Sex differences in human functional brain organization | Hacker News Reader

Sex differences in human functional brain organization

pnas.org

61 pointsgmays15 comments

Unfortunately people make bad conclusions from these kinds of research. Does sex differences exist in the brain? Yes. Should we ban women from jobs for it? No. One should always directly check who does the work best when hiring and avoid using crappy predictors like these. But people will use AI lottery systems for hiring anyway.

I wish brain imaging could answer why this is such a hot topic politically.

Times like this, just sit back pop some popcorn and watch the world go by.

article about the paper: https://med.stanford.edu/news/all-news/2024/02/men-women-bra...

"When the researchers tested the model on around 1,500 brain scans, it could almost always tell if the scan came from a woman or a man."

It's pretty cool to see blackbox models derive reliable signals from basically raw data. However, the results don't really imply sex differences are biological in nature if I'm reading correctly. Being raised male/female probably has some profound impacts on the brain (these were adult brains). I bet a similar methodology would be able to tell who played American football growing up...

This is an important note. Also, even when we are able to find physical variations in brains, that doesn't necessarily lead to any useful conclusions about how the brain works.

For example, male brains tend to be larger than female brains, but the only thing this seems to be correlated with is head size - it doesn't seem like larger brains make you more intelligent or are associated with particular traits.

I wonder how much of brain size is just blood.

Well, akshually...

A major male:female difference relates to hippocampal volume, with large and robust performance differences in hippocampal dependent tasks between the sexes across mammalian species, inc humans. In this space you generally see the vole studies, where the monogamous prairie vole has a smaller HC than the hustler meadow vole. The going theory is most (97%) of mammalian species are not monogamous, thus the males needs to know where his ladies are at, which requires more spatial memory capacity ergo larger HC.

Curiously across species hippocampal function is boosted in post-partem females compared to females without pups/kids, suggesting an evolutionary adaption perhaps.

Anyway, this isn't my niche area of neuroscience so the above is mainly quoted from lectures I attended a few years back. But this paper seems to give an adequate overview; https://www.nature.com/articles/s41386-018-0208-4

No. It is pretty well known that hormones have a significant impact in brain development, and it is pretty well known that sex has a significant impact in hormone balances and regulation.

Brain structure changes even during the menstrual cycle, and before or after pregnancy [1].

[1] https://karger.com/nen/article/111/3/183/220637/Shaping-of-t...

This is tortured reasoning. Or worse, deliberately misleading phrasing on your part.

Let's say that some unspecified statistical technique found two distinct clusters from some given raw data. These two clusters almost exactly line up with another set of clusters, and the reason for that another set of clustering is Z.

Implying that the first set isn't because of Z but it's probably all a confounder is... technically true, but extremely misleading for just about any and all sensemaking that we do.

If we applied this level of epistemic caution to anything at all, we would never pull conclusions about anything ever.

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I'll say the quite part out loud. Blank slatists and their political ilk are not this careful about statistical inferences when it aligns with their preconceptions.

*quiet

Man, this horse has been dead for decades. Stop flogging it.

Male and female brains differ, subtly but robustly and testably, along a variety of axes. The notion that these differences might be down to socialization was never motivated by science, but rather by the fear that such differences justified sexism. This is 60s era, second wave feminism politics and it's been roundly debunked again and again and again (look up David Reimer for a particularly gruesome case study). It's 2024 - can we please accept as a society that people can be different without being superior or inferior, and move on?

https://en.wikipedia.org/wiki/David_Reimer

> It's 2024 - can we please accept as a society that people can be different without being superior or inferior

The existence of difference necessarily means the possibility of superiority or inferiority in certain contexts. The task of social philosophy is accepting that men and women can be morally equal while being different and, on average, better at some things and worse at other things. For example, our moral philosophy will probably have to come to terms with the overrepresentation of men among both geniuses and criminals.

The corollary to that is why modern “diversity” ideology is a step backward. Positing that the races are different, but those differences are all positive ones, is an explosively dangerous idea. Because if the former is true—and I’m not saying it is, and I sincerely hope it’s not—the latter is just wishful thinking. Because if meaningful differences exist, those differences are probably going to be pro-adaptive in some cases and maladaptive in others.

whoa, lots of negative reactions to a pretty mundane comment I made about the science of it all. It's overwhelmingly likely, from other studies, that brains differ, sure. But, the AI derived signal mentioned in this study might not be picking up on that? In fact, it's hard to conclude as such from the experiment run simply because it was run on adults. Run it on infants to control for that confounding factor.

It kind of seems like you are being unscientific and politically motivated.

Yeah, I've never been particularly committed to whether or not brains differ by sex either way, so I don't have a huge horse in this race, but I will say that people that are very committed to biological sex differences in brains seem way too cavilier in how they dismiss the idea that these differences in brains might be the result of living as a certain assigned gender, instead of being differences that were there since birth, considering that we know that the brain changes and adapts fairly drastically to consistent habits and modes of living and so on, due to neuroplasticity. We see this sort of dismissive attitude in the very responses to you, which essentially dismiss your concerns with there being confounding factors out of hand for, in most cases, very poorly argued reasons, mostly to do with the fact that they want to draw a quicker conclusions and don't want to be careful, and so are fine with ignoring a possible confounder in the data that is being analyzed.

The only really good arguments against sex differences in brains being a result of socialization are the David Reimer case proving the gender identity isn't mutable, which might indicate ingrained sex differences in brains as an explanation for that immutability, and studies on trans brains (which tend to align more with the average brains of their desired gender), which is why I'm ambivalent.

On the other hand, the largest meta-analysis regarding sex differences in brains ever performed, using every study on the subject from the past 30 years, failed to find robust sex differences in brains: https://www.sciencedirect.com/science/article/pii/S014976342...

> Abstract: With the explosion of neuroimaging, differences between male and female brains have been exhaustively analyzed. Here we synthesize three decades of human MRI and postmortem data, emphasizing meta-analyses and other large studies, which collectively reveal few reliable sex/gender differences and a history of unreplicated claims. Males’ brains are larger than females’ from birth, stabilizing around 11 % in adults. This size difference accounts for other reproducible findings: higher white/gray matter ratio, intra- versus interhemispheric connectivity, and regional cortical and subcortical volumes in males. But when structural and lateralization differences are present independent of size, sex/gender explains only about 1% of total variance. Connectome differences and multivariate sex/gender prediction are largely based on brain size, and perform poorly across diverse populations. Task-based fMRI has especially failed to find reproducible activation differences between men and women in verbal, spatial or emotion processing due to high rates of false discovery. Overall, male/female brain differences appear trivial and population-specific. The human brain is not “sexually dimorphic.”

I was unable to read the particular methodology and findings of the article for this threat because I can't find it on scihub, and don't have institutional access to through my university, but I suspect that it would fall the foul of the exact sort of problems the above quote is talking about: that the differences it is finding aren't consistent across different populations, or can be more explained by brain size than anything else, and that's what it's picking up on, or something to that effect. In any case I'm more inclined to trust the gigantic meta-analysis than I am an individual study on a subject like this one where failures to replicate and spurious correlations are fairly common.

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