brain sex
Sex beyond the genitalia: The human brain mosaic
“Under absolutely no internal consistency, ∼80% of “brains” showed substantial variability compared with 0.1% that showed internal consistency (Fig. S1E). A comparison of the ±5,000 simulated condition to the actual data, in which 6% of brains showed internal consistency and 35% showed substantial variability, suggests that noise cannot explain the pattern of results we obtained, because less noise is expected to account for the percent of internal consistency but more noise to account for the percent of substantial variability.
The lack of internal consistency in human brain and gender characteristics undermines the dimorphic view of human brain and behavior and calls for a shift in our conceptualization of the relations between sex and the brain.”
–> this study drew criticism for having standards of internal consistency that were too high and unrealistic, to which the researchers replied:
Reply to Del Giudice et al., Chekroud et al., and Rosenblatt: Do brains of females and males belong to two distinct populations?
“ Sex affects the brain, but the prevalence of mosaicism does not support the view that sex effects on the brain produce two distinct types of brains. Current data are not sufficient, however, to fully characterize the relations between sex and the brain (4). Such characterization is necessary for studying sex effects on the brain as well as for studying brain structure, function, and dysfunction in general (4). We hope future studies will soon fill in this gap.”
–> This guy wrote an article about how any study concluding that there are no significant brain differences between the sexes must have been subject to impartiality and bias, which is the natural conclusion you’d come to about a study created by women if you believe in the existence of the lady brain, the lovely ladies responded to this also:
Reaction to “Equal ≠ The Same: Sex Differences in the Human Brain”
“Thus, a critical point that is absent in Cahill’s article is that the effects of sex on the brain can be opposite under different conditions. That is, what is typical in one sex under some conditions may be typical in the other sex under other conditions. Moreover, the specific interactions between sex and other factors (environmental, developmental, genetic) are different for different brain regions, and are not necessarily stable over time. As a result, the brains of women and men each comprise a unique, ever-changing ‘mosaic’ of features, some of which may be more typical in males and some of which may be more typical in females.8Thus brains, in contrast to genitals, do not come in distinct, fixed male or female forms.”
Analysis of Human Brain Structure Reveals that the Brain “Types” Typical of Males Are Also Typical of Females, and Vice Versa
“We have recently discovered that most human brains are composed of unique mosaics of features, and concluded that human brains do not belong to two distinct types, “male” and “female,” and that one’s sex category provides very little information about the specific composition of one’s unique brain mosaic (Joel et al., 2015). The present study supports these conclusions by showing that even when biological relevance is ignored, the structure of human brains does not fit into two distinct types of brain, one typical of males and the other typical of females.”
There is no biological mechanism responsible for transgenderism, it’s entirely environmental.
Incorporating Sex As a Biological Variable in Neuropsychiatric Research: Where Are We Now and Where Should We Be?
“That sex effects may be context dependent also means that one cannot easily generalize from a single study to other conditions and other species.”
Sex Differences and Opposite Effects of Stress on Dendritic Spine Density in the Male Versus Female Hippocampus
“I realized that if certain areas of the brain could change from the typical ‘female form’ to the typical ‘male form’ under stress, there was no point in talking about the female brain and the male brain,” Joel told Haaretz (paywall).
Men and women are from Earth: Examining the latent structure of gender.
“Average differences between men and women are not under dispute, but the dimensionality of gender indicates that these differences are inappropriate for diagnosing gender-typical psychological variables on the basis of sex.”
Sex differences in the adult human brain: Evidence from 5,216 UK Biobank participants
“There were very small correlations between brain variables and the cognitive tests, and these associations did not differ by sex (consistent with a prior meta-analysis on thelink between brain volume and intelligence [49]). Mediation modelling suggested that, for verbal-numerical reasoning, a very large portion (up to 99%) of the modest sex difference was mediated by brain volumetric and surface area measures. Smaller fractions (up to 38%) of the modest link between sex and reaction time could be explained by volume or surface area.”
Basically, there are physiological differences between male and female brains but they don’t necessarily inform sexually disparate outcomes in terms of cognitive performance
From an article about the study:
“….there do appear to be many differences between male and female brains, but there’s also tons of overlap. The obvious question, when it comes to sex-based brain-structure differences, is whether they are the cause of behavioral differences. Differences alone don’t necessarily explain anything: If women are socialized to act differently than men from a very young age, this could lead to different sorts of brain structures, especially in a set of brains whose owners are all middle-aged or older.”
Beyond sex differences: new approaches for thinking about variation in brain structure and function
“ We argue that the existence of differences between the brains of males and females does not unravel the relations between sex and the brain nor is it sufficient to characterize a population of brains…given that sex interacts with other factors to affect the brain, sex effects on the brain must be understood as context-dependent, where context relates to the specific environmental, developmental and genetic conditions under which sex effects were assessed and under which the animals developed.“
The human hippocampus is not sexually-dimorphic: Meta-analysis of structural MRI volumes.
“We conducted the first meta-analysis of male-female difference in hippocampal volume (HCV) based on published MRI studies of healthy participants of all ages, to test whether the structure is reliably sexually dimorphic. Accordingly, studies reporting HCVs corrected for individual differences in TBV or ICV revealed no significant sex differences in left and right HCVs (Hedges’ g ranging from +0.011 to -0.206). In summary, we found that human males of all ages exhibit a larger HCV than females, but adjusting for individual differences in TBV or ICV results in no reliable sex difference. The frequent claim that women have a disproportionately larger hippocampus than men was not supported.”
to summarize: there are observed generalized differences between the brains of males and females HOWEVER they are inconsistent, sometimes contradictory, often exist only under specific testing conditions and are most likely the result of socialization, given that the brain is super plastic and responsive to its environment in terms of structure
a helpful insight from @smittywerbenjaegermannjensen:
“Not only are the trends in male/female behavior not absolute, but there’s no reason to believe that they are genetic or unchanging. Without these patterns being absolute, it’s easily attributed to the way we socialize our children from birth: categorically, but with varying severity. And being that the brain changes every time someone develops a skill, it’s likely that these trends are as impermanent as anything else considered to be ‘the brains wiring.’”
so then why are trans people sometimes found to have brain structures similar to that of the opposite sex, if brain sex isn’t real?
Transsexualism: A Different Viewpoint to Brain Changes
“we may predict that related brain changes result in human adaptation to specific sociocultural environments…He/she imagines himself/herself in his/her preferred gender identity rather than his/her biological sex, and thus tries to adapt his/her values, lifestyle and behaviors to his/her gender identity. Therefore, a subject with GD tries to experience life in his/her preferred gender identity and skews from his/her biological gender and normal culturally contextualized behaviors every day. Depending on how much the subject with GD persists in changing his/her gender (i.e., positive, neutral or negative transgenders) and the extent to which he/she has experienced gender identity, we will observe brain changes and, as a result, related culturally voluntary behaviors.
In general, an overview of brain morphometric and neural activity findings in transgenders demonstrates contradictory results, which cannot reflect masculinization or feminization of the transgenders’ brain"
the brain changes in response to everything from trauma to skill acquisition to socialization, and gender dysphoria is more than capable of creating this perceived similarity; if you’ve been raised to think of yourself as the opposite based on your tastes and preferences (or sexual orientation), your brain may (inconsistently) mirror that of the opposite sex. homosexual people are also often found to have “feminized” or “masculinized” brains, but gay men are not female and neither are trans identified males. it is also worth noting that homosexual and heterosexual transsexual males have different brains from each other, and heterosexual transsexual males brains do not differ along the male/female axis the way that homosexual transsexual males’ brains do, suggesting that “feminized” brain structures among MTFs are largely accounted for by homosexuality:
New MRI Studies Support the Blanchard Typology of Male-to-Female Transsexualism
“[T]he brains of both homosexual and heterosexual male-to-female transsexuals probably differ from the brains of typical heterosexual men, but in different ways. In homosexual male-to-female transsexuals, the difference does involve sex-dimorphic structures, and the nature of the difference is a shift in the female-typical direction. If there is any neuroanatomic intersexuality, it is in the homosexual group. In heterosexual male-to-female transsexuals, the difference may not involve sex-dimorphic structures at all, and the nature of the structural difference is not necessarily along the male–female dimension.”
remember that theory thats flying around about how testosterone exposure in utero can make people trans?
The Last Word on Fetal T
“In light of Jordan-Young’s meticulous synthesis, it’s hard to name any specific feature of male-typical or female-typical behavior that consistently matches up with prenatal T levels across several models of research.”
yup, that’s bullshit too!
Here are some studies that are often thrown around as “proof” of the existence of brain sex as it pertains to trans people who supposedly have the brains of the opposite sex, you’ll find that all of these studies:
have profound self-selection bias
were inconclusive in the sense that no trans male subject had a brain that was as “feminized” as the female subjects
were performed with subjects who have had varying exposure to cross-sex hormones (a confounding variable)
were performed with subjects who have experienced gendered socialization and sociocultural/environmental influences that are known to affect brain structures
Networks of the brain reflect the individual gender identity
—>Links to this study, they like to list these two separately but they’re the same:
White matter microstructure in female to male transsexuals before cross-sex hormonal treatment. A diffusion tensor imaging study
“ The examination revealed significant differences in the microstructure of the brain connections between male and female control subjects. Transgender persons took up a middle position between both genders. “
There’s no evidence that these people were born with brains aligned in any way with their identified sex, and that these results aren’t the result of environment. The average FTM subject in this study was 28, plenty of time for the brain to adapt and change, this doesn’t prove that neither dysphoria not transgenderism are caused by biological etiology. They did have higher fractional anisotropy levels than the test females, but they still weren’t as high as the test males, again they were in the middle and again this is inconclusive evidence because the brain is a plastic organ.
Transgender: Evidence on the biological nature of gender identity
“ According to the researchers the article does have some limitations due to the small numbers of individuals studied and therefore conclusions should be drawn with caution. “
Androgen receptor repeat length polymorphism associated with male-to-female transsexualism.
This was a study done between MTF males and cis males with no female controls, it doesn’t prove anything about trans males having similar brains to females. Having slightly feminized androgen receptors might make one more likely to experience dysphoria, but that doesn’t really contribute anything to the brain sex argument OR the argument that people are born with dysphoria because again, these subjects were not infants or even children. also, correlation is not the same as causation, who’s to say these males weren’t affected hormonally by these feminized androgen receptors in ways that caused them to be PERCEIVED as feminine, which then influenced their gender identity?
“We explored the specific hypothesis that male-to-female transsexualism is associated with gene variants responsible for undermasculinization and/or feminization.”
Those gene variants are fairly likely to have an effect on your sex characteristics, and cause you to be perceived as a particularly feminine male. Being perceived in such a way can certainly influence your gender identity. This is another case of the probable pattern of causation being reversed to suit an agenda.
And only one of the 3 genes showed a correlation.
Sex steroid-related genes and male-to-female transsexualism.
“Transsexuals differed from controls with respect to the mean length of the ERbeta repeat polymorphism, but not with respect to the length of the other two studied polymorphisms. Given the small number of transsexuals in the study, the results should be interpreted with the utmost caution.”
Being born with an increased capacity for experiencing dysphoria is not the same as being born with dysphoria, and experiencing dysphoria does not make you a woman. Correlation doesn’t equal causation, and causation has yet to be established with any of these studies.
Sexual differentiation of the human brain: relevance for gender identity, transsexualism and sexual orientation.
“We have found a female-sized nucleus in the sexually dimorphic central subdivision of the bed nucleus of the stria terminalis (BSTc) in male-to-female
transsexuals. Much to our surprise, however, the sex difference in BSTc volume did not become overt until adulthood.”
The CYP17 MspA1 Polymorphism and the Gender Dysphoria.
A polymorphism of the CYP17 gene related to sex steroid metabolism is associated with female-to-male but not male-to-female transsexualism.
Click-evoked otoacoustic emissions in children and adolescents with gender identity disorder.
Sample size here was fairly small, 24 boys and 23 girls. Given that 63% of children outgrow their GID/GD I’m not sure what this proves, and the causation pattern isn’t clear, if their androgen exposure affected their ear canals then maybe it affected them in other ways that caused them to be PERCEIVED as their identified sex, which influenced their identity. Or maybe androgen exposure increases the risk of one of the many comorbid psychiatric conditions often seen in gender nonconforming children, which makes them more susceptible to experiencing dysphoria.
Increased Cortical Thickness in Male-to-Female Transsexualism.
This is a study comparing MTFs to cis males with no female control. Sample size was small (24) and as I’ve mentioned, neuroanatomical variables like cortical thickness can be influenced by environment.
Sex dimorphism of the brain in male-to-female transsexuals.
“The present data do not support the notion that brains of MtF-TR are feminized.”
Regional gray matter variation in male-to-female transsexualism.
“Results revealed that regional gray matter variation in MTF transsexuals is more similar to the pattern found in men than in women. However, MTF transsexuals show a significantly larger volume of regional gray matter in the right putamen compared to men. ”
Male-to-female transsexuals show sex-atypical hypothalamus activation when smelling odorous steroids.
Sample size was 12, so that’s strike one. Also, neurological activity patterns can be influenced by environmental factors. Even with the small sample size the MTFs “occupied a moderate position” between so-called “male” and “female “ hypothalamus activation.
Male-to-Female Transsexuals Have Female Neuron Numbers in a Limbic Nucleus
First off, this study was done 20 years ago with 7 test subjects.
Second of all, this study did not see any similarities in neuron numbers between MTFs and females until early adulthood, the earliest being 22 years old, which supports my point that any structural similarities are the result of environmental factors. the people in this study claimed to be dysphoric well before they were 22; if they were feeling dysphoric BEFORE their neurons changed, than how could the neurons be causing the dysphoria?
Third: these MTF subjects were being treated with hormone therapy, which can be shown to cause neuro-structural changes, the subjects probably had neuron levels similar to females because of the hormones they were on
A Review of the Status of Brain Structure Research in Transsexualism.
This study was done on homosexual transsexuals. Homosexuality does have neuroanatomical indicators and this study was probably picking up on that. Sexual orientation is coded for by the brain, gender is not, it’s a social construct.
A sex difference in the hypothalamic uncinate nucleus: relationship to gender identity.
Only one of the subjects in this study hadn’t had any kind of hormone therapy that could have confounded results:
“The untreated male gender dysphoric person (S7), who took no hormones and kept transsexual feelings under wraps, appeared to have a large INAH3 volume—in the male range—but a female number of neurons.”
Again, that’s pretty inconclusive, he aligned with males along one measure and females along another measure, and again the brain is super plastic. This study basically had a sample size of one.
Transgender brains are more like their desired gender from an early age
This was done on hypothalamic responses in adolescents and again, by the time they got to that age they would have experienced environmental neural influences that could have changed their brain structure/activity patterns, even without hormones, that proves literally nothing.
This study shows that the hypothalamus and hypothalamic responses are neuroplastic and can change based on stress and early childhood experiences
This study shows that the brain as a whole remains plastic throughout ones lifetime
Anatomical and Functional Findings in Female-to-Male Transsexuals: Testing a New Hypothesis.
“Distinct structural and functional pattern in the own-body image network may represent biological markers for the dysphoric own-body perception in transgender individuals.”
This is speculation, there’s no evidence that this pattern isn’t caused by environment. Even if this pattern does have biological etiology, that doesn’t prove that the brain codes for gender in ways that aren’t contingent on socialization, or that gender identity is an innate characteristic.
“…in regions with reported anatomical sex differences among the controls, FtM-TR followed patterns of the gender assigned at their birth.”
This is a great example of how inconsistent these studies are, sometimes they have slight similarities with their identified sex (again, the strongest puts them at halfway between male and female controls) and sometimes they don’t.
Male-typical visuospatial functioning in gynephilic girls with gender dysphoria - organizational and activational effects of testosterone.
“Girls with GD before testosterone treatment differed significantly in frontal brain activation from the control girls (pFWE = 0.034), suggesting a masculinization of brain structures associated with visuospatial cognitive functions.”
Again, these subjects were homosexual, that’s a confounding variable. These differences can be caused by environment, girls who are diagnosed with gender dysphoria are gender nonconforming and have been raised to believe that the things that they enjoy are only natural for males. There’s no evidence they were born with “masculinization of brain structures associated with visuospatial cognitive functions,” or that those structures would have developed to become “masculinized” without the child being exposed to gendered socialization.
Structural Connectivity Networks of Transgender People
“Specifically, our data suggest that network parameters may reflect unique characteristics of transgender patients, whereas local physiological aspects have been shown to represent the transition from the biological sex to the actual gender identity.”
Trans identified people have a lot of things in common with each other outside of being trans identified, including high co-morbidity of other psychiatric disorders and similar general life experiences. This doesn’t prove that gender identity exists as an innate characteristic. Think about it, if trans people have unique characteristics that are not seen in their “cis” counterparts, doesn’t that suggest that those “cis” people don’t have gender identities and only trans people do? And that those gender identities are just the manifestation of dysphoria? The idea that every single person has a gender identity is not supported by only trans people having these characteristics.
A sex difference in the human brain and its relation to transsexuality.
This study is from 1995.
“A female-sized BSTc was found in male-to-female transsexuals.”
The stria terminalis is a plastic structure, there’s no evidence the subjects were born with a “female-sized BSTc” and, there’s also no evidence that male and female brains are differentiated at birth in the first place. What we consider to be a “female-sized BSTc” could very well be “the size that your BTSc tends to be if you are raised to consider your tastes and preferences to be female”
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@discoursedrome
Uh this does mean that this discussion is split across like three distinct threads now but ~oh well~
Sorry, that’s my fault, for the whole “...and another thing!” style of posting. I think our disagreements here may be irreconcilable, but I think they’re worth explicating, so I’ll condense my specific responses in one post.
The extent to which the current level of trans acceptance is owed to piggybacking on the legitimacy of psychiatric medicine can’t be overstated.
This, I think, is where you and I diverge strongly. I think trans acceptance doesn’t need to rely on the legitimacy of psychiatry, any more than gay acceptance or the equality of woman, and probably shouldn’t try, given the fraught history of the supposed neutrality of medicine being used as a stick to hit people with. Where trans acceptance exists, and where it will come where it does not exist, is through the same basic mechanism as gay acceptance: it’s hard to consign trans people to the Hated Other when you know a bunch of them, they’re out, and the default message of society (conveyed through the law) is Trans People Aren’t Doing Anything Wrong. Medical acceptance is important for trans healthcare specifically, and to a greater degree than it might be for, say, gay men (who don’t need to be plagued by doctors who think Gay Bowel Syndrome is a real thing), but the difference between trans people and LGB people here is of degree and not kind.
doctors in general and psychiatrists in particular are guardians of social order and, in particular, gatekeepers of permissible abnormalities. ... and if that faith lapses then the result will either be that everything relying on psychiatry for legitimation becomes illegitimate, or that some other group ... steps into the breach and becomes the new source of legitimacy, despite having comparable problems in reality
I also don’t think this is true. I think the average view of the medical establishment sees them neither as a true and impartial priesthood or a suspect cabal colluding with Big Pharma for profit, but has a healthy mix of respect and skepticism. I know people whose view lies somewhere along that axis both of rather conservative and extremely leftist positions, so I also don’t think this differs much by political orientation either. If it were true, I think the social consensus on trans people would be changing much faster. To the extent it is true, it is one small, small contribution to a broad array of institutions whose opinions people factor in (to different degrees, depending on their upbringing and worldview) when internalizing for themselves what the range of permissible abnormalities is.
(I think the importance of medical acceptance is an empirical question, but one which would be very difficult to answer except through many surveys asking a bunch of people slight variations on a set of similar questions. I don’t know myself of any substantive data which might point toward one or the other model as lying closer to the truth, except the similar historical examples, which obviously I interpret as being in my favor. But you may disagree on their relevance or their interpretation.)
So it’s no surprise that the common narrative for homosexuality being reclassified as “not a mental illness” is that the original classification was a mistake, and it changed when people learned more about homosexuality. This is a total myth, though! ... Whether or not you classify homosexuality as a mental illness or not has a lot of influence on spin..., but nothing at all to do with the biological/psychological/medical/empirical reality of homosexuality. It’s that way with everything.
I agree. This is basic to the epistemology of medicine specifically, and all taxonomies generally.
I can’t overstate the extent to which society’s willingness to show compassion to people in difficult situations is dependent on their viewing those situations as external, unnatural and out of the subjects’ control. ... You can’t construct durable defenses that don’t rely on these things, at least not under the umbrella of a society that is alien to them.
But this I disagree with. One reason I beat that dead horse to a pulp about liberalism generally is that the humanist/Enlightenment/democratic/rights-based framework, however loose it is as a tendency, that we slap the label “liberalism” tends logically toward an equilibrium of tolerating greater individual diversity, and encouraging/being reinforced by social structures that are tolerant of greater individual diversity (like atomic individualism and moral therapeutic deism).
In more conservative spaces, where that liberal worldview which pervades society has to compete with brainspace with provincial xenophobia, “out of the subject’s control” is a line of argument that can smuggle in the logical consequences of the liberal-democratic worldview to yer dad (in Olly Thorn’s parlance) who otherwise feels icky about the gays and the blacks and the transgenders. In spaces where values of tolerance have less thin and rocky soil to grow in, it’s commensurately less necessary to use “but it’s not a choice!” as a justification for not being shitty to people who are different. You may have to use it with young children, but that’s about it.
I’d be interested to know if our respective attitudes on this point are the product either of the environments we were raised in or the environments we currently live in, though. This is the kind of thing for which one’s personal data set can be... heavily biased by the qualities of the people they’re surrounded with.
“Defining transgenderism in terms of gender dysphoria is the best!” which I definitely don’t believe; I’ve seen a lot worse definitions, but I’m not at all happy with that one, for roughly the usual reasons.
FWIW, I didn’t take that as your position, but I also struggled to articulate what rubbed me the wrong way without feeling like I was stereotyping you as having that position.
That said, here is what “gender dysphoria” has that “gender euphoria” or the combination of the two doesn’t: [list of attributes]
The importance of these attributes varies to the extent that one believes in the importance of trans legitimacy relying on medical legitimacy. Obviously there’s considerable difference between us on that point. One thing I do think “euphoria” conveys more aptly than “preference,” especially in informal discussions, is that it’s not dispassionate or remote from one’s deeply internal/spiritual processes, those aspects of the self which ache and yearn and struggle and weep, far away from any dispassionate process of logic or craven process of calculated self-interest. “Preference” speaks to me of statements like “I prefer a lighter room so I can read this book more easily,” but not more unconscious processes like “it’s December, and it’s been cloudy for three weeks, and I’m going to turn on every light in the house so the bleakness of crushing winter is replaced by the warm glow of cozy joy.”
So the use of the word can be important, because those distinctions in connotation color how these discussions unfold, especially with skeptics, and they’re really hard to pin down otherwise. A “mere preference” can be dismissed. A spiritual yearning (even if it’s for more light in the wintertime) that shoots through to the core of your being is harder to toss away, even rhetorically. In this particular online space we might admit that the word “preference” can subsume the latter meaning, because we’re used to a degree of technical and semantic precision, and to having the space to define our terms. Most everywhere else--at the Christmas dinnertable, on Twitter, in Whatsapp discussions with friends, in the pub, even often in academic essays--conversations don’t proceed on those terms, and the language you deploy has to utilize aesthetics in the pursuit of communicating truth.
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