Talk:Race and intelligence/Archive 4

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Gould

I removed three "rebuttals" from the section on Gould. One was a rebuttal that other scientists claim only that biology has some influence -- this is not a rebuttal since Gould agrees. Another concerned heritability, but misunderstands herritability and simply repeats the previous point (biology has some role). The third amounted to: but many scientists diagree with Gould. Since Gould is disagreeing with some scientists, it goes without saying that some scientists disagree with Gould; this is just unnecessarily wordy Slrubenstein

There are over 1200 words in the Gould's criticisms of the Bell Curve section. However, much of the discussion does not directly related to what Gould said. The contents of this section should probably be broken down into smaller, topic-oriented parts. This section could be reworked into "Interpreting Group Differences" or something like that. Then we could summarize the various interpretations. Taking the APA report as a guide, there are four major interpretations:

  • Socio-economic Factors
  • Caste-like Minorities
  • Minority Culture
  • The Genetic Hypothesis

--Rikurzhen 20:38, Jul 5, 2004 (UTC)

The Gould objections, as written in The Mismeasure of Man, are repeated in too many articles. Detailed consideration of his objections specific to The Bell Curve should be in that article or the other, with only passing references here.

Several Points in Need

(1) "However, many scientists continue to use "race" as a biologically meaningful and useful term, but emphasize that genetic similarities within races are mutable, and recognize that many traits have both genetic and environmental determinants." If anybody understands what the original author meant by "similarities ... are mutable," please reword this passage.(How can a similarity change?) P0M

I was watching this page when that was added. I argued that that line was unclear (search for "genetic similarities within races are mutable"). Still not sure what to do about it.--Rikurzhen 07:07, Jul 3, 2004 (UTC)
The statement does not actually mean anything, unfortunately. What would be an example of a genetic similarity among members of one race? Japanese people have brown eyes, i.e. they are similar in that "all" of them have eyes of some shade of brown. But their similitude is mutable in the sense that each new member of that population has his/her own shade of brown, so that over time the percentage of people with each shade of brown can vary??? Is that what the original author was trying to say? Or was it something entirely different? The author did mean to say "similarities within races" and not "similarities among races" -- I guess. But I only can guess. P0M

(2) "At least some of the phenotypic differences between populations (such as skin color) seem to have functional importance (such as adaptation to climate). Moreover, the distribution of many such differences follows a purely geographic continuum." This isn't always true. I'm fairly dark skinned for a caucasian because of Celtic ancestry, yet those ancestors are from the same latitude as the fair skinned Irish.--Rikurzhen 07:11, Jul 3, 2004 (UTC)

A better example: The maps of skin reflectance values show "isotherms" going north and south rather than east and west at some points. That is, west of the line people are darker than east of the line (or vice-versa, can't remember the map clearly). From the rest of the map it seems fairly clear that migration brought a group adapted to one condition into the latitudes of groups long adapted to conditions there.

(3) "Others, however, hold that this does not mean that there is no relationshio between race and intelligence. Rather, people with middle-class educations usually have a more rigorous education from kindergarten on up through college, as well as much richer lingustic development in the home, especially during the critical years from one to five, when most neural development in thinking and word-procesing occurs. In other words, the culture affects the resulting intelliegence." Non sequiter. Writer purports to give evidence that there is a relationship between race and intelligence and then speaks of environmental influences, culture, etc., but says nothing about any supposed different [racial] factors on which these inputs might operate. P0M

(4) The article confuses [race], ethnicity, and culture. Up to this point, "race" has been used to mean "population," and has been explained in terms of genetic inheritance. "Others, however, hold that this does not mean that there is no relationshio between race and intelligence. Rather, people with middle-class educations usually have a more rigorous education from kindergarten on up through college, as well as much richer lingustic development in the home, especially during the critical years from one to five, when most neural development in thinking and word-procesing occurs. In other words, the culture affects the resulting intelliegence." (Emphasis added.) If the word "race" at the beginning of the quotation were swapped out for "culture", then the passage would be coherent. P0M 17:11, 3 Jul 2004 (UTC)

Good point -- except that several scholars have observed that many people (both popularly, and in academic literature) use the word "race" and "culture" as synonyms. I know this sounds strange -- especially to anyone who has worked hard to desfine race and culture as distinct things -- but I think it is well established that these terms are often substitutable in contemporary discourse. One explanation is that the racist thinking underlying the way "race" was used in the 19th century and, by many, in the first half of the 20th century endures even among people who for reasons of "political correctness" no longer use the word "race." They use the word "culture" either thinking it sounds more sensitive or sophisticated, but use it in exactly the same way they (or others) once used "race." Whether this explanation is correct or not, I think this article just illustrates one form of the phenomena, ad POM points out. POM's intention, I think, is to make the article consistent and sophisticated -- and I agree with him. But I do think that we also need to make clear that despite the mainstream scientific meanings of "race" and "culture," many people, popularly and even in legal discourse, use the terms interchangably. Slrubenstein
If the article has defined race one way and then switches to another understanding of the term without warning the reader that the carefully established definition is being abandoned, that is going to confuse the reader. P0M 06:47, 4 Jul 2004 (UTC)

(5) "Arthur Jensen is a proponent of the hereditarian view of intelligence and seems to support the hypothesis that the IQ gap is at least partly genetic." As it is written, this sentence can be understood two ways, (a) that Jensen is an advocate of the hypothesis, or (b) that there is something about the genetic constitution of Jensen that supports the idea that some people have a genetic IQ gap. Either way, it's a bad sentence. In a scientific discussion, evidence supports a hypothesis. P0M 07:04, 4 Jul 2004 (UTC)

I agree with both points, Slrubenstein
Off-topic alert -> I find this kind of grammatical ambiguity very funny. ("that there is something about the genetic constitution of Jensen that supports the idea that some people have a genetic IQ gap.") The way that so many sentences have ambiguity is one of the quirks with the English langauge. That's why it is so critical to teach grammar and proper English; I constantly come across many statements and articles which (as written) do not mean what the writer thinks the text means! RK 17:11, Jul 5, 2004 (UTC)

(6) The following sentence fails to communicate properly. "Even within a group, if all members of the group grow up in exactly the same environment, it does not mean that heritability is 100%." 100% of what? I could hazard a guess that it means "100% of the reason for any observed differences," but that wasn't the way I took it the first time I read it. I read it as implying a structure analogous to a sentence like, "Herman's performance is 100%!" or "She's a 10!" Writers need to think about how the average well-informed reader (who doesn't already understand the topic well) will interpret each sentence that they write. P0M 16:48, 5 Jul 2004 (UTC)

Again, a good point. RK 17:11, Jul 5, 2004 (UTC)

APA Report from 1996

The APA released a report in 1996 titled "Intelligence: Knowns and Unknowns". Press release summary. Full text here, here or here. The report was authored by psychologists who held diverse and confliting opinions on the topic. However, their mandate seems to have been to find points of consensus on which to report. Items of controversy were reprted to have been be unknown or undetermined at that time. This article could benefit from the inclusion of ideas from that report. However, keep in mind that the report itself is copyrighted. The main section of interest is "V. GROUP DIFFERENCES." Here are a few examples:

If group differences in test performance do not result from the simple forms of bias reviewed above, what is responsible for them? The fact is that we do not know.
The differential between the mean intelligence test scores of Blacks and Whites does not result from any obvious biases in test construction and administration, nor does it simply reflect differences in socio-economic status. Explanations based on factors of caste and culture may be appropriate, but so far there is little direct empirical support for them. There is certainly no such support for a genetic interpretation. At this time, no one knows what is responsible for the differential.
Differences in genetic endowment contribute substantially to individual differences in (psychometric) intelligence, but the pathway by which genes produce their effects is still unknown. The impact of genetic differences appears to increase with age, but it is not known why.
Environmental factors contribute substantially to the development of intelligence, but it is not clearly understood what those factors are or how they work. Attendance at school is certainly important, for example, but it is not known what aspects of schooling are critical.
Considered as predictors of future performance, the tests do not seem to be biased against African Americans.

The only thing to keep in mind is that this report was written nearly a decade ago. Since then, additional work has been done on this topic. --Rikurzhen 20:26, Jul 5, 2004 (UTC)

new intro

I appreciate POM's work but I think the new intro is way, way too wordy. The intro should have the minimum amount needed, with the details in the body or -- since there is a linked article all about "race and debates about the meaning of race -- in the article specifically on race. Slrubenstein

I think I may have put my finger on the problem we have. I'll try to explain, and this may help with the intro. It is true of both the idea "race" and the idea "intelligence" that a strict analysis of its definition is not easy to produce. We can offer an ostensive definition, and give example, but both concepts are "fuzzy". We're trying to be as accurate as possible in the intro to describe these fuzzy/subtle ideas. This produces a wordy intro. There are "consensus" definition to be had -- basically you do a survey of experts and calculate an average definition. For example, among intelligence researchers, 99.3% would include "abstract thinking and reason," 97.7% would say "problem solving ability", and 96% would say "capacity to acquire knowledge." But only 80.5% would say "memory," 71.7% "mental speed," and 62.4% "general knowledge" are elements of intelligence. Likewise with race, biologists have a biological definition, sociologists have a sociological definition, and the "common-sense" definition is quite vague and depends on context.

What we might be able to say something like -- Researchers have recognized and studied many aspects that are associated/correlated with race/intelligence. A complete analysis is lacking because the words are applied to many different but related concepts. Many common-sense and historical notions about race and intelligence have been since abandoned. The current understanding is very nuanced and differs between fields. ... and so on --Rikurzhen

Quote:"For the purpose of economy of expression, this article will use the word "race" as a substitute for the scientifically more precise term "population" and not as an equivalent to "subspecies".

I dont think this is right. Either this article resides in the social world and hence still uses the unfortunate term, "race," or its a scientific article which instead uses "subspecies" and "population." To use the term "race" just because it happens to be in the title, or because it has six less letters, is not valid, in my view. -Stevertigo 03:29, 6 Jul 2004 (UTC)

I like the present version (I was aware that there was a lot of repetition left after I tried to fix that one paragraph. Thanks! Great edit.) I agree with Stevertigo that it would be better not to use the word "race," but I don't know how to get around the problem posed by the fact that most people will ask about race and intelligence and not populations and intelligence. It is especially troubling because the medical researchers suppport in deed if not always in theory the use of "race." Actually, "population" may have an operational definition somewhere that clarifies whether, e.g., the several hundred white-skinned humans in China constitute part of the population of China. But the "Population" article says: "In the most common sense of the word, a population is the collection of people, or organisms of a particular species, living in a geographic area." The "extended family" idea is useful. If orange people are restricted by language, religion, and eating habits from intermarriage with green people, even though the orange people are interspersed through all green communities, they may have a high probability of suffering some diseases that green people rarely catch. There doesn't seem to be a term that adequately suggests both the genetic connection idea and the idea that the genetic connections are "fuzzy." P0M 18:42, 6 Jul 2004 (UTC)

Poverty != Culture

One paragraph suggests that similar histories of being disadvantaged (or even persecuted) ought to result in similar poor levels of academic and intellectual performance. But members of the two groups mentioned, the Chinese and the Jews, all are steeped in the value of education and whatever resources can be spared are devoted to education. If you drop the sixteen year old son or daughter of an educated family barehanded and broke in the middle of a foreign country, that person will be very likely to do o.k. or even to prosper, because s/he has both some learning, a strategy for learning, and the knowledge that success can be won if you're willing to invest time and effort. The same is not true for a young person whose family members have not had the advantage of an education and therefore cannot envision for their childrem, and help them envision for themselves, a life of learning. P0M 06:23, 7 Jul 2004 (UTC)

It is possible that the paragraph you point to makes an arguable point. Of course, it is not for us to make arguments against it -- has anyone published the critique you suggest? We should limit ourselves to providing an account of actual debates. That said, I personally don't agree that someone who is well-eduated has an advantage if plopped into a strange environment. Much research suggests that neither knowledge nor strategies of learning are culture-free or culture-neutral. Someone very well-educated Westerners (or Jews or Chinese) might be plopped into a strange environment (say, the Amazon or inner-city Detroit) and so utterly fail to adapt that they will die or be killed. Slrubenstein

The paragraph I referrred to is as follows:

Cultural explanations for the IQ deficit among blacks and Hispanics compared to whites and Asian minorities are complemented – and sometimes challenged – by the observation that Asian minorities score well on IQ tests and on average enjoy greater economic success than other minorities. Likewise, Jewish populations have suffered past discrimination and persecution, but do not exhibit an IQ deficit. Another confounding observation is the poor economic performance of African nations as compared to Asian countries, despite similar histories of past poor economic performance.

The implicit argument is that Asian and Jewish minorities do well when blacks and Hispanics do poorly despite their common minority status, despite all having suffered past discrimination and persecution and despite all having "similar histories of past poor economic performance," and that there must therefore be some reason that accounts for these different outcomes. Am I wrong to see, in an article entitled "Race and intelligence," that if other factors are nixed then race is the implied cause? P0M 02:29, 8 Jul 2004 (UTC)

Not necessarily. Consult the APA report for a nice break down of the various interpretations. It's a little light on details, but has good organization. There are at least 4 prominent interpretations. Each has strengths and weaknesses. I think this article won't be complete until we mention all four.--Rikurzhen 08:11, Jul 8, 2004 (UTC)


I was talking about the conclusion that the average well-informed reader might draw from that passage, not the interpretations of reality held by specialists looking at the subject matter that passage tried to address. I object to the passage because it is tendentious. Reflecting, and citing, the APA report would not just be somebody's opinion. P0M 00:44, 9 Jul 2004 (UTC)
I am more inclined to argue that "similar histories of past poor economic performance" is so vague as to be meaningless or misleading. It suggests that on the basis of a couple of indicators a country in Africa and a country in Asia are comperable, economically. This is simply not true. The political and economic conditions operation on Asia and Africa are and have been very different -- regardless of how similar certain indicators (the paragraph doesn't say, but maybe GDP or infant mortality) are. Slrubenstein
I agree. P0M 00:44, 9 Jul 2004 (UTC)
Something should be said to address the comparative economic arguments. Even if it is to say that simple comparisons between Asian and Afrian nations are inappropriate because of extranous factors that repress the economic development of African nations. I don't know any literature on such things. Any suggestions? --Rikurzhen 01:28, Jul 9, 2004 (UTC)
Are the economic arguments based on anything to begin with? If not, what are they doing in the article? P0M 05:31, 9 Jul 2004 (UTC)
IQ and the Wealth of Nations is the most prominent/recent example of an economic spin of the issue. Rikurzhen
O.K., but can that be used as a citation to support the article as it is written? P0M 06:50, 9 Jul 2004 (UTC)


I think a link to the article on the book is sufficient. --Rikurzhen 15:56, Jul 9, 2004 (UTC)

Redudant context -- rework into article if possible

Early intelligence tests in America

In early U.S. IQ testing, Americans of black African descent, Jews, and other recent immigrants from Europe, were assigned scores that were significantly lower on average (mean of 85) than "white" people (mean of 100), with "Hispanics" somewhere in between. Some researchers seized upon these early results as evidence for the hypothesis that race determines intelligence. This hypothesis was much later rejected by some as badly flawed for a number of reasons, notably because they did not consider the relationship between IQ and any other factor.

Current research has found a strong correlation between IQ test scores and such factors as education level and family income. For modern researchers, the earlier failure to control or correct for these factors made the earlier studies scientifically useless.

Methodologicial and conceptual problems

Later studies on race and IQ have attempted to make corrections for the earlier lack of controls. Some of these studies show that a measurable IQ gap between people of different races does exist, and is only slightly smaller than previously reported. Many of these studies show no significant IQ gap between "white", "Jewish" and "Asian" people, but they do show a significant IQ gap between these groups and black African Americans. These studies have received a skeptical reception in the scientific community, partly because of methodological problems.

Many people are skeptical of modern tests, and give as a reason the early 20th century studies which showed large IQ deficits in Irish and southern European immigrants to the United States. However, the IQ of people in these groups today is now seen to be the same as that in other groups considered "white".

Some anthropologists argue that intelligence is a cultural category; some cultures emphasize speed and competition more than others, for example. In the view of those anthropologists, timed tests based on word skills may not accurately measure learning ability. That is because IQ tests typically impose time limits and ask people to solve some problems involving factors most often encountered in middle class settings. In this view, low IQ scores are often the result of the subject speaking a different language or dialect from the one that is used in the test questions, growing up in a radically different cultural environment, being given the test by someone from another ethnic group (for reasons of mode of expression and/or an intimidation factor), or simply being tired, malnourished, or ill.

To support this view, it can be noted that during WWI African-Americans from the north tested higher than those from the south. This was simply because African-Americans in the north had received more formal education (see Race: Science and Politics, written by Ruth Benedict in 1940). Others, however, hold that this does not mean that there is no relationshio between race and intelligence. Rather, people with middle-class educations usually have a more rigorous education from kindergarten on up through college, as well as much richer lingustic development in the home, especially during the critical years from one to five, when most neural development in thinking and word-procesing occurs. In other words, the culture affects the resulting intelliegence. In this view, some cultures lead to people with a higher ability to perform problem-solving and ability to engage in abstract thinking. (See the American Anthropological Association's Statement on Race and Intelligence at [1].)

Scientists have firmly established that most genetic variations in individuals are only a part of the picture of how an individual develops. The environment that a person is brought up in is equally important. Further, there are painful social factors involved, such as the high rate of drinking, smoking, and illicit drug use during pregnancy of inner-city teenagers. These activities are known to cause measurable mental deficits in children born to parents engaging in such activities. Thus, as cities and states work to reduce the amount of smoking, alcoholism and illicit drug use, this may significantly reduce much or all of the IQ and SAT score gaps that are currently being measured. In this case, the gap would be a symptom of a wider social problem, and not a statement about race at all.


What's missing?

After moving things around, I think it's easier to see that some aspects of this article are a little more bare than others. What's missing? --Rikurzhen 03:05, Jul 9, 2004 (UTC)

Caste-like minorities. The original reference given for this idea is: Ogbu, J.U. (1978). Minority education and caste: The American system in cross-cultural perspective. NewYork: Academic Press. Does anyone know more about this, or know a more recent, web-accessible source? --Rikurzhen 04:11, Jul 9, 2004 (UTC)

§ Presumably they are trying for groups that most rigidly exclude marriage with people outside the group, right? Or was Ogbu perhaps looking at attitudes and expectations directed toward "lowly" castes vs. those directed toward "nice" castes? P0M 06:30, 10 Jul 2004 (UTC)

§ I believe that one approach would be to systematically organize the issues. The first issue is whether the word "intelligence" can be given an operational definition such that it can be measured. One answer is no, and that ends that branch. One answer is yes, and that brings up the next decision point: Is intelligence heritable or not? If it is not heritable, that branch terminates. If intelligence is heritable, then can quantified intelligence of children be computed on the basis of the quantified intelligence of parents? Of grandparents? How important are contingent environmental factors (education, etc.)? If the quantified intelligence of a n + m generation person is some kind of a statistical function of the IQs of all those in the nth generation, then and only then would the issues such as "caste-like minorities," "pure Dyak descent," "what is a race", etc., come into play. And one would still have to disentangle the measure of "inherited IQ" from the effects of contingent environmental forces in the n + mth generation.

(1) You could try, but some of that material might be better placed in the separate race or the intelligence articles.
(2) These are all empirical questions. Huge amounts of data exist that were collected to address these questions. Of course, the interpretation of these data is a matter of "opinion." However, there is a consensus on at least your first two questions. Is intelligence captured by IQ tests? The consensus is that IQ tests do so better than any other tool -- and are pretty good predictors of the type of things that we associate with intelligence. For an opinion contrary to consensus, see the work of Sternberg or Gardner. Second, is IQ heritable? The consensus is that yes it is. Grossly simplified, the heritability is 50%. The actual heritability increases over a lifetime to 70-90% in the US. (That's a huge heritability for a complex trait.) The Nurture Assumption is a good example of how surprising the results of behavior genetics research can be. The only contrary opinions about heritability (that I know of) are those who point out that heritability is dependent on the population being sampled, and thus heritability studies that include mostly middle-class people in the sample are only directly applicable to middle-class people. A recent study of the heritability if IQ among impoverished children found lower values.
(3) As to the later questions, the data becomes thinner, but still quite strong. The importance of individual environmental factors is known -- I don't know them off the top of my head. The biggest obstacle to solving the overall problem is that there is a dearth of direct evidence. Most of the evidence is indirect -- for example, correlation studies. Such studies cannot directly implicate what is the cause and what is the effect. Income is correlated with IQ, but which is the cause and which is the effect? The main question from my POV--as a geneticist--is "what is the contribution of genes versus environment to the IQ gap?"--this is the one of the basic questions in modern genetics. Direct evidence would come in the form of identifying genes/alleles that contribute to IQ, and seeing whether they differ in their distribution between races. Someday this study will be done (well) and we can put this question behind us. In the meantime, some people argue that the available data is best explained by one theory or another--the two main contenders seem to be 100% environment versus ~50% genetics/~50% environment. --Rikurzhen
§ Very interesting, and very helpful. Has anybody worked out how closely the IQs of each grandchild can be predicted on the basis of the IQs of each of the grandparents? P0M 06:30, 10 Jul 2004 (UTC)

§ Perhaps I should not permit myself to think. Perhaps one can only legitimately reflect what people possessing one kind of status or another have opined about "race and intelligence." But I persist in thinking. I cannot help it because the word "race" is such a squishy tool with which to attempt to form clear thoughts.I believe that if the area of discourse is divided systematically it may well be possible to identify authorities who support each alternative at each level. That is probably all that can be legitimately established. P0M 23:02, 9 Jul 2004 (UTC)

I recommend that you try to outline this further, along with annotations of which groups/people support which theories, before implementing the change. I suspect that you will find that some theories enjoy little support, while others are widely held. --Rikurzhen
If, as you say, "The actual heritability increases over a lifetime to 70-90% in the US," then there may be a "compound interest effect" working on the "capital" laid by in very early language acquisition. And what now might seem to be a definite minority opinion, e.g., that intelligence starts out equal at conception for all human beings, might turn out to be the right one after all the twin studies, etc., were done. Anyway, I don't mind outlining the decision points in this kind of an account of "race and intelligence," but given my present resources I think depending on me for anything like comprehensive evidence on which people are authorities and which authorities support what would be a little like asking your average vegetarian for recommendations on brands of caviar. ;-) P0M 06:30, 10 Jul 2004 (UTC)


Someone will have to explain how heritability increases in an individual in the course of a lifetime. Heritability is calculated for populations, not individuals, for one thing. It should also be independent of individual development. For example, height is highly heritable -- but no one says it is "more" heritable as one gets older, just because as one gets older one gets taller! What does it mean to say heritability increases with age? Also, remember two important things about heritability: first, it can't be used to explain differences between populations; second, even very high heritability doesn't necessarily determine behavioral outcomes/performance. Slrubenstein

What's meant by heritability increasing? It means that when heritability is calculated for particular age groups (e.g. children, adolescents, college students, middle age, old age), the measured heritability is greater for each successive group. For children it is rather low: <40%. It goes up considerably during adolescence. Then by old age the heritabliity is pushing 90% in some studies. The explanation presented in the literature is that in childhood your environment is greatly influenced by others. As you get older, you are able to shape more of your environment. In this way, increasingly genes shape environment, which shapes IQ. Along this line, some people point out that the measure of heritability is quite sensitive to environment. -- Your right, heritability is a measure of the variability that is determined by genes versus environment. However, 100% heritability would indicate that all measured variation in phenotype is caused by genetic variation. --Rikurzhen 18:16, Jul 10, 2004 (UTC)

Sorry -- I understood the grammar of the sentence, I don't understand the method. How is this change of heritability actually measured? I suspect that the literature you cite is actually measuring the predictive power of IQ tests, which is not the same thing of the heritability of "G," or "intelligence," or whatever it is the test claims to (or is said to) measure. I think what you are saying is that performance on IQ tests is less variable as one gets older, but this is not the same thing as measuring heritability. By the way, even if heritability is 100% that does not mean that genes totally trump environment, or that genes totally influence performance or behavior -- heritability may be 100% and environment can still have a major influence on behavior or performance. Slrubenstein

No, I seriously think I remember that they measure heritability with twin/adoption studies and considered people at different ages. The resulting h^2 statistic is low for children and high for 80-year olds. I think these were mostly a cross sectional studies, but there may be some longitudinal data also. I think I also remember that this effect is largely accounted for by changes in g, but I don't recall off the top of my head. This and other facts spurred the conclusions of The Nurture Assumption that parents have little impact on their children (with respect to IQ for example) and that non-shared-by-families environments and genetics are by far stronger influences than the normal range of parenting styles. Steven Pinker gives a nice summary of these ideas in The Blank Slate. p.s. You can watch/liisten to Pinker summarize The Blank Slate here. Rikurzhen
On the separate issue of interpreting heritability. Yet of course heritability only speaks to the degree to which measured variation between individuals is the result of genes/environment. Thus, the frequent claim that heritability of IQ increases in sitations where the environment is enriched and drops in impoverished environments. Rikurzhen

One intersting bit that is missing. I think I remember a report that the black-white IQ gap in the UK is smaller than in the US. Of course, interpretation is up in the air. I'll try to find that report. Rikurzhen

§ As a teacher in a disciplinary school I had the opportunity to observe some children who were bright but very poorly educated. A couple of them remain in my thoughts continually. One of them had an IQ of around 140 but at age 15 he read at 4th grade level and had never learned his multiplication tables. He could not have scored well on an ordinary IQ test. He and I brought his reading level up to 8th grade over the course of a summer vacation. If he continued to make progress on his own he would eventually have tested where he belonged on a standard IQ test. So if he inherited his intelligence from his parents, and if their own educations were sufficiently good to not mask their IQs, then it would seem likely that his intelligence would have proven more "heritable" as he recovered from his original disadvantage.

That's really cool. One data set I've heard about is the case of Asian children (East Asian and born in Asia) adopted by US parents (probably white) that had suffered terribly impoverished early childhoods. (Not to the extent of lost children who don't enounter language during the formative window.) They intially have low IQ scores. Over time and with help their scores rebound. The intersting twist is that on average their scores rebound to a level above their adoptive parents and near the East Asian average. This result is consistent with other adoption studies.Rikurzhen

§ We know that things like PKU can throw monkey wrenches into brain formation. But normally brain formation continues after birth and experience with "wolf children" indicates that there is a crucial window for growing the brain in the areas associated with language acquisition. What if instead of a total absence of spoken communication during the first 3 years or so there is only the most rudimentary communications from people who have no time or inclination to do anything other than to yell, "Shut up!"? I'm told that nobody can become a wei-qi (go) player at the master level unless the game is learned before around age 10.

One thing to keep in mind is that cognitive tests suggest that the heritable component of IQ scores is mostly g (g theory). But that leaves considerable environmental wiggle room for the many subtest-specific abilties. Moreover, there is certainly ample evidence for certain windows of opportunity to gain skills, especially langauge, during childhood. Rikurzhen

§ On the subject of a "decision tree" such as I outlined above, I found a summary by Anne Fausto-Sterling in her Myths of Gender in a section where she is primarily intent on making a critique of studies that purport to show that men are smarter than women. "The most fundamental assumption in Lehrke's hypothesis is that intelligence is an inherited trait coded for by some finite number of factors called 'intelligence genes.' This claim has evoked great controversy, and many well-known biologists have argued convincingly that [1] it is impossible to define intelligence, and [2] we have no means at our disposal to measure its genetic component separately from its environmental determinants." (p. 19) If that is true then some people may at least agree that it is impossible to show that intelligence is inherited. Under "is heritable" the next decision point would be: (1) Cannot be separated from environmental determinants. (2) Can be separated from environmental determinants. How much does the intelligence of identical twins raised together vary? P0M 04:39, 11 Jul 2004 (UTC)

The problem I see with this approach is that it highlights very minority opinions. Consider just your example. What biologists think about defining intelligence seems less central than what psychologists think (I say that without prejudice, I'm a biologist). Likewise, while we can't measure the genetic and environmental determinants of intelligence in absolute terms, we can determine the extent to which individual differences in intelligence are determined by genes and environment -- the methods of behavior genetics. These two questions can thus be reduced to questioning the validity of psychometrics and behavior genetics respectively. Those may be worthwhile points, but could be put very succinctly. p.s. In his book The g Factor, Arthur Jensen seems to think that men and women have equal average IQs, but he does contemplate whether black women have higher average scores then black men. Rikurzhen


I still don't get the point about heritability being higher among a different age group. If you get one measure with children and another with adults, then you are not measuring heritability, but something else. For example, the height of adults does not change very much. The height of children, however, changes a lot. This does not mean there is a change in heritability. Moreover, we know that the heritability of height is not 100% -- some variation within a population is due to nutrition and exposure to disease. We also know that the influence of these environmental variables is greatest during youth (I think there are three particular times in a child's maturation when these variables matter most). This does not mean that heritability of height is lower among children! Heritability is a measure of the amount of variation that owes to genetics. If environment explains some of that variation, that may be because the environment has an impact during childhood or during adulthood -- but when the environmental impact occurs is a separate question from how much variation is explained by the environment. I think that with intelligence as with height, the heritability figure should be calculated among adults. Slrubenstein

Right, your comment about height is a good point, but it's actually the other way around for IQ. So for height we might assume that the heritability is high to begin with and then drops each time a milestone is reach and environment has a big effect. Overall then heritability would decrease with age. For IQ the measured heritability increases with increasing age groups. This means that the early effects of environment are being neutralized by the effects of genes over time. Idential twins raised apart will start out dissimilar and then become more similar with age -- quite contrary to what you'd expect. One the second note, I don't see why it's a problem to measure heritability at different ages; stricting an analysis to adults -- and which age adults? young, midage or old -- seems like throwing out good data. Rikurzhen

If you say (concerning height) that heritability is lower among adults, when in fact all this means is natural growth process slow and stop with maturation, you could just as well say that the percentage of variation owing to environment is lower among adults too, no? To choose genes over environment in how you interpret the data among adults is to understand heritability as a potential. Remember, the environmental determinants that influence height do not always manifest themselves until adulthood. I am not saying to throw away data on childhood height -- or on childhood intelligence. I am just saying that if heritabily measures the variation within a population, you should make age a constant -- thus, not use it to compare adults and children within the same population. Look, almost all pre-pubescent children are much, much shorter than their parents. It would be a huge mistake to assume that this is mostly because of the environment! The environmental impact (nutrition or health) may not become apparent until after puberty. So why are children so much smaller than their parents? Because they are immature! I mean, biologically immature, they haven't gone through the biological maturation process. If you are comparing children and adults, the variation may be due neither to genetic mutation nor to environment but rather to developmental differences which are genetically coded. To exclude developmental issues as a variable, shouldn't you compare only children with children, adults with adults? Slrubenstein


Hmmm, I think things are simpler than you're making them out to be. Consider just a study of identical twins separated at birth. They share only genes and don't share any environment. Researchers find and pair them up. Some are children, some are young adults, some are middle age, and some are in their 80s. Measure IQ for everyone, and then plot twin A on one axis and twin B on the other. They see a positive correlation. Then, being statistics Nazis, they do all kinds of other tests. One thing they find is that age group matters as to how strongly similar the twins are. Child twins are not strongly similar as compared to the overall twin average. 80 year old twins are amazingly similar as compared to the overall twin average. The researchers conclude that heritability increases with age. That over time, the things that make twins different (their environments) become less of an influence on IQ, and the things that make them idential (their genes) makes them more similar. Repeat this kind of experiment in many different ways -- with non-twins, and adoptees, and etc. -- and most of the time the connection between age and heritability is found. Oh, and I have no idea of how the actual heritability of height changes with age; that would be a worthwhile comparison. Rikurzhen

I think you had better check with your professors, I think this is an improper use of statistics, or at least of the concept of heritability. The example you give does not suggest that heritability increases with age, it does suggest that the influence of the environment only manifests itself later in life -- this is not the same point as heritability is making. In general, heritability should be measured among people at the same developmental state, and should not be used to compare individuals or groups of individuals at different developmental stages. I urge you to find a population geneticist -- someone who actively researches and publishes on population genetics -- and check this. Slrubenstein

I may have messed up something in the description of the experiments, but the conclusions are more of less verbatim from literature. One study of 80 years old made the front cover of Science in June of 1997: http://www.sciencemag.org/cgi/content/short/276/5318/1560 (I'm not a population geneticist, so I don't have any professional insight into the question.) Here's what I know, from [2]
"Heritability has two definitions. The first is a statistical definition, and it defines heritability as the proportion of phenotypic variance attributable to genetic variance. The second definition is more common "sensical". It defines heritability as the extent to which genetic individual differences contribute to individual differences in observed behavior (or phenotypic individual differences)."
From this I don't see why the researchers were making a mistake when they compare the measured heritability for 10 year olds amongst a sample to the measured heritability for 80 years olds amongst a sample. They are both from the same population, so everything else is held constant -- that is, the kind of genetic and environmental factors. Thus the heritability measures should be comparable.
Moreover, I think the example suggests that environment is only important early in life and that this importance is diminished by adulthood. Rikurzhen

Thanks for the citation -- I appreciate it and need time to go over the article. I see where you get your point from. I still don't see how they separate out developmental issues. Slrubenstein

Here's an off topic example to consider [3], the same kind of things done with heart disease, and seems to suggest decreasing heritability with age. (I've only read the abstract though.) Rikurzhen

§ I suppose this has been said before, but it may be relevant to the questions of how the measure of heritability changes with the age of the people being tested: There is no direct measure of intelligence. What we measure are in fact competencies, and the rate at which new competencies can be acquired. We infer a causal factor or factors behind the differences in competencies and their rate of acquisition, but we never actually see it/them. If a person with an IQ of 200 is sequestered from people who can read and never taught to read, s/he will be at a severe disadvantage in dealing with written IQ tests -- even for some time after first learning to read. That is because the simple processes of sounding words out and/or learning words as units can be learned by moderately intelligent students in a school year or so, but the ability to read and absorb information grows with practice for years -- actually, probably until such point as the person ceases to be an active reader.

§ It would take some experimentation to pin things down. Maybe it has already been done. I would hazard the guess that the "increased heritability score" results because in any test population there is a significant percentage of individuals who simply need more practice in reading. (The same general argument would go for math.) The situation with regard to heart disease is different because some individuals will take care of themselves better than their parents and some will take risks with their health and these differences will likely be cumulative, at least in individuals whose health practices are fairly consistent. P0M 00:07, 13 Jul 2004 (UTC)

Removed from Article

In western society children commonly play with pencils or crayons and paper from the age of about two onwards.

This can later give them an advantage in any IQ test involving pencil and paper or pen and paper. The advantage will be culturally determined.

The above passage was added by an anon. contributor. I have removed it because, as it stands, it is unsubstantiated. P0M 17:55, 28 Jul 2004 (UTC)

Regarding the removal of the passage about three races

This passage was included in the text for this article

The three predominatelly used racial groupings are Mongoloid(Asians, also American Indians or Amerinds),Caucasianoid(White Europeans) and Negroid(Black). As discussed previously these classifications are not absolute. Some individuals would be classified into two diffrent racial groups, while others would not clearly fit into any group.

I removed them with an edit summary stating that the text was irrelevent and that its inclusion was inherently POV. They were then added back in. To better serve this case, I'll give a better explanation of why I removed them. Firstly, they are irrelevent to the article. This article is not about race it is about "Race and intelligence". The race article certainly discusses similar information in depth with reasonings for such divisions, and enough context. If this passage belongs anywhere it belongs there. By including it, without proper context, in "Race and intelligence" it implies that this article is discussing how the three presented races might differ in intelligence, which is a POV statement, thus its inclusion is inherently POV. Lastly, since there is an article on race, there does not need to be an example of such racial divisions in this article, as those wishing to see what race means itself will be reading the main race article anyways. Lastly, this information implies that currently, the predominent racial divisions used are these 3, which is patently false, as the majority of the scientific community studying race uses more recent ideas, to present this view alone without the other view is POV. Yet it would unwieldly to present all mainstream ideas of race in this article. Thus I belive it is unneeded, irrelevent, and POV. I would most certainly encourage user:207.68.85.89 to edit the race article if he wishes to have this specific information available there. Anyways, I've removed the passage again (but left it here in the talk page), in order to maintain NPOV in this article. If someone can explain to me why this passage is in fact NPOV, I'll encourage them to include the text. siroχo 02:52, Aug 22, 2004 (UTC)


Understood and appreciated I could list reasons why this should be included in the article, and why the three groupings are vaild scientificcly. However, I will wait and see what the majority of the editors of this article think.

Most scientists consider the three groupings invalid. Moreover, they are used today only in a narrow set of circumstances, generally not by scientists (e.g. police in the US often use them). All of these issues are addressed in the article on race itself and as Siroxo observes, do not belong here. Slrubenstein