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Comment by jdthedisciple | Hacker News Reader

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The amount of gray and white matter that the brain has is very much a combination of nature and nurture, as shown by the study on London cab drivers who grew more gray matter in the parts of their brain related to navigation while they were learning to navigate the streets of the city.

So a study showing a difference in gray or white matter between men and women does not immediately prove that this difference has to be due to a biological sex difference, since social gender roles can directly influence this. What makes it even harder is that it would be highly unlikely that any research in this topic can control for all the differences in how men and women lead their daily lives.

Anyway, I'm not criticizing the study cited, but just be careful that to not draw any conclusions about why those brains ended up the way they were from it.

This post has skill issues. The cab driver study has no bearing on a sex difference study. The subject groups are intentionally too different. One cannot port a conclusion from it to the other study. Only as a theme in a hypothesis. Ergo, you can not say that a study that showed a difference in gender brain matter "does not immediately prove" the conclusion due to the cab driver study. It may immediately prove, and it may not. But the reason that it would not is not the cab driver study. The reason would be other aspects of the gender study. Such aspects, like deficiencies in study design, should be in the discussion regardless of the cab driver study. But the real issue is that "immediately prove" is simply unscientific language that should be revised. You're also asking everyone to accept that cross-gender nurture, all other variables accounted for and including "gender role" volunteerism, is definitely the deciding factor. Sorry. And I say that as someone who could care less if my opposite gender has a brain that has 3x "better" architecture according to any study.

Even if, for the sake of argument, the amount of gray matter was 100% nurture, that would show that men for some reason pursue particularly those activities which cause them to end up with 7x more GM on average.

That would still be a very relevant (and curious) finding that would support my argument, given the correlation between GM and Autism, do I see that right?

"useful for what most men do in life" - What are you referring to here? Because my answer to that would be just going through the motions and not thinking very much about anything, like most women too ("most men" is the bottom half of the bell curve plus a few more).

Pursuing professions and passions to do with things rather than people, and in particular with abstract and logical thinking, such as mathematics, technology but even philosophy and musical composition. Generally! (Obv. it's normal distributions all the way down, though with different centers between male and female)

For more fascinating insights on how his starts at birth, see this enlightening classic lecture which is an absolute must watch on this topic:

"Autism and the male brain" [https://www.youtube.com/watch?v=PjE_yaJjXE8]

> Pursuing professions and passions to do with things rather than people

Yes, when dealing with another person you have 2x the amount of gray matter at your disposal compared to dealing with things.

Not sure I quite get what you're saying, is that another scientific finding or a sarcastic remark?

It simply means that you have your own gray matter plus the gray matter of the other person.

Well, apparently only if you are of the same sex as the other person, otherwise the ratio would differ quite a bit..

Lol, most men are barely scraping by and thinking what to eat. Even in richer countries like US or Poland only like top 5% would partake in such activities like you described. On average men do more manual labour that required no abstract thinkng than women.

Yeah you live in a bubble

That’s obviously not true, men don’t have 7x more grey matter.

> In general, men have approximately 6.5 times the amount of gray matter related to general intelligence than women, and women have nearly 10 times the amount of white matter related to intelligence than men. Gray matter represents information processing centers in the brain, and white matter represents the networking of – or connections between – these processing centers.

https://www.sciencedaily.com/releases/2005/01/050121100142.h...

https://www.sciencedaily.com/releases/2021/03/210325115316.h...

> finds that size is the only clear-cut difference between male and female brains. Women's brains are about 11% smaller than men's, in proportion to their body size.

> "This means that the brain differences between large- and small-headed men are as great as the brain differences between the average man and woman," Dr. Eliot said. "And importantly, none of these size-related differences can account for familiar behavioral differences between men and women, such as empathy or spatial skills."

> This means that the brain differences between large- and small-headed men are as great

Well, kind of like a shorter male is still shorter than a taller male yet males are taller than females on average ... which makes it a bit of a 'duh' assessment. Obviously these are distributions.

> And importantly, none of these size-related differences can account for familiar behavioral differences between men and women, such as empathy or spatial skills.

That's a rather unscientific assertion and certainly false, besides the fact that it doesn't even seem to follow from the study itself.

If more gray matter by itself already explains autism, then certainly the gray matter and brain size differences between the sexes must account at least in part for similar cognitive and behavioral differences between the sexes.

The key part here is "related to general intelligence" (not sure how they measured that as I haven't read the whole study). They obviously don't have 6.5 times more gray matter as a whole.

What do you mean by 'obviously' here? How precisely has that manifested to you in such obvious manner? Genuinely curious since you seem to take that as a given.

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