Talk:Heritability of IQ

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[edit] Title change

I suggest changing the title to "Heritability of intellgence" since almost all material is about Heritability. The current title is somewhat POV since it seems to imply genetics. Objections? Ultramarine 02:51, 19 February 2007 (UTC)

Although I second the change in title, I would like to even go further - "intelligence" is a somewhat problematic term, with unscientific connotations, whereas "IQ" has an unambiguous meaning. Thus, "Heritability of IQ" could be even more appropriate as an article title. Harkenbane (talk) 22:58, 8 March 2008 (UTC)
I agree with Harkenbane, go ahead! --Crusio (talk) 10:32, 9 March 2008 (UTC)
As you can see, I've moved the page. But doing so has rendered some passages extraneous; since I'm the one who actually moved the page, I'll try to take responsibility for cleaning the article up over the next few days, but I hope others will try to make necessary changes as well! Harkenbane (talk) 02:26, 10 March 2008 (UTC)

[edit] Just one question

Just one;

If intelligence is hereditary, why is it that the overwhelming majority of ultra smart people in the United States do not come from "noble ancestry?"

I mean, most Americans are descended from "European trash," e.g., the working class. To me that doesn't sound like good genetic pedigree regarding the breeding for brains.

Since the majority, the overpowering majority of Europeans who came here were all from "trash" stock, this country should have no smart people at all.

A big, glaring problem with the heredity argument. Indeed, a college professor of mine, whose brother got into that whole ancestry thing, discovered that their great grandfather was a coal miner. From coal miner, to college professor. Its not the only incident either, there are many others. Many people in this country, who teach at Ivy league institutions, who have won nobel prizes, often descend from the lowest of the low from Europe way back when. In Australia, which was originally a prison colony, there are many people there with high I.Q.'s Most of those people are descended from criminals and brigands the British government had deemed "feeble minded."

Of course, I'm not here to make a statement, but to pose a question; if intelligence is inherent, if its inborn, if its genetic, why is it that at one point all of humanity lived in a state of savagery?

Another question I have is, if Europeans according to tests supposedly have higher level II intelligence, I need to ask, why was it that northern Europeans, the ones promoted as being smarter than everyone else, lived in a state of barbarism for hundreds of years?

If intelligence was truly genetic, you'd think they would have created a civilization as sophisticated as that of ancient India or Persia. Were are all the pyramids in Norway? Were are the ancient cities in Germany? Were are the Ankor Wats of England?

No mean to insult anyone here but Stonehenge, when compared to the pyramids in Central America, is hardly an example of brain power.

Is the heredity of intelligence "science" real science, or, is it racist junk science out to abuse its authority to promote racist views?

Nazi Germany abused science in a similar manner; more worrysome though, is the lack of research in how intelligence can be increased. People seem perfectly comfortable in assuming, what you got is what you got, and there is nothing you can do about it.

Sucks for nonwhites, but very convenient for whites. I'm just saying, I hope racist egotism is not the motivating factor for that "science" and "research."


206.63.78.105stardingo747 —Preceding comment was added at 08:23, 8 November 2007 (UTC)

Oh dear, stardingo747.... There is so much to say about this. Intelligence is not genetic. It has a heritable component. Like most complex characters ("complex" here referring to the underlying causes), genes have an influence, so has environment, and often these two interact (meaning that the effects of one depend on the state of the other). Although your above points are well-taken, they do not contradict at all the article as it currently stands. --Crusio 22:40, 9 November 2007 (UTC)

[edit] What now

Too often people work on articles by picking a POV and looking for sources to back it up. I think the way to research an article is to find out what the notable verifiable sources are and then find out what they say (what views they hold) and then come up with an outline for an article that accommodates their views and whatever arguments exist among them. Following this principle I have discovered that there are plenty of good scientific research on the heritability of traits including IQ. A sample of key studies:

  • Bouchard, Arvey, Keller, Segal, 1992, Genetic Influences on Job Satisfaction: A Reply to Cropanzano and James,” Journal of Applied Psychology 77(1): 89-93
  • Devlin, Daniels, Roeder 1997 “The heritability of IQ” Nature 388: 468-471
  • Jacobs, Van Gestel, Derom, Thiery, Vernon, Derom, and Vlietinck, 2001, “Heritability Estimates of Intelligence in Twins: Effect of Chorion Type,” Behavior Genetics 31(2): 209-217
  • McCartney, Harris, and Bernieri, 1990, “Growing Up and Growing Apart: A Developmental Metanalysis of Twin Studies” Psychological Bulletin 107(2) 226-237
  • Phelps, Davis, Schwartz, 1997, “Nature, Nurture and Twin research Strategies” in Current Directions in Psychological Science 6(6): 117-121
  • Plomin and Loehlin, 1989, “Direct and Indirect IQ Heritability Estimates: a Puzzle” Behavior Genetics 19(3): 33-342
  • Race, Townswend, Hughes, 285-291, “Chorion Type, Birthweight Discordance, and tooth-Size Variability in Australian Monozygotic Twins” Twin Research and Human Genetics 9(2) 285-291 (no, not about IQ – but as it is about other clear phenotypic traits it provides a good benchmark for assessing the value of twin studies and the various factors one must also take into account)
  • Reed, Carmelli, Rosenman, 1991, “Effects of Placentation in Selected Type A Behaviors in Adult males in the national Heart, Lung, and Blood Institute Twin Study,” Behavior Genetics 21(1) 1-19
  • Segal, 19999, Entwined Lives: Twins and What They Tell us About Human Behavior
  • Sokol, Moore, Rose, Williams, reed, and Christian, 1995, “Intrapair Differences in Personality and Cognitive Ability Among Mynozygotic Twins Distinguished by Chorion Type,” Behavior Genetics 25(5) 456-466
  • Stromswold, 2006, “Why Aren’t Identical Twins Linguistically Identical?” Cognition 101(2): 333-383

Now, I have not read most of these, but this is precisely my point: I have not chosen them because they support my POV, but because they are frequently cited by scientists and thus represent notable views, whatever their views are. And this is plenty of material to work through. Slrubenstein | Talk 16:22, 17 December 2007 (UTC)

Actually, I think that most of the key points in the article are already there; most of the revision right now should focus on organizing and formatting the existing material, in my opinion. That stated, I can see a few areas to expand and explore:
  • One thing I've been seeing for quite some time now is that there are not likely to be any genes with major effects on IQ, only a great many with minor and minuscule effects that only become important when these effects are aggregated. If anyone knows of any genes with major effects on IQ, that would be important to add.
  • Also of interest would be whether heritability remains high outside of developed nations; what is the heritability of IQ in, for example, India?
  • Lastly, a brief section on the nature of intelligence may be in order, dealing with g theory and critics who offer alternative models; if intelligence is something besides g, then IQ should not be the focus for the article as it currently is. Harkenbane (talk) 22:54, 8 March 2008 (UTC)
It might be good to also include some comment on the nature of heritability, especially emphasising the fact that heritability is not the same as heredity. We do say that heritability is the relative contribution of genes to variance for a given environment, but maybe we need to emphasise this by specifically saying that it is not a measure of the relative contribution of genes to a trait. It's not at all obvious to the lay person that a contribution to variance is not the same as a contribution to the trait itself. We might also include some small discussion of the validity of hereditary measurements, I know a lot of scientists are sceptical that heritability estimates are at all useful or that they tell us anything worth knowing. There are several papers we can cite for this, in particular David Layzer's paper Heritability Analyses of IQ Scores: Science or Numerology? (it's a bit odd that this very important and directly relevant paper is not cited at all), but also including Commentary: Heritability estimates—long past their sell-by date, The analysis of variance and the social complexities of genetic causation The analysis of variance and the analysis of causes Commentary: Statistical analysis or biological analysis as tools for understanding biological causes, though the emphasis for these latter four deconstructions of heritability should be in the heritability article, which does not seem to contain any critisism of the concept at all. What do you think? Alun (talk) 07:04, 27 March 2008 (UTC)

[edit] Overhaul

Discussion brought over from the Race and Intelligence page:

What do people mean when they claim that racial differences cause differences in IQ? According the the lead, it sounds like some people think that race stands for biological differences. In the "Race" section above Alun demonstrates that for biologists race is subspecies and there are no meaningful human races in a biological sense. The question is whether there is a genetic component to differences in IQ scores and this question has nothing to do with "race." Study on the biology of IQ hinges on twin studies. Here is a fair sample of the major sources:

This isn't an article about "race." Harkenbane (talk) 18:39, 26 March 2008 (UTC)

To start us off, I propose we look at these articles:

  • Bouchard, Arvey, Keller, Segal, 1992, Genetic Influences on Job Satisfaction: A Reply to Cropanzano and James,” Journal of Applied Psychology 77(1): 89-93
  • Devlin, Daniels, Roeder 1997 “The heritability of IQ” Nature 388: 468-471
  • Jacobs, Van Gestel, Derom, Thiery, Vernon, Derom, and Vlietinck, 2001, “Heritability Estimates of Intelligence in Twins: Effect of Chorion Type,” Behavior Genetics 31(2): 209-217
  • McCartney, Harris, and Bernieri, 1990, “Growing Up and Growing Apart: A Developmental Metanalysis of Twin Studies” Psychological Bulletin 107(2) 226-237
  • Phelps, Davis, Schwartz, 1997, “Nature, Nurture and Twin research Strategies” in Current Directions in Psychological Science 6(6): 117-121
  • Plomin and Loehlin, 1989, “Direct and Indirect IQ Heritability Estimates: a Puzzle” Behavior Genetics 19(3): 33-342
  • Race, Townswend, Hughes, 285-291, “Chorion Type, Birthweight Discordance, and tooth-Size Variability in Australian Monozygotic Twins” Twin Research and Human Genetics 9(2) 285-291 (no, not about IQ – but as it is about other clear phenotypic traits it provides a good benchmark for assessing the value of twin studies and the various factors one must also take into account)
  • Reed, Carmelli, Rosenman, 1991, “Effects of Placentation in Selected Type A Behaviors in Adult males in the national Heart, Lung, and Blood Institute Twin Study,” Behavior Genetics 21(1) 1-19
  • Segal, 19999, Entwined Lives: Twins and What They Tell us About Human Behavior
  • Sokol, Moore, Rose, Williams, reed, and Christian, 1995, “Intrapair Differences in Personality and Cognitive Ability Among Mynozygotic Twins Distinguished by Chorion Type,” Behavior Genetics 25(5) 456-466
  • Stromswold, 2006, “Why Aren’t Identical Twins Linguistically Identical?” Cognition 101(2): 333-383

I repeat, the point is not to cherry-pick quotes that we agree or disagree with. The point is to examine reliable sources to find out - yes, find out, as if e may actually learn something new - what the notable views are.

I disagree with the implication that those of us who contribute to this article have not already carried out a literature review - at the very least, that isn't true in my case; I regularly read Intelligence along with other psychological journals. Harkenbane (talk) 18:39, 26 March 2008 (UTC)

From what I gather from this literature, most of the current scholarship - mainstream scholarship - on IQ scores is not even concerned with the debate "is it environmental or is it genetic."

Yes, because the heritability of IQ throughout the developed world has been settled (although the heritability of IQ in developing countries is unknown). Harkenbane (talk) 18:39, 26 March 2008 (UTC)

There is a body of literature, and I provided many citations above, and obviously an article on this research must be organized around the most notable and mainstream views on the matter - it should include all notable views ... but I think that the major notable views should be the principle factor in the organization and presentation of the article.

Virtually all scientific research on the genetic determinants of variation in IQ scores is based on twin studies and above (perhaps now in archived talk) I provided a bibliography of major (i.e. from major peer-reviewed journal journals, and which are frequently cited) articles. These studies indicate an ongoing debate between scientists who measure the heritability of intelligence at .40, and others who measure it at between .60 and .70.

The debate is not ongoing. Research on children shows low heritabilities; on adults, high heritabilities. That the heritability of IQ is below .5 in early childhood and above .7 in late adulthood is commonly accepted throughout the psychological community. Are you aware of any study published in the last 20 years which breaks this trend? Harkenbane (talk) 18:39, 26 March 2008 (UTC)

In addition to these contrasting calculations, there is a debate over the effects of of the shared prenatal environment - some argue that identical blood supply should lead to greater similarities between monochoriatic twins than dichorionic twins; others argue that competition for blood supply should lead to greater differences between monochorionic twins than dichorionic twins. I think we need to have a good article that provides a clear account of this research and these controversies.

You seem to be in a good position to do this; why not simply add it to the present article? Harkenbane (talk) 18:39, 26 March 2008 (UTC)

Perhaps someone who has training in genetics and access to these journals could take the first step in sketching out an article on Heritability and IQ.? Slrubenstein | Talk 20:33, 25 March 2008 (UTC)

[edit] Not about intelligence, not about race

This is an article about the heritability of IQ - specifically, the proportion of variance in IQ which is attributable to genetic variance. Consequently, I don't think this is the place to discuss race, intelligence, or race and intelligence. Questions about whether IQ measures "intelligence," whether "race" exists, or whether different populations differ in IQ for genetic reasons, can be addressed elsewhere. Harkenbane (talk) 19:05, 26 March 2008 (UTC)

Harkenbane, my apologies for my confusion about the deletion of comments. To respond to yours, I only wish to reiterate two points. One, I agree with youcompletely that this is not about "race," but the question of heritability of IQ constantly comes up on the Race and Intelligence page. I do not think this article should be rewritten to be about race (unless that is what the notable sources say), I wish only to point out the relevance of this article to another. Two, none of my comments are directed at you personally and I hope you do not take them personally. I have added other sources and topics I think this article should cover; this in no way disparages the work you or others have already done. Slrubenstein | Talk 12:13, 27 March 2008 (UTC)
No need to tread on eggshells. I will say, however, that the relevance of this article to the article on race and intelligence is not large so long as the article sticks to its subject, for the straightforward reason that within group heritability really says nothing about between group heritability. If users on another page are making claims about the within group heritability for IQ which contradict what is written here, I think they should take their concerns to this article - the information given here, while cluttered and poorly presented, is nevertheless that of the mainstream psychological community. If anyone has any information to the contrary of what currently appears, please make the appropriate changes with proper citations! Harkenbane (talk) 17:59, 28 March 2008 (UTC)
I think that's right Harkenbane. The only relevance it has is to do with heritability, in that some researchers claim that because the heritability of IQ is high for some groups then this indicates a string genetic component to the trait, and also that a high heritability for one group must mean a high heritability for all groups. But this is more about these researchers (notably Jensen) conflating heritability with heredity and making false claims about the validity of between group heritability. This article already makes the specific point about within group heritability not being relevant to between group heritability. I do think this article should be more explicit in distinguishing between heredity and heritability. Alun (talk) 18:57, 28 March 2008 (UTC)