Race and intelligence

The connection between race and intelligence has been a subject of debate in both popular science and academic research since the inception of intelligence quotient (IQ) testing in the early 20th century.

IQ tests performed in the United States have consistently demonstrated a significant degree of variation between different racial groups. With the average score of those with African ancestry lower than that of European ancestry and the average score of those with East Asian ancestry being higher than that of European ancestry. While the existence of racial IQ gaps is well-documented and not subject to much dispute, there is no consensus among researchers as to their cause.

Four contemporary classifications of position regarding study of differences in IQ based on race/ethnicity are seen. The first is that these gaps reflect a real difference in average group intelligence, which is caused by a combination of environmental factors and heritable differences in brain function. A second position is that differences in average cognitive ability between races exist and are caused entirely by social and/or environmental factors. A third position holds that differences in average cognitive ability between races do not exist, and that the differences in average test scores are the result of inappropriate use of the tests themselves. Finally, a fourth position is that either or both of the concepts of race and general intelligence are poorly constructed and therefore any comparisons between races are meaningless.

The American Psychological Association has said that while there are differences in average IQ between racial groups, and there is no conclusive evidence for environmental explanations, "there is certainly no [direct empirical] support for a genetic interpretation," and no adequate explanation for the racial IQ gap is presently available. The position of the American Anthropological Association is that intelligence cannot be biologically determined by race. According to a 1996 statement from the American Association of Physical Anthropologists, although heredity influences behavior in individuals, it does not affect the ability of a population to function in any social setting, all peoples "possess equal biological ability to assimilate any human culture" and "racist political doctrines find no foundation in scientific knowledge concerning modern or past human populations."

History of the debate

Main article: History of the race and intelligence controversy

See also: Scientific racism

Alfred Binet (1857–1911), inventor of the first intelligence test.

The history of the race and intelligence controversy concerns the historical development of a debate, primarily in the United States, concerning possible explanations of group differences in scores on intelligence tests. Historically there have been differences among average scores in IQ tests of different population groups; these have sometimes been called "racial IQ gaps". Researchers believe that environmental (socioeconomic and cultural) factors contribute to this, but have not agreed on whether the gaps are due only to environmental factors, or whether there is any genetic contribution that can be substantiated.

Claims of races having different intelligence were used to justify colonialism, slavery, social darwinism, and racial eugenics. In the late 19th and early 20th centuries, group differences in intelligence were assumed to be due to race and, apart from intelligence tests, research relied on measurements such as brain size or reaction times. The first IQ test was created between 1905 and 1908 and revised in 1916 (the Stanford–Binet Intelligence Scales). Alfred Binet, the developer of these tests, warned that these should not be used to measure innate intelligence or to label individuals. However, at the time there was great concern in the United States about the abilities and skills of recent immigrants. Different nationalities were sometimes thought to comprise different races, such as Slavs. The tests were used to evaluate draftees for World War I, and researchers found that people of southern and eastern Europe scored lower than native-born Americans. At the time, such data was used to construct an ethnically based social hierarchy, one in which immigrants were rejected as unfit for service and mentally defective. It was not until later that researchers realized that lower language skills by new English speakers affected their scores on the tests.

In the 1920s, many scientists reacted to eugenicist claims linking abilities and moral character to racial or genetic ancestry. Despite that, states like Virginia enacted laws based in eugenics, such as its 1924 Racial Integrity Act, which established the one-drop rule as law. Generally, understanding grew about the contribution of environment to test-taking and results (such as having English as a second language). By the mid-1930s most US psychologists had adopted the view that environmental and cultural factors played a dominant role. In addition, psychologists were reluctant to risk being associated with the German Nazi claims of a "master race".

In 1969 Arthur Jensen revived the hereditarian point of view in the article, "How Much Can We Boost IQ and Scholastic Achievement?" It followed changes in public programs introduced to try to correct decades of discrimination against poor African Americans. In 1954 the US Supreme Court ruled in Brown v. Board of Education that public school segregation was unconstitutional. As part of the Great Society programs under President Lyndon Johnson, the Head Start Program was started with the goal of early intervention to help socially disadvantaged children succeed by providing remedial education. Given the effects of segregation and discrimination into the 1960s, many Head Start programs served African-American children.

Jensen's article questioned remedial education for African-American children; he suggested their poor educational performance reflected an underlying genetic cause rather than lack of stimulation at home. Jensen's work, publicized by the Nobel laureate physicist William Shockley, sparked controversy amongst the academic community and student protests.

In their 1988 book The IQ Controversy, the Media, and Public Policy, Mark Snyderman and Stanley Rothman claimed to document a liberal bias in the media coverage of scientific findings regarding IQ. The book builds on the results of a survey of more than 600 psychologists, sociologists and educationalists. 45 percent of those surveyed thought that black-white differences in IQ were the product of both genetic and environmental variation, while 15 percent believed that the differences were entirely due to environmental factors; the rest either declined to answer the question, or thought that there was insufficient evidence to give an answer.

Another debate followed The Bell Curve (1994), a book by Richard Herrnstein and Charles Murray, who argued in favor of the hereditarian viewpoint. It provoked the publication of several interdisciplinary books representing the environmental point of view, as well as some in popular science. They include The Bell Curve Debate (1995), Inequality by Design: Cracking the Bell Curve Myth (1996) and a second edition of The Mismeasure of Man (1996) by Steven J. Gould. One book written from the hereditarian point of view at this time was The g Factor: The science of mental ability (1998) by Jensen. In 1994 a group of 52 scientists, including leading hereditarians, signed the statement "Mainstream Science on Intelligence". The Bell Curve also led to a 1995 report from the American Psychological Association, "Intelligence: Knowns and Unknowns", acknowledging a gap between average IQ scores of whites and blacks as well as the absence of any adequate explanation of it, either environmental or genetic.

The review article "Thirty Years of Research on Race Differences in Cognitive Ability" by Rushton and Jensen was published in 2005. The article was followed by a series of responses, some in support, some critical. Richard Nisbett, another psychologist who had also commented at the time, later included an amplified version of his critique as part of the book Intelligence and How to Get It: Why Schools and Cultures Count (2009). Rushton and Jensen in 2010 made a point-for-point reply to this and again summarized the hereditarian position.

Two public figures claimed in interviews that one of the main causes for poverty in Africa is a low average intelligence which caused great controversy. Following an interview in the monthly supplement of Helsingin Sanomat, Lynn's coauthor Tatu Vanhanen, a political scientist and father of the Prime Minister of Finland Matti Vanhanen, was investigated by the Finnish police between 2002 and 2004. In 2007 James D. Watson, Nobel laureate in biology, gave a controversial interview to the Sunday Times Magazine during a book tour in the United Kingdom. This resulted in the cancellation of a Royal Society lecture, along with other public engagements, and his suspension from his administrative position at Cold Spring Harbor Laboratory. He subsequently cancelled the tour and resigned from his position.

Many of the leading hereditarians, mostly psychologists, have received funding from the Pioneer Fund with Rushton as its current head. The Southern Poverty Law Center lists the Pioneer Fund as a hate group, citing the fund's history, its funding of race and intelligence research, and its connections with racist individuals. On the other hand, Ulrich Neisser writes that "Pioneer has sometimes sponsored useful research—research that otherwise might not have been done at all." Other sources and researches have criticized the Pioneer Fund for promoting scientific racism, eugenics and white supremacy.

Ethics of research

The 1996 report of the APA had comments on the ethics of research on race and intelligence. Gray & Thompson (2004) as well as Hunt & Carlson (2007) have also discussed different possible ethical guidelines. Nature in 2009 featured two editorials on the ethics of research in race and intelligence by Steven Rose (against) and Stephen J. Ceci and Wendy M. Williams (for).

According to critics, research will run the risk of simply reproducing the horrendous effects of the social ideologies (such as Nazism or Social Darwinism) justified in part on claimed hereditary racial differences. Steven Rose maintains that the history of eugenics makes this field of research difficult to reconcile with current ethical standards for science.

Linda Gottfredson argues that suggestion of higher ethical standards for research into group differences in intelligence is a double standard applied in order to undermine disliked results. Flynn, a non-hereditarian, has argued that had there been a ban on research on possibly poorly conceived ideas much valuable research on intelligence testing (including his own discovery of the Flynn effect) would not have occurred.

Validity of "race" and "IQ"

Main articles: Race (classification of humans), Race and genetics, Intelligence quotient, and Intelligence

The concept of intelligence and the degree to which it is measurable is and has been a matter of discussion. Psychology, a psychology textbook by Schacter et al., argue that while there is a general consensus within western science about how to define intelligence, the concept of intelligence as something that can be unequivocally measured by a single figure is not universally accepted. A recurring criticism is that different societies value and promote different kinds of skills and that the concept of intelligence is therefore culturally variable and cannot be measured the same in different societies. Consequently, some critics argue that proposed relationships to other variables are necessarily tentative.

In fields such as psychology, medicine, economics, political science, criminology, and other research on group differences, intelligence is commonly measured using intelligence quotient (IQ) tests. The statement "Mainstream Science on Intelligence" argued that "IQ is strongly related, probably more so than any other single measurable human trait, to many important educational, occupational, economic, and social outcomes ... Whatever IQ tests measure, it is of great practical and social importance". Most of the research on intelligence differences between racial groups is based on IQ testing. These tests are highly correlated with the psychometric variable g (for general intelligence factor). Other tests that are also highly correlated with g are also seen as measures of cognitive ability and have sometimes been used in the research. US examples include the Armed Forces Qualifying Test, SAT, GRE, GMAT and LSAT. International student assessment tests that have been used include the Trends in International Mathematics and Science Study, Programme for International Student Assessment, and Progress in International Reading Literacy Study.

Also the concept of race as a meaningful category of analysis is hotly contested. The authors of two articles in two encyclopedias, the Encyclopædia Britannica and the Encyclopedia of Race, Ethnicity and Society, argue that today the mainstream view is that race is a social construction that is not mainly based in actual biological differences but on folk ideologies that construct groups based on social disparities and superficial physical characteristics. Sternberg, Grigorenko & Kidd (2005) state that the overwhelming portion of the literature correlating race with identity has tacitly adopted folk definitions of race. The American Anthropological Association in 1998 published a "Statement on 'Race'" which rejected the existence of "races" as unambiguous, clearly demarcated, biologically distinct groups. Others argue that this view is restricted to certain fields, while in other fields, race is still seen as a valid biological category.

Race in the studies is almost always determined using self-reports, rather than based on analyses of the genetic history of the tested individuals. According to psychologist David Rowe, self-report is the preferred method for racial classification in studies of racial differences because classification based on genetic markers alone ignore the "cultural, behavioral, sociological, psychological, and epidemiological variables" that distinguish racial groups. Hunt and Carlson write that "Nevertheless, self-identification is a surprisingly reliable guide to genetic composition. Tang et al. (2005) applied mathematical clustering techniques to sort genomic markers for over 3,600 people in the United States and Taiwan into four groups. There was almost perfect agreement between cluster assignment and individuals' self-reports of racial/ethnic identification as White, Black, East Asian, or Latino."

The notions that cluster analysis and the correlation between self-reported race and genetic ancestry supports a view of race as primarily based in biology is contradicted by most anthropologists. For example C. Loring Brace and geneticist Joseph Graves, have argued that while it is certainly possible to find biological and genetic variation that corresponds roughly to the groupings normally defined as races, this is true for almost all geographically distinct populations. The cluster structure of the genetic data is dependent on the initial hypotheses of the researcher and the populations sampled. When one samples continental groups the clusters become continental, if one had chosen other sampling patterns the clusters would be different. Kaplan 2011 therefore concludes that while racial groups are characterized by different allele frequencies, this does not mean that racial classification is a natural taxonomy of the human species, because multiple other genetic patterns can be found in human populations that crosscut racial distinctions. In this view racial groupings are social constructions that also have biological reality which is largely an artifact of how the category has been constructed.

Earl Hunt agrees that racial categories are defined by social conventions, though he points out that they also correlate with clusters of both genetic traits and cultural traits. Hunt explains that due to this, racial IQ gaps are caused by these variables that correlate with race, and race itself is rarely a causal variable. Researchers who study racial disparities in test scores are studying the relationship between the scores and the many factors correlated with race which could potentially affect performance. These factors include health and wealth, biological differences, and education.

Group differences

US test scores

Main article: Achievement gap in the United States

Rushton & Jensen (2005) write that in the United States, self-identified blacks and whites have been the subjects of the greatest number of studies. They state that the black-white IQ difference is about 15 to 18 points or 1 to 1.1 standard deviations (SDs), which implies that between 11 and 16 percent of the black population have an IQ above 100 (the white mean). The black-white IQ difference is largest on those components of IQ tests that best represent the general intelligence factor g. The 1996 APA report "Intelligence: Knowns and Unknowns" and the 1994 editorial statement "Mainstream Science on Intelligence" gave more or less similar estimates. Roth et al. (2001) in a review of the results of a total of 6,246,729 participants on other tests of cognitive ability or aptitude found a black-white gap of 1.1 SD. Consistent results were found for college and university application tests such as the Scholastic Aptitude Test (N = 2.4 million) and Graduate Record Examination (N = 2.3 million), as well as for tests of job applicants in corporate sections (N = 0.5 million) and in the military (N = 0.4 million).

A 2006 study by Dickens and Flynn estimated that the black-white gap closed by about 5 or 6 IQ points between 1972 and 2002, which would be a reduction by about one-third. However this was challenged by Rushton & Jensen who claim the gap remains stable. Murray in a 2006 study agreed with Dickens and Flynn that there has been a narrowing of the gap, "Dickens' and Flynn's estimate of 3–6 IQ points from a base of about 16–18 points is a useful, though provisional, starting point". But he argued that this has stalled and that there has been no further narrowing for people born after the late 1970s. Murray found similar results in a 2007 study.

The IQ distributions of other racial and ethnic groups in the United States are less well-studied. The Bell Curve (1994) stated that the average IQ of African Americans was 85, Latino 89, White 103, Asian 106, and Jews 113. Asians score relatively higher on visuospatial than on verbal subtests. The few Amerindian populations that have been systematically tested, including Arctic Natives, tend to score worse on average than white populations but better on average than black populations.

According to several studies, Ashkenazi Jews score 0.75 to 1.0 standard deviation above the general European average. This corresponds to an IQ of 112–115. Other studies have found somewhat lower values. During the 20th century, they made up about 3% of the US population but won 27% of the US science Nobel Prizes and 25% of the Turing Awards. They have high verbal and mathematical scores, while their visuospatial abilities are typically somewhat lower, by about one half standard deviation, than the European average. See also Ashkenazi intelligence.

The racial groups studied in the United States and Europe are not necessarily representative samples for populations in other parts of the world. Cultural differences may also factor in IQ test performance and outcomes. Therefore, results in the United States and Europe do not necessarily correlate to results in other populations.

International comparisons

Main article: Nations and intelligence

The validity and reliability of IQ scores obtained from outside of the United States and Europe have been questioned due to the possibility of test bias as discussed in a later section. Nevertheless, some researchers have attempted to measure IQ variation in a global context.

Flynn effect

Main article: Flynn effect

Raw scores on IQ tests have been rising. This score increase, primarily in the lower end of the distribution, is known as the "Flynn effect," named for James R. Flynn, who did much to document it and promote awareness of its implications. In the United States the increase has been continuous and approximately linear from the earliest years of testing to the present. For example, in the United States the average scores of blacks on some IQ tests in 1995 were the same as the scores of whites in 1945.

Potential environmental causes

The following environmental factors are some of those suggested as explaining a portion of the differences in average IQ between races. These factors are not mutually exclusive with one another, and some may in fact directly contribute to others. Furthermore, the relationship between genetics and environmental factors may be complicated. For example, the differences in socioeconomic environment for a child may be due to differences in genetic IQ for the parents, and the differences in average brain size between races could be the result of nutritional factors.

Test bias

Studies on other groups and in other nations have argued that IQ tests may be biased against certain groups. The validity and reliability of IQ scores obtained from outside of the United States and Europe have been questioned, in part because of the inherent difficulty of comparing IQ scores between cultures. Several researchers have argued that cultural differences limit the appropriateness of standard IQ tests in non-industrialized communities. In the mid-1970s, for example, the Soviet psychologist Alexander Luria concluded that it was impossible to devise an IQ test to assess peasant communities in Russia because taxonomy was alien to their way of reasoning.

A 1996 report by the American Psychological Association states that controlled studies show that the black-white IQ gaps are not substantially due to bias in the content or administration of the IQ tests. Furthermore, the tests are equally valid predictors of future achievement for black and white Americans. This view is reinforced by Nicholas Mackintosh in his 1998 book IQ and Human Intelligence, and by a 1999 literature review by Brown, Reynolds & Whitaker (1999).

Stereotype threat

Main article: Stereotype threat

Stereotype threat is the fear that one's behavior will confirm an existing stereotype of a group with which one identifies or is defined by; 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 or are expected to score lower. Stereotype threat conditions cause larger than expected IQ differences among groups but do not explain the gaps found in non-threatening test conditions.

Socioeconomic environment

According to the report of a 1996 APA task force regarding the US gaps, socioeconomic status (SES) cannot account for all of the observed racial-ethnic group differences in IQ. Their first reason for this conclusion is 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 shown little effect on IQ. Third, the relationship between IQ and SES is not simply one in which SES determines IQ, but differences in intelligence, particularly parental intelligence, also cause differences in SES, making separating the two factors difficult.

Health and nutrition

Main article: Health and intelligence

Percentage of children aged 1-5 with blood lead levels at least 10 µg/dL. Black and Hispanic children have much higher levels than white children. A 10 µg/dL increase in blood lead at 24 months is associated with a 5.8-point decline in IQ. Although the Geometric Mean Blood Lead Levels (GM BLL) are declining a CDC report (2002) states that: "However, the GM BLL for non-Hispanic black children remains higher than that for Mexican-American and non-Hispanic white children, indicating that differences in risk for exposure still persist."

Environmental factors including lead exposure, breast feeding, and nutrition can significantly affect cognitive development and functioning. For example, iodine deficiency causes a fall, in average, of 12 IQ points. Such impairments may sometimes be permanent, sometimes be partially or wholly compensated for by later growth. The first two years of life is the critical time for malnutrition, the consequences of which are often irreversible and include poor cognitive development, educability, and future economic productivity. The African American population of the United States is statistically more likely to be exposed to many detrimental environmental factors such as poorer neighborhoods, schools, nutrition, and prenatal and postnatal health care.

The Copenhagen consensus in 2004 stated that lack of both iodine and iron has been implicated in impaired brain development, and this can affect enormous numbers of people: it is estimated that one-third of the total global population are affected by iodine deficiency. In developing countries, it is estimated that 40% of children aged four and under suffer from anaemia because of insufficient iron in their diets.

Eppig, Fincher & Thornhill (2010) argue that "From an energetics standpoint, a developing human will have difficulty building a brain and fighting off infectious diseases at the same time, as both are very metabolically costly tasks" and that differences in prevalence of infectious diseases (such as malaria) may be an important explanation for differences in IQ between different regions of the world. They also tested other hypotheses as well, including genetic explanations, concluding that infectious disease was "the best predictor". Christopher Hassall and Thomas Sherratt repeated the analysis, and concluded "that infectious disease may be the only really important predictor of average national IQ".

In order to mitigate the effects of education on IQ, Eppig, Fincher & Thornhill (2010) repeated their analysis across the United States where standardized and compulsory education exists. The correlation between infectious disease and average IQ was confirmed, and they concluded that the "evidence suggests that infectious disease is a primary cause of the global variation in human intelligence".

Education

Several studies have proposed that a large part of the gap can be attributed to differences in quality of education. Racial discrimination in education has been proposed as one possible cause of differences in educational quality between races. According to a paper by Hala Elhoweris, Kagendo Mutua, Negmeldin Alsheikh and Pauline Holloway, teachers' referral decisions for students to participate in gifted and talented educational programs was influenced in part by the students' ethnicity.

The Abecedarian Early Intervention Project, an intensive early childhood education project, was also able to cause an average IQ gain of 4.4 points at age 21 in the black children who participated in it compared to controls. Arthur Jensen agreed that the Abecedarian project demonstrates that education can have a significant effect on IQ, but also said that no educational program thus far has been able to reduce the Black-White IQ gap by more than a third, and that differences in education are thus unlikely to be its only cause.

Rushton and Jensen argue that long-term follow-up of the Head Start Program found large immediate gains for blacks and whites but that these were quickly lost for the blacks although some remained for whites. They argue that also other more intensive and prolonged educational interventions have not produced lasting effects on IQ or scholastic performance. Nisbett argues that they ignore studies such as Campbell & Ramey (1994) which found that at the age 12, 87% black of infants exposed to an intervention had IQs in the normal range (above 85) compared to 56% of controls, and none of the intervention-exposed children were mildly retarded compared to 7% of controls. Other early intervention programs have shown IQ effects in the range of 4–5 points, which are sustained until at least age 8–15. Effects on academic achievement can also be substantial. Nisbett also argues that not only early age intervention can be effective, citing other successful intervention studies from infancy to college.

Logographic writing system

Complex logographic writing systems have been proposed as an explanation for the higher visuospatial IQ scores of East Asians. Critics argue that the causation may be reversed with higher visuospatial ability causing the development of pictorial symbols in writing rather than alphabetic ones. Another argument is that East Asians adopted at birth also score high on IQ tests. Similar relatively higher visuospatial abilities are also found among Inuit and Native Americans whose ancestors migrated from East Asia to the Americas.

Caste-like minorities

A large number of studies have shown that systemically disadvantaged minorities, such as the African American minority of the United States generally perform worse in the educational system and in intelligence tests than the majority groups or less disadvantaged minorities such as immigrant or "voluntary" minorities. The explanation of these findings may be that children of caste-like minorities, due to the systemic limitations of their prospects of social advancement, do not have "effort optimism", i.e. they do not have the confidence that acquiring the skills valued by majority society, such as those skills measured by IQ tests, is worthwhile. They may even deliberately reject certain behaviors seen as "acting white".

This argument is also explored in the book Inequality by Design: Cracking the Bell Curve Myth (1996) which argues 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. One example being Jews in the early 20th century in the US who, the authors argue, scored low on IQ tests. 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. Examples include Koreans, Peruvians and Brazilians in Japan, Burakumin in Japan, Australian Aborigines, Romani in Czechoslovakia, Maori in New Zealand, Afro-Brazilians, Indigenous Brazilians, Pardos and Rural Exiles (as, but not limited to, people from Northeast in Brasília, São Paulo and Rio de Janeiro metropolitan areas, and including a minority of poors of European descent) in Brazil, Afrikaners in South Africa, Catholics in North Ireland, Irish and Scottish in Great Britain, Arabs and Sephardi Jews in Israel, and Dalit, low caste, and tribal people in India. The authors note, however, that the comparisons made in the table do not represent the results of all relevant findings, that sometimes studies have shown more mixed findings, that the tests and procedures varied greatly from study to study, and that there is no simple way to compare the size of group differences. The statement regarding Arabs in Israel, for example, is based on a news report that, in 1992, 26% of Jewish high school, predominantly Ashkenazim, students passed their matriculation exam as opposed to 15% of Arab students. Jay Gould in the The Mismeasure of Man also argued that Jews in the early 20th century scored low on IQ tests. Rushton as well as Cochran, Hardy & Harpending have argued that this is a misrepresentation of the studies and that also the early testing support a high average Jewish IQ.

Murray replies that purely sociocultural factors like this cannot explain the gap, because the size of the gap on any test is dependent on that test's degree of g-loading. As an example, Murray notes that the test of reciting a string of digits backwards is much more g-loaded than reciting it forwards, and the black-white gap is around twice as large on the first test as on the second. According to Murray, there is no way that culture or motivation could systematically encourage black performance on one test while decreasing it on another, when both tests are provided by the same examiner in the same setting.

Cultural traditions valuing education

Nisbett argues cultural traditions valuing education can explain the high results in the US for Ashkenazi Jews (Talmud scholarship) and East Asians (Confucianism and the Imperial examination system).

Black subculture

JR Harris suggested in The Nurture Assumption that different peer group cultures may contribute to the black-white IQ gap. She cites the work of Thomas Kindermann, whose longitudinal studies find that peer groups significantly affect scholastic achievement.

Genetic arguments

A number of scientists, supported by the American Anthropological Association, reject any genetic contribution to racial IQ gaps. The American Psychological Association, while maintaining the causes of the gap are presently unknown, stated that "what little [direct evidence] there is fails to support the genetic hypothesis." Jensen & Rushton and Herrnstein & Murray, however, argue that there is a substantial (50–80% in the US according to Rushton and Jensen) genetic contribution to the black-white IQ gap.

Evolutionary theories

See also: Evolution of human intelligence

One explanation for racial IQ gaps advanced by some researchers is that they are partly the result of evolutionary pressures that varied between geographic regions. C. Loring Brace has argued that such a clinal distribution in the trait is highly improbable, because the evolution of human intelligence is founded on the development of human linguistic behavior, and intelligence is therefore of equal survival value to all human groups. On the other hand, cultural psychologist Richard Nisbett has argued that "(t)here are a hundred ways that a genetic difference in intelligence could have arisen – either in favor of whites or in favor of blacks."

Arthur Jensen explains in The g Factor how evolutionary factors could have potentially contributed to racial IQ gaps. J. Philippe Rushton carries this idea a step further in Race, Evolution, and Behavior, proposing that human groups differ in intelligence due to r/K selection theory, with Africans being more r-selected and Asians more K-selected.

C. Loring Brace regards evolutionary explanations for racial IQ gaps as unfounded speculation. Regarding Rushton’s application of r/K selection to human groups, Joseph L. Graves argues that not only is r/K selection theory considered to be virtually useless when applied to human life history evolution, but Rushton himself does not apply the theory correctly, and displays a lack of understanding evolution in general.

Genetics of Race and intelligence

Main articles: Race and genetics and Genetics and intelligence

The decoding of the human genome has enabled scientists to search for sections of the genome that contribute to cognitive abilities, and there are also ways to study whether the differences in frequency of particular genetic variants between populations contribute to differences in average cognitive abilities. However the geneticist, Alan R. Templeton has argued that this question is muddled by the general focus on "race" rather than on populations defined by gene frequency or by geographical proximity, and by the general insistence on phrasing the question in terms of heritability of intelligence. Templeton argues that racial groups neither represent sub-species or distinct evolutionary lineages, and that therefore there is no basis for making claims about the general intelligence of races. He also argues that phrasing the question in terms of heritability is useless since heritability applies only within groups, but cannot be used to compare traits across groups. Templeton argues that the only way to design a study of the genetic contribution to intelligence is to the correlation between degree of geographic ancestry and cognitive abilities. He argues that this would require a Mendelian experimental design where specimens with different hybrid compositions are subjected to the same environmental influences, and he further argues that when this design has been carried out, it has shown no significant correlation between any cognitive ability and the degree of African or European ancestry.

Intelligence is both a quantitative and polygenic trait. This means that intelligence is under the influence of several genes, possibly several thousand. The effect of most individual genetic variants on intelligence is thought to be very small, well below 1% of the variance in g. 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 due to their small effect sizes, more powerful tools of analysis will be required to detect them. Others assert that no useful answers can be reasonably expected from such research before an understanding of the relation between DNA and human phenotypes emerges. 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". Several candidate genes have been proposed to have a relationship with intelligence. However, a review of candidate genes for intelligence published in Deary, Johnson & Houlihan (2009) 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".

Heritability within and between groups

A frequently cited example of an X-factor from Richard Lewontin describes two populations of corn, one grown in a normal environment, and the other in a nutrient-deficient environment. The height of this corn is 100% heritable when grown in a uniform environment. Therefore, in such a scenario the within-group heritability of height is 100% in both populations, but the substantial differences between groups are due entirely to environmental factors. Another example is human height which is 85-90% heritable but still has increased by a standard deviation or more in a generation or less in several countries of the world.

Heritability is defined as the proportion of interindividual variance in a trait which is attributable to genotype within a defined population in a specific environment. A heritability of 1 indicates that variation correlates fully with genetic variation and a heritability of 0 indicates that there is no correlation between the trait and genes at all. There is broad agreement that individual variation in intelligence is neither fully genetic nor fully environmental, but there is little agreement on the relative contribution of genes and environment on individual intelligence.

It has been argued that intelligence is substantially heritable within populations, with 30–50% of variance in IQ scores in early childhood being attributable to genetic factors in analyzed US populations, increasing to 75–80% by late adolescence. High heritability does not imply that a trait is genetic or unchangeable, however, as environmental factors that affect all group members equally will not be measured by heritability (see the figure) and the heritability of a trait may also change over time in response to changes in the distribution of genes and environmental factors. High heritability also doesn't imply that all of the heritability is genetically determined, but can also be due to environmental differences that affect only a certain genetically defined group (indirect heritability).

Jensen and Rushton have argued that there may be environmental factors ("X factors") that are not measured by the heritability figure, but such factors must have the properties of not affecting whites while at the same time affecting all blacks equally, but, the hereditarians argue, no such plausible factors have been found and other statistical tests for the presence of such an influence in the US are negative.

This argument has been criticized by other researchers using several different arguments. Firstly, as noted earlier, Templeton argues that heritability is relevant only for explaining within group variance, cannot be used to explain variation between groups. Secondly the heritability figure of .8 for White American populations have been frequently been criticized as being highly inflated. Another is arguing that there are many environmental factors, sometimes small and subtle, that together add up to a large difference between blacks and whites. Dickens and Flynn argue that the conventional interpretation ignores the role of feedback between factors, such as those with a small initial IQ advantage, genetic or environmental, seeking out more stimulating environments which will gradually greatly increase their advantage, which, as one consequence in their alternative model, would mean that the "heritability" figure is only in part due to direct effects of genotype on IQ.

Spearman's hypothesis

Main article: Spearman's hypothesis

Spearman's hypothesis states that the magnitude of the black-white difference in tests of cognitive ability is entirely or mainly a function of the extent to which a test measures general mental ability, or g. The hypothesis, first formalized by Arthur Jensen in the 1980s based on Charles Spearman's earlier comments on the topic, argues that differences in g are the sole or major source of differences between blacks and whites observed in many studies of race and intelligence. Various criticisms have been advanced and the validity of the arguments remain unresolved.

Regression toward the mean

Jensen and Rushton argue that regression toward the mean effects observed in studies comparing blacks and whites with high and low IQs to the IQs of their close relatives provide evidence of a polygenetic basis for the black/white IQ gap. However, other researchers have found Jensen's arguments to be unpersuasive, noting that regression to the mean is merely a statistical artifact and cannot be used to isolate potential causal factors.

Gradual gap appearance

Fryer & Levitt (2006) found in test of children aged eight to twelve months only minor differences (0.06 SD) between blacks and whites that disappeared with the inclusion of a limited set of controls including social-economic status. Flynn has argued that the U.S. black-white gap appear gradually which suggests environmental causes. "At just 10 months old, the average score is only one point behind; by the age of 4, it is 4.6 points behind, and by the age of 24, the gap is 16.6 points. This could be due to genes, but the steady rate after the age of 4 (about 0.6 IQ points lost every year) suggests otherwise, since genetically driven differences such as height differences between males and females tend to kick in at a certain age."

Rushton and Jensen argue that the black-white IQ difference of one standard deviation is present at the age of 3 and does not change significantly afterward. Murray, also a hereditarian, argues that the heritability of IQ increases with age which is reflected in the racial IQ gaps gradually increasing.

Uniform rearing conditions

Several studies have been done on the effect of similar rearing conditions on children from different races.

The Minnesota Transracial Adoption Study (1976) examined the IQ test scores of 122 adopted children and 143 nonadopted children reared by advantaged white families. The children were restudied ten years later.

Three other studies found opposing evidence with none finding higher intelligence in white children than in black children.

Moore (1986) compared black and mixed-race children adopted by either black or white middle-class families in the US. Moore observed that 23 black and interracial children raised by white parents had a significantly higher mean score than 23 age-matched children raised by black parents (117 vs 104), and argued that differences in early socialization explained these differences.

Eyferth (1961) studied the out-of-wedlock children of black and white soldiers stationed in Germany after World War 2 and then raised by white German mothers and found no significant differences.

Tizard et al. (1972) studied black (African and West Indian), white, and mixed-race children raised in British long-stay residential nurseries. Three out of four tests found no significant differences. One test found higher scores for non-whites.

The data is summarized below:

Biological parents	Number of children	Average IQ	Raised by
Minnesota Transracial Adoption Study (1976) United States
Black	21	95/89	White non-biological couple
Black-white	55	110/99	White non-biological couple
White	16	118/106	White non-biological couple
Asian or Amerindian	12	101/99	White non-biological couple
White	104	116/109	White biological couple
Moore (1986) United States
Black	17	102.9	Black non-biological couple
Black-white	6	105.7	Black non-biological couple
Black	9	118.0	White non-biological couple
Black-white	14	116.5	White non-biological couple
Eyferth (1961) Germany
Black-white	98	96.5	White biological single mother
White	83	97.2	White biological single mother
Tizard et al. (1972) United Kingdom
Black	15	105.7	Long-stay residential nurseries
Black-white	15	109.8	Long-stay residential nurseries
White	25	101.3	Long-stay residential nurseries

Racial admixture studies

Many people have an ancestry from different geographic regions. For example, African Americans typically have ancestors from both Africa and Europe, with, on average, 20% of their genome inherited from European ancestors. If racial IQ gaps have a partially genetic basis, blacks with a higher degree of European ancestry should on average have higher IQ, because the genes inherited from European ancestors would likely include some genes with a positive effect on IQ.

John C. Loehlin describes several studies that have examined the relationship between ancestry levels and IQ. A 1936 study by Witty and Jenkins examined ancestry among African-Americans with very high IQ, and found that they did not have a higher degree of European ancestry than unselected African-Americans. More recent studies have compared IQ to ancestry estimates based on skin color, and found the correlation of skin color to higher IQ (0.1-0.15) to be very low. Nisbett and Jensen have both argued that skin color is a highly imprecise measure of racial ancestry. According to Loehlin, other studies comparing the IQs of mixed-race children to those two black parents or two white parents have produced similarly inconclusive results.

The frequency of different blood types vary with ancestry. Correlations between degree of European blood types and IQ have varied between 0.05 and -0.38 in two studies from 1973 and 1977. Nisbett writes that one problem with these studies is that white blood genes are very weakly associated with one another in the black population, so they are not a reliable method of estimating ancestry. T. Edward Reed, an expert on blood groups, argues that the methodology used in these studies would have been unable to detect any difference, regardless of whether or not the hereditarian hypothesis is correct.

Some authors have suggested that new studies of the relationship ancestry and IQ should be performed using modern DNA-based ancestry estimations, which would provide a more reliable measure of ancestry than is possible based on skin tone or blood groups.

Brain size

Main articles: Neuroscience and intelligence and Craniometry

In a study of the head growth of 633 term-born children, it was shown that prenatal growth and growth during infancy were associated with subsequent IQ. The study's conclusion was that the brain volume a child achieves by the age of 1 year helps determine later intelligence. Within human populations, Magnetic Resonance Imaging (MRI) studies conducted to determine whether there is a relationship between brain size and a number of cognitive measures have "yielded inconsistent findings with correlations from 0 to 0.6, with most correlations 0.3 or 0.4.". For postmortem studies the correlation is about 0.15. The difference in average brain sizes varies widely from country to country. For instance, the average brain size of the average Maasai person is larger than the average brain size of the average "Caucasoid" person in Egypt. According to Z. Z. Cernovsky Rushton's own study shows that the average cranial capacity of North American blacks is similar to that of Caucasians from comparable climatic zones,

Several studies have reported that races overlap significantly in brain size but differ in average brain size. The magnitude of these differences varies depending on the particular study and the methods used. In general, these studies have reported that East Asians have on average a larger brain size than whites who have on average a larger brain size than blacks. Other researchers have also found variation in average brain size between human groups, but concluded that this variation should be viewed as being based on biogeographic ancestry and independently of "race".

According to an analysis by Jelte Wicherts, the material cited by Rushton is in the form of external or postmortem cranial measurements with none using more modern MRI techniques. Such material only have a correlation of 0.2 with IQ. Furthermore, even using Rushton's data the black-white difference in brain size are small (0.6 SD units) compared to the IQ differences. Wicherts also writes that there is no reason to suppose that brain size is environmentally insensitive. Even if race differences in brain size are assumed to be entirely genetic in origin, they still leave 91–95% of racial IQ gap unaccounted for, the lower number assuming that MRI would show the same results as Rushton's data collection.

Mental chronometry

Main article: Mental chronometry

Mental chronometry is an area of research which measures the elapsed time between the presentation of a sensory stimulus and the subsequent behavioral response by the participant. This time is known as reaction time (RT), and is considered a measure of the speed and efficiency with which the brain processes information. Scores on most types of RT tasks tend to correlate with scores on standard IQ tests as well as with g, and no relationship has been found between RT and any other psychometric factors independent of g. The strength of the correlation with IQ varies from one RT test to another, but Hans Eysenck gives 0.40 as a typical correlation under favorable conditions. According to Jensen individual differences in RT have a substantial genetic component, and heritability is higher for performance on tests that correlate more strongly with IQ. Nisbett argues that some studies have found correlations closer to 0.2, and that the correlation is not always found.

Several studies have found differences between races in average reaction times. These studies have generally found that reaction times among black, Asian and white children follow the same pattern as IQ scores. Rushton and Jensen have argued that reaction time is independent of culture and that the existence of race differences in average reaction time is evidence that the cause of racial IQ gaps is partially genetic instead of entirely cultural. Responding to this argument in Intelligence and How to Get It, Nisbett has pointed to the Jensen & Whang (1993) study in which a group of Chinese Americans had longer reaction times than a group of European Americans, despite having higher IQs. Nisbett also mentions findings in Flynn (1991) and Deary (2001) suggesting that movement time (the measure of how long it takes a person to move a finger after making the decision to do so) correlates with IQ just as strongly as reaction time does, and that average movement time is faster for blacks than for whites.

Policy relevance

Main article: Intelligence and public policy

Jensen and Rushton argue that the existence of biological group differences does not rule out, but raises questions about the worthiness of policies such as affirmative action or placing a premium on diversity. They also argue for the importance of teaching people not to overgeneralize or stereotype individuals based on average group differences, because of the significant overlap of people with varying intelligence between different races.

The environmentalist viewpoint argues for increased interventions in order to close the gaps. Nisbett argues that schools can be greatly improved and that many interventions at every age level are possible. Flynn, arguing for the importance of the black subculture, write that "America will have to address all the aspects of black experience that are disadvantageous, beginning with the regeneration of inner city neighbourhoods and their schools. A resident police office and teacher in every apartment block would be a good start." Researchers from both sides agree that interventions should be better researched.

Especially in developing nations society has been urged to take on the prevention of cognitive impairment in children as of the highest priority. Possible preventable causes include malnutrition, infectious diseases such as meningitis, parasites, and cerebral malaria, in utero drug and alcohol exposure, newborn asphyxia, low birth weight, head injuries, and endocrine disorders.

See also

• Ashkenazi Jewish intelligence
• Sex and psychology

References

Sources

• Alland, Alexander, Jr (2002). Race in Mind. Palgrave Macmillan. pp. 79–80. {{cite book}}: Invalid |ref=harv (help)CS1 maint: multiple names: authors list (link)
• "American Anthropological Association Statement on 'Race' and Intelligence". American Anthropological Association. December 1994.
• "American Anthropological Association Statement on 'Race'". American Anthropological Association. 17 May 1998.
• "AAPA Statement on Biological Aspects of Race". American Journal of Physical Anthropology. 101: 569–570. 1996.
• Aronson, E; Wilson, TD; Akert, AM (2005). Social Psychology (5th ed.). Upper Saddle River, NJ: Prentice Hall. ISBN 0-13-178686-5. {{cite book}}: Invalid |ref=harv (help)
• Bartholomew, David J (2004). Measuring Intelligence: Facts and Fallacies. Cambridge University Press. ISBN 0-521-54478-5. {{cite book}}: Invalid |ref=harv (help)
• Beals, KL; Smith, CL; Dodd, SM (June 1984). "Brain size, cranial morphology, climate, and time machines". Current Anthropology. 25 (3): 301–30. doi:10.1086/203138. {{cite journal}}: Invalid |ref=harv (help)
• Behrman, JR; Alderman, H; Hoddinott, J (2004). "Hunger and Malnutrition" (PDF). Copenhagen Consensus. {{cite journal}}: Invalid |ref=harv (help)
• Bellinger, David C; Stiles, Karen M; Needleman, Herbert L (December 1992). "Low-Level Lead Exposure, Intelligence and Academic Achievement: A Long-term Follow-up Study". Pediatrics. 90 (6): 855–61. PMID 1437425. {{cite journal}}: Invalid |ref=harv (help)
• Berlet, Chip (Summer 2003). "Into the Mainstream". Intelligence Report (110). Southern Poverty Law Center. Retrieved 21 February 2012.{{cite journal}}: CS1 maint: ref duplicates default (link)
• Byrd, Desiree A; Touradji, Pegah; Tang, Ming-Xin; Manly, Jennifer J (2004). "Cancellation test performance in African American, Hispanic, and white elderly". Journal of the International Neuropsychological Society. 10 (3): 401–11. doi:10.1017/S1355617704103081.
• Block, Ned (2002). "How heritability misleads about race". In Fish, Jefferson (ed.). Race and Intelligence: Separating Science from Myth. Lawrence Erlbaum and Associates. {{cite book}}: Invalid |ref=harv (help)
• Borsboom, Denny (September 2006). "The attack of the psychometricians". Psychometricka. 71 (3): 425–40. doi:10.1007/s11336-006-1447-6. PMC 2779444. PMID 19946599. {{cite journal}}: |access-date= requires |url= (help); Invalid |ref=harv (help)
• Bower,, B (12 February 2005). "Asian kids' IQ lift: reading system may boost Chinese scores". Science News.{{cite journal}}: CS1 maint: extra punctuation (link)
• Brace, C Loring (1999). "An Anthropological Perspective on 'Race' and Intelligence: The non-clinal nature of human cognitive capabilities". Journal of Anthropological Research. 55 (2): 245–64. JSTOR 3631210. {{cite journal}}: Invalid |ref=harv (help)
• Brace, C. Loring (2005). Race is a four letter word. Oxford University Press. p. 326. ISBN 978-0-19-517351-2. {{cite book}}: Invalid |ref=harv (help)
• "race". Encyclopædia Britannica (Online ed.). Encyclopædia Britannica Inc. 2012.
• Brown, Robert T; Reynolds, Cecil R; Whitaker, Jean S (1999). "Bias in Mental Testing since "Bias in Mental Testing"". School Psychology Quarterly. 14 (3): 208–38. doi:10.1037/h0089007. {{cite journal}}: Invalid |ref=harv (help)
• Bryc, Katarzyna; Autona, Adam; Nelsonb, Matthew R.; Oksenberg, Jorge R.; Hauser, Stephen L.; Williams, Scott; Froment, Alain; Bodof, Jean-Marie; Wambebeg, Charles (2009). "Genome-wide patterns of population structure and admixture in West Africans and African Americans". Proceedings of the National Academy of Sciences of the United States of America. 107 (2): 786–91. doi:10.1073/pnas.0909559107. PMC 2818934. PMID 20080753.
• Campbell, FA; Ramey, CT (1994). "Effects of early intervention on intellectual and academic achievement: A follow-up study of children from low-income families". Child Development. 65: 684–698. {{cite journal}}: Invalid |ref=harv (help)
• Campbell, Frances A; Ramey, Craig T; Pungello, Elizabeth; Sparling, Joseph; Miller-Johnson, Shari (2002). "Early Childhood Education: Young Adult Outcomes From the Abecedarian Project". Applied Developmental Science. 6: 42–57.
• Caspi, A; Williams, B; Kim-Cohen, J; Craig, Ian W; Milne, Barry J; Poulton, Richie; Schalkwyk, Leonard C; Taylor, Alan; Werts, Helen (2007). "Moderation of breastfeeding effects on the IQ by genetic variation in fatty acid metabolism". Proceedings of the National Academy of Sciences. 104 (47): 18860. Bibcode:2007PNAS..10418860C. doi:10.1073/pnas.0704292104. PMC 2141867. PMID 17984066.
• Ceci, SJ; Williams, WM (2009). "Darwin 200: Should scientists study race and IQ? Yes: the scientific truth must be pursued". Nature. 457 (7231): 788. Bibcode:2009Natur.457..788C. doi:10.1038/457788a. PMID 19212385. {{cite journal}}: Invalid |ref=harv (help)
• Cochran, G; Hardy, J; Harpending, H (2006). "Natural History of Ashkenazi Intelligence" (PDF). Journal of Biosocial Science. 38 (5): 659–93. {{cite journal}}: Invalid |ref=harv (help)
• Cooper, Richard (2005). "Race and IQ: Molecular Genetics as Deus ex Machina". American Psychologist. 60 (1): 71–6. {{cite journal}}: Invalid |ref=harv (help)
• "Controversial Nobel winner resigns". CNN. 25 October 2007. Retrieved 21 February 2012.
• Cronshaw, Steven F; Hamilton, Leah K; Onyura, Betty R; Winston, Andrew S (September 2006). "Case for Non-Biased Intelligence Testing Against Black Africans Has Not Been Made: A Comment on Rushton, Skuy, and Bons". International Journal of Selection and Assessment. 14 (3): 278. doi:10.1111/j.1468-2389.2006.00346.x. {{cite journal}}: Check date values in: |year= / |date= mismatch (help)
• Deary, Ian J (2001). Intelligence: A Very Short Introduction. Oxford University Press. ISBN 0-19-289321-1. {{cite book}}: Invalid |ref=harv (help)
• Deary, IJ; Johnson, W; Houlihan, LM (2009). "Genetic foundations of human intelligence". Human Genetics. 126 (1): 215–32. doi:10.1007/s00439-009-0655-4. PMID 19294424. {{cite journal}}: Invalid |ref=harv (help)
• Demetriou, Andreas; Kui, Zhang Xiang; Spanoudis, George; Christou, Constantinos; Kyriakides, Leonidas; Platsidou, Maria (March–April 2005). "The architecture, dynamics, and development of mental processing: Greek, Chinese, or Universal?". Intelligence. 33 (2): 109–41. doi:10.1016/j.intell.2004.10.003.
• Dick, DM; Aliev, F; Kramer, J; Wang, JC; Hinrichs, A; Bertelsen, S; Kuperman, S; Schuckit, M; Nurnberger, J, Jr (2007). "Association of CHRM2 with IQ: converging evidence for a gene influencing intelligence". Behavioral Genetics. 37 (2): 265–72. doi:10.1007/s10519-006-9131-2. PMID 17160701.{{cite journal}}: CS1 maint: multiple names: authors list (link)
• Dickens, James R; Flynn (2001). "Heritability estimates versus large environmental effects: The IQ paradox resolved". Psychological Review. 108 (2): 346–69. doi:10.1037/0033-295X.108.2.346. PMID 11381833. {{cite journal}}: Invalid |ref=harv (help)
• Dickens, James R; Flynn (2006). "Black Americans Reduce the Racial IQ Gap: Evidence from Standardization Samples" (PDF). Psychological Science. 16 (10): 913–20. {{cite journal}}: Invalid |ref=harv (help)
• Elhoweris, Hala; Mutua, Kagendo; Alsheikh, Negmeldin; Holloway, Pauline (2005). "Effect of Children's Ethnicity on Teachers' Referral and Recommendation Decisions in Gifted and Talented Programs". Remedial and Special Education. 26. PRO-ED, Inc.
• Eppig, Christopher; Fincher, Corey L; Thornhill, Randy (2010). "Parasite prevalence and the worldwide distribution of cognitive ability". Proceedings of the Royal Society B. 277 (1701): 3801–8. doi:10.1098/rspb.2010.0973. PMC 2992705. PMID 20591860. {{cite journal}}: Invalid |ref=harv (help)
• Eppig, Christopher (2011). "Why Is Average IQ Higher in Some Places?". Scientific American. {{cite journal}}: Invalid |ref=harv (help)
• Eyferth, K (1961). "Leistungern verscheidener Gruppen von Besatzungskindern Hamburg-Wechsler Intelligenztest für Kinder (HAWIK)". Archiv für die gesamte Psychologie (in German). 113: 222–41. {{cite journal}}: Invalid |ref=harv (help)
• Eysenck, Hans J (1987). "Intelligence and Reaction Time: The Contribution of Arthur Jensen". In Modgil, S; Modgil, C (eds.). Arthur Jensen: Consensus and controversy. New York, NY: Falmer. {{cite book}}: Invalid |ref=harv (help)
• Falk, Avner (2008). Anti-semitism: a history and psychoanalysis of contemporary hatred. Praeger. p. 312. ISBN 978-0-313-35385-7. {{cite book}}: Invalid |ref=harv (help)
• Fischer, Claude S; Hout, Michael; Sánchez Jankowski, Martín; Lucas, Samuel R; Swidler and, Ann; Vos, Kim (1996). Inequality by Design: Cracking the Bell Curve Myth. Princeton University Press. pp. 191–2.
• Fish, Jefferson M (2002). "Folk Heredity". In Fish, Jefferson M (ed.). Race and Intelligence: Separating Myth from Reality. Laurence Erlbaum Associates. pp. 95, 113. ISBN 0-8058-3757-4. {{cite book}}: Invalid |ref=harv (help)
• Flynn, James R (1991). "Reaction times show that both Chinese and British children are more intelligent than one another". Perceptual and Motor Skills. 72: 544–6. {{cite journal}}: Invalid |ref=harv (help)
• Flynn, James R (3 September 2008). "Perspectives: Still a question of black vs white?". New Scientist (2672) (magazine issue ed.). {{cite journal}}: Invalid |ref=harv (help)
• Flynn, James R (2009). "Would you wish the research undone?" (PDF). Nature. 458 (7235): 146. Bibcode:2009Natur.458..146F. doi:10.1038/458146a. {{cite journal}}: Invalid |ref=harv (help)
• Flynn, James R (2010). "The spectacles through which I see the race and IQ debate" (PDF). Intelligence (4): 363–6. doi:10.1016/j.intell.2010.05.001. {{cite journal}}: Invalid |ref=harv (help)
• Fryer, Roland G, Jr; Levitt, Steven D (March 2006). "Testing for Racial Differences in the Mental Ability of Young Children" (PDF). National Bureau of Economic Research (NBER Working Paper No. W12066 ed.). {{cite journal}}: Invalid |ref=harv (help)CS1 maint: multiple names: authors list (link)
• Gale, CR; O'Callaghan, FJ; Bredow, M; Martyn, CN; Avon Longitudinal Study of Parents and Children Study Team (2006). "The Influence of Head Growth in Fetal Life, Infancy, and Childhood on Intelligence at the Ages of 4 and 8 Years". Pediatrics. 118 (4): 1486–92. doi:10.1542/peds.2005-2629. PMID 17015539.
• Goleman, Daniel (10 April 1988). "An Emerging Theory on Blacks' I.Q. Scores". New York Times. Retrieved May 17, 2010.{{cite news}}: CS1 maint: ref duplicates default (link)
• Gottfredson, Linda S (1997). "Mainstream Science on Intelligence (editorial)" (PDF). Intelligence. 24: 13–23. doi:10.1016/S0160-2896(97)90011-8. {{cite journal}}: Invalid |ref=harv (help)
• Gottfredson, Linda S (2007). "Applying Double Standards to 'Divisive' Ideas: Commentary on Hunt and Carlson". Perspectives on Psychological Science. 2 (2): 216–220. {{cite journal}}: Invalid |ref=harv (help)
• Gould, Stephen Jay (1981). The Mismeasure of Man. New York, London: Norton. ISBN 0-393-30056-0. {{cite book}}: Invalid |ref=harv (help)
• Graves, Joseph L. (2001). The Emperor's New Clothes: Biological Theories of Race at the Millennium (Kindle ed.). Rutgers University Press. ASIN B000SARS70. {{cite book}}: Invalid |ref=harv (help)
• Graves, Joseph L (2002a). "The Misuse of Life History Theory: JP Rushton and the Pseudoscience of Racial Hierarchy". In Fish, Jefferson M (ed.). Race and Intelligence: Separating Myth from Reality. Laurence Erlbaum Associates. pp. 57–94. ISBN 0-8058-3757-4. {{cite book}}: Invalid |ref=harv (help)
• Graves, Joseph L, Jr (2002b). "What a tangled web he weaves: Race, reproductive strategies and Rushton's life history theory". Anthropological Theory. 2 (2): 131–54. doi:10.1177/1469962002002002627. {{cite journal}}: Invalid |ref=harv (help)CS1 maint: multiple names: authors list (link)
• Gray, Jeremy R; Thompson, Paul M (2004). "Neurobiology of intelligence: science and ethics" (PDF). Nature Reviews Neuroscience. 5 (6): 471–82. doi:10.1038/nrn1405. PMID 15152197. {{cite journal}}: Invalid |ref=harv (help)
• Grossman, James B; Kaufman (2001). "Evolutionary Psychology: Promise and Perils". In Sternberg, Robert J; Kaufman, James C (eds.). The evolution of intelligence. Routledge. ISBN 0-8058-3267-X. {{cite book}}: Invalid |ref=harv (help); More than one of |first1= and |first= specified (help)
• "Comments in interview could bring charges of inciting racism against PM Vanhanen's father". Helsingin Sanomat (International Edition ed.). 12 February 2004. {{cite news}}: |edition= has extra text (help)
• Herrnstein, Richard J; Murray, Charles (1994). The Bell Curve: Intelligence and Class Structure in American Life. New York: Free Press. ISBN 0-02-914673-9. {{cite book}}: Invalid |ref=harv (help)
• Ho, KC; Roessmann, U; Straumfjord, JV; Monroe, G (1980a). "Analysis of brain weight: I. Adult brain weight in relation to sex, race, and age". Archives of Pathology and Laboratory Medicine. 104 (12): 635–40. PMID 6893659.
• Ho, KC; Roessmann, U; Straumfjord, JV; Monroe, G (1980b). "Analysis of brain weight: I. Adult brain weight in relation to body height, weight and surface area". Archives of Pathology and Laboratory Medicine. 104 (12): 640–5. PMID 6893660.
• Horn, John (1989). "Models of intelligence". In Linn, Robert L (ed.). Intelligence: measurement, theory, and public policy : proceedings of a symposium in honor of Lloyd G. Humphreys. University of Illinois Press. p. 63. ISBN 978-0-252-01535-9. {{cite book}}: |journal= ignored (help); Invalid |ref=harv (help)
• Hothersall, David (2003). "History of Psychology" (4th ed.). McGraw-Hill: 440–1. ISBN 0-07-284965-7. {{cite journal}}: Cite journal requires |journal= (help); Invalid |ref=harv (help)
• Hunt, Earl (2010). Human Intelligence. Cambridge University Press. ISBN 978-0-521-70781-7. {{cite book}}: Invalid |ref=harv (help)
• Hunt, Earl; Carlson, Jerry (2007). "Considerations relating to the study of group differences in intelligence". Perspectives on Psychological Science. 2 (2): 194–213. doi:10.1111/j.1745-6916.2007.00037.x. {{cite journal}}: Invalid |ref=harv (help)
• Hunt, Earl; Wittmann, Werner (January–February 2008). "National intelligence and national prosperity". Intelligence. 36 (1): 1–9. doi:10.1016/j.intell.2006.11.002.{{cite journal}}: CS1 maint: ref duplicates default (link)
• Irvine, SH (1983). "Where intelligence tests fail". Nature. 302 (5907): 371. Bibcode:1983Natur.302..371I. doi:10.1038/302371b0. {{cite journal}}: Invalid |ref=harv (help)
• Irvine, SH; Berry, JW, eds. (1988). "Human Abilities in Cultural Context". Cambridge University Press. ISBN 0-521-34482-4. {{cite journal}}: Cite journal requires |journal= (help)CS1 maint: ref duplicates default (link)
• Ivanovic, DM; Leiva, BP; Pérez, HT; Olivares, MG; Díaz, NS; Urrutia, MS; Almagià, AF; Toro, TD; Miller, PT (2004). "Head size and intelligence, learning, nutritional status and brain development. Head, IQ, learning, nutrition and brain". Neuropsychologia. 42 (8): 1118–31. doi:10.1016/j.neuropsychologia.2003.11.022. PMID 15093150.
• Jensen, Arthur R (1969). "How Much Can We Boost IQ and Scholastic Achievement?". Harvard Educational Review. 39: 1–123. {{cite journal}}: Invalid |ref=harv (help)
• Jensen, Arthur R (1973). Educability and Group Differences. London: Methuen. ISBN 0-06-012194-7. {{cite book}}: Invalid |ref=harv (help)
• Jensen, Arthur R; Whang, PA (1993). "Reaction times and intelligence: a comparison of Chinese-American and Anglo-American children". Journal of Biosocial Science. 25 (3): 397–410. PMID 8360233. {{cite journal}}: Invalid |ref=harv (help)
• Jensen, Arthur R (1998). The g factor: The science of mental ability. Westport, CT: Praeger. ISBN 0-275-96103-6. {{cite book}}: Invalid |ref=harv (help)
• Jensen, AR (2006). Clocking the mind: Mental chronometry and individual differences. Amsterdam: Elsevier. ISBN 978-0-08-044939-5. {{cite book}}: Invalid |ref=harv (help)
• Jensen; Johnson, Arthur R (May–June 1994). "Race and sex differences in head size and IQ". Intelligence. 18 (3): 309–33. doi:10.1016/0160-2896(94)90032-9. {{cite journal}}: Invalid |ref=harv (help)
• Kaplan, Jonathan Michael (January 2011). "'Race': What Biology Can Tell Us about a Social Construct". Encyclopedia of Life Sciences (ELS). Chichester: John Wiley & Sons, Ltd. doi:10.1002/9780470015902.a0005857.{{cite journal}}: CS1 maint: ref duplicates default (link)
• Kaszycka, Katarzyna A.; Štrkalj, Goran; Strzałko, Jan (2009). "Current Views of European Anthropologists on Race: Influence of Educational and Ideological Background". American Anthropologist. 111 (1). American Anthropological Association: 43–56. doi:10.1111/j.1548-1433.2009.01076.x. {{cite journal}}: Invalid |ref=harv (help)
• Kindermann, Thomas A (1993). "Natural peer groups as contexts for individual development: The case of children's motivation in school". Developmental Psychology. 29 (6): 970–7. doi:10.1037/0012-1649.29.6.970. {{cite journal}}: Invalid |ref=harv (help)
• Lee, James J (2010). "Review of intelligence and how to get It: why schools and culture count". Personality and Individual Differences. 48 (2): 247–55. doi:10.1016/j.paid.2009.09.015. {{cite journal}}: Invalid |ref=harv (help)
• Lieberman, Leonard (February 2001). "How 'Caucasoids' Got Such Big Crania and Why They Shrank: From Morton to Rushton" (PDF). Current Anthropology. 42: 69–95. doi:10.1086/318435. PMID 14992214. {{cite journal}}: Invalid |ref=harv (help)
• Loehlin, John C (2000). "Group Differences in Intelligence". In Sternberg, Robert J (ed.). The Handbook of Intelligence. Cambridge: Cambridge University Press. {{cite book}}: Invalid |ref=harv (help)
• Ludy, Benjamin T (2006). "Brief History of Modern Psychology". Wiley-Blackwell: 188–91. ISBN 1-4051-3206-X. {{cite journal}}: Cite journal requires |journal= (help); Invalid |ref=harv (help)
• Lynn, Richard; Vanhanen, Tatu (2002). IQ and the wealth of nations. Westport, CT: Praeger. ISBN 0-275-97510-X. {{cite book}}: Invalid |ref=harv (help)
• Mackenzie, Brian (November 1984). "Explaining race differences in IQ: The logic, the methodology, and the evidence". American Psychologist. 39 (11): 1214–33. {{cite journal}}: Invalid |ref=harv (help)
• Mackintosh, NJ (1998). IQ and Human Intelligence. Oxford University Press. ISBN 0-19-852367-X. {{cite book}}: Invalid |ref=harv (help); Unknown parameter |laydate= ignored (help); Unknown parameter |laysummary= ignored (help)
• Manly, JJ; Byrd, DA; Touradji, P; Stern, Yaakov (2004). "Acculturation, Reading Level, and Neuropsychological Test Performance Among African American Elders". Applied Neuropsychology. 11 (1): 37–46. doi:10.1207/s15324826an1101_5. PMID 15471745.
• Manly, Jennifer J; Jacobs, Diane M; Touradji, Pegah; Small, Scott A; Stern, Yaakov (2002). "Reading level attenuates differences in neuropsychological test performance between African American and White elders". Journal of the International Neuropsychological Society. doi:10.1017/S1355617702813157.
• Maltby, John; Day, Liz; Macaskill, Ann (2007). Personality, Individual Differences and Intelligence. Pearson Education. pp. 334–47. ISBN 0-13-129760-0. {{cite book}}: Invalid |ref=harv (help)
• Mickelson, Roslyn Arlin (2003). "When Are Racial Disparities in Education the Result of Racial Discrimination? A Social Science Perspective". {{cite journal}}: Cite journal requires |journal= (help); Invalid |ref=harv (help)
• Miele, Frank (2002). Intelligence, Race and Genetics: Conversations with Arthur R. Jensen. Basic Books. p. 256. {{cite book}}: Invalid |ref=harv (help)
• MMWR (27 May 2005). "Blood Lead Levels—United States, 1999–2002". Morbidity and Mortality Weekly Report (MMWR). 54 (20). Centers for Disease Control and Prevention: 513–6.{{cite journal}}: CS1 maint: ref duplicates default (link)
• Mountain, Joanna L; Risch, Neil (2004). "Assessing genetic contributions to phenotypic differences among 'racial' and 'ethnic' groups". Nature Genetics. Nature. doi:10.1038/ng1456. {{cite journal}}: Invalid |ref=harv (help)
• Moore, Elsie G (May 1986). "Family socialization and the IQ test performance of traditionally and transracially adopted Black children". Developmental Psychology. 22 (3): 317–26. doi:10.1037/0012-1649.22.3.317.{{cite journal}}: CS1 maint: ref duplicates default (link)
• Munsinger, Harry (September 1975). "The adopted child's IQ: A critical review". Psychological Bulletin. 82 (5): 623–59. doi:10.1037/0033-2909.82.5.623.{{cite journal}}: CS1 maint: ref duplicates default (link)
• Murray, Charles (2005). "The Inequality Taboo". 120 (2). New York: Commentary—American Jewish Committee: 13–22. {{cite journal}}: Cite journal requires |journal= (help); Invalid |ref=harv (help)
• Murray, Charles (2006). "Changes over time in the black–white difference on mental tests: Evidence from the children of the 1979 cohort of the National Longitudinal Survey of Youth". Intelligence. 34 (6): 527–540. doi:10.1016/j.intell.2006.07.004. {{cite journal}}: Invalid |ref=harv (help)
• Murray, Charles (July–August 2007). "The magnitude and components of change in the black–white IQ difference from 1920 to 1991: A birth cohort analysis of the Woodcock–Johnson standardizations". Intelligence. 35 (4): 305–18. doi:10.1016/j.intell.2007.02.001.{{cite journal}}: CS1 maint: ref duplicates default (link)
• Neisser, Ulric (1997). "Never a dull moment". American Psychologist. 52: 79–81. doi:10.1037/0003-066X.52.1.79. {{cite journal}}: Invalid |ref=harv (help)
• Neisser, Ulric (2004). "Serious Scientists or Disgusting Racists?". Contemporary Psychology: APA Review of Books. 49 (1): 5–7. doi:10.1037/004224. {{cite journal}}: Invalid |ref=harv (help)
• Neisser, Ulric; Boodoo, Gwyneth; Bouchard, Thomas J, Jr; Boykin, A. Wade; Brody, Nathan; Ceci, Stephen J; Halpern, Diane F; Loehlin, John C; Perloff, Robert (1996). "Intelligence: Knowns and unknowns" (PDF). American Psychologist. 51: 77–101. doi:10.1037/0003-066X.51.2.77.{{cite journal}}: CS1 maint: multiple names: authors list (link)
• Nisbett, Richard (2005). "Heredity, environment, and race differences in IQ: A commentary on Rushton and Jensen" (PDF). Psychology, Public Policy, and Law. 11 (2): 302–10. doi:10.1037/1076-8971.11.2.302. {{cite journal}}: Invalid |ref=harv (help)
• Nisbett, Richard (2009). Intelligence and How to Get It: Why Schools and Cultures Count. W. W. Norton & Company. ISBN 0-393-06505-7. {{cite book}}: Invalid |ref=harv (help)
• Niu, Weihua; Brass, Jillian (2011). "Intelligence in Worldwide Perspective". In Sternberg, Robert J; Kaufmann, Scott Barry (eds.). The Cambridge Handbook of Intelligence. Cambridge University Press. ISBN 0-521-51806-7. {{cite book}}: Invalid |ref=harv (help)
• Ogbu, John (1978). "Minority education and caste: The American system in cross-cultural perspective". New York: Academic Press. {{cite journal}}: Cite journal requires |journal= (help); Invalid |ref=harv (help)
• Ogbu, John U (1994). "From cultural differences to differences in cultural frames of reference". In Greenfield, PM; Cocking, RR (eds.). Cross-cultural roots of minority child development. Hillsdale, NJ: Lawrence Erlbaum Associates. pp. 365–91. {{cite book}}: Invalid |ref=harv (help)
• Olness, K (April 2003). "Effects on brain development leading to cognitive impairment: a worldwide epidemic". Journal of Developmental and Behavioral Pediatrics. 24 (2): 120–30. doi:10.1097/00004703-200304000-00009. PMID 12692458. {{cite journal}}: Invalid |ref=harv (help)
• Outtz, James Lawrence (2010). Adverse Impact: Implications for Organizational Staffing and High Stakes Selection. CRC Press. p. 548. ISBN 978-0-8058-6374-1. {{cite book}}: Invalid |ref=harv (help)
• Pesta, Bryan J; Poznanski, Peter J (2008). "Black-White differences on IQ and grades: The mediating role of elementary cognitive tasks". Intelligence. 36 (4): 323–29. {{cite journal}}: Invalid |ref=harv (help)
• Pickren, Wade E; Rutherford, Alexandra (2010). A History of Modern Psychology in Context. Wiley. {{cite book}}: Invalid |ref=harv (help)
• Plomin, R; Kennedy, J; Craig, I (2005). "The quest for quantitative trait loci associated with intelligence". Intelligence. 34 (6): 513. doi:10.1016/j.intell.2006.01.001. {{cite journal}}: Invalid |ref=harv (help)
• Plotnik, Rod; Kouyoumdjian, Haig (2011). "Intelligence". Introduction to Psychology. Cengage Learning. {{cite book}}: Invalid |ref=harv (help)
• Posthuma,, Daniëlle; De Geus, Eco JC; Baaré,, Wim FC; Hulshoff Pol, Hilleke E; Kahn, René S; Boomsma, Dorret I (February 2002). "The association between brain volume and intelligence is of genetic origin". Nature Neuroscience. 5 (2): 83–4. doi:10.1038/nn0202-83. PMID 11818967.{{cite journal}}: CS1 maint: extra punctuation (link)
• Qian, M; Wang, D; Watkins, WE; Gebski, V; Yan, YQ; Li, M; Chen, ZP (2005). "The effects of iodine on intelligence in children: a meta-analysis of studies conducted in China". Asia Pacific Journal of Clinical Nutrition. 14 (1): 32–42. PMID 15734706.
• Reed, TE (1997). "'The Genetic Hypothesis': It Was Not Tested but It Could Have Been". American Psychologist. 52 (1): 77–8. {{cite journal}}: Invalid |ref=harv (help)
• Regalado, Antonio (16 June 2006). "Scientist's Study Of Brain Genes Sparks a Backlash". The Wall Street Journal. {{cite news}}: Invalid |ref=harv (help)
• Reuning, Helmut (1988). "Testing Bushmen in the Central Kalahari". In Irvine, SH; Berry, JW (eds.). Human Abilities in Cultural Context. Cambridge University Press. doi:10.1017/CBO9780511574603.018. ISBN 978-0-511-57460-3. {{cite encyclopedia}}: Invalid |ref=harv (help)
• Richardson, K (2004). "Book Review: IQ and the Wealth of Nations". Heredity. 92 (4): 359–60. doi:10.1038/sj.hdy.6800418. {{cite journal}}: Invalid |ref=harv (help)
• Rose, Steven (2009). "Darwin 200: Should scientists study race and IQ? NO: Science and society do not benefit". Nature. 457 (7231): 786–8. Bibcode:2009Natur.457..786R. doi:10.1038/457786a. PMID 19212384. {{cite journal}}: Invalid |ref=harv (help)
• Roth, PL; Bevier, CA; Bobko, P; Switzer, FS, III; Tyler, P (2001). "Ethnic group differences in cognitive ability in employment and educational settings: A metaanalysis". Personnel Psychology. 54: 297–330.{{cite journal}}: CS1 maint: multiple names: authors list (link)
• Rouvroy, Antoinette (2008). "Human genes and neoliberal governance: a Foucauldian critique". Routledge: 86. ISBN 0-415-44433-0. {{cite journal}}: Cite journal requires |journal= (help); Invalid |ref=harv (help)
• Rowe; David C (January 2005). Rodgers, Joseph (ed.). "Under the Skin: On the Impartial Treatment of Genetic and Environmental Hypothesis of Racial Differences". American Psychologist. 60 (1): 60–70. doi:10.1037/0003-066X.60.1.60. PMID 15641922.
• Rushton, J. Philippe (1991). "Mongoloid-Caucasoid differences in brain size from military samples [and NASA]". Intelligence. 15 (3): 351–9. doi:10.1016/0160-2896(91)90043-D. {{cite journal}}: Invalid |ref=harv (help)
• Rushton, J. Philippe (1995). Race, evolution, and Behavior. Piscataway, NJL: TransAction Books. {{cite book}}: Invalid |ref=harv (help)
• Rushton, J. Philippe (1997a). "Cranial size and IQ in Asian Americans from birth to age seven". Intelligence. 25: 7–20. doi:10.1016/S0160-2896(97)90004-0. {{cite journal}}: Invalid |ref=harv (help)
• Rushton, J. Philippe (1997b). "Race, Intelligence, And The Brain" (PDF). Personality and Individual Differences. 23: 169–180. doi:10.1016/S0191-8869(97)80984-1. {{cite journal}}: Invalid |ref=harv (help)
• Rushton, J. Philippe (2003). "Race differences in g and the 'Jensen effect'". In H. Nyborg (ed.). The scientific study of general intelligence: tribute to Arthur R. Jensen. London: Pergamon. {{cite book}}: Invalid |ref=harv (help)
• Rushton, J. Philippe; Jensen, Arthur R (2005). "Thirty Years of Research on Race Differences in Cognitive Ability" (PDF). Psychology, Public Policy and Law. 11 (2): 246–8. doi:10.1037/1076-8971.11.2.235. {{cite journal}}: Invalid |ref=harv (help)
• Rushton, J. Philippe; Jensen, Arthur R (2006). "The Totality of Available Evidence Shows the Race IQ Gap Still Remains" (PDF). Psychological Science. 16 (10): 921–2. doi:10.1111/j.1467-9280.2006.01803.x. PMID 17100794. {{cite journal}}: Invalid |ref=harv (help)
• Rushton, J. Philippe; Jensen, Arthur R (2010). "Race and IQ: A theory-based review of the research in Richard Nisbett's Intelligence and How to Get It" (PDF). The Open Psychology Journal. 3: 9–35. doi:10.2174/1874350101003010009. {{cite journal}}: Invalid |ref=harv (help)
• Saloojee, Haroon; Pettifor, John M (December 2001). "Iron deficiency and impaired child development". BMJ. 323 (7326): 1377–8. doi:10.1136/bmj.323.7326.1377. PMC 1121846. PMID 11744547.{{cite journal}}: CS1 maint: ref duplicates default (link)
• Schacter, Daniel; Gilbert, Daniel; Wegner, Daniel (2007). "Psychology". New York: Worth Publishing. ISBN 0-7167-5215-8. {{cite journal}}: Cite journal requires |journal= (help); Invalid |ref=harv (help)
• Schaefer, Richard T., ed. (2008). "Race". Encyclopedia of Race, Ethnicity and Society. Vol. 2. SAGE. p. 1091.{{cite book}}: CS1 maint: ref duplicates default (link)
• Serpell, Robert (2000). "Intelligence and Culture". In Sternberg, Robert J. (ed.). Handbook of Intelligence. Cambridge University Press. pp. 549–577. ISBN 978-0-521-59648-0. {{cite book}}: Invalid |ref=harv (help)
• Shuttleworth-Edwards, AB; Kemp, RD; Rust, AL; Muirhead, JG; Hartman, NP; Radloff, SE (October 2004). "Cross-cultural effects on IQ test performance: a review and preliminary normative indications on WAIS-III test performance". Journal of Clinical and Experimental Neuropsychology. 26 (7): 903–20. doi:10.1080/13803390490510824. PMID 15742541.
• Snyderman, Mark; Rothman, Stanley (1987). "Survey of expert opinion on intelligence and aptitude testing". 42. American Psychologist: 137–44. {{cite journal}}: Cite journal requires |journal= (help); Invalid |ref=harv (help)
• Sternberg, Robert J; Grigorenko, Elena L; Kidd, Kenneth K (2005). "Intelligence, Race, and Genetics" (PDF). American Psychologist. 60 (1): 46–59. doi:10.1037/0003-066X.60.1.46. PMID 15641921. {{cite journal}}: Invalid |ref=harv (help)
• Tang, H; Quertermous, T; Rodriguez, B; Kardia, SL; Zhu, X; Brown, A; Pankow, JS; Province, MA; Hunt, SC (February 2005). "Genetic structure, self-identified race/ethnicity, and confounding in case-control association studies". American Journal of Human Genetics. 7 (2): 268–75. doi:10.1086/427888. PMID 15625622.
• Templeton, Alan R (2002). "The Genetic and Evolutionary Significance of Human Races". In Fish, Jefferson (ed.). Race and Intelligence: Separating Science from Myth. Lawrence Erlbaum Associates. {{cite book}}: Invalid |ref=harv (help)
• Thompson, Paul; Cannon, Tyrone D; Narr, Katherine L; van Erp, Theo; Poutanen, Veli-Pekka; Huttunen, Matti; Lönnqvist, Jouko; Standertskjöld-Nordenstam, Carl-Gustaf; Kaprio, Jaakko (2001). "Genetic influences on brain structure" (PDF). Nature Neuroscience. 4 (12): 1253–58. doi:10.1038/nn758. PMID 11694885.
• Tizard, Barbara; Cooperman, Oliver; Joseph, Anne; Tizard, Jack (June 1972). "Environmental effects on language development: A study of young children in long-stay residential nurseries". Child Development. 43 (2). Blackwell Publishing: 337–58. doi:10.2307/1127540. JSTOR 1127540.
• Tucker, William H (2002). The Funding of Scientific Racism: Wickliffe Draper and the Pioneer Fund. University of Illinois Press. ISBN 0-252-02762-0. {{cite book}}: Invalid |ref=harv (help)
• Verney, Steven P; Granholn; Marshall, Sandra P; Malcarne, Vanessa L; Saccuzzo, Dennis P (September 2005). "Culture-Fair Cognitive Ability Assessment". Assessment. 12 (3): 303–19. doi:10.1177/1073191105276674. PMID 16123251.
• Weinberg, Richard A.; Scarr, Sandra; Waldman, Irwin D. (1992). "The Minnesota Transracial Adoption Study: A Follow-Up of IQ Test Performance at Adolescence". Intelligence. 16 (1): 117–35. doi:10.1016/0160-2896(92)90028-P. {{cite journal}}: Invalid |ref=harv (help)
• Wicherts, Jelte M; Borsboom, Denny; Dolan, Conor V (2010). "Why national IQs do not support evolutionary theories of intelligence". Personality and Individual Differences. 48: 91–6. doi:10.1016/j.paid.2009.05.028. {{cite journal}}: Invalid |ref=harv (help)
• Wicherts, Jelte M; Dolan, Conor V; van der Maas, Han LJ (January–February 2010). "A systematic literature review of the average IQ of Sub-Saharan Africans". Intelligence. 38 (1): 1–20. doi:10.1016/j.intell.2009.05.002. {{cite journal}}: Invalid |ref=harv (help)CS1 maint: date and year (link)
• Witelson, SF; Beresh, H; Kigar, DL (2006). "Intelligence and brain size in 100 postmortem brains: sex, lateralization and age factor". Brain. 129 (2). Oxford University Press: 386–98. doi:10.1093/brain/awh696. PMID 16339797. {{cite journal}}: Invalid |ref=harv (help)
• Wooldridge, Adrian (1995). "Measuring the Mind: Education and Psychology in England c. 1860-c. 1990". Cambridge University Press. ISBN 0-521-39515-1. {{cite journal}}: Cite journal requires |journal= (help); Invalid |ref=harv (help)
• Wroe, Andrew (2008). The Republican Party and Immigration Politics: from Proposition 187 to George W. Bush. Macmillan. p. 294. ISBN 978-0-230-60053-9. {{cite book}}: Invalid |ref=harv (help)
• Zinkstok, Janneke R; De Wilde, Odette; Van Amelsvoort, Therese AMJ; Tanck, Michael W; Baas, Frank; Linszen, Don H (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. PMC 1864987. PMID 17445278.{{cite journal}}: CS1 maint: unflagged free DOI (link)

External links

• June 2005 issue of Psychology, Public Policy and Law, containing papers arguing various perspectives about race and intelligence.
• Debate between James Flynn and Charles Murray about whether the black/white IQ gap is shrinking or staying the same - November 2006.
• Race and Intelligence: Science's last taboo, a TV documentary made by the UK's Channel 4 public television station, featuring Somali-British journalist Rageh Omaar - October 2009.