Does male over-representation increase as IQ decreases/mental retardation increases?

To take one study* which seems to be representative of the overall trend, mental retardation was at 15.1% for males and 9.1% for females. Mental retardation can be broken down into borderline, mild, moderate and severe. Does male over-representation increase as mental retardation increases/IQ decreases? If so, what do the ratios look like at each stage/IQ decapoints?
*The prevalence of mental retardation by gender, age of diagnosis and location in Zonguldak province, Turkey - PubMed

I have no source to cite, but I’ve read that men are typically the extremes of both ends. They are the smartest of the smart and the dumbest of the dumb. So if you were to scrape the barrel for the absolute lowest of IQ, I would expect it to be mostly men, yes.

No answer to the OP, but here’s some more generalized data from the CDC that shows a similar link between gender and intellectual disability:

I just am wary of claims that a study localized to a very specific part of Turkey, the UK, Amsterdam, or wherever are “representative,” even if they are.

When the parents are exposed to teratogenic substances, they are less likely to have boy babies. This because boys are less likely to survive genetic defects.

That’'s a fact. What follows is a guess: Miscarriage / Stillbirth is one end of the continuum: Boys are over-represented at the bottom because they are less genetically robust.

You’d be more convincing if you provided a cite. But, out of curiosity, a google search for males less genetically robus (sp)* yielded this article as the top hit:

Females Are Genetically Protected from Autism

*And I am ashamed to admit I have to include my search’s spelling error in my reply because, re-doing the search with “robust” spelled correctly come up with different results. And yet “robust” is spelled properly in the article!

Couldn’t one also say that males are more genetically vulnerable to being colorblind? Having a trait depend on one chromosome rather than two can increase variability.

That is one potential contributor the article posits (and I was tempted to posit myself, even absent a source), but it notes that some of the disparity may also be due to social or cultural factors that lead to certain developmental abnormalities or delays being under-reported in females. Which is why I was skeptical of a study looking at a particular part of a single country, even before I came across a source. It’s just proper skepticism.

Perhaps this? Variability hypothesis - Wikipedia

"The notion of greater male variability — at least in respect to physical characteristics — can be traced back to the writings of Charles Darwin. When he expounded his theory of sexual selection in The Descent of Man and Selection in Relation to Sex, Darwin noted that in many species, including humans, males tended to show greater variation than females in sexually selected traits:

“Throughout the animal kingdom, when the sexes differ from each other in external appearance, it is the male which, with rare exceptions, has been chiefly modified; for the female still remains more like the young of her own species, and more like the other members of the same group” (p. 272, vol 1, chapter VIII)"

““By the 1890’s several studies had been conducted to demonstrate that variability was indeed more characteristic of males…The biological evidence overwhelmingly favored males as the more variable sex.””

I’m wondering what the size of the effect is. E.g.: Is it 2/1 at IQ80, 5/1 at IQ70, 10/1 at IQ60? Is it the same at the other end of the scale?

One thing I read talked about X expression effects of genetics. Women have 2 X chromosomes, men only have one. So any genetic problems with the X chromosome are more evident with males. With Females, the genes on X may turn on randomly from either chromosome, so disorders that result from a failure of development or chemical processes is more likely to occur in males than in females, and be more pronounced in males. Thus men are over-represented in the extremes, i.e. the Bell curve of such characteristics will be flatter and wider for men.

The Y-chromosome has a lot fewer genes than the X, so a lot of what is on X to control human development does not occur on Y. So for example if a defect in X contributes to autism, or genius, or retardation, or any other disorder, men are more likely to happen to be in the category. Of course, provided the cause is something linked to an X-chromosome gene.

What kinds of things does the Y chromosome affect? I’m aware you can’t provide an exhaustive list.

I’ve been led to believe it is commonly associated with gender, though to what extent has been subject to debate (for perfectly understandable reasons, by my view, to be clear).

Not an expert on biology by any means, but my understanding is that the Y has lost a lot of content over the evolutionary timeline, since the matching X fills in the gap if genes are not present on it. It definitely determines physical gender of males and associated characteristics so it can’t lose those genes. (XY - male; XX- female) However, anything to do with genetics is a complex and interesting field and weird things can happen in biology.

Apparently it’s not rare for segments of chromosomes to be missed or duplicated or switch from one of the pair to the other or even a different chromosome during the copying phase. If this does not hurt, or has an advantage, it may spread across the species.

For the OP’s question, imagine the difference between - “Roll the dice and see what you get”, or “roll the dice twice and pick the average”; assuming some of the intelligence-related genes are on the X.

Would it be accurate to say that testosterone has a magnifying effects on some traits? The magnification itself it neutral and whether it’s positive or negative depends on the positivity/negativity of the trait that gets magnified?

Do prepubescent girls and boys show the same difference in trait variability as adult men and women?

So basically what you’re asking is do men get stupid after puberty? Hmmm…

Joking aside, AFAIK intelligence manifests at an early age. Plus, there are noticeable gender differences between boys and girls, some of which are not explainable by culture/nurture.

Perhaps what you are also asking is whether competitiveness and aggressiveness due to testosterone can alter test results. But then it would manifest in overconfident males, not stupider, but trying to pretend they are not as stupid as they look. It wouldn’t really alter the actual distribution of intelligence or its lack.

This explains a lot. Women have a spare X chromosome, which is also the largest one, and men usually do not. The ones who do have Klinefelter syndrome (XXY) which in itself can cause mental disability (but often does not).

Men and women tend to test differently on different topics like spatial and verbal abilities. Does that difference appear in 1st grade or later? Does it show an uptick around puberty?

Anecdotally, it does seem that some boys get stupider around puberty.