Since my interlocutors have done everything to change the subject, I was inclined to start a new thread, where I shall demonstrate that every recent controlled studies demonstrate that the difference of IQ between black and whites is caused by environmental reasons and not racial. Later on, I shall provide other studies demonstrating that the higher level of violence among blacks correlate with the lower IQ among blacks (which is environmental based) rather than their “races.” And to finish, I shall return to the other thread and answer to our two racist members.
To start with, I shall post an article written by Dr. Richard E. Nisbett whom present the old studies and compare them with the newest ones and is inclined to conclude that studies demonstrate that it is the environment which is responsible of the lower IQ. (note, I realise that I may have made a mistake with the study of adopted children, the total number of children in the study was 100, and not 100 black children, only about 20 or so were black, this fact discredit further the study in question.)
First evidences to the court of this board against the other party consisting of two racists.
-----
The article has been published in the work C. Jencks and M. Phillips (Eds.) Black-White Test Score Differences. Washington, D. C.: Brookings Institution. The article has been published in the work C. Jencks and M. Phillips (Eds.) Black-White Test Score Differences. Washington, D. C.: Brookings Institution. Another version of this article(a less recent one) appeared in the work: The Bell Curve Wars (1995), edited by Steven Fraser.
RACE, GENETICS, AND IQ
Richard E. Nisbett
The question of whether IQ differences between blacks and whites have a genetic basis goes back at least a thousand years, to the time when the Moors invaded Europe. The Moors speculated that Europeans might be congenitally incapable of abstract thought. But by the 19th century most Europeans probably believed that they were congenitally superior to Africans in intellectual skills. The IQ test, developed early in the 20th century, re-enforced this view, since whites scored higher then blacks. (Northern Europeans also outscored southern and eastern Europeans, as well as Jews.) Many psychologists assumed that these group differences were genetic in origin. Some U. S. psychologists also argued that continued immigration by low-scoring groups posed severe economic and social risks. Yet by the last quarter of the twentieth century Jews and many of the other European groups initially found wanting in intelligence had higher average IQ scores and higher average incomes than northern Europeans in the United States.
Unlike the differences among European ethnic groups, the IQ difference between European and African Americans persisted throughout the twentieth century, and many Americans continue to believe that a substantial portion of the difference is genetic in origin. For decades, whites scored about 15 points higher than blacks on IQ test. If such a difference were wholly or substantially genetic in origin, the implications for American society would be dire. It would mean that even if the environmental playing field were leveled, a much higher proportion of blacks than whites would have trouble supporting themselves, and a much lower proportion of blacks than whites would be professionals and successful business people. A recent example of this claim can be found in the phenomenally successful book The Bell Curve (1994), by Richard Herrnstein and Charles Murray.
In this chapter I review the evidence on whether the black-white IQ difference (which I refer to as the B/W IQ gap) is wholly or in substantial part due to genetic factors (other than obvious ones like skin color, which affect the way Americans treat each other.) Because The Bell Curve has played such a central role in recent discussions of this issue, I often focus on its claims. For this purpose I will accept the mainstream view on IQ tests and their correlates, including the following assumptions.
1) IQ tests measure something real about intelligence as defined in the modern West.
2) Children's IQ scores predict important life outcomes such as success in school, delinquency and crime, and productive economic behavior. This relationship persists even when we control family background and other social correlates of IQ.
3) Among whites, variation in IQ is to some extent heritable. That is to say, IQ scores vary independently of environmental conditions. Expert estimates suggest that anywhere between 30 and 80 percent of the variation in IQ scores is determined by genetic factors, with 50 to 60 percent being the most commonly accepted range.
4) Estimates of heritability within a given population tell us nothing about the degree to which differences between populations are genetically determined. The classic example is an
experiment in which a random mix of wheat seeds is grown on two different plots of land. Within either plot, the environment is kept uniform, so the height of the different plants is largely or entirely genetically-determined. Yet the average difference between the two plots is still entirely environmental, because the mix of genotypes in each plot is identical. (For a particularly lucid account of heritability and genetic determination in relation to IQ, see Block, 1995).
Despite the fact that the heritability of a characteristic within a population has no necessary relationship to the heritability of differences between populations, many people believe that the large IQ difference between blacks and whites "must" be partly genetic in origin. They argue that if the heritability of IQ within populations is high (especially if it is as high as .8), and if the B/W IQ gap is as large as one standard deviation, the one must assume implausibly large environmental differences between blacks and whites to explain the B/W IQ gap in exclusively environmental terms.
Evidence bearing on the heritability of the B/W IQ gap is of two broad types.
1) Studies of African Americans that correlate their IQ scores with the percentage of their genes that are "European". These are by far the most relevant studies. They are also relatively easy to do in the United States because America classifies individuals as "black" even when they have a very large percentage of "white" ancestors. As much as 30 percent of the "black" American gene pool consists of "European" genes. The conventional genetic hypothesis is that blacks with more European genes should have higher IQ scores. Of course, such a correlation could also arise for environmental reasons. Blacks with lighter skins and more Caucasian features might have social and economic advantages that would make it more likely that they would have high IQs. As a consequence, if there were to be very weak associations between degree of Europeanness and IQ, this would be particularly damaging to the genetic hypothesis.
2) Studies examining the effect of the family environment in which black children are raised. The conventional genetic hypothesis is that rearing blacks in family environments like those of whites should result in little or no gain for blacks. (Of course, even when black children reared in white homes they would be subject to other cultural and social influences that might well depress their IQ scores.)
Despite the assertions of some scholars, including Herrnstein and Murray, a review of the evidence in each of these areas provides almost no support for genetic explanations of the B/W gap.
Studies Directly Assessing Heritability
Five types of studies can make some claim to studying heritability directly. Three types estimate the Europeanness of the genetic heritage of individual blacks — by assessing skin color, by examining blood groups, and by simply asking individuals about their parents and grandparents.
Studies of skin color. Studies relating darkness of skin color and IQ are easy to do and many have been reported over the years. This literature consistently shows that the correlation of IQ with skin color in the black population is quite low. Even Audrey Shuey (1966), one of the most vehement supporters of the view that the B/W IQ gap is genetic in origin, reached the conclusion that IQ is only weakly associated with skin color. Typical correlations are in the range of .15 (and are even less with degree to which facial features are rated as "Negroid"). Even if we ignore the advantages that might accrue to "blacks" with light skin, a correlation of 0.15 does not suggest that European ancestry exerts a strong genetic influence on IQ. On the other hand, many of the studies reviewed by Shuey had small samples and dubious sampling procedures, and moreover the . 15 estimate could be low due to error of measurement. Both skin color and IQ are measured with high reliability, but a major problem with these studies is that while skin color may seem to be a straightforward indicator of degree of European ancestry, it is not. Skin color varies substantially in Sub-Saharan African populations. As a result, some Africans have relatively light skin for reasons that have nothing to do with European ancestry. A strong test of the "European ancestry" hypothesis therefore requires a more reliable indicator.
Studies measuring European ancestry via blood group indicators. Fortunately there are data available that reinforce the null implications of the skin color studies. The frequency of different blood groups varies by race. Under the genetic hypothesis, blacks with mor "European" blood types should have more European genes and hence higher IQs. But Sandra Scarr and her colleagues (Scarr, Pakstis, Katz, & Barker, 1977) found that the correlation between IQ and "European" heritage among blacks was only 0.05 in a sample of 144 black adolescent twin pairs. When skin color and socio-economic status were controlled, the correlation dropped slightly to - .02. Importantly, although they found the typical correlation of. 15 between skin color and IQ, suggesting that the comparable correlations in other studies are due not to Europeanness of genes but to some other factor associated with skin color in the black population.
Loehlin and colleagues (1973) also correlated the estimated Europeanness of blood groups (rather than the Europeanness of individuals, estimated from their blood groups) with IQ in two different small samples of blacks. They found a .01 correlation in one sample and a nonsignificant -.38 correlation in the other sample, with the more African blood groups having higher IQ.
Reported white ancestry. A third approach to estimating blacks' white ancestry is to ask them. Imagine a 15 point B/W IQ difference that is fully genetic in origin. Then think of two groups of blacks: one has only African genes and one has 30 percent European genes. According to the pure genetic model, the first group would be expected to have an IQ 4.5 points lower than the second. If we singled out everyone who had an extremely high IQ — say of 140 — we would expect to find several times as many individuals in the group with 30 percent European genes as in the pure-African gene group.
A study by Witty and Jenkins (1934) identified 63 children in a sample of black Chicago schoolchildren with IQs of 125 or above and 28 with IQs of 140 or above. On the basis of their self reports about ancestry, the investigators classified the children into several categories of Europeanness. The children with IQs of 125 or above, as well as those with IQs of 140 or above, had slightly less European ancestry than the best estimate for the American black population at the time. This study is not ideal. It would have been better to compare the degree of European ancestry of high IQ Chicago children to that of other black Chicago children rather than to the entire black population. But once again, the results are consistent with a model of zero genetic contribution to the B/W gap or, perhaps, a slight genetic advantage for Africans.
Children born to black and white American soldiers in World War II. Eyferth (1961) [ADD UMLAUT TO FURS] examined the IQs of several hundred German children fathered by black American GIs during the post-1945 occupation were compared to those fathered by white GIs. The children fathered by black GIs had an average IQ of 96.5 and the children fathered by white GIs had an average IQ of 97. Inasmuch as the (phenotypic) B/W gap in the military as a whole was close to that in the general population, these data imply that the B/W gap in the U.S. population as a whole is not genetic in origin (Flynn, 1980, pp. 87-88). Note also that the children of the two groups of GIs had similar IQs even though common sense would suggest that environmental conditions were probably inferior for black children.
Mixed race children born to white vs. black mothers. If the black-white IQ gap is entirely genetic, children of mixed parentage should have the same average IQ regardless of which parent was black. If mothers are more important than fathers to the intellectual socialization of their children, and if the socialization practices of whites favor the acquisition of skills that result in high IQ scores, children of white mothers and black fathers should score higher than children of black mothers and white fathers. In fact, [(Willerman et al., 1974) children of white mothers and black fathers have a nine point IQ advantage over those with black mothers and white fathers. This result suggests that most, but perhaps not all of the B/W IQ gap is environmental.
To start with, I shall post an article written by Dr. Richard E. Nisbett whom present the old studies and compare them with the newest ones and is inclined to conclude that studies demonstrate that it is the environment which is responsible of the lower IQ. (note, I realise that I may have made a mistake with the study of adopted children, the total number of children in the study was 100, and not 100 black children, only about 20 or so were black, this fact discredit further the study in question.)
First evidences to the court of this board against the other party consisting of two racists.
-----
The article has been published in the work C. Jencks and M. Phillips (Eds.) Black-White Test Score Differences. Washington, D. C.: Brookings Institution. The article has been published in the work C. Jencks and M. Phillips (Eds.) Black-White Test Score Differences. Washington, D. C.: Brookings Institution. Another version of this article(a less recent one) appeared in the work: The Bell Curve Wars (1995), edited by Steven Fraser.
RACE, GENETICS, AND IQ
Richard E. Nisbett
The question of whether IQ differences between blacks and whites have a genetic basis goes back at least a thousand years, to the time when the Moors invaded Europe. The Moors speculated that Europeans might be congenitally incapable of abstract thought. But by the 19th century most Europeans probably believed that they were congenitally superior to Africans in intellectual skills. The IQ test, developed early in the 20th century, re-enforced this view, since whites scored higher then blacks. (Northern Europeans also outscored southern and eastern Europeans, as well as Jews.) Many psychologists assumed that these group differences were genetic in origin. Some U. S. psychologists also argued that continued immigration by low-scoring groups posed severe economic and social risks. Yet by the last quarter of the twentieth century Jews and many of the other European groups initially found wanting in intelligence had higher average IQ scores and higher average incomes than northern Europeans in the United States.
Unlike the differences among European ethnic groups, the IQ difference between European and African Americans persisted throughout the twentieth century, and many Americans continue to believe that a substantial portion of the difference is genetic in origin. For decades, whites scored about 15 points higher than blacks on IQ test. If such a difference were wholly or substantially genetic in origin, the implications for American society would be dire. It would mean that even if the environmental playing field were leveled, a much higher proportion of blacks than whites would have trouble supporting themselves, and a much lower proportion of blacks than whites would be professionals and successful business people. A recent example of this claim can be found in the phenomenally successful book The Bell Curve (1994), by Richard Herrnstein and Charles Murray.
In this chapter I review the evidence on whether the black-white IQ difference (which I refer to as the B/W IQ gap) is wholly or in substantial part due to genetic factors (other than obvious ones like skin color, which affect the way Americans treat each other.) Because The Bell Curve has played such a central role in recent discussions of this issue, I often focus on its claims. For this purpose I will accept the mainstream view on IQ tests and their correlates, including the following assumptions.
1) IQ tests measure something real about intelligence as defined in the modern West.
2) Children's IQ scores predict important life outcomes such as success in school, delinquency and crime, and productive economic behavior. This relationship persists even when we control family background and other social correlates of IQ.
3) Among whites, variation in IQ is to some extent heritable. That is to say, IQ scores vary independently of environmental conditions. Expert estimates suggest that anywhere between 30 and 80 percent of the variation in IQ scores is determined by genetic factors, with 50 to 60 percent being the most commonly accepted range.
4) Estimates of heritability within a given population tell us nothing about the degree to which differences between populations are genetically determined. The classic example is an
experiment in which a random mix of wheat seeds is grown on two different plots of land. Within either plot, the environment is kept uniform, so the height of the different plants is largely or entirely genetically-determined. Yet the average difference between the two plots is still entirely environmental, because the mix of genotypes in each plot is identical. (For a particularly lucid account of heritability and genetic determination in relation to IQ, see Block, 1995).
Despite the fact that the heritability of a characteristic within a population has no necessary relationship to the heritability of differences between populations, many people believe that the large IQ difference between blacks and whites "must" be partly genetic in origin. They argue that if the heritability of IQ within populations is high (especially if it is as high as .8), and if the B/W IQ gap is as large as one standard deviation, the one must assume implausibly large environmental differences between blacks and whites to explain the B/W IQ gap in exclusively environmental terms.
Evidence bearing on the heritability of the B/W IQ gap is of two broad types.
1) Studies of African Americans that correlate their IQ scores with the percentage of their genes that are "European". These are by far the most relevant studies. They are also relatively easy to do in the United States because America classifies individuals as "black" even when they have a very large percentage of "white" ancestors. As much as 30 percent of the "black" American gene pool consists of "European" genes. The conventional genetic hypothesis is that blacks with more European genes should have higher IQ scores. Of course, such a correlation could also arise for environmental reasons. Blacks with lighter skins and more Caucasian features might have social and economic advantages that would make it more likely that they would have high IQs. As a consequence, if there were to be very weak associations between degree of Europeanness and IQ, this would be particularly damaging to the genetic hypothesis.
2) Studies examining the effect of the family environment in which black children are raised. The conventional genetic hypothesis is that rearing blacks in family environments like those of whites should result in little or no gain for blacks. (Of course, even when black children reared in white homes they would be subject to other cultural and social influences that might well depress their IQ scores.)
Despite the assertions of some scholars, including Herrnstein and Murray, a review of the evidence in each of these areas provides almost no support for genetic explanations of the B/W gap.
Studies Directly Assessing Heritability
Five types of studies can make some claim to studying heritability directly. Three types estimate the Europeanness of the genetic heritage of individual blacks — by assessing skin color, by examining blood groups, and by simply asking individuals about their parents and grandparents.
Studies of skin color. Studies relating darkness of skin color and IQ are easy to do and many have been reported over the years. This literature consistently shows that the correlation of IQ with skin color in the black population is quite low. Even Audrey Shuey (1966), one of the most vehement supporters of the view that the B/W IQ gap is genetic in origin, reached the conclusion that IQ is only weakly associated with skin color. Typical correlations are in the range of .15 (and are even less with degree to which facial features are rated as "Negroid"). Even if we ignore the advantages that might accrue to "blacks" with light skin, a correlation of 0.15 does not suggest that European ancestry exerts a strong genetic influence on IQ. On the other hand, many of the studies reviewed by Shuey had small samples and dubious sampling procedures, and moreover the . 15 estimate could be low due to error of measurement. Both skin color and IQ are measured with high reliability, but a major problem with these studies is that while skin color may seem to be a straightforward indicator of degree of European ancestry, it is not. Skin color varies substantially in Sub-Saharan African populations. As a result, some Africans have relatively light skin for reasons that have nothing to do with European ancestry. A strong test of the "European ancestry" hypothesis therefore requires a more reliable indicator.
Studies measuring European ancestry via blood group indicators. Fortunately there are data available that reinforce the null implications of the skin color studies. The frequency of different blood groups varies by race. Under the genetic hypothesis, blacks with mor "European" blood types should have more European genes and hence higher IQs. But Sandra Scarr and her colleagues (Scarr, Pakstis, Katz, & Barker, 1977) found that the correlation between IQ and "European" heritage among blacks was only 0.05 in a sample of 144 black adolescent twin pairs. When skin color and socio-economic status were controlled, the correlation dropped slightly to - .02. Importantly, although they found the typical correlation of. 15 between skin color and IQ, suggesting that the comparable correlations in other studies are due not to Europeanness of genes but to some other factor associated with skin color in the black population.
Loehlin and colleagues (1973) also correlated the estimated Europeanness of blood groups (rather than the Europeanness of individuals, estimated from their blood groups) with IQ in two different small samples of blacks. They found a .01 correlation in one sample and a nonsignificant -.38 correlation in the other sample, with the more African blood groups having higher IQ.
Reported white ancestry. A third approach to estimating blacks' white ancestry is to ask them. Imagine a 15 point B/W IQ difference that is fully genetic in origin. Then think of two groups of blacks: one has only African genes and one has 30 percent European genes. According to the pure genetic model, the first group would be expected to have an IQ 4.5 points lower than the second. If we singled out everyone who had an extremely high IQ — say of 140 — we would expect to find several times as many individuals in the group with 30 percent European genes as in the pure-African gene group.
A study by Witty and Jenkins (1934) identified 63 children in a sample of black Chicago schoolchildren with IQs of 125 or above and 28 with IQs of 140 or above. On the basis of their self reports about ancestry, the investigators classified the children into several categories of Europeanness. The children with IQs of 125 or above, as well as those with IQs of 140 or above, had slightly less European ancestry than the best estimate for the American black population at the time. This study is not ideal. It would have been better to compare the degree of European ancestry of high IQ Chicago children to that of other black Chicago children rather than to the entire black population. But once again, the results are consistent with a model of zero genetic contribution to the B/W gap or, perhaps, a slight genetic advantage for Africans.
Children born to black and white American soldiers in World War II. Eyferth (1961) [ADD UMLAUT TO FURS] examined the IQs of several hundred German children fathered by black American GIs during the post-1945 occupation were compared to those fathered by white GIs. The children fathered by black GIs had an average IQ of 96.5 and the children fathered by white GIs had an average IQ of 97. Inasmuch as the (phenotypic) B/W gap in the military as a whole was close to that in the general population, these data imply that the B/W gap in the U.S. population as a whole is not genetic in origin (Flynn, 1980, pp. 87-88). Note also that the children of the two groups of GIs had similar IQs even though common sense would suggest that environmental conditions were probably inferior for black children.
Mixed race children born to white vs. black mothers. If the black-white IQ gap is entirely genetic, children of mixed parentage should have the same average IQ regardless of which parent was black. If mothers are more important than fathers to the intellectual socialization of their children, and if the socialization practices of whites favor the acquisition of skills that result in high IQ scores, children of white mothers and black fathers should score higher than children of black mothers and white fathers. In fact, [(Willerman et al., 1974) children of white mothers and black fathers have a nine point IQ advantage over those with black mothers and white fathers. This result suggests that most, but perhaps not all of the B/W IQ gap is environmental.
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