Race and intelligence

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Category: Race

Race and intelligence have in some cases been claimed to be correlated. Contemporary debate on this issue focuses on the nature, causes, and rectifications of ethnic differences in intelligence test scores. The question of the relative roles of nature and nurture in causing individual and group differences in cognitive ability is seen as fundamental to understanding the debate.[1] This is controversial [2][3][4] because theories and hypotheses on racial differences in intelligence are based on correlations in test score and socio-economic achievement differences and not on genetic or neural evidence, [5] and correlation does not prove causation. Genome projects and other biological studies have found no genetic differences which cause differences in intelligence capacity or differences in neural wiring between humans based on race.[6]

Some recent controversy surrounding intelligence and race focuses primarily on the results of intelligence testing studies conducted since the 1950s and onward in the United States, Western Europe, and other industrialized nations.[7] There are also controversies over the nature of race, the purpose and quantifiability of intelligence, and whether the intelligence quotient (IQ) is a culturally biased measure thereof.


[edit] History

The opinion that there are differences in the brain structures or sizes of different racial and ethnic groups was widely held and studied during the 19th and early 20th centuries.[8] During this time period, research on race and intelligence was often used to claim that one race was superior to another, justifying the poor status and treatment of the "inferior" race.[9]

The writings of Sir Francis Galton, a psychometrician and polymath (1822–1911), spurred interest in the study of mental abilities, particularly as they relate to heredity and eugenics.[10] Galton claimed from his field observations in Africa that the African people were significantly below Anglo-Saxons' position in the normal frequency distribution of general mental ability; these claims continue to spark controversy in academia today.[11]

The scientific debate on the contribution of nature versus nurture to individual and group differences in intelligence can be traced back to at least the mid-19th century.[12] Beginning in the 1930s, race difference research and hereditarianism — the belief that genetics are the primary cause of differences in intelligence among human groups — began to fall out of favor in psychology and anthropology after major internal debates.[13] By 1961, the mainstream view was that there were no race differences in intelligence, or if there were, they were solely the result of environmental factors.[14]

[edit] Contemporary issues

Cumulative IQ gaps by race or ethnicity based on 1981 U.S. distributions. According to these findings, WAIS IQs for Whites (mean = 101.4, SD = 14.7) were higher than those for Blacks (mean = 86.9, SD = 13.0); distributions for Hispanics (mean = 91) and East Asians (mean = 106, SD = not provided) are less precise because of overlap and small sample size. Based on Reynolds et al. 1987, p. 330.

The most controversial and most publicized part of the debate is whether group IQ differences also reflect a genetic component. Hereditarianism hypothesizes that a genetic contribution to intelligence could include genes linked to neuron structure or function, brain size or metabolism, or other physiological differences which could vary with biogeographic ancestry.

[edit] The 1970s debates

The modern debate was prompted by psychology professor Arthur Jensen's 1969 publication of the controversial article, "How Much Can We Boost IQ and School Achievement?".[15]

All we are left with are various lines of evidence, no one of which is definitive alone, but which, viewed together, make it a not unreasonable hypothesis that genetic factors are strongly implicated in the average negro-white intelligence difference. The preponderance of evidence is, in my opinion, less consistent with a strictly environmental hypothesis than with a genetic hypothesis, which, of course, does not exclude the influence of environment or its interaction with genetic factors.[15]

According to Peter Singer, the article was widely reported in the popular press "as an attempt to defend racism on scientific grounds".[16]

Physicist William Shockley spent much of his later life focused on the questions of race, intelligence, and eugenics. He began giving speeches on population problems and published several controversial papers arguing that intelligence is primarily hereditary.[17][18] He postulated that the higher reproduction rate of those with lower intelligence was having a dysgenic effect on society and proposed that individuals with IQs below 100 be paid to undergo voluntary sterilization. Biologists and geneticists criticized his theories and compared his arguments for eugenics with the rationale used by the Nazis for their racial policies. He was attacked in the media and in scientific journals. Shockley described his work on the issue as the most important of his career.[19]

Population geneticist Luigi Luca Cavalli-Sforza on several occasions publicly debated Arthur Jensen and William Shockley arguing that environmental factors could explain the black-white IQ gap.[20] In 1981, Stephen Jay Gould published The Mismeasure of Man, which argued against the concept of g, the general factor of cognitive ability.

[edit] The 1990s debates

The question of whether group differences in average IQ are purely social, economic, and cultural in nature or whether genetic factors may also be involved has continued to receive wide media coverage; this prompted a number of academic bodies to make public statements on their views. For example, the American Anthropological Association issued a declaration which dismissed the debate on the grounds that they view 'race' to be a biologically meaningless categorisation of human beings,[21] while the American Psychological Association released a statement in which they acknowledged the reality of inter-group IQ differences, but said that the current evidence, while scarce, did not support a genetic cause.[22] The claim that there are genetic causes for the differences in average IQ scores of different races has been forwarded by scholars such as Charles Murray, Michael Levin, and J. Philippe Rushton. Their research has been criticized by other scholars such as Stephen Jay Gould,[23] Richard Levin, Richard Lewontin[24] and Joseph L. Graves.[25]

The publication of The Bell Curve, a best-selling 1994 book by American psychologist Richard Herrnstein and American Enterprise Institute political scientist Charles Murray, which included a discussion of racial differences in intelligence, received much attention in the popular press and ignited renewed debate within academia and amongst the general public. Its central point is that intelligence is a better predictor of many factors including financial income, job performance, unwed pregnancy, and crime than parents' socioeconomic status or education level. Also, the book argued that those with high intelligence (the "cognitive elite") are becoming separated from the general population of those with average and below-average intelligence, and that this was a dangerous social trend. Much of the controversy concerned Chapters 13 and 14, in which the authors wrote about the enduring racial differences in intelligence and discussed implications of those differences. The authors were reported throughout the popular press as arguing that racial IQ differences are genetic, although they state no position on the issue in the book, and write in the introduction to Chapter 13 that "The debate about whether and how much genes and environment have to do with ethnic differences remains unresolved."

Shortly after publication, many people rallied both in criticism and defense of the book. Some critics denounced the book and its authors as supporting scientific racism. A number of critical texts, including The Bell Curve Debate and The Mismeasure of Man (second edition), were published in response to the book. Several collective statements were released by groups of scholars.

The American Psychological Association's Board of Scientific Affairs in 1995 established a special task force to publish an investigative report on the research presented in the book. The report, titled "Intelligence: Knowns and Unknowns"[22] and published in the February 1996 issue of American Psychologist, agreed with some of the book's statements on intelligence;[26] however, regarding the book's genetic implications, it states:

It is sometimes suggested that the Black/White differential in psychometric intelligence is partly due to genetic differences (Jensen, 1972). There is not much direct evidence on this point, but what little there is fails to support the genetic hypothesis.[27]

The January 1997 issue of American Psychologist published an article with eleven critical responses to the American Psychological Association (APA) report, most of which agreed with the substance of the report, but suggested ways in which the report could have been improved. According to the report's lead author, only Lynn and Rushton "dispute[d] the task force's conclusion that there is no direct evidence for a genetic interpretation of the Black—White IQ difference."[28] The APA report concluded with a call for more reflection in debates on intelligence and for a "shared and sustained effort" in more research to answer the many unanswered questions that remain.

A collective statement titled "Mainstream Science on Intelligence" was published in the Wall Street Journal on December 13, 1994.[29] It was written by psychology professor Linda Gottfredson, and signed by Gottfredson and 51 other professors specializing in intelligence and related fields. It listed 25 statements which claimed to uphold findings on the subject of intelligence research discussed in the The Bell Curve. This statement was reprinted in the psychology journal Intelligence in 1997 with additional information and a bibliography. Regarding the cause of racial-ethnic group differences in IQ, the statement says:

There is no definitive answer to why IQ bell curves differ across racial-ethnic groups. The reasons for these IQ differences between groups may be markedly different from the reasons for why individuals differ among themselves within any particular group (whites or blacks or Asians). In fact, it is wrong to assume, as many do, that the reason why some individuals in a population have high IQs but others have low IQs must be the same reason why some populations contain more such high (or low) IQ individuals than others. Most experts believe that environment is important in pushing the bell curves apart, but that genetics could be involved too.[30]

In 1994, the American Anthropological Association published a statement, declaring the organization was:

deeply concerned by recent public discussions which imply that intelligence is biologically determined by race. Repeatedly challenged by scientists, nevertheless these ideas continue to be advanced. Such discussions distract public and scholarly attention from and diminish support for the collective challenge to ensure equal opportunities for all people, regardless of ethnicity or phenotypic variation.[31]

[edit] Policy debates

See also: Intelligence and public policy

Public policy implications of IQ and race research are one of the greatest sources of controversy surrounding this issue. Regardless of the source of the IQ gap, most educators agree that it must be addressed; they often advocate equitable funding for education.[32][33] An achievement gap refers to the observed disparity on a number of educational measures between the performance of groups of students, including groups defined by race or ethnicity.

Some proponents of a genetic interpretation of the IQ gap, such as Rushton and Jensen (2005a) and Gottfredson (2005b), have sometimes argued that their interpretation does not in itself demand any particular policy response: while a conservative/libertarian commentator[34] may feel the results justify, for example, reductions in affirmative action, a liberal commentator may argue from a Rawlsian point of view (that genetic advantages are undeserved and unjust) for substantial affirmative action.[35] Since all races have representatives at all levels of the IQ curve, this means any policy based on low IQ affects members of all races.

In the book Practical Ethics, philosopher Peter Singer wrote that:

Let us suppose that the genetic hypothesis turns out to be correct... I believe that the implications of this supposition are less drastic than they are often supposed to be... First, the genetic hypothesis does not imply that we should reduce our efforts to overcome other causes of inequality between people... Perhaps we should put special efforts into helping those who start from a position of disadvantage, so that we end with a more egalitarian result. Second, the fact that the average IQ of one racial group is a few points higher than that of another does not allow anyone to say that all members of the higher IQ group have higher IQs... The point is that these figures are averages and say nothing about individuals... The third reason... is simply that, as we saw earlier, the principle of equality is not based on any actual equality that all people share. I have argued that the only defensible basis for the principle of equality is equal consideration of interests... Equal status does not depend on intelligence. Racists who maintain the contrary are in peril of being forced to kneel before the next genius they encounter.

Policies focused on geographical regions or nations may have disproportionate influences on certain racial groups and on cognitive development.[who?] Differences in health care, nutrition, regulation of environmental toxins, and geographic distribution of diseases and control strategies between the developing world and developed nations have all been subjects of policies or policy recommendations (see Health and intelligence).

Eugenics advocates the improvement of human hereditary traits through various forms of intervention. After World War II, both the public and the scientific communities associated eugenics with Nazi abuses, such as enforced racial hygiene, human experimentation, and the extermination of undesired population groups. Beginning in the 1980s, the history and concept of eugenics were again widely[citation needed] discussed as knowledge about genetics advanced significantly; developments in genetic, genomic, and reproductive technologies raised many new questions and concerns about eugenics and its ethical and moral status in the modern era.

[edit] Test score difference

[edit] United States

The observed differences in average test score achievement between ethnic groups varies depending on the populations studied and the type of tests used. Self defined black and white United States citizens have been the subjects of the greatest number of studies. Black-White average IQ differences appear to increase with age, averaging nearly 17 points by age 24.[36] According to James Flynn, the overall average Black-White gap has reduced by one third over the last 30 years.[36] A large (21,260 children) and probably the most recent (1998) study found that the Black-White gap for young children in reading and math scores was much smaller than in earlier studies.[37] Black-White differences on school achievement tests shrunk over the last 30 years, but some of the improvements did not continue through the 1990s. The average black-white IQ difference also varies depending on test content. For example, two subsections of the WISC IQ test, known as forward and reverse digit-span, ask children to repeat a long series of numbers either forwards or backwards. The black-white difference on forward digit span is relatively small, while the difference on reverse digit span is relatively large. Across a battery of tests, the size of the Black-White gap is correlated with the extent to which the tests measure the psychometric factor g, which also accounts for most of the variation in interindividual differences in IQ test performance.[38] Using a variety of statistical techniques, Dolan and colleagues have found that the black-white IQ gap can be accounted for by differences in g and the other interindividual ability factors measured by IQ tests, and also that IQ tests measure roughly the same mix of abilities in both black and white populations.[39][40][41] Gaps are seen in other tests of cognitive ability or aptitude, including university admission exams such as the SAT and GRE as well as employment tests for corporate settings and the military.[42]

The IQ distributions of other racial and ethnic groups in the United States are less well studied. Hispanic and Native American populations, including Arctic Natives,[43][44] tend to score worse on average than White populations but better on average than Black populations.[45] East Asian populations may score higher on average than White populations in the United States as they do elsewhere.[46] Studies such as that of Backman (1972), Levinson (1959) and Romanoff (1976) estimate Ashkenazi Jews to score 0.75 to 1.0 standard deviations above the general European average in verbal IQ, or crystallized IQ, corresponding to an IQ of 112-115. A recent review by Lynn (2004) concludes that the advantage is slightly less, only half a standard deviation.[47][48] For each of these populations, there is some evidence that the mixture of ability factors that distinguish individuals are differentially distributed between groups. For example, East Asian populations tend to outscore White populations on tests of visuospatial ability, whereas the test score differences skew towards higher verbal ability for Ashkenazi-White differences. However, the mixture of abilities within groups appears to be nearly identical across many ethnic groups.[49] The stability of these differences is also less well studied than Black-White differences.

[edit] Worldwide

According to Richard Lynn, J. Philippe Rushton, and others, IQ test score differences are observed cross-culturally and around the world. Lynn has published three books summarizing IQ test scores from around the world.[50] The accuracy of the cross cultural IQ scores is highly controversial, but many scholars use the results as an estimate of worldwide IQ scores.[51][52][53][54] Lynn's meta-analysis lists East Asians (105), Europeans (99), Inuit (91), Southeast Asians and Amerindians (87 each), Pacific Islanders (85), Middle Easterners (including South Asians and North Africans) (84), sub-Saharan Africans (67), and Australian Aborigines (62).[55][56][57] International achievement test scores, including TIMSS and PISA, have also been used to estimate average IQ worldwide with similar results where data is available.[54][58][59][60] The very low IQ scores reported for sub-Saharan African populations is especially controversial. For example, Wicherts argues that the average IQ of sub-Saharan Africans is poorly measured and is more likely 78.[61] Sternberg, a critic of Rushton and Lynn, reported an average IQ of 70 for "young adolescents" in Kenya.[62] There is a paradox from IQ studies in Africa that has yet to be resolved. Europeans with an IQ of 70 are considered mentally handicapped. However, the Africans found to have an IQ of 70 were perfectly normal with the apparent ability to function normally in their social environment. This has led to questions of the validity of these IQ tests[63][64] A 1995 study published in the Journal of Nutrition concluded that IQ scores of children in the West Indies are depressed to some extent by environmental conditions, such as macronutrient and micronutrient deficiencies[65][66] and even blood lead levels.[67] The study suggested the existence of broader links between malnutrition and IQ levels across the developing world as a whole.[68]

Furthermore, studies by James Flynn have shown that African-American children generally have IQs around 95.4 at age four and lose IQ points as they get older down to about 85. This phenomenon demonstrates some of the fluidity and malleability of IQ.[69] Other examples of the Flynn effect include the phenomenon of Ashkenazi Jewish immigrants at the turn of the century scoring low on IQ tests[70], which was used by eugenicists and racists at the time to bludgeon them and push anti-Jewish immigration policies[71][72] where as now Ashkenazi Jews often score very high on IQ tests. Similarly, southern Italian immigrants in the US scored below 80 on IQ tests in the early 20th century[73] but had improved their average scores in later decades, bringing the validity of theories of genetically fixed and racially based IQ into further question. Other such factors which throw the validity of racial IQ into question is the fact that Americans generally have IQ that are different from that of the IQ of the people in their country of ancestral origin.[74]

[edit] Genetic and environmental factors

The cause(s) of group average IQ test score differences are not known but hypotheses have been proposed. Many scholars have offered descriptions of the variety of hypotheses that have been proposed. These descriptions usually distinguish between those hypotheses which invoke a contribution of genetic factors and those which solely invoke environmental (i.e., non-genetic) factors. Some descriptions of the positions are themselves controversial. In a review published in 2007, Hunt and Carlson listed four positions.[75] The first position, attributed to Jensen and Rushton, is that group differences in IQ reflect differences in intelligence that are "due in substantial part to genetically determined differences in brain structure and/or function"[75] The second position, attributed to Ogbu and Sowell, is that the differences in intelligence test scores are due to social factors. The third view, attributed to Sternberg and colleagues, is that the use of IQ scores to argue for differences in intelligence is an inappropriate use of tests in different groups. The fourth position, attributed to Fish and others, is that there is no such thing as race: "a term motivated by social concerns and not a scientific concept".[75]

Prominent proponents of the genetic hypothesis are predominately psychologists or experts in intelligence testing, such as Charles Spearman, Hans Eysenck, Arthur Jensen, J. Philippe Rushton, Linda Gottfredson, Richard Herrnstein, and David C. Rowe. A few prominent proponents have come from other fields, such as political scientist Charles Murray, evolutionary psychologist Satoshi Kanazawa, and philosophers Michael Levin and Neven Sesardic. Not all proponents share the same views, nor have all of their views been constant throughout their careers. Prominent critics come from many backgrounds, and hold a diversity of views. They include psychologists and experts in intelligence testing such as James Flynn (prior to his work on IQ Flynn was a political scientist), Ulric Neisser, Robert Sternberg, and a number of less well known psychometricians who criticize the underlying IQ test data. Other critics include economists Thomas Sowell and Roland G. Fryer Jr. anthropologists such as Ashley Montagu, Leonard Lieberman, and Jonathan Marks argue that "race" is a social and not a biological concept. For example Marks (1996) argues that the eugenics movement of the 1920s identified Ashkenazi Jews from Europe as intellectually inferior due to their genetics, but that Murray and Herrnstein claim this group as a "cognitive elite" in The Bell Curve, concluding that "race" is a social construct that does not reflect underlying biology.[76] Sociologists John Ogbu, Claude S. Fischer and Troy Duster, paleontologist Stephen Jay Gould, geneticist Richard C. Lewontin and evolutionary biologist and physiologist Jared Diamond also oppose the genetic hypothesis.

The genetic hypothesis has been characterized as inherently racist. For example, Turkheimer argues that proponents of a genetic contribution, whom he calls "racialists", deserve "vigorous disapprobation" and do not deserve "respect".[77] Turkheimer writes that he disagrees with his colleagues, such as Flynn and Ceci, who "agree that the question is a legitimate matter for scientific inquiry, to be settled by cool-headed evaluation of the empirical evidence".[77] Flynn does not accept Turkheimer's arguments.[78] Rushton and Jensen argue that the policy issues should be regarded as separate from the academic inquiry.[79]

[edit] What is heritability?

An environmental factor that varies between groups but not within groups can cause group differences in a trait that is otherwise 100% heritable. The height of this "ordinary genetically varied corn" is 100% heritable, but the difference between the groups is totally environmental. This is because the nutrient solution varies between populations, but not within populations.[80]

The consensus among intelligence researchers is that IQ differences between individuals of the same racial-ethnic group reflect real, functionally and socially significant, and substantially heritable differences in intelligence.[81][82][83][84][85][86][87][88][89]

Concordance rates for IQ from twin studies and other study designs consistently fall in the range of 50% to 80%, with the estimated heritability in young (preschool) children in the lower range and adults in the higher range.

Critics have also questioned the interpretation of heritability as a whole. Lewontin suggests that some genotypes are more influenced by environments than others, leading to the possibility that populations that have similar genetic variance in the same environment can have different heritabilities because of their different genotypes.[90] David Layzer (1974) contends that the development of a trait can be influenced by genetic differences qualitatively and that heritability estimates cannot measure such qualitative differences, as such it is possible that even with a heritability of close to 100% it is possibly for phenotypic variance to be due largely to environment.[91]

[edit] Genetic hypothesis

Socioeconomic status (SES) varies both between and within populations, but Black-White differences in IQ persist among the children of parents matched for SES, and the gap is largest among the children of wealthiest and best educated parents.[92]

Much of the research on explaining group differences stems from an observation promoted first by Arthur Jensen and later James Flynn and others regarding an environmental explanation for group differences. According to Jensen[93] the very high within-group heritability of IQ (within both white and black populations) presents a problem for environmental explanations of group differences in IQ. They consider two general classes of environmental factors: common environmental factors and X-factors. Common environmental factors vary within and between populations. X-factors vary between populations, but do not vary substantially within populations. They first consider common environmental factors. To account for a 1 SD B-W IQ gap only in terms of common environmental factors would require very large environmental differences. For example, if the within-group heritability of IQ is 80%, then a B-W IQ difference of 2.24 SD in common environmental factors is required. For a heritability of 40%, a difference of 1.29 SD is required. Jensen and Flynn agree that it is an empirical question whether common environmental factors that influence IQ differ between whites and blacks to such an extent, and both agree that most commonly suggested environmental factors do not. Jensen believes that empirical evidence supports the view that the B-W IQ gap is caused by both common environmental factors and genetic factors. Flynn disagrees and believes that empirical evidence supports the view that the B-W IQ gap is caused by yet unrecognized environmental factors.[94]

The alternative to common environmental factors is to hypothesize that X-factors account for the B-W IQ gap. A frequently-cited example from Lewontin describes the effect of a hypothetical X-factor. Imagine that the height of "ordinary genetically varied corn" is 100% heritable when grown in a uniform environment. Further imagine that two populations of corn are grown: one in a normal nutrient environment and the other in a deficient nutrient environment. Consequently, the average height of the corn grown in the deficient nutrient environment is less than the average height of the corn grown in the normal environment. In such a scenario, the within-group heritability of height is 100% in both populations, but the substantial difference between groups are due entirely to environmental factors. The quality of the nutrient is an "X-factor" in the language of Jensen and Flynn. With respect to the B-W IQ gap, Jensen suggests that effects associated with racism (both overt and institutionalized racism) might be X-factors. Flynn believes that attributing the B-W gap to the effects of racism is incorrect, because the most plausible ways in which discrimination could affect IQ are themselves common environmental factors. These may include psychological effects such as stereotype threat; biological effects such as poor nutrition, health care and living close to toxic environments; and educational effects such as a lack of good schools. Instead, Flynn and his colleague William Dickens have developed more complicated models to explain the black-white gap in terms of environmental factors. One initial motivation of the Dickens-Flynn theory was Flynn's observation that IQ test scores have been rising over time in countries around the world – termed the Flynn effect. Flynn and others believe an explanation for the Flynn effect may elucidate the cause of the B-W gap. Jensen and others disagree.

A few of the notable proponents of the partly genetic hypothesis are Raymond B. Cattell, Arthur Jensen and Hans Eysenck.

Rushton and Jensen examined 10 categories of research evidence from around the world to contrast "a hereditarian model" (50% genetic-50% cultural) and a culture-only model (0% genetic-100% cultural). Their article "Thirty Years of Research on Race Differences in Cognitive Ability" was published in the APA journal Psychology, Public Policy and Law showing evidence that they believe supports the hereditarian model.[95][96] Rushton and Jensen (2005a) believe that the best explanation for the gap is that 50%-80% of the group differences in average US IQ is genetic.[97]

Other evidence, such as the Minnesota Transracial Adoption Study, certain racial admixture studies, behavior genetic modeling of group differences, "life-history" traits, and evolutionary explanations have also been proposed to indicate a genetic contribution to the IQ gaps and explain how these arose.[98]

The decoding of the human genome has enabled scientists to search for sections of the genome that contribute to cognitive abilities. Current studies using Quantitative trait loci have yielded little success in the search for genes influencing intelligence. Robert Plomin is confident that QTLs responsible for the variation in IQ scores exist, but that more powerful tools of analysis will be required to detect them.[99]

[edit] Environmental effects

Critics of the significantly genetic view, such as Robert Sternberg, argue that these studies are either flawed and thus inconclusive, or else that they support a primarily environment (<20% genetic) hypothesis.[100] For example, Dolan and Hamaker (2001) argue that the statistical methods linking the Black-White gap to g are insufficient. They reanalyzed the data from several earlier studies and concluded that Spearman's hypothesis is not an "empirically established fact" (i.e., that Black-White IQ differences may be due to differences in common factors other than g) due to insufficient power in the data to choose between alternative models. "This leaves the validity of Spearman's hypothesis, considered a central justification for the genetic explanation, an unresolved question." However, they did confirm that the Black-White IQ gap is not due to measurement artifacts, and is instead due to some measured factor that varies both within and between groups.

Nisbett (2005) argues that many studies find results that do not support the genetic hypothesis. They include studies on IQ and skin color that reported that the average correlation between skin color and IQ is .1 (the average correlation between IQ and judged “Negroidness” of features is even lower); IQ and self-reported European ancestry; IQ and blood groups showing degree of European Ancestry; IQ among children in post WWII Germany born to black and white American soldiers; and IQ among mixed-race children born to either a black or a white mother. He argues that these are direct tests of the genetic hypothesis and of more value than indirect variables, such as skull size and reaction time. He argues that "There is not a shred of evidence in this literature, which draws on studies having a total of five very different designs, that the gap has a genetic basis." He argues further that many intervention and adoption studies also find results that do not support the genetic hypothesis. He also argues "that the Black-White IQ gap has lessened considerably in recent decades."[101] Hunt and Carlson[46] argue that Nisbett's interpretations are far too strong in light of problems with these studies that have been recognized for decades.[102] Gottfredson writes that the studies Nisbett cites "actually lack the ability to rule out any hypothesis at all, genetic or not".[103]

Dickens (2005) states that "Although the direct evidence on the role of environment is not definitive, it mostly suggests that genetic differences are not necessary to explain racial differences. Advocates of the hereditarian position have therefore turned to indirect evidence...The indirect evidence on the role of genes in explaining the black-white gap does not tell us how much of the gap genes explain and may be of no value at all in deciding whether genes do play a role. Because the direct evidence on ancestry, adoption, and cross-fostering is most consistent with little or no role for genes, it is unlikely that the black-white gap has a large genetic component."[104]

Fryer and Levitt (2006), with data from "the first large, nationally representative sample" of its kind, report finding only a very small racial difference when measuring mental function for children aged eight to twelve months, and that even these differences disappear when including a "limited set of controls". "On tests of intelligence, Blacks systematically score worse than Whites, whereas Asians frequently outperform Whites. Some have argued that genetic differences across races account for the gap. Using a newly available nationally representative data set that includes a test of mental function for children aged eight to twelve months, we find only minor racial differences in test outcomes (0.06 standard deviation units in the raw data) between Blacks and Whites that disappear with the inclusion of a limited set of controls. The only statistically significant racial difference is that Asian children score slightly worse than those of other races." They argue that their report poses "a substantial challenge to the simplest, most direct, and most often articulated genetic stories regarding racial differences in mental function." They conclude that "to the extent that there are any genetically-driven racial differences in intelligence, these gaps must either emerge after the age of one, or operate along dimensions not captured by this early test of mental cognition."[105]

[edit] The Flynn effect

The secular, international increase in test scores, commonly called the Flynn effect, is seen by Flynn and others as reason to expect the eventual convergence of average black and white IQ scores. Flynn argues that the average IQ scores in several countries have increased about 3 points per decade during the 20th century, which he and others attribute predominantly to environmental causes.[106] This means, given the same test, the mean performance of African Americans today could be higher than the mean for white Americans in 1920, though the gains causing this appear to have occurred predominantly in the lower half of the IQ distribution.[107] If an unknown environmental factor can cause changes in IQ over time, they argue, then contemporary differences between groups could also be due to an unknown environmental factor. An added complication to this hypothesis is the question of whether the secular IQ gains can be predominantly a real change in cognitive ability. Flynn's face-value answer to this question is "No",[108] and some other researchers have found reason to concur. In terms of the mixture of ability factors that IQ tests were designed to measure, such as g and verbal and mathematical ability, changes in IQ scores over time are different than either within-group individual differences and between group differences.[109][110] For example, there has been little increase over time in performance on either the forward digit-span or reverse digit-span subtests, and tests of school achievement have been less affected than tests of abstract reasoning.[111] Other recent studies have found that g has improved substantially.[112][113] Cranial vault size has increased and the shape changed during the last 150 years in the US; these changes must occur by early childhood because of the early development of the vault.[114] It also estimated that the average white IQ in past decades was lower than current average black IQs, a fact which shows the change of IQ over time. [115] But while black Americans in the early 21st century may score higher than white Americans in the early 19th century, the fact remains that the roughly 1 standard deviation IQ gap between black and white Americans living at the same time has held constant since the earliest days of intelligence testing, convincing some observers like Richard Lynn that the black-white gap in the U.S. is not only genetic, but 100% genetic. Indeed Arthur Jensen is struck by how consistent the gap has been, despite the enormous rise in the scores of both races.

[edit] Health

Percentage of children aged 1-5 with blood lead levels at least 10 µg/dL. Black and Hispanic children have measurably higher levels than white children. High levels of lead at an early age may affect intelligence.

Numerous explanations beside genetics have been proposed to account for the IQ gaps in the U.S.[116] High rates of low birth-weight babies, lower rates of breastfeeding, and exposure to toxins are some factors. The Flynn effect is often cited as evidence that average IQ scores have changed greatly and rapidly, for reasons poorly understood, thus the IQ gap between races could change in the future or is changing, especially if the Flynn effect started earlier for Whites.

High levels of lead at an early age may affect intelligence; studies indicate that black and Hispanic children have measurably higher levels than white children. A 10 µg/dL increase in blood lead at 24 months of age is associated with a 5.8-point lower IQ later in life.[117] In 1976 77.8% of all children had at least this much lead in their blood.[118]

Exposure to lead is frequently attributed to housing conditions including lead based paint, which is no longer used but has accumulated in older buildings; people of lower economic means are more frequently exposed to lead from housing.[119]

[edit] Stereotype threat

Stereotype threat is the fear that one's behavior will confirm an existing stereotype of a group with which one identifies; this fear may in turn lead to an impairment of performance.[120] Testing situations that highlight the fact that intelligence is being measured tend to lower the scores of individuals from racial-ethnic groups that already score lower on average. Stereotype threat conditions cause larger than expected IQ differences among groups but do not fully explain the gaps found in non-threatening test conditions.

[edit] Quality of education

Some researchers have written that studies that find test performance gaps between races even after adjusting for education level, such as the analysis found in The Bell Curve, fail to adjust for the quality of education. Not all high school graduates or college graduates have received the same quality of education. A 2006 study reported that years of education is an inadequate measure of the educational experience among multicultural elders, and that adjusting for quality of education greatly reduced the overall effect of racial differences on the tests.[121] A 2004 study reported that quality of education and cultural experience influence how older African Americans approach neuropsychological tasks and concluded that adjustment for these variables may improve specificity of neuropsychological measures.[122] Yet another study reported that, although significant differences were observed between the ethnic groups when matched for years of education, equating for literacy level eliminated all performance differences between African Americans and European Americans on both cancellation tasks which assess visual scanning[123] (like reaction time tests, cancellation task tests are sometimes regarded as "culture free" tests of intelligence). Eric A. Hanushek and Steven G. Rivkin wrote in their 2006 book that unequal distributions of inexperienced teachers and of racial concentrations in schools can explain all of the increased achievement gap between grades 3 and 8.[124] In recent years there have also been studies into the degrees in which many minorities, especially blacks, have internalized pathologies about their supposed lack of intelligence and the effects it has in their self-confidence, quality of learning and achievement.[125] Additionally, Jensen's studies (Jensen, 1974b) show that 7% of black children of black professionals have mean IQs below that of white children from low-income families, yet this seems to have little to no detriment on the black children's success.[126]

A 2004 study in South Africa found highly significant effects for both level and quality of education within the black African first language groups taking the Wechsler IQ tests. The scores of black African first language groups with advantaged education were comparable with the US standardization, whereas scores for black African first language participants with disadvantaged education were significantly lower than this. The study cautioned that faulty conclusions may be drawn about the effects of ethnicity and the potential for neuropsychological misdiagnosis.[127]

[edit] Racial discrimination in education

Roslyn Arlin Mickelson writes that racial discrimination in education arises from actions of institutions or individual state actors, their attitudes and ideologies, or processes that systematically treat students from different racial/ethnic groups disparately or inequitably.[128] Despite advancement in education reform efforts, to this day African American students continue to experience inequities within the educational system. Hala Elhoweris, Kagendo Mutua, Negmeldin Alsheikh and Pauline Holloway conducted a study of the effect of students' ethnicity on teachers' educational decision making. The results of this study indicated that the student's ethnicity did make a difference in the teachers' referral decisions for gifted and talented educational programs.[129] Recently, a number of scholars have examined the issue of disproportionate representation of minority students in special education programs[130][131]

Teachers' perceptions of a students cultural background may affect school achievement. African American students with African American cultural backgrounds, for example, have been found to benefit from culturally responsive teaching.[132] In a 2003 study researchers found that teachers perceived students with African American culture-related movement styles as lower in achievement, higher in aggression, and more likely to need special education services than students with standard movement styles irrespective of race or other academic indicators.[133]

Ellis Cose writes that low expectations may have a negative impact on the achievement of minorities. He writes that black people did not need to read The Bell Curve to be aware of the low expectations held for them by the majority culture. He recalls examples of low expectations from his teachers in school who regarded his use of AAVE as "laziness" and teachers who did not feel it was important to purchase new text books because they did not expect the students to be able to read anything complex. He contrasts these low expectations with the high expectations philosophy of Xavier University where, using the ideas Whimbey articulated in his book Intelligence can be Taught teachers created a program called SOAR. SOAR raised the performance of black students and lead Xavier to become the university that sends the greatest number of black students to medical school in the United States. The SOAR program produced gains equivalent to 120 points on an SAT test. Cose writes that "..we must treat people, whatever their color, as if they have unlimited intellectual capacity."[134]

[edit] Caste-like minorities

The book Inequality by Design: Cracking the Bell Curve Myth claims that it is not lower average intelligence that leads to the lower status of ethnic minorities, it is instead their lower status that leads to their lower average intelligence test scores. The following table from the same book compares social status or caste position to test scores and school success in countries around the world.[135]

Group Differences Around the World
  Status or Caste Position Test Scores, School Success
Country High Low High Low
United States[136] Whites Blacks Whites Blacks
  Asians Latinos Asians Latinos
  East Asians Southeast Asians East Asians Southeast Asians
  Whites American Indians[137] Whites American Indians
Great Britain[138] English Irish, Scottish English Irish, Scottish
Northern Ireland[139] Protestants Catholics Protestants Catholics
Australia[140] Whites Aborigines Whites Aborigines
New Zealand[141] Whites Maoris Whites Maoris
South Africa[142] English Afrikaners English Afrikaners
Belgium[143] Flemish French Flemish French
Israel[144] Jews Arabs Jews Arabs
  Western Jews Eastern Jews Western Jews Eastern Jews
India[145] Nontribals Tribal people Nontribals Tribal people
  Brahmin Dalit Brahmin Dalit
  High caste Low caste High caste Low caste
Czechoslovakia[146] Slovaks Gypsies Slovaks Gypsies


  1. Czechoslovakia split into the Czech Republic and Slovakia in 1993.
  2. The Flemish are not a minority in Belgium. The PISA 2006 results for schoolchildren 15 years of age showed that the Flemish outperformed the Walloons (French).[147]
  3. Afrikaans speakers make up the majority of the white population; most South Africans, however, identified themselves in the census as black, and speak one of the Bantu languages as their home language[148]

[edit] Viewpoints of notable scientists and researchers

Given the observed differences in IQ scores between certain groups, a great deal of debate revolves around the significance of these observations. Various interpretations of test data lead to a multitude of conflicting conclusions as to which specific explanations the data support.

The range of views among contemporary scholars include:

  • James Flynn argues that differences in cognitive abilities between races exist and are of social/environmental origin.
  • Arthur Jensen argues that differences in cognitive abilities between races exist and are caused by both social/environmental disparities and also genetic differences between races.
  • Ashley Montagu and Joseph L. Graves, amongst others, argue that race is not a biological concept, but rather is socially constructed, and hence measurements of IQ differences between races cannot reflect an underlying intrinsic biological cause.[149][150][151]
  • Robert Sternberg argues that the use of differences in test scores to argue for race differences in intelligence is a case of the inappropriate use of tests in different groups.

Researchers who believe that there is no significant genetic contribution to race differences in intelligence include:

Flynn (1980), Brody (1992), Neisser et al. (1996), Nisbett (1998), Mackintosh (1998), Jencks and Phillips (1998), and Fish (2002).

Some scientists who emphasize cultural explanations do not necessarily exclude a small genetic influence. Reynolds (2000) suggests up to 20% genetic influence be included in the cultural explanation.

Researchers who believe that there are significant genetic contributions to race differences in intelligence include:

McGurk (1953), Garrett (1961), Shuey (1966), Shockley (1968), Eysenck (1971), Baker (1974), Loehlin et al. (1975), Vernon (1979), Lynn (1991a), Waldman et al. (1994), Scarr (1995), Levin (1997), Jensen (1998b), Rushton (2000), and Gottfredson (2005b).[152]

Coming advances in genetics and genomics are expected to soon provide the ability to test hypotheses about group differences more rigorously than has as yet been possible.[153]

Jared Diamond's Guns, Germs and Steel instead argues that historical differences in economic and technological development for different geographic areas can be explained by differences in geography (which affects factors like population density and spread of new technology) and differences in available crops and domesticatable animals. Richard Nisbett argues in his 2004 The Geography of Thought that some of these regional differences shaped lasting cultural traits, such as the collectivism required by East Asian rice irrigation, compared with the individualism of ancient Greek herding, maritime mercantilism, and money crops wine and olive oil[154] However, it has been suggested that these environmental differences may operate in part by selecting for higher levels of IQ.[155]

J. Philippe Rushton, a professor of psychology at the University of Western Ontario and the current head of the Pioneer Fund, has written a controversial book called Race, Evolution, and Behavior: A Life History Perspective. Rushton claims in the book that race is a valid biological concept and that racial differences frequently arrange in a continuum of Mongoloids (Orientals, East Asians) at one extreme, Negroids (blacks, Africans) at the opposite extreme, and Caucasoids (whites, Europeans) in the middle.[156] It has been heavily criticized.

Differing rates of economic growth have also been attributed to numerous factors other than racial IQ gaps such as local availability of resources, climate, and sociopolitical factors. See for example the Global Competitiveness Report, the Ease of Doing Business Index, and the Index of Economic Freedom or works by Kenneth Pomeranz,[157] Eric Jones,[158] Joel Mokyr,[159] and Douglass C. North.[160]

[edit] Criticisms

[edit] Outdated methodology

A 2006 paper by Professor Denny Borsboom argues that mainstream contemporary test analysis does not reflect substantial recent developments in the field and "bears an uncanny resemblance to the psychometric state of the art as it existed in the 1950s."[161] It also claims that some of the most influential recent studies on group differences in intelligence, in order to show that the tests are unbiased, use outdated methodology. In particular the reliance on classical test theory rather than more sophisticated measurement models as found in item response theory. In response to criticism proponents of the genetic hypothesis claim they use a standard for intelligence known as g. G is measured by performance on test items without the influence of language or math

[edit] Utility of research

Theories of race and intelligence have been challenged on grounds of their utility. Critics want to know what purpose such research could serve and why it has been an intense an area of focus for a few researchers. Some defend the research, saying it has egalitarian aims. IQ is, after all, a predictor of educational achievement and special needs. Accordingly, as a matter of public policy, resources can be better allocated by reducing the data to better understand the challenges; it is considered a pure science. Still others say that the true motivation for the research is the same as that of the eugenics movement and other forms of scientific racism.[162][162] Even supporters of intelligence research have described such research as analogous to "working with dynamite" or "dangerous play" in sports.[163]

As to whether research in this area is desirable, John C. Loehlin wrote in 1992, "Research on racial differences in intelligence is desirable if the research is appropriately motivated, honestly done, and adequately communicated." [emphasis original] Defenders of the research suggest that both scientific curiosity and a desire to draw benefits from the research are appropriate motivations.[citation needed] Researchers such as Richard Lynn have suggested that conclusions from the research can help make political decisions, such as the type of educational opportunities and expectations of achievement policy makers should have for people of different races.[citation needed] Charles Murray, a political scientist of the American Enterprise Institute has used their conclusions to criticize social programs based on racial equality that fail, he claims, to recognize the realities of racial differences.[citation needed]

[edit] Test construction

While the existence of average IQ test score differences has been a matter of accepted fact for decades, a great deal of controversy exists among scholars over the question of whether these score differences reflected real differences in cognitive ability. Some claim that there is no evidence for test bias since IQ tests are equally good predictors of IQ-related factors (such as school performance) for U.S. Blacks and Whites.[164] The performance differences persist in tests and testing situations in which care has been taken to eliminate bias.[164] It has also been suggested that IQ tests are formulated in such a way as to disadvantage minorities.[164] Controlled studies have shown that test construction does not substantially contribute to the IQ gap.[164] However, some psychometricians are not satisfied that the question of test bias is fully answered by these results.[165][166][167] Also, all commenters reject the common misconception that IQ is meant to measure "innate" differences in intelligence, and they agree that average IQ scores on their own say nothing about the cause of the differences.[citation needed]

The preponderance of evidence indicates that IQ tests measuring general intelligence are crossculturally valid. There is little or no evidence of population-specific cultural effects apart from the obvious example of language bias.[168] For example, Robert Sternberg et al. found that the IQ of 12- to 15-year-old Kenyans predicted school grades at about the same level as they do in the West.[169] IQ also predicted university performance equally well in African and non-African engineering students in South Africa in a 2004 study.[170] Salgado et al. (2003) demonstrated the international generalizability of general mental ability across 10 member countries of the European Community and differences in a nation’s culture, religion, language, socioeconomic level or employment legislation did not affect the predictive validity of IQ tests.[171]

However, other studies have found evidence for bias. A 2005 study finds some evidence that the WAIS-R is not culture-fair for Mexican Americans.[172] Other recent studies have questioned the culture-fairness of IQ tests when used in South Africa.[173][174]

[edit] Source of funding

Proponents of genetic explanations of race/IQ correlation, such as Rushton, Lynn, and Jensen, have often been criticized for receiving funding from the Pioneer Fund, a group that had ties to Nazis and the eugenics of the early 20th century. The Southern Poverty Law Center considers the Pioneer Fund to be a hate group. Rushton is the current head of the Pioneer Fund and has spoken at conferences of the American Renaissance magazine, in which he has also published articles.[175] Anti-racist Searchlight Magazine described one of these articles as a "veritable 'who’s who' of American white supremacy.".[176]

Proponents of genetic explanations of race-IQ correlation have in turn accused their critics of suppressing scientific debate in the name of political correctness. They claim harassment and interference with both their work and funding. The Pioneer Fund, whose stated purpose is "to advance the scientific study of heredity and human differences", makes "no grants to individuals but only to research institutions, mainly universities, mostly for specialized 'niche' projects, which have difficulty attracting funds from government sources or from larger foundations".[177]

[edit] See also

[edit] Notes

  1. ^ Rushton J. Philippe and Jensen Arthur R."Thirty Years of Research on Race Differences In Cognitive Ability" p. 240 Psychology, Public Policy, and Law 2005, Vol. 11, No. 2, 235–294 DOI: 10.1037/1076-8971.11.2.235
  2. ^ The Bell Curve Wars. Race, Intelligence, and the Future of America
  3. ^ Race Differences in Intelligence
  4. ^ [1]
  5. ^ http://www.genpaku.org/skepticj/iqrace.html
  6. ^ On the peculiarities of the Negro brain
  7. ^ "Black-White-East Asian IQ differences at least 50% genetic, major law review journal concludes" Innovations Report 2005-04-26
  8. ^ Broca 1873; Bean 1906; Mall 1909; Morton 1839; Pearl 1934; Vint 1934
  9. ^ Social Darwinism, Scientific Racism, and the Metaphysics of Race Rutledge M. Dennis The Journal of Negro Education, Vol. 64, No. 3, Myths and Realities: African Americans and the Measurement of Human Abilities (Summer, 1995), pp. 243–252
  10. ^ Eugenics: America's Darkest Days
  11. ^ Francis Galton: British Psychologist
  12. ^ Degler 1992; Loehlin et al. 1975
  13. ^ According to historian of psychology Graham Richards there was widespread critical debate within psychology about the conceptual underpinnings of this early race difference research (Richards 1997). These include Estabrooks (1928) two papers on the limitations of methodology used in the research; Dearborn and Long’s (1934) overview of the criticisms by several psychologists (Garth, Thompson, Peterson, Pinter, Herskovits, Daniel, Price, Wilkerson, Freeman, Rosenthal and C.E. Smith) in a collection they edited and Klineburg, who wrote three major critiques, one in 1928, and two in 1935. Richards also notes that with over a 1000 publications within psychology during the interwar years there had been a large internal debate. Towards the end of the time period almost all those publishing, including most of those who began with a pro-race differences stance, were firmly arguing against race differences research. Richards regards the scientific controversy to be dead at this point, although he also suggests reasons for its re-emergence in the late nineteen sixties.
  14. ^ Lynn 2001 pp. 67–69
  15. ^ a b Jensen 1969
  16. ^ Practical Ethics
  17. ^ Bill Shockley, Part 3 of 3
  18. ^ William Shockley - MSN Encarta
  19. ^ Shockley, William (1992). Shockley on Eugenics and Race: The Application of Science to the Solution of Human Problems. Washington, D.C.: Scott-Townsend Publishers. ISBN 978-1878465030. 
  20. ^ A Genetic and Cultural Odyssey: The Life and Work of L. Luca Cavalli-Sforza by Linda Stone, pages 76, 168 ISBN 0231133960.
  21. ^ [2] AAA statement on race and intelligence
  22. ^ a b Stalking the Wild Taboo - APA Statement on The Bell Curve - Intelligence: Knowns and Unknowns
  23. ^ Gould, Stephen Jay (1996), The Mismeasure of Man, Sagebrush Education Resources, ISBN 0613181301 
  24. ^ Lewontin, Richard (2001), It Ain't Necessarily So: The Dream of the Human Genome and Other Illusions, New York review of Books, ISBN 0940322951 
  25. ^ What a tangled web he weaves: Race, reproductive strategies and Rushton's life history theory by Joseph L Graves
  26. ^ The authors of the report agreed that IQ scores have high predictive validity for individual differences in school achievement. They confirmed the predictive validity of IQ for adult occupational status, even when variables such as education and family background have been statistically controlled. They agree that individual differences in intelligence are substantially influenced by genetics (75% in adults). Contrary to Hernstein and Murray's findings, they state that prolonged malnutrition during childhood does have long-term intellectual effects.
  27. ^ amp51020077.tif
  28. ^ Neisser, U. (1997). "Never a Dull Moment". American Psychologist 52: 79-81.[3]
  29. ^ Gottfredson, Linda (December 13, 1994), Mainstream Science on Intelligence. Wall Street Journal, p A18.
  30. ^ Mainstream science on intelligence
  31. ^ AAA Statement on "Race" and Intelligence
  32. ^ Achieving Equitable Education in Calhoun County
  33. ^ Educational Studies: A Jrnl of the American Educ. Studies Assoc.
  34. ^ For example, the policy recommendations of The Bell Curve were denounced by many.[citation needed] Herrnstein and Murray (1994) wrote: "We can imagine no recommendation for using the government to manipulate fertility that does not have dangers. But this highlights the problem: The United States already has policies that inadvertently social-engineer who has babies, and it is encouraging the wrong women. If the United States did as much to encourage high-IQ women to have babies as it now does to encourage low-IQ women, it would rightly be described as engaging in aggressive manipulation of fertility. The technically precise description of America's fertility policy is that it subsidizes births among poor women, who are also disproportionately at the low end of the intelligence distribution. We urge generally that these policies, represented by the extensive network of cash and services for low-income women who have babies, be ended. (p. 548)" Two year later the 1996 U.S. welfare reform substantially cut these programs. In a discussion of the future political outcomes of an intellectually stratified society, they stated that they: "fear that a new kind of conservatism is becoming the dominant ideology of the affluent - not in the social tradition of an Edmund Burke or in the economic tradition of an Adam Smith but ’conservatism’ along Latin American lines, where to be conservative has often meant doing whatever is necessary to preserve the mansions on the hills from the menace of the slums below. (p. 518)"Moreover, they fear that an increasing welfare will create a "custodial state": "a high-tech and more lavish version of the Indian reservation of some substantial minority of the nation’s population. They also predict increasing totalitarianism: It is difficult to imagine the United States preserving its heritage of individualism, equal rights before the law, free people running their own lives, once it is accepted that a significant part of the population must be made permanent wards of the states. (p. 526)"
  35. ^ Gottfredson 2005b
  36. ^ a b James R. Flynn, The Black-White IQ Gap
  37. ^ Roland G. Fryer Jr. and Steven D. Levitt, "Understanding the Black-White Test Score Gap in the First Two Years of School," The Review of Economics and Statistics 86, no. 2 (2004).
  38. ^ Arthur Jensen (1998). The g Factor. 
  39. ^ Dolan, C. V. (1997). A note on Schönemann's refutation of Spearman's hypothesis. Multivariate Behavioral Research, 32, 319-325.
  40. ^ Dolan, C. V. (2000). Investigating Spearman's hypothesis by means of multi-group confirmatory factor analysis. Multivariate Behavioral Research, 35, 21-50.
  41. ^ Dolan, C. V., & Hamaker, E. L. (2001). Investigating black-white differences in psychometric IQ: Multi-group confirmatory factor analyses of WISC-R and K-ABC and a critique of the method of correlated vectors. In F. Columbus (Ed.), Advances in psychology research (Vol. 6, pp. 30-59). Huntington, NY: Nova Science.
  42. ^ Roth et al. 2001
  43. ^ Berry, J. W. (1966). Temne and Eskimo perceptual skills. International Journal of Psychology, 1, 207-222.
  44. ^ MacArthur, R. S. (1968). Some differential abilities of northern Canadian native youth. International Journal of Psychology, 3, 43-51.
  45. ^ Roth, P. L., Bevier, C. A., Bobko, P., Switzer, F. S. III, & Tyler, P. (2001). Ethnic group differences in cognitive ability in employment and educational settings: A meta-analysis. Personnel Psychology, 54, 297-330.
  46. ^ a b Hunt, Earl & Carlson, Jerry. Considerations Relating to the Study of Group Differences in Intelligence. Perspectives on Psychological Science 2 (2), 194-213.
  47. ^ Lynn, Richard (2003). The Intelligence of American Jews. Elsevier Ltd. doi:10.1016/S0191-8869(03)00079-5.
  48. ^ Cochran, Gregory & Hardy, Jason & Harpending, Henry. Natural History of Ashkenazi Intelligence. Journal of Biosocial Science, Vol. 38, No. 05. (2005), pp. 659-693.
  49. ^ Carretta, T. R., & Ree, M. J. (1995). Near identity of cognitive structure in sex and ethnic groups. Personality and Individual Differences, 19, 149-155.
  50. ^ IQ and the Wealth of Nations, Race Differences in Intelligence, and IQ and Global Inequality
  51. ^ Satoshi Kanazawa, Temperature and evolutionary novelty as forces behind the evolution of general intelligence
  52. ^ Steven M. Shatz, IQ and fertility: A cross-national study
  53. ^ The decline of the world's IQ
  54. ^ a b Relevance of education and intelligence at the national level for the economic welfare of people
  55. ^ Herrnstein and Murray 1994; Lynn 1991a; Lynn 2006
  56. ^ Rushton, J. P. (2006). "Lynn Richard, Race Differences in Intelligence: An Evolutionary Analysis, Washington Summit Books, Augusta, GA (2005) ISBN 1-59368-020-1, 318 pages., US$34.95". Personality and Individual Differences 40 (4): 853–855. doi:10.1016/j.paid.2005.10.004. 
  57. ^ Lynn, R. and Vanhanen, T. (2002). IQ and the wealth of nations. Westport, CT: Praeger. ISBN 0-275-97510-X
  58. ^ Rindermann, H. (2006). What do international student assessments measure?. Psychologische Rundschau, 57, 69–86.
  59. ^ Relevance of education and intelligence for the political development of nations: Democracy, rule of law and political liberty
  60. ^ National differences in intelligence and educational attainment
  61. ^ Wicherts, J.M. (December, 15, 2006). The dark past, obscure present, and bright future of African IQ. 7th Annual Conference of the International Society for Intelligence Research (ISIR), San Francisco, CA, US.
  62. ^ Sternberg, R. J., Nokes, C., Geissler, P. W., Prince, R., Okatcha, F., Bundy, D. A., & Grigorenko, E. L. (2001). The relationship between academic and practical intelligence: A case study in Kenya. Intelligence, 29, 401-418.
  63. ^ Sarich (2004). "Race and Behavior". Race. Boulder, Colo.: Westview Press. ISBN 0813340861. 
  64. ^ Nathan (2004]). "A review of Race: the Reality of Human Differences" (PDF). http://www.epjournal.net/filestore/ep03255262.pdf. 
  65. ^ Few U.S. Moms Meet Six-Month Breastfeeding Goal
  66. ^ Breastfeeding among Low Income, African-American Women: Power, Beliefs and Decision Making by Margaret E. Bentley, Deborah L. Dee and Joan L. Jensen
  67. ^ Even minute levels of lead in blood can lead to low IQ in kids
  68. ^ [4]
  69. ^ Closing the Black/White IQ Gap? - James Flynn and Charles Murray search for a solution. by Ronald Bailey. December 1, 2006
  70. ^ Immigrant America By Alejandro Portes, Rubén G. Rumbaut
  71. ^ [http://www.politicalaffairs.net/article/articleview/3447/ Immigration Policy: An Historical Perspective By Norman Markowitz]
  72. ^ Racism Resurgent: How Media Let The Bell Curve's Pseudo-Science Define the Agenda on Race
  73. ^ The Science and Politics of I.q. By Leon J. Kamin
  74. ^ [5]
  75. ^ a b c Blackwell Synergy - Perspect on Psych Science, Volume 2 Issue 2 Page 194-213, June 2007 (Article Abstract)
  76. ^ Marks, J. (1996) "Science and Race", American Behavioral Scientist 40: 123-133. doi:10.1177/0002764296040002003
  77. ^ a b Cato Unbound » Blog Archive » Race and IQ
  78. ^ Cato Unbound » Blog Archive » Rational Discussion of the Offensive is Okay
  79. ^ doi:10.1037/1076-8971.11.2.235
  80. ^ How Heritability Misleads about Race
  81. ^ R. J. Sternberg (2000) Handbook of Intelligence. Cambridge: Cambridge University Press
  82. ^ David J. Bartholomew (2004) Measuring Intelligence: Facts and Fallacies. Cambridge: Cambridge University Press
  83. ^ Ian J. Deary. (2001) Intelligence: A Very Short Introduction. Oxford: Oxford University Press
  84. ^ Neisser, U., Boodoo, G., Bouchard, T. J., Boykin, A. W., Brody, N., Ceci, S. J., Halpern, D. F., Loehlin, J. C., Perloff, R., Sternberg, R. J. and Urbina, S. (February 1996). "Intelligence: Knowns and Unknowns". American Psychologist 51 (2): 77-101.
  85. ^ Gottfredson, L. S. (Ed.). (1997). Intelligence and social policy [Special issue]. Intelligence, 24(1).
  86. ^ Gottfredson, L. S. (1997). Mainstream science on intelligence: An editorial with 52 signatories, history, and bibliography. Intelligence, 24(1), 13-23.
  87. ^ Robert Plomin, John C. DeFries, Gerald E. McClearn, and Peter McGuffin (2000) Behavioral Genetics. Worth Publishers; Fourth Edition edition
  88. ^ Brody, N. (1992). Intelligence (2nd ed.). San Diego, CA: Academic Press.
  89. ^ Snyderman, M., & Rothman, S. (1988). The IQ controversy, the media and public policy. New Brunswick, NJ: Transaction Press.
  90. ^ Lewontin, R. (1970) "Race and Intelligence". Science and Public Affairs March, pp. 2-8
  91. ^ Layzer, David. (1974) "Heritability analyses of IQ scores: Science or numerology?" Science 183 pp. 1259-66
  92. ^ Reviewed in Neisser et al. (1996). Data from the NLSY as reported in figure adapted from Herrnstein and Murray (1994), p. 288.
  93. ^ Jensen (1998) The g Factor
  94. ^ Flynn (1980) and Flynn (1999)
  95. ^ http://psychology.uwo.ca/faculty/rushtonpdfs/PPPL1.pdf Thirty Years of Research on Race Differences in Cognitive Ability
  96. ^ http://www.innovations-report.de/html/berichte/studien/bericht-43536.html Black-White-East Asian IQ differences at least 50% genetic, major law review journal concludes
  97. ^ Rushton and Jensen (2005a), cited in "Black-White-East Asian IQ differences at least 50% genetic, scientists conclude in major law journal", and Murray (2005)
  98. ^ Reviewed by Rushton and Jensen (2005).
  99. ^ Plomin (2005). "The quest for quantitative trait loci associated with intelligence". Intelligence 34: 513. doi:10.1016/j.intell.2006.01.001. 
  100. ^ For example: Nisbett (2005), Suzuki and Aronson (2005), Sternberg (2005), Dickens (2005)
  101. ^ Heredity, Evironment, and Race differences in IQ. A Commentary on Rushton and Jensen (2005) Richard E. Nisbett, Psychology, Public Policy, and Law: June 2005 Vol. 11, No. 2, 302-310
  102. ^ Loehlin, J.C., Lindzey, G., & Spuhler, J. (1975). Racial Differences in Intelligence. San Francisco: Freeman.
  103. ^ http://www.udel.edu/educ/gottfredson/reprints/2007doublestandards.pdf
  104. ^ Genetic Differences and School Readiness Dickens, William T. The Future of Children - Volume 15, Number 1, Spring 2005, pp. 55-69
  105. ^ Roland G. Fryer Jr. and Steven D. Levitt, "Understanding the Black-White Test Score Gap in the First Two Years of School," The Review of Economics and Statistics 86, no. 2 (2004). Testing for Racial Differences in the Mental Ability of Young Children
  106. ^ Flynn 1987, Flynn 1987b, Flynn 1999, Flynn 1999b
  107. ^ Colom et al. 2005
  108. ^ Flynn 1999
  109. ^ Flynn (2007)
  110. ^ Wicherts et al. (2004) wrote that "the gains cannot be explained solely by increases at the level of the latent variables (common factors), which IQ tests purport to measure". In other words, according to this study, some of the inter-generational difference in IQ is attributable to bias or other artifacts, and not real gains in general intelligence or higher-order ability factors.
  111. ^ James Robert Flynn (2007) What is Intelligence?: Beyond the Flynn Effect. Cambridge University Press: Cambridge
  112. ^ Are cognitive differences between immigrant and majority groups diminishing?Te Nijenhuis Jan; De Jong Mart-Jan; Evers Arne; Van Der Flier Henk; European journal of personality (Eur. j. pers.) 2004, vol. 18, no5, pp. 405-434
  113. ^ Secular Gains in Fluid Intelligence: Evidence from the Culture-Fair Intelligence Test Roberto Colom and Oscar Garcia-Lopez, Journal of Biosocial Science (2003), 35: 33-39 Cambridge University Press
  114. ^ "Changes in vault dimensions must occur by early childhood because of the early development of the vault." Secular change in craniofacial morphology "During the 125 years under consideration, cranial vaults have become markedly higher, somewhat narrower, with narrower faces. The changes in cranial morphology are probably in large part due to changes in growth at the cranial base due to improved environmental conditions. The changes are likely a combination of phenotypic plasticity and genetic changes over this period." Cranial change in Americans: 1850-1975.
  115. ^ None of the above - The New Yorker
  116. ^ Joel Wiesen, "An Annotated List of Many Possible Reasons for the Black-White Mean Score Differences Seen With Many Cognitive Ability Tests: Notes to File," Applied Personnel Research, March 18, 2005.
  117. ^ Low-Level Lead Exposure, Intelligence and Academic Achievement: A Long-term Follow-up Study David C. Bellinger PhD, MSc1, Karen M. Stiles PhD, MN1, and Herbert L. Needleman MD1. Pediatrics Vol. 90 No. 6 December 1992, pp. 855-861
  118. ^ Blood Lead Levels — United States, 1999–2002 CDC.
  119. ^ Mfume Calls Lead Paint Poisoning "The Silent Epidemic" NAACP Press Release 17 July 01
  120. ^ Aronson, Wilson, & Akert, 2005
  121. ^ Reading level attenuates differences in neuropsychological test performance between African American and White elders Jennifer J. Manly, Diane M. Jacobs, Pegah Touradji, Scott A. Small and Yaakov Stern
  122. ^ Acculturation, Reading Level, and Neuropsychological Test Performance Among African American Elders Jennifer J. Manly, Desiree A. Byrd, Pegah Touradji, Yaakov Stern‌
  123. ^ Cancellation test performance in African American, Hispanic, and White elderly Desiree A. Byrd, Pegah Touradji, Ming-Xin Tang and Jennifer J. Manly
  124. ^ School Quality and the Black-White Achievement Gap Eric A. Hanushek and Steven G. Rivkin 2006
  125. ^ Race and Intelligence: Separating Science from Myth By Jefferson M. Fish
  126. ^ Race, Social Class, and Individual Differences in I.Q. By Sandra Scarr
  127. ^ Cross-cultural Effects on IQ Test Performance: A Review and Preliminary Normative Indications on WAIS-III Test Performance Journal of Clinical and Experimental Neuropsychology Volume 26, Number 7 / October 2004
  128. ^ When Are Racial Disparities in Education the Result of Racial Discrimination? A Social Science Perspective by Roslyn Arlin Mickelson University of North Carolina at Charlotte
  129. ^ Effect of Children's Ethnicity on Teachers' Referral and Recommendation Decisions in Gifted and Talented Programs Journal article by Negmeldin Alsheikh, Hala Elhoweris, Pauline Holloway, Kagendo Mutua; Remedial and Special Education, Vol. 26, 2005
  130. ^ (Salend, Garrick Duhaney, & Montgomery, 2002; Townsend, 2002)
  131. ^ Racial Inequity in Special Education. Losen, Daniel J., Ed.; Orfield, Gary, Ed. Harvard Education Publishing Group.
  132. ^ (Gay, 2000; Irvine & Armento, 2001; Ladson-Billings, 1994, 2001)
  133. ^ The Effects of African American Movement Styles on Teachers' Perceptions and Reactions Journal article by Scott T. Bridgest, Audrey Davis Mccray, La Vonne I. Neal, Gwendolyn Webb-Johnson; Journal of Special Education, Vol. 37, 2003
  134. ^ Color-Blind Ellis Cose. Page 50
  135. ^ Inequality by Design: Cracking the Bell Curve Myth by Claude S. Fischer, Michael Hout, Martín Sánchez Jankowski, Samuel R. Lucas, Ann Swidler, and Kim Vos. Page 192. (The footnotes given are also from this book.)
  136. ^ The Bell Curve and many other places.
  137. ^ Church Academic Achievement
  138. ^ Richard Lynn discussed in Benson Ireland's 'Low' IQ
  139. ^ Lynn et al. Home Background
  140. ^ Klich Aboriginal Cognition and Psychological Science; Clark and Halford, Does Cognitive Style Account for Cultural Differences?
  141. ^ Ogbu, Minority Education and Caste
  142. ^ Verster and Prinsloo, The Diminishing Test Performance Gap
  143. ^ Raven, The Raven Progressive Matrices esp fig. 2
  144. ^ Kugelmass et al., Patterns of Intellectual Ability
  145. ^ Das and Khurana, Catse and Cognitive Processes
  146. ^ Adamovic, Intellectual Development and Level of Knowledge in Gypsy Pupils
  147. ^ http://www.pisa.oecd.org/dataoecd/31/60/39705905.xls
  148. ^ http://www.statssa.gov.za/census01/html/RSAPrimary.pdf; South African Census Results, see graph on pg. 8 (15 in the.pdf)
  149. ^ Lieberman, Leonard; Alice Littlefield and Larry T. Reynolds. "The Debate over Race: Thirty Years and Two Centuries Later." in "Race and I.Q." (1975) Ashley Montague (ed.) ISBN 0-19-510220-7. ""Those who study I.Q. scores of different groups do so with the assumption that there are homogeneous races, when in fact that is not the case. Populations being very similar to each other to begin with, and being interbred with eah other - and humans have interbred throughout their evolution - makes it impossible to explain differences in I.Q. scores largely on the basis of heredity".
  150. ^ Montagu, Ashley "The I.Q. Mythology" in "Race and I.Q." (1975) Ashley Montagu (ed) ISBN 0-19-510220-7: "I have stated, and I think the statement long overdue, that both the term "race" and the term "IQ" are delusive because in the one case the social conception of "race" was the deliberate invention of a slave-owning caste attempting to justify its conduct, and in the other case because "IQ" tests do not measure what they have generally been claimed to measure, namely, innate intelligence ... The statistical treatment of data in any investigation may be quite unexceptional, but when unexceptional statistical methods are applied to the analysis of unsound data to begin with, based on assumptions that are equally unsound, one can only end up with conclusions that are equally unsound. Such are the erroneous constructs of "race" and "IQ"."
  151. ^ Graves, Joseph, L. "The Race Myth: Why we Pretend Race Exists in America". (2004) Dutton, New York, New York. p174. "The Bell Curve's arguments are plausible only if one assumes that biologically defined races exist within our species and that they correspond to the socially defined American races, that IQ really does determine the majority of the differential in social stature in societies, and that IQ tests reliably measure all pertinent aspects of cognitive function and are unbiased.
  152. ^ http://en.wikipedia.org/wiki/Talk:Race_and_intelligence/references
  153. ^ Pinker (2006), Rowe (2005), Stock (2002) pp. 44–47.
  154. ^ (pp. 34-35).
  155. ^ This theory is discussed by Jensen (1998b) (pp. 435-437), Lynn (1991b) and Rushton (2000) in general and by both Wade (2006) and Steve Sailer with respect to Guns, Germs, and Steel. See Race and intelligence (Explanations)#Rushton's application of r-K theory. .. Voight et al. (2006) state generally that "a number of recent studies have detected more signals of adaptation in non-African populations than in Africans, and some of those studies have conjectured that non-Africans might have experienced greater pressures to adapt to new environments than Africans have" (Kayser et al. 2003, Akey et al. 2004, Storz et al. 2004, Stajich and Hahn 2005, Carlson et al. 2005).
  156. ^ Rushton, J. P. (1995) (PDF). Race, Evolution, and Behavior: A Life History Perspective (2nd special abridged ed.). Port Huron, MI: Charles Darwin Research Institute. http://www.charlesdarwinresearch.org/Race_Evolution_Behavior.pdf. 
  157. ^ Pomeranz, Kenneth (2001). The Great Divergence. Princeton, NJ: Princeton University Press.
  158. ^ Jones, Eric (1997). The European Miracle. Cambridge: Cambridge University Press.
  159. ^ Mokyr, Joel (1992). The Lever of Riches. Oxford: Oxford University Press.
  160. ^ North, Douglass (1976). The Rise of the Western World. Cambridge: Cambridge University Press.
  161. ^ The attack of the psychometricians. Denny Borsboom. Psychometrika Vol. 71, No. 3, 425–440. September 2006.
  162. ^ a b e.g., Sternberg, 2003, pp. 386–387
  163. ^ Hunt & Carlson, in press
  164. ^ a b c d Neisser, U., Boodoo, G., Bouchard, T. J. Jr., Boykin, A. W., Brody, N., Ceci, S. J. et al. (1996). Intelligence: Knowns and unknowns. American Psychologist, 51, 77–101.
  165. ^ Dolan, C. V. (1997). A note on Schönemann's refutation of Spearman's hypothesis. Multivariate Behavioral Research, 32, 319–325.
  166. ^ Dolan, C. V. (2000). Investigating Spearman's hypothesis by means of multi-group confirmatory factor analysis. Multivariate Behavioral Research, 35, 21–50.
  167. ^ Dolan, C. V., & Hamaker, E. L. (2001). Investigating Black-White differences in psychometric IQ: Multi-group confirmatory factor analyses of WISC-R and K-ABC and a critique of the method of correlated vectors. In F. Columbus (Ed.), Advances in psychology research (Vol. 6, pp. 30–59). Huntington, NY: Nova Science.
  168. ^ http://www.charlesdarwinresearch.org/PRSL2007.pdf
  169. ^ Sternberg, R. J., Nokes, C., Geissler, P. W., Prince, R., Okatcha, F., Bundy, D. A. & Grigorenko, E. L. 2001 The relationship between academic and practical intelligence: a case study in Kenya. Intelligence 29, 401–418.
  170. ^ Construct validity of Raven’s Advanced Progressive Matrices for African and non-African engineering students in South Africa.
  171. ^ Salgado, J. F., Anderson, N., Moscoso, S., Bertua, C. & Fruyt, F. D. 2003 International validity generalization of GMA and cognitive abilities: a European community meta-analysis. Pers. Psychol. 56, 573–605.
  172. ^ Culture-Fair Cognitive Ability Assessment Steven P. Verney Assessment, Vol. 12, No. 3, 303-319 (2005)
  173. ^ Cross-cultural effects on IQ test performance: a review and preliminary normative indications on WAIS-III test performance. Shuttleworth-Edwards AB, Kemp RD, Rust AL, Muirhead JG, Hartman NP, Radloff SE. J Clin Exp Neuropsychol. 2004 Oct;26(7):903-20.
  174. ^ Case for Non-Biased Intelligence Testing Against Black Africans Has Not Been Made: A Comment on Rushton, Skuy, and Bons (2004) 1*, Leah K. Hamilton1, Betty R. Onyura1 and Andrew S. Winston International Journal of Selection and Assessment Volume 14 Issue 3 Page 278 - September 2006
  175. ^ http://www.splcenter.org/intel/intelreport/article.jsp?pid=214#27
  176. ^ http://www.searchlightmagazine.com/index.php?link=template&story=162
  177. ^ The Pioneer Fund, Inc.

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