced in homosexual transsexual men, in contrast to hetero- or bisexual transsexual men. Thus in homosexual transsexual men, an intravenous injection of 20 mg Presomen (Premarin) produced a significant decrease of serum LH levels followed by a significant increase above the initial LH values. In hetero- or bisexual transsexual men, by contrast, intravenous oestrogen administration, while producing a significant decrease of serum LH levels, was not followed by an increase above the initial LH values. A positive oestrogen feedback effect on LH secretion was also found in homosexual non-transsexual men, in contrast to heterosexual men. These findings suggest that transsexual as well as non-transsexual homosexual men possess a predominantly female-differentiated brain which may be based, at least in part, on androgen deficiency during sexual differentiation of the central nervous system. Homosexual transsexual men also showed an increased LH and FSH response to LH-RH as compared to hetero- or bisexual transsexual men.”

Note that non-exclusively-androphilic (“heterosexual or bisexual”) transwomen did NOT have the female like positive estrogen feedback effect on LH serum levels.  Of course, according the Blanchard’s work, all “non-homosexual” MTF transsexuals should also be in the same taxon, so we would predict that so-called, asexual transsexuals should also show the lack of this positive feedback, and indeed, this too was found, as discribed in the Dörner’s (1976) earlier paper,

“In transsexual men with homosexual behaviour and intact testicular function, as well as in homosexual men with normal gender identity, following a negative oestrogen feedback effect a delayed positive oestrogen feedback action on LH secretion was evoked. By contrast, in transsexual men with hypo- or asexuality and intact testes or hypergonadotrophic hypo- or agonadism, as well as in heterosexual men with normal gender identity, a negative oestrogen feedback effect was not followed by a positive feedback action on LH release. In transsexual women with homosexual behaviour and oligo- and/or hypomenorrhoea, only a weak or at best moderate positive oestrogen feedback action on LH release was evocable, similarly as in castrated and oestrogen-primed heterosexual men. By contrast, in a transsexual woman with bisexual behaviour and eumenorrhoea, a strong positive oestrogen feedback action on LH secretion was evocable, as well as in heterosexual women with normal gender identity.”

Note that in this paper we see a mirror like difference between FtM “homosexual transsexuals” (gynephilic transmen) who respond more like heterosexual men and bisexual FtM transmen who respond more like heterosexual women.  Thus, this data would lend support for there being a taxonic difference between exclusively gynephilic and non-exclusively gynephilic transmen, mirroring the taxonic difference between the two types of transwomen.


These papers, detailing a specific, repeatable, laboratory based test that can differentiate the two types of transsexuals described by Blanchard, “Homosexual” and “Non-Homosexual”, offers both supporting evidence for the two type taxonomy but potentially also a way of independently sorting the two types in future studies.  This difference is a classic medical biomarker for the two types.  Should anyone one doubt the weight of statistical evidence, we can also point to the biomedical evidence via laboratory tests.


Dörner G, Rohde W, Schott G, Schnabl C., “On the LH response to oestrogen and LH-RH in transsexual men.” Experimental Clinical Endrocrinology (1983)

Dörner G., “Neuroendocrine response to estrogen and brain differentiation in heterosexuals, homosexuals, and transsexuals.” Archives of Sexual Behavior (1988)

Dörner G, Rohde W, Seidel K, Haas W, Schott GS.”On the evocability of a positive oestrogen feedback action on LH secretion in transsexual men and women.” Endokrinology (1976)


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Gender Allusions

Posted in Brain Sex, Science Criticism by Kay Brown on February 24, 2015

critical-thinkingIs “Gender Identity” biological?  For most people, the answer is intuitively obvious, “duh!”.  Of course, for these people, they usually also insist that the markers for such identity is some privileged and testable characteristic, like genitalia, which is easy to observe, or karyotype (sex chromosome configuration) which requires a microscope.  But for people with Disorders of Sexual Development (DSD), these markers may not be all that clear.  Further, what are we to make of the gender identities of transsexual and transgendered people, people whose experienced / stated gender identity is at odds with all currently known sex markers?  IS there a biological etiology?  And is that etiology the same as that that gives rise to the gender identity of non-trans people? A recent review article attempts to answer these very questions.  Sadly, I believe that it falls far short of a conclusive answer.  In fact, as I will show, it invokes conclusions from several papers as evidence that are quite questionable.  Further, the authors failed to note the very probable multiple etiologies for Gender Dysphoria and their associated gender identity resolutions suggested by the Freund/Blanchard two type taxonomy of MTF transsexuality. First, they reviewed evidence for a biological basis for the phenomenological existence of “gender identity” in non-transfolk which comes from those with certain DSDs,

A seminal study by Meyer-Bahlburg et al involving outcomes of XY individuals raised as females due to severe non-hormonal, anatomic abnormalities of sex development has provided the most convincing evidence that gender identity is fixed. These congenital abnormalities include penile agenesis, cloacal exstrophy, and penile ablation. For many years, female gender assignment along with surgical feminization was the dominant approach for these patients. In this study, it was observed that 78% of all female-assigned 46 XY patients were living as females. While the majority of these patients did not initiate a gender change to male, none of the 15 male raised 46 XY patients initiated a gender change to female. Thus, risk of questioning gender identity was higher in those patients raised as females than in those raised as males among 46 XY subjects with one of these conditions. A study by the same group that examined the degree of satisfaction with surgical intervention reported by patients with 46 XY genotype also found that those subjects raised as boys were considerably more comfortable with their gender identity. – Another seminal study relevant to this topic was by Reiner and Gearhart in their review of 16 XY genotype subjects with cloacal exstrophy who underwent female gender reassignment surgery. Out of the 14 individuals raised as girls, 4 announced they were male and 4 later chose to live as boys when they became aware of their genotype. The 2 individuals who were raised as males identified as males throughout life. The sexual behavior and attitudes of all 16 subjects ultimately reflected strong masculine characteristics regardless of gender assignment. Thus, children who were born genetically and hormonally male identified as males despite being raised as females and undergoing feminizing genitoplasty at birth. Although cohort size in these studies is small, these data provide the strongest evidence for biological underpinnings of gender identity.  …  In a study of affected subjects, gender role changes were reported in 56-63% of cases with 5 alpha-reductase-2 and 39-64% of cases with 17-beta-hydroxy-steroid dehydrogenase-3 who were raised as girls (6). These data support the concept that gender identity might be attributed to hormone milieu during intrauterine development on some occasions.

These studies are indeed very strong evidence.  Looking at the data, we see that of those raised as girls, 22% of of these subjects in the first study and 57% in the second study, while in the third study, those with hormonal abnormalities, 56-63%, chose to socially transition from female-to-male.  Compare that to the very, very small number of 46XX individuals in the general population who experience severe gender dysphoria and choose to transition.  As an aside, the fact that not all chose to transition should not be taken as proof that gender identity is all that malleable, but should probably be taken as a demonstration that social transition has very high social costs and is not undertaken lightly. Strangely, this paper did not explicitly mention that the majority of these individuals, whether they experienced gender dysphoria or not, were exclusively gynephilic, but they did allude to it.  Also puzzling was their failure to include the converse situation of individuals with 46XY and complete androgen insensitivity syndrome (CAIS), all raised as female, who are extremely unlikely to experience gender dysphoria or sex reassignment, and are universally exclusively androphilic.  Or the even more interesting case of 46XX progestin influenced females raised as male, 50% of whom transitioned from male to female and all are exclusively androphilic.

Thus, they failed to explicitly show the very high correlation of brain sex with gender identity, gendered behavior, and sexual orientation. Having shown that there is indeed very strong evidence that “gender identity might be attributed to hormone milieu during intrauterine development on some occasions”, which supports the notion that gender identity has a basis in biology (as opposed to being purely a social construct overlain on observable sex differences), it is tempting to say that transsexuality, all transsexuality and transgender identity, is also the result of mismatched hormonal milieu.  In fact, many transsexuals hold to just such a position.

But they would be dead wrong.

The logical leap that all transsexuals have such an etiology is not supported by the above evidence.  In fact, given the very probable differing etiologies for Gender Dysphoria and their associated gender identity resolutions suggested by the Freund/Blanchard two type taxonomy of MTF transsexuality, at least one of these types must NOT have been caused by such.  Blanchard went on to predict that this would be born out by studies of the sexually dimorphic structures in the brain, predicting that the exclusively androphilic MTF transsexual would show shifts toward the female morphology, while the other type would not. It is here that this recent paper has its biggest failings, in that not only did they not discuss this issue, but included very problematic studies by Swaab that purported to have shown female like shifts in non-exclusively androphilic transwomen.  These papers did show the shifts in the BSTc and INAH3, but incorrectly concluded that they had existed prior to exogenous HRT and incorrectly concluded that these features in the brain were organization effects of endogenous hormones in utero, when the data clearly demonstrated the opposite, that these shifts were purely activational effects from exogenous estrogenic and anti-androgenic HRT.  To be fair, they did mention that the BSTc was potentially questionable, but completely failed with regards to the INAH3, which demonstrably is not evidence for a biological basis of gender identity.

In reviewing the recent grey and white matter studies, they failed to note that it fits and supports Blanchard’s prediction, which had they done so, would have strengthened their argument for a biological basis for a conventional gender identity in exclusively androphilic MTF transsexuals.  That is to say, that they experience the same feminine “gender identity” as females because their brains are female like.  Conversely, they would also have evidence for a biological underpinning to autogynephiles sexuality, a non-sexually-dimporphic one, which lead to an epiphenomically generated “female gender identity” later in adulthood.  (See my essay on the different origins of cross-gender identity in transsexuals.)

The authors reviewed the literature on possible genetic factors that could lead to transsexuality, noting that they were inconclusive. Totally absent in this paper was any mention of the papers that document the fraternal birth order effect found in exclusively androphilic MTF transsexuals. All in all, I was disappointed in this paper.

I found it shallow, lacking in both depth and breadth, and literally out of step with much of the literature on the cutting edge of the science.

(Addendum 7/7/2015:  I got suspicious of this paper as it reads like a cherry-picked list of papers that support the brain sex hypothesis for all transsexuals, including “late onset” transwomen, so I checked into the background of the authors.  Sure enough, one of the authors is transgendered.  While that alone is NOT damning (after all, so am I), it does explain why this paper only referenced the studies it did, and did not include those studies that when considered as a whole, would show that while one subset of the larger transsexual population could possibly be explained by the brain sex hypothesis, most transwomen could not.  This paper then can and should be considered part of the ongoing effort by some in the transgender community to deny the evidence of the two type taxonomy.)


Aruna Saraswat, MD, Jamie D. Weinand, BA, BS; Joshua D. Safer, MD, “Evidence Supporting the Biological Basis of Gender Identity” (2015) DOI:10.4158/EP14351.RA

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Shades of Grey…

Posted in Brain Sex, Confirming Two Type Taxonomy, Female-to-Male by Kay Brown on February 23, 2015

shrinking brainShades of Grey… Matter

We live in exciting times – At least scientifically.  We can now peer into the heads of transsexuals to see if their brains exhibit sexually dimorphic features that match their natal sex or their preferred gender.  Years ago, Ray Blanchard made a prediction, based on early evidence that there was a taxonic difference between “homosexual” and “non-homosexual” transwomen in sexuality, natural gendered mannerisms, age of transition, etc, that the former would show sexually dimorphic features in the brain that were shifted in the female direction while the latter would not, but would show features that were different than controls, but that they would not be sexually dimorphic features, and definitely not shifted in the female direction.  We now have yet more evidence that that prediction is correct, giving more weight to the two type taxonomy of MTF transsexuality, namely exclusively androphilic vs. autogynephilic.

The best evidence would be to use two populations of transwomen, one known to be exclusively androphilic and the other not, and test them for the same features, using the same type of measurement.  We now have that data for grey matter distribution in the brains of both types of transsexual.

In the earlier Savic and Arver paper, they compared grey matter distribution of 24 gynephilic transwomen, before HRT to that of heterosexual men and women.  (Remember, HRT itself causes a shift in sexually dimorphic features due to activational effects of sex hormones, and the lack of such hormones.)  The conclusion?

“The present data do not support the notion that brains of (gynephilic) MtF-TR are feminized.”

In the later Simon paper, they compared grey matter distribution of 10 exclusively androphilic transwomen, and 7 exclusively gynephilic FtM transmen, before HRT to that of heterosexual men and women.  The conclusion?

“Our findings support the notion that structural differences exist between subjects with GID and controls from the same biological gender. We found that transsexual subjects did not differ significantly from controls sharing their gender identity but were different from those sharing their biological gender in their regional GM volume of several brain areas, including the left and right precentral gyri, the left postcentral gyrus (including the somatosensory cortex and the primary motor cortex), the left posterior cingulate, precueneus and calcarinus, the right cuneus, the right fusiform, lingual, middle and inferior occipital, and inferior temporal gyri. Additionaly, we also found areas in the cerebellum and in the left angular gyrus and left inferior parietal lobule that showed significant structural difference between transgender subjects and controls, independent from their biological gender.”

The choice to explore only “homosexual” transsexuals in this study was informed by the researchers’ knowledge of the Freund/Blanchard taxonomy and of Blanchard’s prediction, as they explained,

“Both MTF and FTM patients were eligible for the study, but only those with homosexual orientation. The rationale for this choice was based on the Blanchard typology which considers two fundamentally different types of transsexualism: homosexual and nonhomosexual. Homosexual transsexual individuals are sexually attracted to the same biological gender, while nonhomosexual transsexual individuals are attracted to either the opposite gender or show no sexual orientation/attraction at all. According to Blanchard, homosexual transsexuals are usually younger at initial presentation of gender identity disorder and show more pronounced and frequent childhood femininity, as well as different anthropometric data. One might argue that mixing individuals from both transsexual groups in one study targeting the neurobiological background of transsexualism might bias the results by introducing heterogeneity in the sample. Thus, in our study, only homosexual transsexual individuals were included preventing our findings from the aforementioned bias.”

This points to growing recognition within the scientific community that the two type taxonomy is correct.  They went further, indirectly referring to the taxonomy and Blanchard’s prediction,

“In another study also limited to MTF transsexuals Savic and Arver, reported no “feminization” of any brain region with regard to structure. Nonetheless, certain brain areas (clusters ≥100 voxels) showed characteristic structural features in the transsexual group compared with both male and female control groups. Specifically, they found reduced thalamus and putamen volumes and increased GM volumes in the insular and inferior frontal cortex and in the right temporo-parietal junction (angular gyrus and superior temporal gyrus) in the transsexual group compared with both control groups. In our study, however only the angular gyrus (but in the left hemisphere) was affected among these areas, showing lower regional GM concentration in both FTM and MTF transgender subjects compared to controls, independent of their biological gender. When comparing the results reported by Savic and Arver to either our study or to other imaging studies in the literature of transsexualism, it has to be taken into consideration that their reported results were obtained from a solely nonhomosexual transsexual group of patients. The lack of real overlap between our and Savic and Arvers’ findings, despite the very similar methodology used, might at least in part be explained by the difference of the sexual orientation of the two samples.”

Truly, exiting times.


Ivanka Savic, Stefan Arver, “Sex Dimorphism of the Brain in Male-to-Female Transsexuals”

Lajos Simon, Lajos R. Kozák, Viktória Simon, Pál Czobor, Zsolt Unoka, Ádám Szabó, Gábor Csukly, “Regional Grey Matter Structure Differences between Transsexuals and Healthy Controls—A Voxel Based Morphometry Study”

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Autistic Sky

Posted in Brain Sex, Confirming Two Type Taxonomy, Female-to-Male by Kay Brown on September 21, 2014

shrinking brainFor the past several years, evidence has been accumulating that there is a fairly high comorbitity between transsexuality / transgenderism and the autism spectrum.  Interestingly, and perhaps not totally surprisingly, among MTF transwomen, it appears to be exclusively found in the non-exclusively androphilic population.  This fits the Freund/Blanchard taxonomy and more importantly, Blanchard’s prediction that “non-homosexual” (with respect to natal sex) MTF transwomen would exhibit neurological / brain differences from control males but these differences would NOT be a shift toward female like brains.

Autism and autism spectrum disorders are found in four to five  times as many men as women.  There are a number of theories as to why this happens, including the rather intriguing “hypermasculine brain hypothesis”, in which a link between the slight differences between men and women, as groups, having different cognitive and social behaviors and the apparent similarity, or rather, exaggeration of these differences between men and women, found in those on the autism spectrum.  If autism is a form of hypermasculinization, it would not surprise us to learn that FTM transmen were more autistic-like than most women… and that is what one group of researchers found.

Using a 50 item, Likert scored, instrument called the Autism Spectrum Quotient (AQ), Jones, et Al., found that FTM transmen as a group, scored 23.2, higher than control women AND men!  This puts about half of the FTM onto the high functioning autism spectrum!!   (The lower AQ cut-off for ASD is 23.)  Non-exclusively-androphilic transwomen scored essentially the same as the control men, while exclusively androphilic transwomen scored essentially the same as the control women, and definitely (statistically significant: p<0.03 ) below both the control men and non-androphilic transwomen.

Group:               Men                  Women       FTM                 Non-Androphilic           Androphilic
.                                                                                                     MTF  N=129                   MTF N=69

Score (SD):       17.8 (6.8)        15.4 (5.7)     23.2 (9.1)        17.4 (7.4)                         15.0 (5.6)

The implication is clear, FTM’s are masculine, perhaps even hypermasculine, while the data also supports the Freund/Blanchard two type taxonomy for MTF transwomen.  In the discussion section of the paper, the authors remarked,

“Interestingly, with the 198 transwomen group, there were 6 individuals (i.e. 3%) with a diagnosis of AS. This rate is about 3 times as many as in the general population.”

These authors didn’t state what the sexuality of the six AS individuals were; but if they conform to the greater likelihood that they were non-androphilic, found in other papers, the incidence rate for such non-androphilic transwomen would be closer to five times the rate found in the general population, however, that is only about twice as high as that found in the male population.

(Addendum: 1/21/2017:  Looking at the data again, this time from the perspective of effect sizes with respect to men vs. women and non-androphilic vs. androphilic aids us in understanding how important this difference is.  First, the effect size between men and women is 0.38 a modest but still very noticable difference in the populations.  Now, let’s look at the diffence between non-androphilic and androphilic at 0.37, nearly identical to the difference between men and women.  So, lets compare the difference between men and non-androphilic tranwomen at 0.06 which is tiny.  And similarly, when we compare between women and androphilic transwomen it is only 0.07 which again is very tiny.  That is to say, these statistical tests shows that the difference between men and women is the same size as between non-androphilic and androphilic transwomen, while there is effectly no difference between men & non-androphilic and women & androphilic transwomen respectively.  That is to say, that non-androphilic transwomen are identical to men in general, while androphilic transwomen are essentially the same as women in general.  Further the difference between the two types of transwomen exactly matches the difference between men and women, which strongly supports the Two Type Taxonomy.)


Jones, et Al, “Female-To-Male Transsexual People and Autistic Traits”, J. Autism Dev. Discord. DOI: 10.1007/s10803-011-1227-8

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