On the Science of Changing Sex

Sex Chromosomes Expression Associated With Brain Sex?

Posted in Brain Sex by Kay Brown on July 27, 2020

Teenage-brainThere has been a long term assumption that sexually dimorphic brain features developed solely from hormonal difference, both organizational and activational.  Some have long suspected that at least some of the sexually dimorphic features were from differential expression of the sex chromosomes themselves.  An association between such features and differential expression has now been found in a recent study.

There is a great essay at Wired that I would recommend you read before continuing to read my essay here.  (Link)

A few comments are warranted here.

First, the hormonal hypothesis is not negated, only modified.  There remain several possibilities, first that the hormonal influence simply triggers which genes are expressed in the brain at and that it is only coincidental that some are on the sex chromosomes; second, that hormonal influence works independently from the sex chromosome expression control.  Of course, it could even be some combination of the two (and my bet is on this third possibility).  Remember, many of the genes differentially expressed are NOT on the sex chromosomes, and even those on the X chromosome, available to both sexes, are differentially expressed.

Please note:  Genes on the X chromosome are NOT all automatically expressed in women nor are they automatically repressed in men.  Further, not all of the genes found on the X chromosome relate to sexually dimorphic development (e.g. color vision receptor).

Second, we don’t know what the FUNCTIONAL differences the sex chromosomes mediate vs. the autosomal chromosomes.  We don’t know how different the behaviors would really be with such differential expression.  These difference could be related not to behaviors but to immune responses for example.  When one is confronted with ignorance, it is important to recognize it and not make conclusions that the data doesn’t support.

Third, a reminder that these differences can NOT be directly associated with important cognitive mechanisms, else females would be at an extreme disadvantage not able to express genes that lie only on the Y chromosome.  We know this because men and women have shown only tiny differences in cognitive performance of specific tasks and that general cognitive ability (IQ – g factor) do not differ between the sexes.  (Male chauvinists be damned!)

Fourth, speculating on what effect this might have on gender atypicality and the degree to which such atypical individuals may resemble the opposite sex in brain sexual dimorphism is inescapable.  Most of it will likely be found wrong later.

One can imagine certain transphobic groups using this material to show that gender atypical transsexuals (HSTS) aren’t “really” a man or a woman… cause… “biology” (essentialism based on karyotype).  But that is not the germain issue as we KNOW that other mechanisms are also involved.

Further Reading:

Essay on hormonal effects on sexually dimorphic brain development

Essay on gene control of sexually dimorphic behaviors

Further External Reading:

Wired Article

Reference:

Liu, et Al.,”Integrative structural, functional, and transcriptomic analyses of sex-biased brain organization in humans”, PNAS (2020)
https://doi.org/10.1073/pnas.1919091117

Comments Off on Sex Chromosomes Expression Associated With Brain Sex?

2D:4D Evidence Supports Transexual Taxonomy

Posted in Brain Sex, Confirming Two Type Taxonomy, Female-to-Male by Kay Brown on January 30, 2020

handA new paper provided both new direct evidence and a meta-analysis of measurements of 2D:4D finger ratios in transsexuals, both FtM and MTF.  Such measurements are interesting because it is known to be influenced by testosterone levels in utero and thus an indirect measure of testosterone exposure that might influence brain sexual dimorphism.

What is doubly exciting about this paper is that the authors fully comprehend the overwhelming evidence for the two type taxonomy and of the (mild) scientific controversy regarding sexual orientation vs. age of onset as the best clinical markers for the two taxons.  The study is open access so I highly recommend following the link to it and reading it for yourself.  The study is also interesting because of where it was conducted; Iran.

Iran is a Muslim country which while being extremely homophobic, both culturally and legally, treats transsexuals fairly well, at least legally and medically.  Make no mistake, culturally, it is far from truly accepting.  Further, Iran is considered a “Collectivist Society” according to the Hofstede Individualism vs. Collectivism Index.  Lawrence has shown that this index highly correlates with the percentage of non-androphilic (and thus likely autogynephilic / late onset) transwomen transitioning in a given culture.  Thus, we would expect that there were fewer such transwomen in the study and the reported data bear this out.

Let’s look at the new data they provide:

Table 1

Means (and SD) for 2D:4D in the left and right hand for transmen, transwomen, control women, and control men

Transmen

Control women

Transwomen

Control men

Left 2D:4D

0.991 (0.034)

0.991 (0.032)

0.981 (0.033)

0.974 (0.029)

n = 104

n = 53

n = 88

n = 56

Right 2D:4D

0.981 (0.030)

0.983 (0.033)

0.972 (0.029)

0.959 (0.033)

n = 104

n = 53

n = 89

n = 56

Table 2

Means (and SD) for 2D:4D in transsexuals’ left and right hand as a function of early or late onset of gender dysphoria

Transwomen

Transmen

Early onset

Late onset

Early onset

Late onset

Left 2D:4D

0.982 (0.034)

0.975 (0.022)

0.988 (0.033)

1.009 (0.031)

n = 80

n = 8

n = 92

n = 12

Right 2D:4D

0.973 (0.029)

0.963 (0.026)

0.977 (0.028)

1.007 (0.027)

n = 81

n = 8

n = 92

n = 12

Before the analysis of transfolk, it would be a good idea to scale the effect by looking at the effect size between the controls.  The difference between control women and men is d= 0.56 for the left hand and d= 0.76 for the right. This is only a moderate effect size.

Although the number of late onset is small, and thus must be viewed with caution, the analysis is still very interesting and would seem to confirm (agree) with the two type hypothesis.  Consider that the two MTF types have a small but distinct difference of d= 0.24 for the left hand and d= 0.22 for the right.  When we compare early onset type to the male controls we get d= 0.25 and d= 0.45 for the right.   When we compare early onset to female controls we get d= -0.27 for the left and d= -0.32 on the right.  This shows that early onset transwomen are roughly halfway between the controls, and if anything a bit closer to the female controls.

But even more intriguing, and the reason for trusting this interpretation is that when we compare the late onset population to the male controls we see that it exactly agrees with the hypothesis that the late onset type is essentially like the majority heterosexual male population and not at all feminized, with effect sizes that are, statistically speaking, non-existent at d= 0.04 and d= 0.12 for the left and right hands respectively.

This shows that early onset MTF type has notably hypomasculine (feminized) hands while the late onset MTF type does not, and thus in agreement with other data that supports the two type MTF taxonomy.

But what about the FtM transmen?  Here we see an even more intriguing set of data.

The two FtM types have a moderate to substantial, very notable, difference of d= -0.66 for the left hand and d = -1.07 for the right, indicating that early onset transmen are far more masculine than late onset.  When we compare the early onset FtM to female controls we find effect sizes of d= -0.09 for the left hand and d= -0.20 for the right indicating a non-existent to small masculinization signal.

However when we compare the late onset FtM to female controls we see a very different pattern with effect sizes of d= 0.57 for the left and d= 0.80 for the right.  The positive sign indicates that late onset transmen have a more feminine 2D:4D ratio than control women (!!).  And the effect size difference between early and late onset transmen is far greater than the difference between control men and women (!!!).

This, if replicated, is very big news.  It would support the notion that transmen also exhibit two taxons as has long been suspected, one that is masculinized in both behavior, sexual orientation, and very mildly in appearance, the other that is very feminine, androphilic, and autoandrophilic, the mirror image of late onset transwomen.

Further Reading:

Essay on 2D:4D History

Essay on Cultural Difference in Percentage of HSTS vs. AGP Transwomen

Essay on Androphilic Transmen

Reference:

Sadr, M., Khorashad, B.S., Talaei, A. et al. “2D:4D Suggests a Role of Prenatal Testosterone in Gender Dysphoria” Archives of Sexual Behavior (2020)
https://doi.org/10.1007/s10508-020-01630-0

Tagged with: , ,

Comments Off on 2D:4D Evidence Supports Transexual Taxonomy

(Cherry) Picking The Transgender Brain

Posted in Brain Sex, Editorial by Kay Brown on May 31, 2018

27867072_1811649452220144_4426664495691531655_nOr, How To Ignore Brain Science That Tells A Story You Don’t Like

Psychology graduate student and computer coding instructor Sophie Searcy, responding to the recent over-hyped study of transkids brains (mentioned in previous post) has produced an excellent example of transgender brain science cherry picking.  The one that REALLY stands out as egregious is that she cites the Joel study that she claims… well… let Searcy tell it,

“Indeed, not only is the existing literature on sex differences in brain imaging likely biased, but recent work does significant damage to the idea that there are distinct, separate, “male brains” and “female brains” at all. A research group led by Daphna Joel summarizes the findings of their meta-analysis that included brain images from 1,400 participants: “Brains with features that are consistently at one end of the ‘maleness-femaleness’ continuum are rare. Rather, most brains are comprised of unique ‘mosaics’ of features, some more common in females compared with males, some more common in males compared with females, and some common in both females and males.”

So what’s the problem?  Well, it’s dishonest cherry picking to cite a study that another group (Chekrouda, et. al) responded in the same journal with a similar study that showed that if Joel had conducted a multi-variate analysis they would have found out that male and female brains scans WERE in fact differentiable by a mathematical model at 93% accuracy.  As I explained previously 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.

Searcy should have noticed this second paper which shows that Joel’s paper does NOT debunk the hypothesis that discernible male and female brains exist.

So, why did she write this article and cherry pick the science?  Perhaps we can get a clue from another statement she makes,

“In a 2017 paper, Bakker and colleagues summarized similar work on adults as finding that “adults with GD [gender dysphoria] differ from both cis-gender [sic] men and women.” In other words, adult trans brains appear to be distinct from adult cis brains of either sex. Should trans adults be worried? In that same paper, the researchers actually found mixed results for adolescents. They looked at nine brain regions each for trans girls and trans boys. Of those 18 regions, the researchers reported significant differences in only four out of 18 areas. One area where trans girls differ from both cis girls and cis boys, two areas where trans girls are similar to cis girls, and one area where trans boys are similar to cis boys. What does this mixed bag suggest if we are to believe that trans brains must be similar to cis brains in order to be seen as legitimately transgender?

Ummm… this result is in complete agreement with another hypothesis that many transwomen find uncomfortable, one made by Ray Blanchard, in which he hypothesized that late transitioning transwomen would have brain structure differences from both men and women that would NOT be sexually dimorphic; while young (“homosexual”) transsexuals would show shifts in sexually dimorphic structures toward female morphologies.  There was an earlier review of previous studies (which I also wrote a post about) that had shown that hypothesis to be supported.

Searcy is likely to have written her article in an attempt to discount the growing evidence from transgender brain scan research that shows that the two type taxonomy for transwomen is supported.  Where once older transitioning transwomen cherry picked the brain structure research in an attempt to spin it such that all transwomen had female brains.  She is spinning the science to lead us to believe that brain structure research is unimportant and should be ignored, first by saying that there is no brain structure sexual dimorphism of any consequence and then say that what differences between transgender folk and nontransfolk is unimportant anyway.  I believe it represents a growing fear by autogynephilic transwomen that the brain scan science will undermine their own identity as transwomen if the public were to become aware of what the evidence means.

Further Reading:

Essay on Chekrouda paper

Essay on Transgender Brain Sex Review

Essay on Cherry Picking Brain Research to Prove All Transwomen Have Female Brains

References:

https://www.them.us/story/brain-scans-transgender-identity

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

 

Comments Off on (Cherry) Picking The Transgender Brain

Autism and Transgender

Posted in Brain Sex, Female-to-Male by Kay Brown on May 24, 2018

critical-thinkingCo-Morbidity of Gender Dysphoria and Autism Spectrum

More studies show that there is a higher than expected by random chance of co-morbidity of gender dysphoria and autism spectrum disorders.  It’s seems to be true for both MTF and FtM.  There are hints that it may be more likely in “nonhomosexual” individuals.  The question not yet answered is whether this is an independent path to gender dysphoria in adults or is co-morbid with autogynephilia and autoandrophilia, though we have seen adolescents with and without autogynephilia in earlier studies.

From the Shumer study abstract:

“There is evolving evidence that children and adolescents with gender dysphoria have higher-than-expected rates of autism spectrum disorder (ASD)… We conducted a retrospective review of patient chart data from 39 consecutive youth ages 8 to 20 years (mean age 15.8 years, natal male: n = 22, natal female: n = 17) presenting for evaluation at a multidisciplinary gender clinic in a large U.S. pediatric hospital from 2007 to 2011 to evaluate the prevalence of ASD in this patient population. … Overall, 23.1% of patients (9/39) presenting with gender dysphoria had possible, likely, or very likely Asperger syndrome as measured by the Asperger Syndrome Diagnostic Scale.”

From the Pasterski study abstract:

“The current study examined this co-occurrence of GD and autistic traits in an adult population, to see whether this heightened prevalence persisted from childhood as well as to provide further comparison of MtF versus FtM transsexuals and homosexual versus nonhomosexual individuals. Using the Autistic Spectrum Quotient (AQ), 91 GD adults (63 male-to-female [MtF] and 28 female-to-male [FtM]) undertaking treatment at a gender clinic completed the AQ. The prevalence of autistic traits consistent with a clinical diagnosis for an autism spectrum disorder (ASD) was 5.5 % (n = 3 MtF and n = 2 FtM) compared to reports of clinical diagnoses of 0.5–2.0 % in the general population. In contrast to the single previous report in adults, there was no significant difference between MtF and FtM on AQ scores; however, all of those who scored above the clinical cut-off were classified as nonhomosexual with respect to natal sex. Results were considered in the context of emerging theories for the observed co-occurrence of GD and autistic traits.”

This was not a very large enough sample size given the small number of individuals found on the spectrum, but note that all five were nonhomosexual.

Further Reading:

Autistic Sky

Further External Reading:

Why we need to respect sexual orientation, gender diversity in autism by John Strang

Large study finds significant overlap between “transgender” identity and autism

References:

Pasterski, et al., “Traits of Autism Spectrum Disorders in Adults with Gender Dysphoria”, Archives of Sexual Behavior (2013)
https://doi.org/10.1007/s10508-013-0154-5

Shumer et al., “Evaluation of Asperger Syndrome in Youth Presenting to a Gender Dysphoria Clinic”, LGBT Health (2016)
https://doi.org/10.1089/lgbt.2015.0070

van der Meisen, et al., “Prevalence of the Wish to be the Opposite Gender in Adolescents and Adults with Autism Sprectrum Disorder”, Archives of Sexual Behavior (2018)
https://doi.org/10.1007/s10508-018-1218-3

Comments Off on Autism and Transgender

Brain Maps…

Posted in Brain Sex, Science Criticism by Kay Brown on September 19, 2017

phrenologyOr Searching for the Lost Continent of Atlantis

A recently popular counter argument to evidence of the two type taxonomy that arises in the transgender communities is that transsexuals brains have cross-sexed maps of the body.  It sounds so reasonable doesn’t it?  That is to say, if our bodies are sexually dimorphic with respect to genitalia and secondary sexual characteristics, shouldn’t our brains be as well?  And if the sexes have sexually dimorphic brain mapping of those body parts, could it not be that transsexuals have been “cross-wired”?  And further, couldn’t that explain all transsexuals and maybe even non-gender-dysphoric transgender people?

Trusting “truthiness” gut feelings is how we form false beliefs.  We need to look at this issue objectively, both open-mindedly to see if true, and skeptically to find the flaws in this hypothesis to prove it wrong if it is wrong.  So let’s look at the evidence shall we?

First, this idea seems to have cropped up BEFORE any supporting evidence.  Thus, it may be that when this idea is being explored, it will be subject to strong confirmation bias.  I’ve already written about such an incident in a previous essay when, ten years ago, Vilayanur Subramanian Ramachandran tried to pass off experimentally and statistically flawed data to support this hypothesis by comparing the experience of phantom limb sensations of a small group of control men who had penectomies with post-op MTF transwomen.  The study was roundly and rightly criticized by Anne Lawrence for not showing what it purported to show.  When writing about it, I discussed the theoretical objections to the notion of sexually dimorphic neural maps of the genitalia in the brain,

“First and foremost of which is that the genitalia are not really all that different in quality… and only superficially different in quantity.  Nearly each feature of the external and even of some of the internal structures are homologous.  That is, for each feature found in a male, there is a feature that matches it in the female, which is only different in degree, not in kind.  The most obvious example is the glans of the penis is homologous with the glans of the clitoris.  Inside of the penis, and down into its root inside of the body, is spongy tissue that expands when blood pressure fills it with blood.  Inside of the clitoris and down into its root inside of the body, is spongy tissue that expands when blood pressure fills it with blood.  Quite literally, a penis is a very large clitoris; And a clitoris is a very small penis.  Oh there are differences in how the urethra is routed, but even there, they start in the same place.  In men there are two glands called the Cowper’s, which produce a clear fluid that aids in lubrication during sex.  In women there are two glands called the Bartholin’s which produce a clear fluid that aids in lubrication during sex.  Why are they called two different names?  Finally, the scrotal sac is the same tissue as the labia majora, but have fused together.  Thus, the two sexes, which seem so different to a naive observer, are really very nearly the same to a student of anatomy.  So, given that the two are really very nearly the same, shouldn’t the neural maps be the same?”

I stand by my objections with regard to genitalia being sexually dimorphically represented in the brain.  But could there be other areas that are sexually dimorphically represented in the brain?  There could be, in fact… there SHOULD be.  To be specific, those areas of the body which are not homologous between the sexes should be expressed non-homologously in the brain.  Specifically, the uterus and fallopian tubes.  Further, these areas of female anatomy are not served by the pudendal nerves like the genitalia so may experience quite different representation in the brain.

Consider also the phenomena of neural atrophy.  If the brain is not stimulated by external events… for example someone born blind, the portion of the brain not stimulated does not fully develop while it may also be “repurposed” for another function.  That is to say, it is remapped and recruited by neurologically nearby functions.  So, we would expect to find sexually dimorphic maps of the somatic sensation processing functions associated with organs which are non-homologous.

However, under this analysis, we would NOT expect to find a section of a male-to-female transsexual’s brain waiting for input from non-existent non-homologous female anatomy!  That is the equivalent of searching for the Lost Continent of Atlantis.  You can put it one your paper map of the globe, but that won’t mean that you can find it on the real earth.  It sank into mythology a long time ago.

So, can there be sexually dimorphic brain development involving somatic maps where the opposite happens?  That is, can the brain fail to develop a map for a somatically sexually dimorphic feature that does exist?  This might be possible in theory.

Consider breast tissue.  This is superficially sexually dimorphic after puberty, but largely homologous.  But we have evidence from studies in mice that certain nerves leading to the milk glands begin to form in both sexes, but later atrophy in males in utero.  I haven’t been able to find data on humans regarding the same phenomena.  Mice, being rodents, are close cousins of primates, and thus humans.  But evolution does not always conserve every detail.  So we may or may not have the same phenomena.  However, lets for the moment entertain such a notion.  This would suggest that males would fail to develop brain functions that respond to the sensation of milk gland fullness, fail to develop the needed sensory map for the signals from an infant needing to nurse, and fail to send the needed signals back from other unconscious functions to “let down” the milk to an awaiting baby.  This let down signal is triggered by the sight, sound, and feel of a baby wanting to nurse.  It is thought that originally, only the sensations on the nipple bring about ‘let down’, but soon a mother learns by association the sight and sounds (baby hunger cry) that precede nursing.  It is theoretically possible that we could find the location of this somatic sensorium map and how it feeds the let down function in the human brain and see if it is a) sexually dimorphic and b) anomalous in transsexuals.

body2bmapping2bon2bthe2bbrain2b_new2bscientist2bhomunculusIt is also possible, though I’m not totally convinced, that the maps that allow one to experience touch on the nipples as erotic are also sexually dimorphic.  Interestingly we have discovered that the neural map on the neocortex between the genitalia and the nipples are contiguous and overlapping.  But it turns out, that the very same areas also map for the penis and nipples in males.  Thus, the maps are all in the same place on the sensory cortex.  Both men and women have reported that nipple simulation adds to sexual arousal.  This suggests that this is NOT very sexually dimorphic and is homologous between the sexes.

However, hypothesis were meant to be tested and there is a new paper from Case, et al. that deals with FtM transmen and the possibility of anomalous neurological findings regarding somatic representation.

But before I discus that aspect of the study, I have to share a pet peeve of mine that this paper is guilty of.  It peeves me when I see paper after paper by authors making reference to earlier papers that have clearly been shown to not support a given thesis, especially if those earlier refuted papers are their own.  For example, Swaab’s later papers keep referencing his earlier one regarding transsexuals and BSTc as though that study still had any validity regarding transsexual etiology.  As a reminder, it was Swaab himself that proved it didn’t… but you would never know that from his later papers which keep referring to it as though it did.  In this new paper that also includes Ramachandran as a co-author it references his earlier paper regarding phantom penises as though it supported the notion that MTF transwomen experience fewer of them than control men with penectomies.  But as I mentioned earlier, Lawrence demolished that paper showing that it showed no such thing, not passing even the simplest statistical ‘sniff test’ while I showed not only theoretical problems with the notion but that his purported controls did not qualify as such.  I can forgive not having read my blog, but not of ignoring Lawrence’s reply published in the same journal as the original paper.  My pet peeve is that authors of papers, when they make these references without also referencing those later papers that cast their conclusions into doubt, are guilty of the worst sin of bad science, cherry picking.

Further, the Case paper references xenomelia and observes that this may be similar to transgender, but ascribes it to somatic mapping issues while failing to note that we have another name for xenomelia, “apotemnophilia”, the erotic desire to be an amputee and how that desire arises out of an Erotic Target Location Error (ETLE) for the primary erotic target of amputees.  The authors thus sweep the well documented erotic motivations of both amputation “wannabees” and of autogynephilic transwomen under the rug in order to further their thesis of transgender as a brain mapping issue alone.

But for the moment, lets put these transgressions aside and look at the actual study.  Actually… not much to say about it.  They noted that FtM’s seem to have a reduced somatic awareness of their pre-top-surgery chests as shown by functional brain scans.  And although the authors offer a nod to the notion that their higher level conscious aversion to their breasts, i.e. somatic gender dysphoria, might mean that they repress awareness of touch sensations that announced that they have breasts, they bend over backwards to posit that the direction of causality is reversed.

Ummm… No.

That would mean that non-transmen would also have to have less awareness of their chests… and that has never been noted to happen.

All in all, this paper has interesting details on how psychophysical experiments can be conducted using brain scanning, a topic that is very much of interest to me as one whose career has been in applied psychophysics.  It also discloses sexually dimorphic differences in white matter distribution in parts of the brain in which the FtM subjects differed from female controls, thus adding to the growing pool of data that show that gynephilic transmen are, like androphilic transwomen, gender atypical in brain development.  But it does not show any convincing data for a somato-sensory brain map issue as being causitive of transsexuality.

Further Reading:

Essay on phantom penises

Essay on xenomelia / apotemnophilia and its relationship to autogynephilia

References:

Case, et al., “Altered White Matter and Sensory Response to Bodily Sensation in Female-to-Male Transgender Individuals” (2017) Archives of Sexual Behavior
https://link.springer.com/article/10.1007/s10508-016-0850-z

 

Comments Off on Brain Maps…

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

Reference:

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

Comments Off on An Issue Whose Time Has Come:

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, and other early androphilic transactivists, as “mocking women” at the 1973 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.

Article on Gender Difference by Olivia Goldhill

References:

Pasterski, V., “Fetal Androgens and Human Sexual Orientation: Searching for the Elusive Link”, (2017) Archives of Sexual Behavior
https://link.springer.com/article/10.1007/s10508-017-1021-6

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
http://www.sciencedirect.com/science/article/pii/S0018506X15000033#f0005

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

 

Comments Off on Because Boys Must Be Boys…

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 populations 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.

Addendum 7/17/2019:

We now have a replication of this study which, as the authors put it,

“Our results corroborate the original study (with a comparable if somewhat smaller effect size)…”

There effect size was still very large at D=2.10 on average in the English speaking world.

Further Reading:

Essay on Sexually Dimorphic Brain Mosaic

Essay on Sexually Dimorphic Motor Behaviors

Reference:

Guidice, et Al, “The Distance Between Mars and Venus: Measuring Global Sex Differences In Personality”
http://dx.doi.org/10.1371/journal.pone.0029265

Kaiser, T., et al, “Global Sex Differences in Personality: Replication with an Open Online Dataset” (2019) Journal of Personality
https://www.researchgate.net/publication/334279951_Global_Sex_Differences_in_Personality_Replication_with_an_Open_Online_Dataset

Comments Off on Mars and Venus in Conjunction…

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

Reference:

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

 

Comments Off on Pink and Blue…

Brainstorm

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.

References:

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

 

Comments Off on Brainstorm