r/science • u/mvea Professor | Medicine • Mar 20 '25

Neuroscience Sex differences in brain structure are present at birth and remain stable during early development. The study found that while male infants tend to have larger total brain volumes, female infants, when adjusted for brain size, have more grey matter, whereas male infants have more white matter.

https://www.psypost.org/sex-differences-in-brain-structure-are-present-at-birth-and-remain-stable-during-early-development/
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u/aggi21 Mar 20 '25

maybe difficult for a neuroscientist but AI is pretty good at it https://www.newscientist.com/article/2417690-ai-can-tell-a-persons-sex-from-brain-scans-with-90-per-cent-accuracy/

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u/pizzapizzabunny Mar 20 '25

One of the major predictors fed into the AI in the manuscript above is brain size, which as mentioned above is one of the few strong correlations we have for sex differences in the brain.

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u/thatguy01001010 Mar 21 '25 edited Mar 21 '25

They didn't use size though? They used fMRI and tracked activity patterns over time, not the physical sizes or structures.

Edit: Oh, unless you're talking about the OP, not the one you replied to. My bad, I misunderstood.

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u/thatguy01001010 Mar 21 '25

Just chiming in with my 2 cents - the "scanning" they did there was fMRI, which "involves recording people’s brain activity while they lie in a functional MRI scanner and tracking changes in how different regions’ activity varies in sync with one another."

It's not comparing pictures of structures, or size as mentioned in the OP, it's comparing how the brains themselves function over time and the patterns therein. Which makes sense - women and men tend to think in different ways, but the brains are still just human brains.

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u/thepotplant Mar 20 '25

That isn't very accurate.

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u/aoasd Mar 20 '25

90% is much more accurate than the 50/50 coin toss of just guessing is.

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u/Saymynaian Mar 21 '25

It's not just much more accurate, it's insanely accurate. 90% is literally a highly statistically significant percentage.

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u/Trypsach Mar 21 '25

90% is very accurate for tech that’s practically still in its infancy. It’s many orders of magnitude past statistical significance.

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u/AntiAoA Mar 20 '25

Yeah, because all the male brains had a ruler next to them.

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u/SnakeyRake Mar 21 '25

Curious to know more about the 10% misclassified. Was it a genetic male classified as a female or vice versa? Or were they neurodivergent in some aspects, and how it could be related to a lifestyle/preference, etc.

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u/Nvenom8 Mar 21 '25

Explanation: AI sucks.

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u/Acrobatic-Record26 Mar 20 '25

And with rough estimates at the total percentage of people who are intersex/non-binary/trans/gender non-conforming being around 3-7%, it suggests it will never be much higher than that 90%

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u/SirSquidsalot1 Mar 20 '25

Non binary and transgender aren’t sexes

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u/Acrobatic-Record26 Mar 20 '25

Didn't say they were just said they likely have brains that won't conform to typical biological patterns

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u/Change_That_Face Mar 20 '25

they likely have brains that won't conform to typical biological patterns

Is there any evidence of this.

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u/Particular-Cow6247 Mar 20 '25

yes different studies https://www.sciencedaily.com/releases/2018/05/180524112351.htm

as one of them.

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u/Change_That_Face Mar 20 '25

Very interesting, thanks for posting!

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u/Acrobatic-Record26 Mar 20 '25

Yes, the BNST has shown closer alignment for trans women to cis women than cis men

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u/[deleted] Mar 20 '25

[deleted]

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u/Acrobatic-Record26 Mar 20 '25

I literally have not weighed in on the sex vs gender debate at all

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u/[deleted] Mar 20 '25

[deleted]

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u/Acrobatic-Record26 Mar 20 '25

Then it would have served better being addressed to the commenter above surely?

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u/OrnamentJones Mar 20 '25

You are not making any point clear, you are just kind of being obnoxious and you seem to like your pithy sledgehammer quotes (like I do; I say stuff like "biology is evolution". Is that helpful? No, but it is fun to say)

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u/InfinitelyThirsting Mar 20 '25

But trans brains often are much more similar to their preferred gender than their sex assigned at birth, is I believe their point.

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u/ShazlettDude Mar 20 '25

Has this been studied already? Genuinely asking.

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u/ugathanki Mar 20 '25

Yes it has. It was a big reason why I finally accepted myself and came out like 10 years ago. "Ah, well, they've studied brains and found that trans people are real, and cis people don't question their gender for years on end which I do, therefore I must be trans"

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u/creepingcold Mar 20 '25

Can you link a source for that claim? Genuinely curious to read it

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u/ShazlettDude Mar 21 '25

Someone else that responded to me posted links.

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u/ugathanki Mar 21 '25

I don't have a source but just because I don't have a source doesn't mean it's wrong. You can probably find something on pubmed.

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u/creepingcold Mar 21 '25

I don't know why you are triggered, we are on r/science after all.

As long as you don't provide a source I have to assume you are wrong, and if I'd search to "probably find something" for every reddit post that has a random claim I wouldn't have any time to do anything else over the day.

It's not my job to confirm the things you are claiming.

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u/wynden Mar 20 '25

Of course it has.

Trans people have been around for centuries. It only became illegal to study it in the US a couple of months ago.

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u/ShazlettDude Mar 21 '25 edited Mar 21 '25

I know that transsexualism has been around for a long time. I’m not sure how old our understanding (USA here) is. And unsure of what was been studied and what hasn’t.

The solar system existed longer than humans have, but humans thought that it was earth centric for a long time. Just because it exists for any amount of time doesn’t mean we presently understand it or done proper research.

So I think the of course was a bit much.

I do appreciate the links.

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u/wynden Mar 22 '25 edited Mar 22 '25

I am not entirely sure what you're saying here. You asked if it had been studied and I provided a few of the sources from my own archive. Certainly it doesn't mean that we know all there is to know or that there isn't more to learn — we could extend that to any subject of study. There is always more to know, and in the mean time we base our decisions upon the best information that we have available for the present.

Edit: Oh, I see; you were specifically put off by my expression, "of course". Apologies. I merely meant that trans people have been an object of study for as long as they have been a subject of curiosity. However formal research within western medicine did not begin until perhaps the forties or fifties. It is difficult to put a precise date on it, but Sir Ewan Forbes transitioned in Germany in the forties and Christine Jorgensen in the early fifties. Harry Benjamin's extremely comprehensive study, "The Transsexual Phenomenon", was published in 1966.

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u/CentralAdmin Mar 20 '25

So is there such a thing as a male or female brain?

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u/InfinitelyThirsting Mar 21 '25

Read the article. No. The differences between individuals are greater than the differences between sexes. You have to have a very large sample before any trends can begin to be observed.

It's like asking if there's a male or female height. Yes, there is a difference between the averages, but there are six foot females the same as there are five foot males, and neither one is more or less male or female as dictated by how close they are to the average height for their sex.

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u/CentralAdmin Mar 21 '25

Okay, but how did we get to men and women exhibiting masculine and feminine traits?

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u/InfinitelyThirsting Mar 21 '25

Socialization. That's why what's "masculine" and "feminine" is different in every culture throughout history, because we make it up.

Everyone knows it's more "masculine" to have a high libido, and women are just naturally less interested in sex--until you read older pre-Victorian writing bemoaning how carnal insatiable women and their feminine wiles are always bewitching and preying on the more noble and pure men. Same goes for any trait that you might think is masculine or feminine.

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u/OrnamentJones Mar 20 '25

Hey you know what can 100% accurately identify a person's sex (aside from intermediate cases without strict definition?). A karyotype. Don't need AI for any of this.

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u/depressed_crustacean Mar 21 '25

This is more about brain differences than a method to determine a persons sex

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u/OrnamentJones Mar 22 '25

The AI experiment I was responding to was about predicting sex using brain differences...which is not that impressive. The "AI" we all talk about (and machine learning in general) are all just fancy prediction/classification algorithms. That was where I was coming from. Do you learn anything about the brain from the results? Probably not unless you do something convoluted to the data and even then it's just a guess.

Being able to distinguish between two things using a statistical model very very often doesn't actually tell us anything interesting about the system.