Talk:Heritability of IQ

Biological siblings, raised together as adults

Hi, I think I remember reading a scientific journal paper where it said the correlation between biological siblings raised in the same environment as adults is about 0.24. This is consistent with the parent-child raised apart correlation and the adopted child-parent correlation for adult child. I can't for the life of me find it, can someone confirm this? It's not easy, these correlations are not static, the figure I quoted is the median correlation I believe. 87.198.51.173 (talk) 13:14, 6 October 2016 (UTC)

I found it! Here it is. If it's okay with the bigwig editors I might include it in the article. It clearly implies an adult-biological sibling correlation of 0.24 but doesn't out and out state it. It's clearly implied because it describes the drop in adopted sibling correlation from 0.28 to 0.04 and than says compare this to biological sibling correlation of 0.24. 87.198.51.173 (talk) 13:53, 6 October 2016 (UTC)

Political discussion

• there is no political diskussion in this article
  • Cyril Burt, Raymond Cattell und Charles Spearman are diskussed to have cheating in their publication in order to prove "Inheritance of intelligence" as a fact.
  • 'Inheritance of intelligence' is used to to sanctify an elite among man
  • Stephen Jay Gould says that intelligence as an thing and the Inheritance of intelligence as a whole is an myth. (The Mismeasure of Man) --Nerd

Regression to the mean

Ctrl+F in the cited work (ISBN 978-1-4292-3719-2) pulls up no discussion of regression to the mean, at all. Neither do either of the two specifically referenced pages(405–6)discuss it. I propose removing the sentence the citation was intended to support, unless someone comes up with a reliable source. Windkin (talk) 09:52, 7 November 2015 (UTC)

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User [NukeHarvard] added a citation for the claim that "parents whose IQ is at either extreme are more likely to produce offspring with IQ closer to the mean" The first source provided, Human Molecular Genetics 4th edition, pages 80-81 says no such thing. In fact, it says of the oversimplied model provided:

"In the simple model of Figure 3.25 there is a hidden assumption: that there is random mating. For each class of mothers, the average IQ of their husbands is assumed to be 100. Thus, the average IQ of the children is actually the mid-paren­tal IQ, as common sense would suggest. In the real world, highly intelligent women tend to marry men of above average intelligence (assortative mating). The regression would therefore be less than halfway to the population mean, even if IQ were a purely genetic character."

It goes on to say:

"A second assumption of our simplified model is that there is no dominance."

In light of this, I propose removing the first citation. I suspect the second citation is equally nebulous, but since the source is from 1978 and behind a pay wall, it may take more time. Windkin (talk) 08:01, 11 November 2015 (UTC)

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Regression towards the mean mentioned as wikipedia cite is a statistical concept relating to measurements. It cannot be applied to a single case (one set of parents and one offspring). Statistical regression toward the mean is not a causal phenomenon.

Here, it means that if you accidentally pick in your measurement two individuals with high IQ (extreme) and then measure that the offspring has high IQ (another extreme). The average IQ of the entire population (not an extreme) would then be lower. Regression towards the mean tells you how the average of a large set would behave: It corrects the effect of extreme values in the measured set.

The regression towards the mean states that in small measurement sets extreme values (IQs) bias the result. It does not imply that two high IQ parents produce offspring with lower IQ. The cite and the term might be wrong here. I would remove the entire sentence or changed it to something like:

The research studying the inheritance of IQ of the offspring from high IQ parents might be compromised as the extreme IQs in small sets bias the results and must be corrected using the concept of regression towards the mean [13][14].

Dv3 (talk) 19:34, 6 December 2015 (UTC)

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Hi Dv3, Above, you said: "It does not imply that two high IQ parents produce offspring with lower IQ." But that isn't true. The phenomenon of regression toward the mean does imply that two high IQ parents will produce offspring with an IQ closer to the mean. Here's an excerpt from Jensen and Rushton's "Thirty years of research on race differences in cognitive ability" which explains why:

"Regression toward the mean provides still another method of testing if the group differences are genetic. Regression toward the mean is seen, on average, when individuals with high IQ scores mate and their children show lower scores than their parents. This is because the parents pass on some, but not all, of their genes to their offspring. The converse happens for low IQ parents; they have children with somewhat higher IQs. Although parents pass on a random half of their genes to their offspring, they cannot pass on the particular combinations of genes that cause their own exceptionality. This is analogous to rolling a pair of dice and having them come up two 6's or two 1's. The odds are that on the next roll, you will get some value that is not quite as high (or as low). Physical and psychological traits involving dominant and recessive genes show some regression effect. Genetic theory predicts the magnitude of the regression effect to be smaller the closer the degree of kinship between the individuals being compared (e.g., identical twin; full-sibling or parent–child; half-sibling)."

Bzzzing (talk) 17:30, 7 December 2015 (UTC)

Intelligence exclusively maternal

I don't know if anyone can read Portuguese, but some Portuguese Scientists claim that only two or three genes are responsible for intelligence and they all come from the mothers. http://www.cmjornal.xl.pt/nacional/portugal/detalhe/inteligencia-vem-da-mae.html 89.180.101.160 (talk) 06:45, 27 November 2015 (UTC)

These particular Portuguese scientists may well have only two or three genes for intelligence, but that is certainly not true generally.--Victor Chmara (talk) 08:29, 27 November 2015 (UTC)

What a stupid and unhelpful comment, Victor Chmara, please strike it as we do not engage in stupid, childish attacks on scientists who we dont agree with. Nobody actually cares about your opinion. This is the place to help improve this article not engage in attacks on Portuguese scientists. The article does state what you say, anon, re 2 or 3 genes, but the bit abut men choosing (ie sexual selection, mate choice) women 3 times more intelligent than themselves seems dubious. Even more problematic, this source, Correio da Manhã doesnt seem great for science, indeed wikipedia describes it as a tabloid, a judgement I wouldnt disagree with; given the controversial nature of this article we shuld wait for it to appear in a more scientifically prestigious journal. ♫ RichardWeiss talk contribs 15:49, 27 November 2015 (UTC)

Beside the article doesnt mention IQ (QI in Portuguese). Do please try to find other sources for this study but until then we should not include this. ♫ RichardWeiss talk contribs 15:58, 27 November 2015 (UTC)

The claims made by these scientists -- assuming they are correctly described in the source -- are self-evidently absurd and deserve only mockery.--Victor Chmara (talk) 16:48, 27 November 2015 (UTC)

That is your personal and entirely unwanted opinion. This is the page to discuss improvements to the article, not the page where we have to put up with your tedious opinions, please keep them to yourself in the future. ♫ RichardWeiss talk contribs 15:34, 7 December 2015 (UTC)

It's not only my opinion but also that of all reliable sources. If you think that intelligence is determined by two or three genes and inherited maternally, you should not edit this article.--Victor Chmara (talk) 08:46, 9 December 2015 (UTC)

Apparently false claim in 'Caveats' section

The second caveat includes the text:

If the environmental variation encountered by different individuals increases, then the heritability figure would decrease. On the other hand, if everyone had the same environment, then heritability would be 100%.

The first sentence makes a claim that seems obviously true, however given that genotype is not deterministically productive, but random, purely developmental (i.e. non-environmental) factors may affect phenotype, it seems that we should expect hereditability to be close to but not exactly 100% with the same environment. I would be WP:BOLD and change this, but since the article is controversial, I thought I should check on talk before making an unsourced change to the article. — Charles Stewart (talk) 08:42, 24 May 2016 (UTC)

You're right, but if you use an inclusive definition of 'environment', as behavioral genetic research often does, then developmental "noise" is part of the environment and if it, along with other environmental differences, were removed, then heritability would be 100%.

I think the whole section Caveats should be removed and its contents merged with other sections. That section at the beginning frontloads the article with certain notions before the topic is even properly discussed.--Victor Chmara (talk) 09:09, 24 May 2016 (UTC)

Heritability figure

I fixed a mis-citation of Plomin & von Stumm (2018). The heritability mentioned in that article is 50%, not 20-50%. The 20-50% figure is the percentage of the heritability for which "genome-wide association studies have successfully identified inherited genome sequence differences" (quote is from abstract of Plomin & von Stumm...see text of paper for 50% heritability figure) Jeremy.wilmer (talk) 14:46, 19 January 2018 (UTC)

When reading the abstract, I have the impression that 20% is about the genes, with 50% the heritability, so I agree. Thanks, —PaleoNeonate – 15:57, 19 January 2018 (UTC)

I have found a general problem with Plomin. I agree he 'says' 50%, but this figure comes from his own book and from another of his own papers. I did not download the book, but the other of his own references he cites estimates 80%. Plomin gets the 80% figure from another researcher which ACTUALLY said 86%. So Plomin is doing something strange with his numbers: 86% become 80% became 50% which is now falsely interpreted as 20%. How did we get from 86% down to 20%???? There is an acronym for this type of number fudging: L.Y.I.N.G.