Sex brain differences

[Albadross]

I've read/listened to just about everything Prof Robert Sapolsky has ever said, including an entire year's worth of his human evolutionary biology lectures at Harvard. I just went back to remind myself of what he said about homosexuality/transexuals and found it quite interesting in terms of conversations we have here so I wanted your thoughts.

He does sort of use gender/sex interchangeably in this video, but doesn't refer to transgender at all in this (I'm not sure what year this is mind you)

What's really key is that he mentions neurobiology of lesbians matches straight men, and vice versa with gay men matching straight women. He also says that brains have one neuron that is reliably bigger in men, and that transsexuals match the opposite sex to the one they had at birth. I'm not sure if there's been any further research to challenge this so please chip in.

My views on the transgender debate are more around the lack of understanding of what the experience of being a woman is like, and I think it's very problematic that women's spaces are being encroached upon and our rights pushed to the back of the queue again. I also share people's concerns about transitioning children and how we can really tell who has genuine dysphoria because of the huge number of factors at play, but could we not use the differences in the brain he talks about from about 3:30 in the video? Granted I have no idea if you need to cut up the brain to actually see this difference!

He said this in a written article

This is the transgendered world, and some intriguing science hints at its neurobiological bases. There are a number of places in the human brain that are “sexually dimorphic” (where the size, structure, function, and/or chemical makeup of the area differ by sex). The differences aren’t big enough so that you could identify someone’s sex just by knowing the size of one of those regions.

Caitlyn Jenner and Our Cognitive Dissonance - Issue 28: 2050 - Nautilus
m.nautil.us/issue/28/2050/caitlyn-jenner-and-our-cognitive-dissonance

He seemed to be in that lecture tending towards the idea one can determine sex by just looking at a brain.

I may of course have completely misinterpreted the article and the lecture.

No one can tell the race of a brain by just looking at it in a jar, nor can they tell the sex of a brain by looking at it in a jar.

These studies are not scientific as they are not double blind trials. As they are done on live humans they are subject to all sorts of bias. Simply, the conclusions are biased (and a complete waste of time and money).

Idk much about this sort of thing but I do wonder why people seem so obsessed with trying to prove sex differences in the brain....what good can come of it?

The study of the brain is fascinating.

Do remember the repeated studies which show distinct differences between London black cabbies and the general population, and how these are currently) held to be indicative of the brain's plasticity - ie how you use it actually shapes it.

So there may well be differences, but these may well be a result of life experiences not some inborn life-path predictor.

London cabbies have a larger part in their brain. Also think piano tuners have a part that is larger than average.

I ate,

One positive benefit of studying sex brain differences is effectively targeting drugs. This is quite important and, in animal models, there are clearly different responses to therapeutic drugs in males and females.

Another, if the differences imply different learning modalities, is educating both boys and girls as effectively as possible.

Finally, it could contribute (positively) to the whole trans debate.

There are medical researchers who are discouraged from doing this type of research due to its sensitivity.

On the other hand, Larry, one good reason for being jumpy about this is that there is an enormously long track record of researchers, from Victorian times onwards, looking for brain sex differences and then using spurious as a justification for treating men and women differently (women can't do medical degrees, for instance...) that makes most women understandably wary and want to look at this sort of research very carefully. Educate men and women differently? That's the sort of reasoning that led my school, back in the 70s, to make biology compulsory as the girly science, thus eating up time I could have spent on a language or history, because (as a physicist) I needed to do physics and chemistry.

The last brain differences paper I read in any detail, I was shocked it made it through peer review. It was one of those "density of a particular type of neurone in a particular region of the brain" papers. The sample sizes were tiny - about 20 each of men and women who identified as men and women, about 5 to 10 transwomen and transmen. The other thing that leapt out was that the differences they claimed to have found relied on samples which looked incredibly similar except for one outlier in the male group (which made me think "you need a much bigger sample size") and two samples (one transwoman, one woman) with no - that's nada, zilch, zero - neurones of the relevant type at all (which made me think "blatant error with your tissue sample techniques - did you make any attempt at all to quality-control your data before doing your statistical analysis?")

And as far as I can see, a lot of the research in this area routinely conflates sample statistics and population statistics. They quote T values as if this were a measure of something interesting at population level whereas in fact it is a minimum condition on whether your sample is likely to be a representative sample of the population at large, while not discussing d values (how different the two populations are).

Also, as IC points out, they entirely ignore brain plasticity. Even if you measure a difference in adult brains, there's no way of telling whether this is down to nature or nurture, and to then design education policy when it could well be down to nurture, thus reinforcing socially driven gender differences still further, strikes me as downright unethical.

That's the sort of reasoning that led my school, back in the 70s, to make biology compulsory as the girly science, thus eating up time I could have spent on a language or history, because (as a physicist) I needed to do physics and chemistry

In England and Wales? The only compulsory subjects we had in Scotland in the 70s , and only at Ordinary Grade, not Higher, were English, Maths and Arithmetic.

Mostly,

Your post is a good reason for high quality research to be done. The fact that there is so little recent research on this is that it cannot be funded because the researchers (and those who fund it) are attacked.

Let the research be done and the results found one way or the other. They can then be used to help both sexes attain their potential.

Mostly,

Incidentally the research I read last concerned different responses of male and female rat brains to certain drugs. I suspect that did not ignore neuroplasticity.

Yes Lass. Individual schools can make whatever subjects they fancy compulsory, on top of the national curriculum/curriculum for excellence. They still do it now.

There's an increasing demand for sex based research, actually. Hopefully, it will help dismiss myths or show differences that can be addressed to help both sexes.

The main problem is that most male or female characteristics are not black or white and it's easy to have confounding with gender.

I agree Mostly, the statistical gymnastics undertaken in pretty much every published piece of research on the subject are absurd, the extrapolations are nebulous at best. Yours and IC's points about neuroplasticity are also pertinent.

An example:

www.womenshealth.northwestern.edu/blog/nih-bolsters-sex-based-research

There's no doubt that there are anatomical and physiological differences in males and females that mean that sex based clinical and pre-clinical trials are an excellent idea, however, I thought we were discussing the concept of "brain sex" here. My apologies for getting that wrong.

It was just an example of more funding and interest in sex based research. From a quick Google
I didn't look specifically for brain research.

Although, brains are body parts, not ethereal entities. And their functioning is based on biology.

I've posted this picture before, but I think it's an important one. d is (caveat - may be more complex for some distributions) given by
d= mean1 mean2 / sqrt( sd_1 sd2)
and is a measure of how much two populations overlap (or fail to overlap) by.

You can see from the first picture that large d values mean less overlap.

The second picture is the probability distributions for one of the most obviously sexually dimporphic characteristics in humans, height. You can see that even for this, if all you were told about a person was, say, that their height was 5'5", while you would be right in making an educated guess that they were much more likely to be female than male, you would not want to bet your mortgage on it. And that's for one of the most obviously sexually dimorphic characteristics.

Lise Elliott (neuroscientist whose specialisation is brain plasticity in early childhood) has an excellent discussion of this in her book Pink Brain, Blue Brain (which I would really recommend to anyone who liked Fine's Delusions of Gender). Even leaving aside the issue of brain plasticity and nurture (which Fine is excellent on), insofar as we can measure cognitive differences between the sexes in ways which are statistically significant and correct for confounding factors (e.g. average age of reaching a particular reading level, performance in maths tests at age 7), in the rare experiments where differences have been found, the differences are tiny - d-values below 0.5.

That's the top left panel in picture one - such enormous overlap that basing education policy on such a difference, i.e. seeking to educate boys and girls differently, would be crazy and dangerous, and a huge number of girls (and boys) would be disadvantaged by such an approach. The more important message surely is to accept huge variability within the overall population as a whole, and allow for those differences in thinking about teaching methods.

(Lass - this was in England, and wasn't a blanket thing, it was just the particular school I went to. But my primary school for eg didn't let girls do woodwork, and talking to other women of my age who went through the English educational system, my experience seems not to be unusual.)

I take it pink represents females and blue represents male in those graphs? Because if it is, then that is bias right there.

You can only 100% discern sex from a human/mammal skeleton by looking at the pelvis, if it exists and if it is post pubertal. There are some differences in the skull, chin, head ridges, but this isn't definitive, also post pubertal. Pre pubertal skeletons are the same.

You cannot of course discern gender.

Just wanted to say thanks, M0stly - I've struggled to understand the significance of d values when I've previously got in a debate with a believer in brain sex. You've just explained it perfectly and now I get it. I'll be better equipped next time!

I had understood that research into brain sex was actually pretty easy to get funding for these days, comparatively. It's a hot topic. And damn right it always makes women twitchy, given the history.

It's interesting that he made such a point of it - I respect him enormously and it can be hard to be objective when in general you think someone's work is important. It does seem odd that he would've been fooled by a study with too small a sample size though.

Does anyone know how they would go about finding out the length of the neurons he refers to?

Thanks larry, I never thought about medications but that makes sense. I'm at bit wary about the targeting education differently thing though...makes me think of Borat

If anyone has any easy to understand links on this subject I'd be grateful .

One positive benefit of studying sex brain differences is effectively targeting drugs. This is quite important and, in animal models, there are clearly different responses to therapeutic drugs in males and females

Pain medication could be an area where there is a difference.
For too long clinical trials have been performed on white men and an assumption has been made that other populations will respond in the exactly the same way.

It is mostly post pubertal males who apply to the last stages of a drug trial that is to be used as a pan sexual drug. Unless it is designed for females. In that case it is given to those who live in non western societies, mainly transitional pubertal females - those going through puberty. Both trials are marketed as a financial inducement.