How does someone end up identifying differently?

[meridannight]

You ask some interesting questions, but I don't have any answers for you. What is masculine or feminine can vary across culture, but I am of the mind that there's more to it than that.

That might be true, but I think this particular topic is about a person feeling being either masculine or feminine. Which is not at all the same as what is considered masculine or feminine in a society, (or even self-expression along the gender lines). One is an inner sense of self, another is an external set of identifying characteristics/traits. The former is always in the brain, the latter in the external world.

Since @meridannight is getting into the biology/chemistry stuff and clearly has a good understanding of it, I want to ask him if he's heard about the studies on gay and lesbian brains that show gay male brains tend to resemble straight female ones and lesbian brains tend to resemble straight male ones. I forget all the details about it - I think it was that, like women, gay men tend to have better brain development in communication I think?

I am going to try to answer this as best as I can without getting into complex research data and interpretation of raw material in the context of human experience. This is very very difficult to do, and all inferences have to be carefully made and considered.

Yes, I know of the study you mention. But be very careful with the statement ''gay male brains resemble straight female ones and lesbian brains resemble straight male ones''. That is, in fact, completely incorrect. It is a popularistic surface interpretation of research data without adequate comprehension of the scientific context that data is in. Stupid people will just latch on to such statements and another science myth will be born.

What the study was about, was studying sexually dimorphic structures and brain activation in men and women, homosexual and heterosexual. (It was run by Savic, Berglund, and Lindstrom, in 2006 or 2005). They looked at olfactory activation in the brain and correlated it to sexual orientation.

For the purposes of clarity I am not going to explain the pheromones used in the study or human olfactory sense either. All you need to know is that androstadienone (AND) is the pheromone secreted by men (in sweat) and estratetraenol (EST) secreted by women (urine), and humans appear to be able to sense them.

Here's the outline: upon exposure to AND the brains of heterosexual women were activated (in certain hypothalamic areas) whereas heterosexual men's brains were not. Exposure to EST activated adjacent areas in heterosexual men's brains, but not in women. In homosexual men, those areas were activated in response to AND but not EST, and in lesbians the same areas are activated by EST but not AND. In conclusion, the patterns of activation to human sex pheromones were similar in homosexual men and heterosexual women, and in heterosexual men and lesbian women. (This in itself should not be interpreted as proof or manifestation of sexuality).

The same scientists studied connectivity among the brain regions in heterosexual and homosexual men and women (2008). What they found was that in homosexual men and heterosexual women the left amygdala was strongly connected to the right amygdala, whereas in heterosexual men and lesbians the same connectivity was local (i.e. the left and right amygdala were not strongly connected). Amygdala is the region in the brain implicated in fear conditioning and other emotional responses.

Structurally the brains of homosexual men are similar to the brains of heterosexual men, and the brains of straight women to those of lesbians. Sexually dimorphic areas currently known in the human brain are:
--interstitial nucleus of the anterior hypothalamus (INAH3), larger in (heterosexual and homosexual) males.
--the bed nucleus of stria terminalis (BNST); it's larger in males (both homosexual and heterosexual) and small in women. This conforms for the transsexual population, male-to-female individuals had it the size comparable to women, and in female-to-male transsexual individuals it was the size comparable to males.

So, structurally, male brains are similar whether homosexual or heterosexual, and both are different from female brains. The connectivity between certain areas has been shown to share similarities between homosexual males and heterosexual females, and heterosexual men and lesbians. And it has been shown that the brains of homosexual men get activated upon exposure to male pheromones in a similar pattern that heterosexual females' brains do (which is not to say identically), which is hardly surprising given the fact that both are attracted to the same gender. Everything has a manifestation in the brain.

Homosexual male brains are structurally clearly different from female brains. What similarities there have been found in connectivity between the two have to take account of the underlying substrate of differences in structure. Which is all very very far from a conclusion of resemblance.


There is widespread sexual differentiation in the brains of males and females. The best image I could find on the net:




This is the size of the bed nucleus of stria terminalis (from left: heterosexual men, homosexual men, heterosexual women, male-to-female transsexuals):



(The 'BSTc' just denotes the central division of the nucleus).

If you're interested in more, the best way to search this topic is by the key technical term 'sexual dimorphism in the human brain'.


My principal source for the above:
Kandel et al, Principles of Neural Science, 5th ed., McGraw-Hill.

[TonyAndonuts]

^I understood, like, half of that, but it was still all very fascinating to read. Thanks! :biggrin:

[TonyAndonuts]

No research has so far been done on the brains of people who identify as neither gender (or something else entirely), so it's not really possible to say anything authoritative on that matter. (Personally, I think it's just a psychological identity crisis or a desire to be unique where this type of thing is stemming from. I do not consider non-binary gender identification as a genuine gender expression, since there are only two genders physiologically. But that is my informed opinion, for now. I have no scientific research to back it up).

Someone linked me to this article that talks about gender identity. It's kinda long, but an interesting read. It went over some of the stuff you talked about, but also goes over non-binary and bigender individuals, as well as the existence of third genders in different places. If you check it out, what do you guys think of it?

[Emiliano]

thank you for writing all that out [MENTION=21405]meridannight[/MENTION]. I'm a casual scientist, to put it nicely. I like reading the articles but I don't usually grasp the full point, so thanks for explaining it more for me. It's interesting stuff. And mind blowing what we do and do not know about ourselves.