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Race and intelligence is a controversial and even taboo topic, which has received considerable attention in the United States and elsewhere. At the heart of the issue is the observation that the members of racial and ethnic groups tend to cluster around different averages on tests of cognitive ability. Some scholars regard the topic as scientifically meaningless based on their interpretation of the meanings and significance of race and intelligence. Some likewise question whether it is possible to scientifically address the question in a way that is ethical. Others reject both of these positions, arguing instead that the social implications are too important to forego research.

It is generally agreed that there are significant differences in the average test scores of different population groups (with particular focus on self-identified US Blacks and Whites). The distribution of test scores for each group are largely overlapping, but groups differ in where individuals tend to cluster along the test score continuum. For this reason, racial or ethnic identity does little to predict the IQ of any particular individual. Statistics for group differences, however, are well established in the United States, with black Americans performing poorly on average compared to whites; Americans of Chinese, Japanese and Jewish ancestry performing better on average than gentile whites; and Latino Americans performing intermediately to blacks and whites. It is also agreed that these test score differences are not simply a reflection of biased tests, and thus they they have important social implications, especially in the areas of academic and social achievement. Yet the existence and importance of test score differences says nothing about their causes.

Although research and debate on race and intelligence encompasses a variety of topics, the nature versus nurture question attracts the most public attention. Some scholars argue that it is impossible for genetic differences to cause test score difference between racial and ethnic groups, but others reject this position, arguing that evidence is needed to decide the extent to which genetic factors contribute to group difference in IQ. Public statements from several groups of psychologists indicate that no definitive answer exists on what causes test score differences between groups. Numerous interpretations have been proposed, but none are generally considered to be well-supported by research. While genetic factors are agreed to contribute to IQ differences among people of the same race, it is the subject of debate whether this also applies to differences in average IQ between groups. Many psychologists believe that environmental factors could contribute, and many factors have been suggested as explanations, such as self-discipline and a culture that emphasizes engagement with learning, but no specific environmental factor has been identified as a definitive cause. These psychologists also consider the available evidence for a genetic contribution to group differences, which is based in part of studies of twins reared apart as well as adoption studies, to be inconclusive. Nonetheless, intense debate continues on that topic, with some scholars arguing that the available evidence favors an entirely environmental cause and others arguing that the evidence favors a contribution from both genes and environment.

Overview

In 1995, a task force of the American Psychological Association (APA) headed by psychologist Ulric Neisser published a report entitled Intelligence: Knowns and Unknowns which intended to present a summary of the findings of scientific research regarding intelligence, which also commented upon the topic of racial-ethnic group differences in IQ. According to this report, psychometric testing, although one of the most fruitful approaches to studying intelligence, has yet to produce answers to many questions regarding intelligence. Psychometricians have devised ways to measure the distinct yet intercorrelated abilities believed to play an important role in the development of intelligence. IQ tests measure these abilities well. As intelligence test scores correlate moderately well with measures of educational and occupational success, it is apparent that such tests measure important skills. However, educational achievement is not only determined by intelligence, although intelligence test scores do correlate significantly with other important outcomes later in life.

The APA report further noted that, while both twin and adoption studies indicate that genetic and environmental variables are involved in the manifestation of intelligence, the role of genetics has been found to increase in importance with age. Why this happens in not yet understood, but while the influence of genetic factors increases with age the influence of family rearing environment fades away. Nonetheless, there are several important environmental factors which are known to affect the development of intelligence, such as formal education and general health. The much-discussed "Flynn effect", which refers to the striking worldwide mean IQ increase of 15+ points over the last 50 years, may be the result of similar environmental factors or some other hitherto unrecognized factor, and may not reflect a real increase in intelligence.

On the topic of racial-ethnic group differences in IQ, the APA task force wrote that, as the measured differences in IQ between various ethnic groups is the result of complex patterns, any conclusions which require broad generalizations run the risk of oversimplifying the issue as well as misrepresenting the available data. At the same time, intelligence test scores in some minority populations are reasonably good indicators of educational achievement levels in later life. The long-standing 15 +/- point difference between the intelligence test scores of African Americans and White Americans, though it might have shrunk during the 20th century, remains unaccounted for despite proposed explanations claiming systematic bias, differences in culture or socioeconomic status (SES), or genetics as underlying causes.

Suitability for study

Some scholars have expressed the view that the study of race differences in intelligence is meaningless, unethical or both. This is an on-going debate with proponents and opponents of this view making statements in the academic literature in support of their respective positions.

For example, according to Robert Sternberg and colleagues, intelligence (often approximated using IQ) is not a well defined construct, and IQ tests do not provide definitive measures of intelligence. They argue that race and ethnicity are socially defined groups—rather than biological observations—whose membership isn't homogeneous; races and ethnicities are often defined by affiliation with very large geographical areas (Asian) or common language (Hispanic). For these reasons, they conclude that discussions of correlations between race and intelligence which extrapolate a genetic causation are fundamentally flawed.

In another example, Richard E. Nisbett, who believes that the available evidence favors an entirely environmental explanation for differences in test scores between blacks and whites, nonetheless rejects the argument that studying these differences is meaningless and also rejects the argument that the research is unethical. Rather, Nisbett endorses the view that the cause of group differences can be resolved with empirical study. Similarly, James Flynn argues that we should prioritize the search for truth above the supposed unwelcome consequences. Flynn cites the flow of new research stimulated by the work of Arthur Jensen in support of his view.

Test score differences

Most of the evidence of intelligence differences between racial and ethnic groups is based on studies of intelligence test scores. Intelligence tests measure many important abilities, such as verbal and quantitative reasoning, and can predict socially-relevant outcomes such as academic performance and occupational outcomes. However, intelligence test scores do not reflect all of the intricacies of the everyday meaning of intelligence, so researchers take care to distinguish between IQ test results and intelligence.

Some studies of intelligence tests use statistical methods to extract so-called latent variables from the IQ test scores. One such variable is the general intelligence factor, or g, which accounts for most of the differences in IQ test scores between individuals. There are other latent variables in addition to g, and IQ tests vary in their ability to measure these latent variables, if they measure them at all. IQ tests scores, while often summarized as a single overall number, are actually multidimensional in nature. Transforming IQ test scores into latent variables is an attempt to find one or dimensions on which to compare IQ test scores.

Latent variables are also sometimes called factors or constructs. The construct validity of an IQ test score is a key criteria for judging whether the IQ test score differences are meaningful. Tests which do not measure difference in important latent variables for some group are said to have measurement bias. The construct validity of most commonly used IQ tests has been fairly well established within multiple racial-ethnic groups in developing countries such as the United States. That is, test score difference within each racial-ethnic group are valid indicators of differences in latent variables such as g.

The question of cultural bias in IQ tests is another facet of the construct validity question. One previously held view of IQ tests was that they only measure bits of information or skills that would be learned by children raised in a middle-class White culture. It would follow that lower-scoring ethnic-minority children would score lower simply because they lack exposure to the information and skills promoted by this culture. This view has since been discarded in favor of the view that IQ test score differences reflect real differences in mental abilities and that group differences in IQ are not a product of cultural bias.

There is a consensus that test score differences between Black and White people in the United States have predictive validity (also called predictive invariance), meaning that test scores predict the same socially-relevant outcomes regardless of the race of the person being tested. To further address this question, three studies using sophisticated statistical techniques have shown that Black-White differences in IQ test scores are not a result of measurement bias (a criteria called measurement invariance). These studies imply that Black-White IQ differences reflect very general differences in some underlying latent variables, but they are unable to differentiate precisely which latent variables differ under a variety of models. These studies were performed in response to previous investigations which suggested that Black-White IQ differences are primarily differences in g in particular.

United States

There are observed differences in average test score achievement between racial-ethnic groups, which vary 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, reaching an average of nearly 17 points by age 24, which is slightly more than 1 standard deviation. According to James Flynn and others, the overall average Black-White gap has reduced by one third over the course of the 20th century. For example, the black men inducted into the US armed forces during World War II averaged about 1.5 standard deviations below their white counterparts. This improvement is also reflected in Black-White differences on school achievement tests, which have shrunk from about 1.2 to about 0.8 standard deviations. However, these improvements may have stalled for people born after the early 1970s.

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. 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.

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, tend to score worse on average than White populations but better on average than Black populations. East Asian populations may score higher on average than White populations in the United States as they do elsewhere. A 1960 study of 1236 American teenagers calculated six IQ measures for Jews relative to white gentiles. The results found that the relative IQ of American Jews varied from a low of 91.3 (visual reasoning) to a high of 109.7 (Mathematics). A recent review by Lynn (2004) used a 10 word vocabulary test to estimate the IQ of American Jews. The population of 150 Jews scored half a standard deviation above the 5300 white gentiles in verbal IQ.

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 in performance IQ, whereas the test score differences skew towards higher verbal IQ for Ashkenazi-White differences. However, the mixture of abilities within groups appears to be nearly identical across many ethnic groups. The stability of these differences is also less well studied than Black-White differences.

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. The inaccuracy of the cross cultural IQ scores is well documented, but many scholars use the results as an estimate of worldwide IQ scores. Lynn's meta-analysis lists East Asians (105), Europeans (99), Inuit (91), Southeast Asians and Amerindians (87 each), Pacific Islanders (85), South Asians/North Africans (84), Non-Bushmen sub-Saharan Africans (67), Australian Aborigines (62) and Bushmen (54). International achievement test scores, including TIMSS and PISA, have also been used to estimate average IQ worldwide with similar results where data is available.

The very low IQ scores reported for sub-Saharan African populations are especially controversial. For example, Wicherts argues that the average IQ of sub-Saharan Africans is poorly measured by studies summarized by Lynn and is more likely 82. Lynn argues that representative samples instead yield an average of 68. According to anthropologist Mark Cohen, the frequently reported African mean IQ of 70 is "preposterous". Using Western standards, this would mean that African countries evidencing such a low IQ would be largely dysfunctional. Given that individuals in these countries lead "vibrant artistic, symbolic and spiritual lives", this is, according to Cohen, clearly not the case. Thus, he concludes, the IQ test results from Africa do not reflect actual intelligence levels.

Differences in education, prolonged malnutrition, exposure to toxin, exposure to stress, and exposure to disease are all generally expected to contribute to the lower scores observed in developing countries. However, direct experimental evidence to confirm the role of individual factors is difficult to acquire in most cases because each of these factors tends to also be associated with one another and with unfavorable socioeconomic conditions. In the case of some toxins, such as lead, a negative effect on IQ scores has been established. Two other factors that have as well established negative association with IQ are severely premature birth and severe low birth weight.

Hypotheses

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 major contribution of genetic factors (hereditarian) and those which invoke mainly environmental (i.e., non-genetic) factors. Some descriptions of the positions are themselves controversial.

In a review published in 2007, Hunt and Carlson categorized four explanations for observed differences in IQ scores between groups. The strongest hereditarian 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" A second position, attributed to Ogbu and Sowell, is that the differences in intelligence test scores are due to social factors. Third, Sternberg and colleagues are attributed with the view 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".

Socioeconomic factors

According to the report of a 1996 APA task force, socioeconomic factors (SES) cannot be the whole explanation for racial-ethnic group differences in IQ. Their first reason for this conclusion is that that the black-white test score gap is not eliminated when individuals and groups are matched on SES. Second, excluding extreme conditions, nutritional and biological factors that may vary with SES have little effect on IQ. Third, the relationship between IQ and SES is not simply one in which SES determines IQ, rather it is more likely that intelligence causes differences in SES than the other way around. Lastly, they argue that income and education simply fail to capture important categories of cultural experience which differ between racial and ethnic groups.

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. 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 explain the gaps found in non-threatening test conditions.

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. 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. 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.

Nichols (1987) critically summarized the argument as follows:

(1) We do not know what causes the test score changes over time. (2) We do not know what causes racial differences in intelligence. (3) Since both causes are unknown, they must, therefore, be the same. (4) Since the unknown cause of changes over time cannot be shown to be genetic, it must be environmental. (5) Therefore, racial differences in intelligence are environmental in origin (p. 234).

Flynn and other research have found reason to doubt the construct validity of secular increases in IQ scores. In terms of the latent variables 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. 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. At least one study has found that measurement bias contributes to the Flynn effect, which is not seen in black-white IQ differences.

Heritability

There is a consensus among intelligence researchers that IQ differences between individuals within the same population (usually self identified "Black" or "White" in studies) are significantly heritable. It should be noted that heritability is a property of a population and may vary significantly between populations.

Concordance rates for IQ from twin studies and other study designs consistently fall in the range of 30% to 80%, with the estimated heritability in young (preschool) children in the lower range and adults in the higher range.

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 the very high within-groupheritability 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.

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.

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. David Layzer (1974) contends that the development of a trait can be influenced by genetic differencesqualitatively 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 forphenotypic variance to be due largely to environment. As a comparison, schizophrenia is estimated to be at least 70% heritable, of which 30% of the actual genes have been accounted for.

Black and biracial children raised by white parents

Studies in which white parents raise black and biracial children have been variously regarded as inconclusive, supportive of an environmental interpretation, or supportive of a hereditarian interpretation. Three studies are commonly cited: the Minnesota Transracial Adoption Study, Moore (1986), and Eyferth (1961). The Moore and Eyferth studies have been criticized due to concern that children and parents in these studies are not representative for reasons such as their age and circumstances that led their inclusion in the studies. A similar study on black, white, and mixed-race children raised in an educationally-enriched nursery groups is cited by Nisbett; the study found IQs at age 5 of 108 for black children, 103 for white, and 106 for mixed-race. Like Moore (1986), the IQ of the parents is unknown, and the results could be distorted by the selective migration of the West Indian parents of the black children.

African ancestry and IQ

African Americans typically have ancestors from both Africa and Europe, with on average 20% their genomes inherited from European ancestors. Several studies performed without the use of DNA-based ancestry estimation attempted to correlated estimates of African or European ancestry with IQ. These studies have been variously regarded as inconclusive, supportive of an environmental interpretation, or supportive of a hereditarian interpretation. These studies are generally criticized for using unreliable methods to estimate ancestry and for their small samples sizes.

Rowe (2005) and others have suggested using DNA-based methods to reproduce these studies with reliable estimates of ancestry. Such experiments have never been published, although the requirements for such a study have been discussed in the academic literature.

Molecular genetic studies

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. Some researchers have expressed reluctance to investigate possible links between genes and intelligence, due to the controversy it can produce.

A 2005 literature review article on the links between race and intelligence in American Psychologist stated that no gene has been shown to be linked to intelligence, "so attempts to provide a compelling genetic link of race to intelligence are not feasible at this time". Two 2007 studies found that DTNBP1 and CHRM2 appear to influence intelligence depending on which allele of it a person carries. However, a study published in 2009 by Deary et al.. failed to find evidence of an association between these genes and general intelligence, stating "there is still almost no replicated evidence concerning the individual genes, which have variants that contribute to intelligence differences".

Health

Numerous explanations beside genetics have been proposed to account for the IQ gaps in the U.S. 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. In 1976 77.8% of all children had at least this much lead in their blood.

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.

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. 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. 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 (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. 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. 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.

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.

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. 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. Recently, a number of scholars have examined the issue of disproportionate representation of minority students in special educationprograms

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. 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.

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."

Structural equation models have been used to test for possible uncommon factors in the development of children belonging to different ethnic groups, which would include the results of racial discrimination. However, these tests have concluded that black, white, Hispanic and Asian children follow developmental processes which are "nearly identical."

Caste-like minorities

The book Inequality by Design: Cracking the Bell Curve Myth (1996) claims that it is not lower average intelligence that leads to the lower status of racial and ethnic minorities, it is instead their lower status that leads to their lower average intelligence test scores. To substantiate this claim, the book presents a table comparing social status or caste position with test scores and measures of school success in several countries around the world. The authors note, however, that the comparisons made in the table do not represent the results of all relevant findings, nor do they reflect the fact that the tests and procedures varied greatly from study to study. The comparison of Jews and Arabs, for example, is based on a news report that, in 1992, 26% of Jewish high school students passed their matriculation exam, as opposed to 15% of Arab students.

Other views

Jared Diamond's Guns, Germs and Steel 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 However, it has been suggested that these environmental differences may operate in part by selecting for higher levels of IQ.

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 theIndex of Economic Freedom or works by Kenneth Pomeranz, Eric Jones, Joel Mokyr, and Douglass C. North.

Debating the hereditarian position

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. 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.

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.

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." 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 onclassical 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.

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. The performance differences persist in tests and testing situations in which care has been taken to eliminate bias. It has also been suggested that IQ tests are formulated in such a way as to disadvantage minorities. Controlled studies have shown that test construction does not substantially contribute to the IQ gap. However, some psychometricians are not satisfied that the question of test bias is fully answered by these results.

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. 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. IQ also predicted university performance equally well in African and non-African engineering students in South Africa in a 2004 study. Salgado et al. (2003) demonstrated the international generalizability of general mental ability across 10 member countries of theEuropean Community and differences in a nation’s culture, religion, language, socioeconomic level or employment legislation did not affect the predictive validity of IQ tests.

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

Lack of direct evidence

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." Hunt and Carlson argue that Nisbett's interpretations are far too strong in light of problems with these studies that have been recognized for decades. Gottfredson writes that the studies Nisbett cites "actually lack the ability to rule out any hypothesis at all, genetic or not".

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."

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."

Source of funding

Vocal proponents of partially genetic explanations of race/IQ correlation, such as Rushton, Lynn, and Jensen, have been criticized for receiving funding from the Pioneer Fund, a group that has been reported as having had ties to German eugenicists working under theNazi regime as well as to other US eugenicists of the early 20th century. The Southern Poverty Law Centerconsiders 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.

Proponents of genetic explanations of race-IQ correlation have in turn accused their critics ofsuppressing 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".

History of debate

Development of the debate

The idea 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. 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.

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.

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. 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. 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.

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.

The 1970s debates

See also: Arthur Jensen

Publication in 1969 of psychology psychologist Arthur Jensen's controversial article, "How Much Can We Boost IQ and School Achievement?" triggered the modern debate. In it, he wrote, "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." Philosopher Peter Singer wrote that Jensen's article was widely reported in the popular press "as an attempt to defend racism on scientific grounds".

An advocate of population control, physicist William Shockley focused on questions of race, intelligence, and eugenics and published several controversial papers arguing that intelligence is primarily hereditary. He postulated that the higher reproduction rate of those with lower intelligence has 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, comparing them to rationale used by the Nazis in carrying out their genocidal policies. Criticism of Shockley's racial ideas appeared in scientific journals and was reflected in the popular press.

Arguing that environmental factors could explain the black-white IQ gap, population geneticist Luigi Luca Cavalli-Sforza debated Jensen and Shockley.

The 1990s Bell Curve debates

See also: The Bell Curve

Discussion centers on whether group differences in average IQ are purely social, economic, and cultural or are hard-wired in genetics. The American Anthropological Association has declared that "differentiating species into biologically defined 'races' has proven meaningless and unscientific as a way of explaining variation," while the American Psychological Association has stated that the causes of inter-group IQ differences are unknown.

Academics such as Michael Levin and J. Philippe Rushton differ from the American Anthropological Association in their claims that IQ score differences are traceable to genetics. Stephen Jay Gould, Richard Levin, Richard Lewontin and Joseph L. Graves contend that the proponents of the genetics explanation are wrong.

The book The Bell Curve by psychologist Richard Herrnstein and American Enterprise Institute political scientist Charles Murray wrote: "The debate about whether and how much genes and environment have to do with ethnic differences remains unresolved. The universality of the contrast in nonverbal and verbal skills between East Asians and European whites suggests, without quite proving, genetic roots." Herrnstein and Murray said intelligence is a better predictor of many factors including financial income, job performance, unwed pregnancy, and crime than parents' socioeconomic status or education level.

The Bell Curve attracted attention, both critical of and in defense of the book. Critics called it scientific racism. Several books were written in response, including The Bell Curve Debate and The Mismeasure of Man (second edition) and scholarly associations released statements of opinion.

The American Psychological Association's Board of Scientific Affairs in 1995 established a task force which produced a report, "Intelligence: Knowns and Unknowns" The psychology association report authors wrote that IQ scores have high predictive validity for individual differences in school achievement, for adult occupational status, even when variables such as education and family background have been statistically controlled, and they said individual differences in intelligence are substantially influenced by genetics (75% in adults). Contrary to Herrnstein and Murray's findings, they wrote that prolonged malnutrition during childhood does have long-term intellectual effects. The APA report confirmed the existence of racial IQ differences, while remaining agnostic about their underlying causes:

The differential between the mean intelligence test scores of Blacks and Whites (about one standard deviation, although it may be diminishing) does not result from any obvious biases in test construction and administration, nor does it simply reflect differences in socio-economic status. Explanations based on factors of caste and culture may be appropriate, but so far have little direct empirical support. There is certainly no such support for a genetic interpretation. At present, no one knows what causes this differential.

The APA report concluded with a call for more reflection in debates on intelligence and for a "shared and sustained effort" for more research to answer the many unanswered questions that remain.

Eleven critical responses appeared in the January 1997 issue of American Psychologist, suggesting ways in which the APA report could have been improved. The responses by Richard Lynn and J. Philippe Rushton disputed the task force's conclusion that there is no direct evidence for a genetic interpretation of the IQ difference between blacks and whites.

On December 13, 1994, psychologist Linda Gottfredson and 51 specialists in intelligence and related fields asserted on the opinion page of the Wall Street Journal that IQ bell curves differ across racial and ethnic groups for varying reasons. They maintained that, "Most experts believe that environment is important in pushing the bell curves apart, but that genetics could be involved too."

In 1994, the American Anthropological Association declared itself "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."

In August 1995, at the National Bureau of Economic Research economist Sanders Korenman and Harvard University sociologist Christopher Winship claimed to have found certain errors in Murray and Herrnstein's methodology. Korenman and Winship concluded: "... there is evidence of substantial bias due to measurement error in their estimates of the effects of parents` socioeconomic status. In addition, Herrnstein and Murray`s measure of parental socioeconomic status (SES) fails to capture the effects of important elements of family background (such as single-parent family structure at age 14). As a result, their analysis gives an exaggerated impression of the importance of IQ relative to parents` SES, and relative to family background more generally. Estimates based on a variety of methods, including analyses of siblings, suggest that parental family background is at least as important, and may be more important than IQ in determining socioeconomic success in adulthood."

Significance of group IQ differences

See also: Practical importance of IQ

Within societies

Scope

The distribution of IQ scores among individuals of each race overlap substantially. In a random sample of equal numbers of US Blacks and Whites, Jensen estimates most variance in IQ would be unrelated to race or social class. The average IQ difference between two randomly paired people from the U.S. population is approximately 17 points, and this only increases to 20 points when the pair are black and white. When the pair are siblings, the average difference is still 12 points.

In essays accompanying the publication of The Bell Curve, Herrnstein and Murray argue that whether the cause of the IQ gap is partly genetic (20-80% genetic) or entirely environmental does not really matter because that knowledge alone would not help to eliminate the gap and that knowledge should not impact the way that individuals treat one another. They argue that group differences in intelligence ought not to be treated as more important or threatening than individual differences, but suggest that one legacy of Black slavery has been to exacerbate race relations such that Blacks and Whites cannot be comfortable with group differences in IQ or any other traits.

Moreover, although it may appear paradoxical, it could be argued that an indirect outcome of social egalitarianism would be to raise the genetic contribution to intelligence to as high as possible, by minimizing environmental inequalities and any negatively IQ-impacting cultural and socio-economic differences. If all such inequalities could somehow be completely eliminated, any remaining group (but not individual) IQ differences would then be 100% hereditary: the only remaining factor that could potentially contribute to race-based outcome differences.

Practical importance

The appearance of a large practical importance for intelligence makes some scholars claim that the source and meaning of the IQ gap is a pressing social concern. The IQ gap is reflected by gaps in the academic, economic, and social factors correlated with IQ. However, some dispute the general importance of the role of IQ for real-world outcomes, especially for differences in accumulated wealth and general economic inequality in a nation. (See "Practical importance of IQ".)

The effects of differences in mean IQ between groups (regardless if the cause is social or biological) are amplified by two statistical characteristics of IQ. First, there seem to be minimum statistical thresholds of IQ for many socially valued outcomes (for example, high school graduation and college admission). Second, because of the shape of the normal distribution, only about 16% of the population is at least one standard deviation above the mean. Thus, although the IQ distributions for Blacks and Whites are largely overlapping, different IQ thresholds can have a significant impact on the proportion of Blacks and Whites above and below a particular cut-off.

Small differences in IQ, while relatively unimportant at the level of an individual, could theoretically have large effects for the United States population as a whole. As a demonstration of these possible effects, Herrnstein and Murray used a resampling technique to show that, all else equal, a simulated 3-point drop in average IQ had little effect on factors like marriage, divorce, or unemployment. However, a simulated drop in IQ from 100 to 97-points increased poverty rates by 11% and the proportion of children living in poverty by 13%. In the simulation, similar rises occurred in rates of children born to single mothers, men in jail, high school drop-out, and men prevented from working due to health-related problems. In contrast, when they simulated an increase in average IQ of 3-points to 103, they calculated that poverty rates fell 25%, children living in poverty fell 20%, and high school drop-out rates fell 28%.

Controlling for IQ

Because IQ correlates with or predicts a number of social and economic outcomes that have been found to differ between the black and white populations overall, it is possible that some of the disparities in outcomes are due to group differences in IQ. Studies from The Bell Curve and elsewhere find that, when IQ is statistically controlled for, the probability of having a college degree or working in a high-IQ occupation is higher for Blacks than Whites. Controlling for IQ shrinks the income gap from thousands to a few hundred dollars. Controlling for IQ cuts differential poverty by about three-quarters and unemployment differences by half. However, controlling for IQ has little effect on differential marriage rates. For many other factors, controlling for IQ eliminates the differences between Whites and Hispanics, but the Black-White gap remains (albeit smaller).

Another study found that wealth, race and schooling are important to the inheritance of economic status, but IQ is not a major contributor and the genetic transmission of IQ is even less important. Conversely, controlling for IQ in the above studies also reduces the apparent effect of wealth, race and schooling due to this same correlation.

For additional discussion of the effects of controlling for group differences on a variety of outcomes and groups, see Nyborg and Jensen (2001), and Kanazawa (2005).

Between nations

Some people have attributed differential economic growth between nations to differences in the intelligence of their populations. One example is Richard Lynn's IQ and the Wealth of Nations. The book, is sharply criticized in the peer-reviewed paper The Impact of National IQ on Income and Growth. Another peer-reviewed paper, Intelligence, Human Capital, and Economic Growth: An Extreme-Bounds Analysis, finds a strong connection between intelligence and economic growth.

Jared Diamond's Guns, Germs and Steel instead argues that historical differences in economic and technological development for different 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. However, these environmental differences may operate in part by selecting for higher levels of IQ. This theory is discussed by Jensen, Lynn and Rushton in general and by both Wade and Steve Sailer with respect to Guns, Germs, and Steel. 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"

For high-achieving minorities

The book World on Fire notes the existence in many nations of minorities that have created and control a disproportionate share of the economy, a market-dominant minority. Examples include Chinese in Southeast Asia; Whites, Indians, Lebanese and Igbo people of Western Africa; Whites in Latin America; and Jews in pre-World War II Europe, modern America, and modern Russia. These minorities are often resented and sometimes persecuted by the less successful majority.

In the United States, Jews, Asian Indians, Japanese, and Chinese earn incomes 1.72, 1.42, 1.32, and 1.12 times the American average, respectively. Jews and East Asians have higher rates of college attendance, greater educational attainment, and are many times overrepresented in the Ivy League and many of the United States' most prestigious schools, even though affirmative action discriminates against Asians in the admissions process (relative to Whites as well as to other minorities) At Harvard, for example, Asian American and Jewish students together make up 51% of the student body, though only constituting roughly 6% of the US population. In various Southeast Asian nations, Chinese control a majority of the wealth despite being a minority of the population and are resented by the majority, in some cases being the target of violence.

Achievement in science, a high-complexity occupation in which practitioners tend to have IQs well above average, also appears consistent with some group IQ disparity. Only 0.25% of the world population is Jewish, but Jews make up an estimated 28% of Nobel prize winners in physics, chemistry, medicine, and economics. In the U.S., these numbers are 2% of the population and 40% of winners.

Some studies have shown significant variation in IQ subtest profiles between groups. In one analysis of IQ studies on Ashkenazi Jews, for example, high verbal and mathematical scores, but average or below average visuospatial scores were found. In a separate study, East Asians demonstrated high visuospatial scores, but average or slightly below average verbal scores. The professions in which these populations tend to be over-represented differ, and some believe the difference is directly related to IQ subtest score patterns asserted to exist. The high visiuospatial/average to below average verbal pattern of subtest scores has also been asserted to exist in fully assimilated third-generation Asian Americans, as well as in the Inuit and Native Americans (both of Asian origin).

Policy implications

See also

• Height and intelligence
• Hominid intelligence
• Neuroscience and intelligence
• Sex and intelligence

Related publications:

• The Bell Curve (1994)
• Intelligence: Knowns and Unknowns (1996)
• IQ and Global Inequality (2006)
• The Mismeasure of Man (1981)
• Mainstream Science on Intelligence (1994; 1997)
• Race Differences in Intelligence (2006)
• Survey of Expert Opinion on Intelligence and Aptitude Testing (1987)

Other medical:

• Ancestry and health
• Population groups in biomedicine

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67. Layzer, David. (1974) "Heritability analyses of IQ scores: Science or numerology?" Science 183 pp. 1259-66
68. Schizophrenia and Bipolar Disorder Share Genetic Roots
69. Jianxin S, et al. Common variants on chromosome 6p22.1 are associated with schizophrenia. July 1, 2009, Nature
70. Stefansson H, et al. Common variants conferring risk of schizophrenia. July 1, 2009, Nature
71. Purcell SM, et al. Common polygenic variation contributes to risk of schizophrenia that overlaps with bipolar disorder. July 1, 2009, Nature
72. Waldman, Weinberg, & Scarr, 1994
73. Weinberg, Scarr, & Waldman, 1992
74. Flynn 1980
75. Tizard, Barbara; Cooperman, Oliver; Joseph, Anne; Tizard, Jack. (1972).Environmental effects on language development: A study of young children in long-stay residential nurseries.
76. ^ Nisbett 2009 Intelligence and how to get it: Why schools and cultures count
77. Plomin (2005). "The quest for quantitative trait loci associated with intelligence". Intelligence. 34: 513. doi:10.1016/j.intell.2006.01.001.
78. Antonio Regalado.Scientist's Study Of Brain Genes Sparks a Backlash.The Wall Street Journal. June 16, 2006.
79. Janneke R Zinkstok, Odette de Wilde, Therese AMJ van Amelsvoort, Michael W Tanck, Frank Baas and Don H Linszen (2007). "Association between the DTNBP1 gene and intelligence: a case-control study in young patients with schizophrenia and related disorders and unaffected siblings". Behavioral and Brain Functions 3:19 doi:10.1186/1744-9081-3-19
80. Dick DM, Aliev F, Kramer J, Wang JC, Hinrichs A, Bertelsen S, Kuperman S, Schuckit M, Nurnberger J Jr, Edenberg HJ, Porjesz B, Begleiter H, Hesselbrock V, Goate A, Bierut L (2007). “Association of CHRM2 with IQ: converging evidence for a gene influencing intelligence.” Behavioral Genetics 37(2):265-72
81. Deary (2009). "Genetic foundations of human intelligence". doi:0.1007/s00439-009-0655-4. {{cite journal}}: Check |doi= value (help); Cite journal requires |journal= (help)
82. 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.
83. 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
84. Blood Lead Levels — United States, 1999–2002 CDC.
85. Mfume Calls Lead Paint Poisoning "The Silent Epidemic" NAACP Press Release 17 July 2001
86. 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
87. Acculturation, Reading Level, and Neuropsychological Test Performance Among African American Elders Jennifer J. Manly, Desiree A. Byrd, Pegah Touradji, Yaakov Stern‌
88. Cancellation test performance in African American, Hispanic, and White elderly Desiree A. Byrd, Pegah Touradji, Ming-Xin Tang and Jennifer J. Manly
89. School Quality and the Black-White Achievement Gap Eric A. Hanushek and Steven G. Rivkin 2006
90. Race and Intelligence: Separating Science from Myth By Jefferson M. Fish
91. Social Class, and Individual Differences in I.Q. By Sandra Scarr
92. Cross-cultural Effects on IQ Test Performance: A Review and Preliminary Normative Indications on WAIS-III Test PerformanceJournal of Clinical and Experimental Neuropsychology Volume 26, Number 7 / October 2004
93. 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
94. 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
95. (Salend, Garrick Duhaney, & Montgomery, 2002; Townsend, 2002)
96. Racial Inequity in Special Education. Losen, Daniel J., Ed.; Orfield, Gary, Ed. Harvard Education Publishing Group.
97. (Gay, 2000; Irvine & Armento, 2001; Ladson-Billings, 1994, 2001)
98. 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
99. Color-Blind Ellis Cose. Page 50
100. Rowe, David C., Vazsonyi, Alexander T. and Flannery, Daniel J. [0]=2115 No More Than Skin Deep: Ethnic and Racial Similarity in Developmental Process. Psychological Review 101,3 (July 1994): 396-413
101. Rowe, David C. and Hobart H. Cleveland.Academic achievement in Blacks and Whites: Are the developmental processes similar? Intelligence Volume 23, Issue 3, November-December 1996, Pages 205-228.
102. ^ 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. Cite error: The named reference "bell myth" was defined multiple times with different content (see the help page).
103. (pp. 34-35).
104. This theory is discussed by Jensen (1998b) (pp. 435-437), Lynn (1991b) and Rushton (2000) in general and by both Wade (2006) andSteve Sailer with respect to Guns, Germs, and Steel. SeeRace 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).
105. Pomeranz, Kenneth (2001).The Great Divergence. Princeton, NJ: Princeton University Press.
106. Jones, Eric (1997). The European Miracle. Cambridge: Cambridge University Press.
107. Mokyr, Joel (1992). The Lever of Riches. Oxford: Oxford University Press.
108. North, Douglass (1976). The Rise of the Western World. Cambridge: Cambridge University Press.
109. http://psychology.uwo.ca/faculty/rushtonpdfs/PPPL1.pdf Thirty Years of Research on Race Differences in Cognitive Ability
110. http://www.innovations-report.de/html/berichte/studien/bericht-43536.htmlBlack-White-East Asian IQ differences at least 50% genetic, major law review journal concludes
111. 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)
112. Reviewed by Rushton and Jensen (2005).
113. The attack of the psychometricians. Denny Borsboom. Psychometrika Vol. 71, No. 3, 425–440. September 2006.
114. ^ 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.
115. Dolan, C. V. (1997). A note on Schönemann's refutation of Spearman's hypothesis. Multivariate Behavioral Research, 32, 319–325.
116. Dolan, C. V. (2000). Investigating Spearman's hypothesis by means of multi-group confirmatory factor analysis. Multivariate Behavioral Research, 35, 21–50.
117. 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.
118. http://www.charlesdarwinresearch.org/PRSL2007.pdf
119. 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.
120. Construct validity of Raven’s Advanced Progressive Matrices for African and non-African engineering students in South Africa.
121. 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.
122. Culture-Fair Cognitive Ability Assessment Steven P. Verney Assessment, Vol. 12, No. 3, 303-319 (2005)
123. 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.
124. 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
125. 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
126. Hunt, Earl & Carlson, Jerry. Considerations Relating to the Study of Group Differences in Intelligence. Perspectives on Psychological Science 2 (2), 194-213.
127. Loehlin, J.C., Lindzey, G., & Spuhler, J. (1975). Racial Differences in Intelligence. San Francisco: Freeman.
128. http://www.udel.edu/educ/gottfredson/reprints/2007doublestandards.pdf
129. Genetic Differences and School Readiness Dickens, William T. The Future of Children - Volume 15, Number 1, Spring 2005, pp. 55-69
130. 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). for Racial Differences in the Mental Ability of Young Children
131. Southern Poverty Law CenterInto the Mainstream; An array of right-wing foundations and think tanks support efforts to make bigoted and discredited ideas respectable. Retrieved April 15, 2008.
132. The American Breed: Nazi Eugenics and the Origins of the Pioneer Fund Retrieved Oct 27, 2009.
133. http://www.splcenter.org/intel/intelreport/article.jsp?pid=214#27
134. The Pioneer Fund, Inc.
135. Broca 1873; Bean 1906; Mall 1909; Morton 1839; Pearl 1934; Vint 1934
136. 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
137. Eugenics: America's Darkest Days
138. Degler 1992; Loehlin et al. 1975
139. 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.
140. Lynn 2001 pp. 67–69
141. Harvard Educational Review 39: 1-123
142. Practical Ethics 2nd edition by Peter Singer 1999 Princeton University Press ISBN 978-0521439718
143. William Shockley, Part 3 of 3
144. William Shockley - MSN Encarta
145. 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.
146. A Genetic and Cultural Odyssey: The Life and Work of L. Luca Cavalli-Sforza by Linda Stone, pages 76, 168 ISBN 0231133960.
147. American Anthropological Association (December 19, 2005). "Statement On "Race" And Intelligence". American Anthropological Association. {{cite web}}: Check date values in: |year= / |date= mismatch (help)
148. Gould, Stephen Jay (1996), The Mismeasure of Man, Sagebrush Education Resources, ISBN 0613181301
149. Lewontin, Richard (2001), It Ain't Necessarily So: The Dream of the Human Genome and Other Illusions, New York review of Books, ISBN 0940322951
150. What a tangled web he weaves: Race, reproductive strategies and Rushton's life history theory by Joseph L Graves
151. American Psychological Association findings on predictive value of intelligence tests
152. Neisser, U. (1997). "Never a Dull Moment". American Psychologist 52: 79-81.
153. Gottfredson, Linda (December 13, 1994), "Mainstream Science on Intelligence". Wall Street Journal, p A18.
154. Mainstream science on intelligence
155. AAA Statement on "Race" and Intelligence
156. http://ssrn.com/abstract=225294 Korenman, Sanders and Winship, Christopher, "A Reanalysis of The Bell Curve" (August 1995). NBER Working Paper Series, Vol. w5230, 1995.
157. p. 357. Equal-sized random samples of children from California schools were used for this analysis. Social class was rated on a ten-point scale based on parents' education and occupation. Only 30% of total variance in IQ is associated with differences between race and social class, whereas 65% exists within each racial and social class group. The single largest source of IQ variance exists between siblings within the same family.
158. Murray, C. (2005). "The Inequality Taboo". Commentary Magazine. 120 (2): 13–22. {{cite journal}}: Unknown parameter |month= ignored (help)
159. The Blank Slate, pp. 106-107.
160. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi: 10.1037/0003-066x.59.1.7 , please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi= 10.1037/0003-066x.59.1.7 instead.: "Sub-group differences in performance on high-stakes tests represent one of American society's most pressing social problems, and mechanisms for reducing or eliminating differences are of enormous interest" (p.11).
161. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi: 10.1016/S0160-2896(97)90017-9, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi= 10.1016/S0160-2896(97)90017-9 instead.
162. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi: 10.1016/S0160-2896(97)90014-3, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi= 10.1016/S0160-2896(97)90014-3 instead.
163. ^ The criteria for the "Middle-Class Values" index were: (for men) obtained high school degree (or more), were in labor force (but could be unemployed) throughout previous year (1989), never incarcerated, were still married to their first wife; (for women) obtained a high school degree, had never given birth out of wedlock, never incarcerated, were still marreid to their first husband. Individuals unable to work and those still in school were excluded from this analysis, as well as never-married individuals who satisfied all the other criteria. Poverty is not a criterion, nor is having children.
164. For this calculation, Herrnstein and Murray altered the mean IQ (100) of the U.S. National Longitudinal Survey of Youth's population sample by randomly deleting individuals below an IQ of 103 until the population mean reached 103. Their random deletion procedure was conducted twice and the calculated results were averaged together. Herrnstein and Murray note that their calculation ignore secondary effect. (Herrnstein and Murray 1994, pp. 364-368)
165. Bowles, S. and Gintis, H. (2002). "The inheritance of inequality" (PDF). Journal of Economic Perspectives. 16 (3): 3–30. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link). Note that race, schooling and IQ are all correlated, so considering them as separate factors lessens the apparent effect of IQ.
166. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi: 10.1016/S0160-2896(00)00042-8, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi= 10.1016/S0160-2896(00)00042-8 instead.
167. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi: 10.1016/j.joep.2004.05.001 , please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi= 10.1016/j.joep.2004.05.001 instead.
168. Thomas Volken, "The Impact of National IQ on Income and Growth."
169. Jones, Garett, and Schneider, Joel W (2005). "Intelligence, Human Capital, and Economic Growth: a Bayesian Averaging of Classical Estimates (BACE) Approach" (PDF). {{cite journal}}: Cite journal requires |journal= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
170. 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 (pp. 34-35).
171. Lynn, R. (1991b). "The Evolution of Racial Differences in Intelligence". Mankind Quarterly. 32: 99–173. {{cite journal}}: Cite has empty unknown parameter: |month= (help)
172. Rushton, J. P. (2000). Race, Evolution, and Behavior: A Life History Perspective (3rd ed.). Port Huron, MI: Charles Darwin Research Institute. ISBN 0-9656836-1-3. {{cite book}}: Cite has empty unknown parameters: |coauthors= and |month= (help)
173. Wade, Nicholas (2006). Before the Dawn: Recovering the Lost History of Our Ancestors. New York: Penguin Press. ISBN 1-59420-079-3.
174. http://www.isteve.com/diamond.htm
175. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi: 10.1371/journal.pbio.0040072, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi= 10.1371/journal.pbio.0040072 instead.
176. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi: 10.1093/molbev/msg092, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi= 10.1093/molbev/msg092 instead.
177. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi: 10.1371/journal.pbio.0020286, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi= 10.1371/journal.pbio.0020286 instead.
178. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi: 10.1093/molbev/msh192, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi= 10.1093/molbev/msh192 instead.
179. Attention: This template ({{cite pmid}}) is deprecated. To cite the publication identified by PMID 15356276, please use {{cite journal}} with |pmid= 15356276 instead.
180. Attention: This template ({{cite pmid}}) is deprecated. To cite the publication identified by PMID 16251465, please use {{cite journal}} with |pmid= 16251465 instead.).
181. Sowell, T. (1981). Ethnic America: A History. ISBN 0-465-02075-5. {{cite book}}: Cite has empty unknown parameters: |coauthors= and |month= (help), p. 5
182. Sowell, T. (1981). Ethnic America: A History. ISBN 0-465-02075-5. {{cite book}}: Cite has empty unknown parameters: |coauthors= and |month= (help), pp. 7, 93
183. A study by Princeton researchers Espanshade, T. J., Chung, C. Y. (2005). "The Opportunity Cost of Admission Preferences at Elite Universities" (PDF). Social Science Quarterly. 86 (2): 293–305. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link) analyzes the effects of admission preferences at elite universities in terms of SAT points (1600-point scale): Blacks +230; Hispanics +185; Asians -50; Recruited athletes +200; Legacies (children of alumni) +160. "Our results show that removing consideration of race would have a minimal effect on white applicants to elite universities. The number of accepted white students would increase by 2.4%." Asian percent of accepted students, in contrast, would increase by 33% (from 23.7% to 31.5%). "Nearly four out of every five places in the admitted class not taken by African-American and Hispanic students would be filled by Asians."
184. Hacker, Andrew (2005). "The Truth About the Colleges". The New York Review of Books. 52 (17). {{cite journal}}: Unknown parameter |month= ignored (help)
185. Sowell, T. (1981). Ethnic America: A History. ISBN 0-465-02075-5. {{cite book}}: Cite has empty unknown parameters: |coauthors= and |month= (help), pp. 133-134
186. Purdey, J. E., University of Melbourne (2002). http://eprints.unimelb.edu.au/archive/00000840/
187. Weyl, Nathaniel (1969). "Some comparative performance indexes of American ethnic minorities". Mankind Quarterly. 9: 106–128. {{cite journal}}: Cite has empty unknown parameter: |month= (help); External link in |author= (help)CS1 maint: numeric names: authors list (link)
188. Weyl, Nathaniel (1989). The Geography of American Achievement. Washington, D.C.: Scott-Townsend. {{cite book}}: Cite has empty unknown parameters: |coauthors= and |month= (help); External link in |author= (help)CS1 maint: numeric names: authors list (link), cited by Lynn, R. (1991a). "Race Differences in Intelligence: A Global Perspective". Mankind Quarterly. 31: 255–296. {{cite journal}}: Cite has empty unknown parameter: |month= (help).
189. jinfo.org (2004). "Jewish Nobel Prize Winners," Accessed December 2005.
190. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi: 10.1017/S0021932005027069, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi= 10.1017/S0021932005027069 instead., p. 4
191. Lynn,
192. Mackintosh, N. J. (1998). IQ and human intelligence. Oxford; New York: Oxford University Press. ISBN 0-19-852368-8. {{cite book}}: Cite has empty unknown parameters: |coauthors= and |month= (help), p.178)
193. Lynn, R. (1991a). "Race Differences in Intelligence: A Global Perspective". Mankind Quarterly. 31: 255–296. {{cite journal}}: Cite has empty unknown parameter: |month= (help)

External links

Collective statements

• APA Task Force Examines the Knowns and Unknowns of Intelligence
• Statement on "Race" and Intelligence. American Anthropological Association. Adopted December 1994.
• Mainstream Science on Intelligence. Intelligence, v24 n1 p. 13–23 January–February 1997

Review papers

• James Flynn and Charles Murray debate – news summary
• June 2005 issue of Psychology, Public Policy, and Law, Vol. 11, No. 2.
  • Thirty Years of Research on Race Differences in Cognitive Ability J. Philippe Rushton & Arthur R. Jensen
  • There Are No Public-Policy Implications Robert J. Sternberg
  • What if the Hereditarian Hypothesis is True? Linda S. Gottfredson
  • Heredity, Environment, and Race Differences in IQ Richard E. Nisbett
  • The Cultural Malleability of Intelligence and Its Impact on the Racial/Ethnic Hierarchy Lisa Suzuki & Joshua Aronson
  • Wanted: More Race Realism, Less Moralistic Fallacy J. Philippe Rushton & Arthur R. Jensen
• Race, Genetics and IQ Richard E. Nisbett (PDF)
• The Inequality Taboo Charles Murray archived version

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