Race and intelligence
Encyclopedia
The connection between race and intelligence has been a subject of debate in both popular science
and academic research since the inception of intelligence testing in the early 20th century. There are no universally accepted definitions of either race or intelligence
in academia, and any discussion of their connection involves studies from multiple disciplines, including psychology
, anthropology
, biology
, and sociology
.
The official position of the American Anthropological Association
is that intelligence cannot be biologically determined by race. 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 even less empirical support for a genetic interpretation, and no adequate explanation for the racial IQ gap is presently available. 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, and 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."
Intelligence quotient
(IQ) tests performed in the United States have consistently demonstrated a significant degree of variation between different racial groups
, with the average score of the African American
population being lower— and that of the Asian American
population being higher— than that of the European-American population. At the same time, there is a considerable overlap between these group scores, and individuals of each group can be found at all points on the IQ spectrum. Similar findings have been reported for related populations around the world, although these studies are generally considered less reliable due to the relative paucity of test data and the difficulties inherent in the cross-cultural comparison of intelligence test scores. 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 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, some scientists reacted to eugenicist claims linking abilities and moral character to racial or genetic ancestry. Despite that, states such as 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 School 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
. Similarly, Ullica Segerstråle points out that a number of critics of the hereditarian point of view have been self-admittedly motivated by a Marxist ideology, and supported by organizations such as Science for the People
whose goals are political as well as scientific.
of research on race and intelligence. Gray and Thompson (2004) as well as Hunt and Carlson (2007) have also discussed different possible ethical guidelines. Nature
in 2009 invited 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. Stephen Rose maintain 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.
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. Other variables with much lower correlations such as brain size and reaction time have also been used.
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. et all (2005) argue 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, including anthropology in some other nations, 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 Jonathan Kaplan and geneticist Joseph Graves, have argued that while there 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 therefore 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. Weiss and Fullerton have noted that if one sampled only Icelanders, Mayans and Maoris, three distinct clusters would form and all other populations could be described as being composed of admixtures of Maori, Icelandic and Mayan genetic materials. Kaplan 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.
, 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 deviation
s (SDs). 15% to 20% of the black IQ distribution exceeds the white median IQ, so many blacks obtain scores above the white average. The black-white IQ difference is largest on those tests that best represent the general intelligence factor
g. The 1996 APA report "Intelligence: Knowns and Unknowns
" and the 1994 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 agree 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 argues that this has stalled and that there has been no further narrowing for people born after the late 1970s. He 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 Prize
s and 25% of the Turing Award
s. 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 a random sample
of the populations in other parts of the world. Therefore, results from data in the US and Europe do not necessarily apply to the rest of the world.
, 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.
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 Robert Brown et al.
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.
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.
A 2009 meta-analysis by Jelte Wicherts found evidence of significant publication bias in 55 studies of stereotype threat and its effect on IQ, in which those that found a strong effect were more likely to be published than those that did not. Reviewing both published and unpublished studies, Wicherts found that stereotype threat did not have an effect on all test-taking settings in which a difference in average scores is observed between races, and therefore was not an adequate explanation for the racial IQ gap.
Rushton and Jensen argue that controlling for SES only reduces the black-white gap by a third or 5 points. If there are racial genetic differences, then this figure is overstated since part of the differences in parental SES are due to differences in parental IQ. Furthermore, they argue, an environment-only explanation predicts that the IQ gap would be smaller at higher levels of parental SES since these children would be less exposed to the environmental factors lowering IQ. However, the gap is actually larger at higher parental SES levels. They also point to studies finding higher average IQ for East Asians, American Indians, and Inuit with similar or worse SES than blacks. Comparing black and white children in terms of socioeconomic indicators found that the black children from the best areas and schools (those producing the highest average scores) still average slightly lower on IQ than the white children with the worst socioeconomic factors.
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 of the possible prenatal and perinatal detrimental environmental factors.
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, and Thornhill (2009) argue that "From an energetics standpoint, a developing human will have difficulty building a brain and fighting off infectious disease
s 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, and Thornhill (2011) 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".
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 a study by Ramey and colleagues, 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.
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 American Indians whose ancestors migrated from East Asia to the Americas.
", 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-Brazilian
s, Indigenous Brazilians, Pardo
s 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, Flemish
in Belgium, 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 et al. have argued that this is a misrepresentation of the studies and that also the early testing support a high average Jewish IQ.
Hereditarians reply 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, Charles 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.
) as well as Chinese (Confucianism
and the Imperial examination
system).
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.
has argued that such a clinal distribution in the trait is not possible, 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. Jensen points out that larger and more complex brains are very metabolically expensive, so they evolve only when they provide a strong selective advantage. According to Jensen, as early humans migrated out of Africa, the need to adapt to colder climates created a stronger selective pressure for intelligence in Europe and Asia than existed in Africa. 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.
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 lineage
s, 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
"common garden" 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 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 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".
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).
Hereditarians 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.
Hereditarians argue that the same group differences are repeated worldwide, both when comparing regions and when comparing the different groups in the same region, and that non-hereditarians have particular difficulty explaining the higher results for East Asians compared to whites.
the average IQs of relatives to blacks and whites with the same IQ should be different. He argues that studies confirm this. Nisbett (2009) agrees that this seems to be the case but he sees this as a weak argument since this effect would also be expected from environmental factors depressing average black IQ more than average white IQ. Rushton and Jensen have replied that the results are seen for siblings who should have a very similar environment, that relatives of those scoring low regress upwards, and that, when looking at the magnitude of regression, the results are as predicted by a partial genetic hypothesis. Rushton agrees that these results could also be explained without a genetic contribution, but he argues that such an explanation would be contrived.
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.
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. Nisbett has criticized the study for a number of weaknesses that are acknowledged by the authors. Rushton and Jensen have criticized this and argued for the significance of this study.
Three other studies found opposing evidence with none finding higher intelligence in white children than in black children. Rushton and Jensen have criticized some of them for being small and all of them for, unlike the Minnesota Transracial Adoption Study, not measuring IQ after puberty
since, they argued, the importance of the family environment is shown to decline with age. Nisbett has argued that there is significant heritability at age seven which makes the absence of differences quite telling.
Moore (1986) compared black and mixed-race children adopted by either black or white middle-class families in the US. There was no difference in IQ between black and mixed-race children, whether raised by black or white families. Moore also 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. The study was criticized by Rushton and Jensen for 20-25% of the "blacks" being North Africans and that the African Americans were an elite group because the Army General Classification Test
excluded 30% of African Americans tested compared to 3% of whites. Nisbett writes that Flynn has argued that the army testing could not have produced more than a 3 IQ point advantage for the African Americans soldiers compared to the general African Americans population and that the North Africans would change the results only by a small amount.
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:
Rushton and Jensen point to 3 adoption studies of East Asian children which in all cases scored significantly above the national averages in the US and Belgium although none had control groups from other races.
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. This study based its estimates of ancestry on self-reporting by the subjects in interviews. Mackenzie (1984) has criticized this study for comparing its sample group to a group that was not representative of the national average. More recent studies have compared IQ to ancestry estimates based on skin color, and found a correlation of 0.1-0.15 between lighter skin color and higher IQ. Nisbett considers this correlation too low to be significant, while Arthur Jensen has argued that because skin color is a highly imprecise measure of ancestry, no correlation higher than 0.2 could be expected if the hereditarian hypothesis is correct. 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 type
s 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. Such experiments have never been published, although the requirements for such a study have been discussed in the academic literature.
(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. A study on twins
showed that frontal gray matter
volume also was correlated with g
and highly heritable. A related MRI study has reported that the correlation between brain size (reported to have a heritability
of 0.85) and g is 0.4, and that correlation is mediated entirely by genetic factors.
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".
Proponents of both the environmental and hereditarian perspective believe that this variation is relevant to the racial IQ gap, although they disagree as to its cause. Ulric Neisser
, The Chair of the APA's Task Force on intelligence, acknowledges the brain size difference, but points out that brain size is known to be influenced by environmental factors such as nutrition, and that this fact has been demonstrated experimentally in rats. He thus believes that data on brain size cannot be considered strong evidence for a genetic component to the IQ difference. Rushton and Jensen disagree, citing several studies of malnourished East Asians showing that they have larger brains than whites, and studies demonstrating the brain size difference at birth and prenatally just a few weeks after conception. They argue that correcting for brain size between blacks and whites does not eliminate the IQ gap, which means that factors other than brain size contribute to intelligence differences; however, matching blacks and whites for IQ eliminates the difference in average brain size, suggesting that brain size is still a contributing factor.
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. Rushton argues that a 1994 MRI study in the UK on Africans and West Indians compared to Caucasians support his view although he acknowledges that the study provided no details on how, or if, the samples had been matched for age, sex, or body size.
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. A 2007 study found Statistical mediation
between reaction time tests and a traditional IQ test, in that controlling for race differences on the RT tasks resulted in the race difference on the IQ test no longer being significant. Jensen has argued that since the black-white difference in RT tasks has a rank-order correlation
with the tasks' g-loadings, this is evidence for the validity of Spearman's hypothesis
.
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 a 1993 study by Jensen and Whang in which a group of Chinese Americans had longer reaction times than a group of European Americans, despite having higher IQs. Nisbett also mentions a pair of studies by Flynn and Deary 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. In a 2010 review of Nisbett's book, Rushton and Jensen argue that Nisbett has underestimated the strength of reaction time's correlation with IQ, and the degree to which differences in reaction time are due to g.
concerned the significance of the group differences in IQ for the future achievements of the groups in the US. The book argued for the importance of IQ for factors such as future educational achievements, employment
, income
, divorce
rates, and crime
. The book's critics argued that it overstated the importance of IQ.
Earl Hunt
discusses the relationship between cognitive ability, job performance and income in his 2011 book Human Intelligence. According to Hunt, cognitive test scores have a predictive validity of 0.3 to 0.6 for job performance, and also influence income. Hunt states that racial gaps exist in job performance and income, and that the gaps in job performance are about what would be predicted based on the correlation between cognitive test scores and performance. However, he also mentions that according to a 1997 study, the variation in income associated with test scores is less than the authors of The Bell Curve claimed it was.
Lynn in the 2008 book The Global Bell Curve
, aiming to build on The Bell Curve, argues that group differences in IQ are an important explanation for different achievements for different groups worldwide. One example being that when East Asians arrived in Latin America as indenture
d plantation workers as replacement for slaves, their descendents quickly became elite groups. Lynn argues that also environmental explanations are important, as well as non-IQ genetic group differences, such as average genetic group differences on personality variables.
The mainstream explanations of social scientists and historians for international inequality
, including the North-South divide
, is as the result of historical and political factors such as the heritage of colonialism
including conflicts and violence, discrimination
, economic exploitation by developed nations, and cultural factors such as work ethic
s, corruption
, and human capital
theories where groups receive different education.
or redistribution in favor of the less successful group. They also argue for the importance of teaching not to stereotype
from average differences, because of the significant overlap of people with varying intelligence between different races. Rushton, writing on the North African/South Asian average IQ, has argued that "Immigration
policy too, must be adjusted. Mass immigration from the region is very likely to lower the average IQ of the receiving Western countries, and consequently be dysfunctional."
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.
Gregory Stock
argues that modern biotechnology
will allow parents to select desired genes in their children meaning "current debates about whether some of the differences among ethnic and racial groups are cultural or biological will soon become irrelevant, given the coming [malleability of biological traits]" He writes that such technology may allow parents to select intelligence or racially identifying traits (such as human skin color
; see gene SLC24A5
).
Popular science
Popular science, sometimes called literature of science, is interpretation of science intended for a general audience. While science journalism focuses on recent scientific developments, popular science is broad-ranging, often written by scientists as well as journalists, and is presented in many...
and academic research since the inception of intelligence testing in the early 20th century. There are no universally accepted definitions of either race or intelligence
Intelligence
Intelligence has been defined in different ways, including the abilities for abstract thought, understanding, communication, reasoning, learning, planning, emotional intelligence and problem solving....
in academia, and any discussion of their connection involves studies from multiple disciplines, including psychology
Psychology
Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...
, anthropology
Anthropology
Anthropology is the study of humanity. It has origins in the humanities, the natural sciences, and the social sciences. The term "anthropology" is from the Greek anthrōpos , "man", understood to mean mankind or humanity, and -logia , "discourse" or "study", and was first used in 1501 by German...
, biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
, and sociology
Sociology
Sociology is the study of society. It is a social science—a term with which it is sometimes synonymous—which uses various methods of empirical investigation and critical analysis to develop a body of knowledge about human social activity...
.
The official position of the American Anthropological Association
American Anthropological Association
The American Anthropological Association is a professional organization of scholars and practitioners in the field of anthropology. With 11,000 members, the Arlington, Virginia based association includes archaeologists, cultural anthropologists, biological anthropologists, linguistic...
is that intelligence cannot be biologically determined by race. The American Psychological Association
American Psychological Association
The American Psychological Association is the largest scientific and professional organization of psychologists in the United States. It is the world's largest association of psychologists with around 154,000 members including scientists, educators, clinicians, consultants and students. The APA...
has said that while there are differences in average IQ between racial groups, and there is no conclusive evidence for environmental explanations, there is even less empirical support for a genetic interpretation, and no adequate explanation for the racial IQ gap is presently available. According to a 1996 statement from the American Association of Physical Anthropologists
American Association of Physical Anthropologists
The American Association of Physical Anthropologists is an American-based international scientific society of physical anthropologists. It was formed in 1930, with Morris Steggerda as one of its founding members. They have 1,700 members. They publish the American Journal of Physical...
, although heredity influences behavior in individuals, it does not affect the ability of a population to function in any social setting, and 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."
Intelligence quotient
Intelligence quotient
An intelligence quotient, or IQ, is a score derived from one of several different standardized tests designed to assess intelligence. When modern IQ tests are constructed, the mean score within an age group is set to 100 and the standard deviation to 15...
(IQ) tests performed in the United States have consistently demonstrated a significant degree of variation between different racial groups
Race in the United States
The United States is a racially diverse country. Modern issues of "race", as well as its impact in the political and economic development of the nation, have been examined by numerous historians and researchers across a variety of academic disciplines....
, with the average score of the African American
African American
African Americans are citizens or residents of the United States who have at least partial ancestry from any of the native populations of Sub-Saharan Africa and are the direct descendants of enslaved Africans within the boundaries of the present United States...
population being lower— and that of the Asian American
Asian American
Asian Americans are Americans of Asian descent. The U.S. Census Bureau definition of Asians as "Asian” refers to a person having origins in any of the original peoples of the Far East, Southeast Asia, or the Indian subcontinent, including, for example, Cambodia, China, India, Indonesia, Japan,...
population being higher— than that of the European-American population. At the same time, there is a considerable overlap between these group scores, and individuals of each group can be found at all points on the IQ spectrum. Similar findings have been reported for related populations around the world, although these studies are generally considered less reliable due to the relative paucity of test data and the difficulties inherent in the cross-cultural comparison of intelligence test scores. 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
General intelligence factor
The g factor, where g stands for general intelligence, is a statistic used in psychometrics to model the mental ability underlying results of various tests of cognitive ability...
are poorly constructed and therefore any comparisons between races are meaningless.
History of the debate
Claims of races having different intelligence were used to justify colonialism
Colonialism
Colonialism is the establishment, maintenance, acquisition and expansion of colonies in one territory by people from another territory. It is a process whereby the metropole claims sovereignty over the colony and the social structure, government, and economics of the colony are changed by...
, slavery
Slavery
Slavery is a system under which people are treated as property to be bought and sold, and are forced to work. Slaves can be held against their will from the time of their capture, purchase or birth, and deprived of the right to leave, to refuse to work, or to demand compensation...
, social darwinism
Social Darwinism
Social Darwinism is a term commonly used for theories of society that emerged in England and the United States in the 1870s, seeking to apply the principles of Darwinian evolution to sociology and politics...
, 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
Alfred Binet
Alfred Binet was a French psychologist who was the inventor of the first usable intelligence test, known at that time as the Binet test and today referred to as the IQ test. His principal goal was to identify students who needed special help in coping with the school curriculum...
, 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, some scientists reacted to eugenicist claims linking abilities and moral character to racial or genetic ancestry. Despite that, states such as Virginia enacted laws based in eugenics, such as its 1924 Racial Integrity Act, which established the one-drop rule
One-drop rule
The one-drop rule is a historical colloquial term in the United States for the social classification as black of individuals with any African ancestry; meaning any person with "one drop of black blood" was considered black...
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
Germans
The Germans are a Germanic ethnic group native to Central Europe. The English term Germans has referred to the German-speaking population of the Holy Roman Empire since the Late Middle Ages....
Nazi claims of a "master race
Master race
Master race was a phrase and concept originating in the slave-holding Southern US. The later phrase Herrenvolk , interpreted as 'master race', was a concept in Nazi ideology in which the Nordic peoples, one of the branches of what in the late-19th and early-20th century was called the Aryan race,...
".
In 1969 Arthur Jensen
Arthur Jensen
Arthur Robert Jensen is a Professor Emeritus of educational psychology at the University of California, Berkeley. Jensen is known for his work in psychometrics and differential psychology, which is concerned with how and why individuals differ behaviorally from one another.He is a major proponent...
revived the hereditarian point of view in the article, "How Much Can We Boost IQ and School 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
Brown v. Board of Education
Brown v. Board of Education of Topeka, 347 U.S. 483 , was a landmark decision of the United States Supreme Court that declared state laws establishing separate public schools for black and white students unconstitutional. The decision overturned the Plessy v. Ferguson decision of 1896 which...
that public school segregation was unconstitutional. As part of the Great Society
Great Society
The Great Society was a set of domestic programs in the United States promoted by President Lyndon B. Johnson and fellow Democrats in Congress in the 1960s. Two main goals of the Great Society social reforms were the elimination of poverty and racial injustice...
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
William Shockley
William Bradford Shockley Jr. was an American physicist and inventor. Along with John Bardeen and Walter Houser Brattain, Shockley co-invented the transistor, for which all three were awarded the 1956 Nobel Prize in Physics.Shockley's attempts to commercialize a new transistor design in the 1950s...
, 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
The Bell Curve
The Bell Curve is a best-selling and controversial 1994 book by the Harvard psychologist Richard J. Herrnstein and political scientist Charles Murray...
(1994), a book by Richard Herrnstein
Richard Herrnstein
Richard J. Herrnstein was an American researcher in animal learning in the Skinnerian tradition. He was one of the founders of quantitative analysis of behavior....
and Charles Murray
Charles Murray (author)
Charles Alan Murray is an American libertarian political scientist, author, columnist, and pundit working as a fellow at the American Enterprise Institute, a conservative think tank in Washington, DC...
, 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
Popular science
Popular science, sometimes called literature of science, is interpretation of science intended for a general audience. While science journalism focuses on recent scientific developments, popular science is broad-ranging, often written by scientists as well as journalists, and is presented in many...
. They include The Bell Curve Debate
The Bell Curve Debate
The Bell Curve Debate is a response to The Bell Curve, by Richard J. Herrnstein and Charles Murray. It includes 81 articles by 81 authors including K. Anthony Appiah, Gregg Easterbrook, Howard Gardner, Eugene D. Genovese, Nathan Glazer, Stephen Jay Gould, Bob Herbert, Christopher Hitchens, Irving...
(1995), Inequality by Design: Cracking the Bell Curve Myth
Inequality by Design: Cracking the Bell Curve Myth
Inequality by Design: Cracking the Bell Curve Myth is a book by Claude S. Fischer, Michael Hout, Martín Sánchez Jankowski, Samuel R. Lucas, Ann Swidler, and Kim Voss...
(1996) and a second edition of The Mismeasure of Man
The Mismeasure of Man
The Mismeasure of Man , by Stephen Jay Gould, is a history and critique of the statistical methods and cultural motivations underlying biological determinism, the belief that “the social and economic differences between human groups — primarily races, classes, and sexes — arise from inherited,...
(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
The g Factor
The g Factor: The Science of Mental Ability is a book by Arthur Jensen on the general factor of human mental ability .-External links:* , Psycoloquy, Volumes 10, 1999 and 11, 2000...
(1998) by Jensen. In 1994 a group of 52 scientists, including leading hereditarians, signed the statement "Mainstream Science on Intelligence
Mainstream Science on Intelligence
Mainstream Science on Intelligence was a public statement issued by a group of academic researchers in fields allied to intelligence testing that claimed to present those findings widely accepted in the expert community...
". The Bell Curve also led to a 1995 report from the American Psychological Association
American Psychological Association
The American Psychological Association is the largest scientific and professional organization of psychologists in the United States. It is the world's largest association of psychologists with around 154,000 members including scientists, educators, clinicians, consultants and students. The APA...
, "Intelligence: Knowns and Unknowns
Intelligence: Knowns and Unknowns
Intelligence: Knowns and Unknowns was a 1995 report issued by a Task Force created by the Board of Scientific Affairs of the American Psychological Association.- Background :...
", 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
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
is a low average intelligence which caused great controversy. Following an interview in the monthly supplement of Helsingin Sanomat
Helsingin Sanomat
Helsingin Sanomat is the largest subscription newspaper in Finland and the Nordic countries, owned by Sanoma. Except after certain holidays, it is published daily. In 2008, its daily circulation was 412,421 on weekdays and 468,505 on Sundays...
, Lynn's coauthor Tatu Vanhanen
Tatu Vanhanen
Tatu Vanhanen is a Professor Emeritus of Political Science at the University of Tampere in Tampere, Finland...
, a political scientist
Political science
Political Science is a social science discipline concerned with the study of the state, government and politics. Aristotle defined it as the study of the state. It deals extensively with the theory and practice of politics, and the analysis of political systems and political behavior...
and father of the Prime Minister of Finland
Prime Minister of Finland
The Prime Minister is the Head of Government of Finland. The Prime Minister is appointed by the President, who is the Head of State. The current Prime Minister is Jyrki Katainen of the National Coalition Party.-Overview:...
Matti Vanhanen
Matti Vanhanen
Matti Taneli Vanhanen is a Finnish politician. He is a former Prime Minister of Finland and a former Chairman of the Centre Party. In the second half of 2006 he was President of the European Council. In his earlier career he was a journalist...
, was investigated by the Finnish police between 2002 and 2004. In 2007 James D. Watson
James D. Watson
James Dewey Watson is an American molecular biologist, geneticist, and zoologist, best known as one of the co-discoverers of the structure of DNA in 1953 with Francis Crick...
, Nobel laureate in biology, gave a controversial interview to the Sunday Times Magazine during a book tour in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
. This resulted in the cancellation of a Royal Society
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...
lecture, along with other public engagements, and his suspension from his administrative position at Cold Spring Harbor Laboratory
Cold Spring Harbor Laboratory
The Cold Spring Harbor Laboratory is a private, non-profit institution with research programs focusing on cancer, neurobiology, plant genetics, genomics and bioinformatics. The Laboratory has a broad educational mission, including the recently established Watson School of Biological Sciences. It...
. He subsequently cancelled the tour and resigned from his position.
Many of the leading hereditarians, mostly psychologists, have received funding from the Pioneer Fund
Pioneer Fund
The Pioneer Fund is an American non-profit foundation established in 1937 "to advance the scientific study of heredity and human differences." Currently headed by psychology professor J. Philippe Rushton, the fund states that it focuses on projects it perceives will not be easily funded due to...
with Rushton as its current head. The Southern Poverty Law Center
Southern Poverty Law Center
The Southern Poverty Law Center is an American nonprofit civil rights organization noted for its legal victories against white supremacist groups; legal representation for victims of hate groups; monitoring of alleged hate groups, militias and extremist organizations; and educational programs that...
lists the Pioneer Fund as a hate group
Hate group
A hate group is an organized group or movement that advocates and practices hatred, hostility, or violence towards members of a race, ethnicity, religion, gender, sexual orientation or other designated sector of society...
, 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
Scientific racism
Scientific racism is the use of scientific techniques and hypotheses to sanction the belief in racial superiority or racism.This is not the same as using scientific findings and the scientific method to investigate differences among the humans and argue that there are races...
, eugenics
Eugenics
Eugenics is the "applied science or the bio-social movement which advocates the use of practices aimed at improving the genetic composition of a population", usually referring to human populations. The origins of the concept of eugenics began with certain interpretations of Mendelian inheritance,...
and white supremacy
White supremacy
White supremacy is the belief, and promotion of the belief, that white people are superior to people of other racial backgrounds. The term is sometimes used specifically to describe a political ideology that advocates the social and political dominance by whites.White supremacy, as with racial...
. Similarly, Ullica Segerstråle points out that a number of critics of the hereditarian point of view have been self-admittedly motivated by a Marxist ideology, and supported by organizations such as Science for the People
Science for the People
Science for the People is a left-wing organization that emerged from the antiwar culture of the United States in the 1970s. A similar organization of the same name was founded in 2002....
whose goals are political as well as scientific.
Ethics of research
The 1996 report of the APA had comments on the ethicsEthics
Ethics, also known as moral philosophy, is a branch of philosophy that addresses questions about morality—that is, concepts such as good and evil, right and wrong, virtue and vice, justice and crime, etc.Major branches of ethics include:...
of research on race and intelligence. Gray and Thompson (2004) as well as Hunt and Carlson (2007) have also discussed different possible ethical guidelines. Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
in 2009 invited two editorials on the ethics of research in race and intelligence by Steven Rose
Steven Rose
Steven P. Rose is a Professor of Biology and Neurobiology at the Open University and University of London.-Life:...
(against) and Stephen J. Ceci
Stephen J. Ceci
Stephen J. Ceci is an American psychologist at Cornell University. He studies the accuracy of children's courtroom testimony , and he is an expert in the development of intelligence and memory...
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
Nazism
Nazism, the common short form name of National Socialism was the ideology and practice of the Nazi Party and of Nazi Germany...
or Social Darwinism
Social Darwinism
Social Darwinism is a term commonly used for theories of society that emerged in England and the United States in the 1870s, seeking to apply the principles of Darwinian evolution to sociology and politics...
) justified in part on claimed hereditary racial differences. Stephen Rose maintain that the history of eugenics
Eugenics
Eugenics is the "applied science or the bio-social movement which advocates the use of practices aimed at improving the genetic composition of a population", usually referring to human populations. The origins of the concept of eugenics began with certain interpretations of Mendelian inheritance,...
makes this field of research difficult to reconcile with current ethical standards for science.
Linda Gottfredson
Linda Gottfredson
Linda Susanne Gottfredson is a professor of educational psychology at the University of Delaware and co-director of the Delaware-Johns Hopkins Project for the Study of Intelligence and Society. Gottfredson's work has been influential in shaping U.S...
argues that suggestion of higher ethical standards for research into group differences in intelligence is a double standard
Double standard
A double standard is the unjust application of different sets of principles for similar situations. The concept implies that a single set of principles encompassing all situations is the desirable ideal. The term has been used in print since at least 1895...
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
Flynn effect
The Flynn effect is the name given to a substantial and long-sustained increase in intelligence test scores measured in many parts of the world. When intelligence quotient tests are initially standardized using a sample of test-takers, by convention the average of the test results is set to 100...
) would not have occurred.
The validity of "race" and "IQ"
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 SchacterDaniel Schacter
Daniel Lawrence Schacter is an American psychologist. He is a Professor of Psychology at Harvard University. His research has focused on psychological and biological aspects of human memory and amnesia, with a particular emphasis on the distinction between conscious and nonconscious forms of...
et
Daniel Wegner
Daniel M. Wegner is an American social psychologist. He is a professor of psychology at Harvard University and a fellow of the American Association for the Advancement of Science...
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
Intelligence
Intelligence has been defined in different ways, including the abilities for abstract thought, understanding, communication, reasoning, learning, planning, emotional intelligence and problem solving....
is commonly measured using intelligence quotient
Intelligence quotient
An intelligence quotient, or IQ, is a score derived from one of several different standardized tests designed to assess intelligence. When modern IQ tests are constructed, the mean score within an age group is set to 100 and the standard deviation to 15...
(IQ) tests. The statement "Mainstream Science on Intelligence
Mainstream Science on Intelligence
Mainstream Science on Intelligence was a public statement issued by a group of academic researchers in fields allied to intelligence testing that claimed to present those findings widely accepted in the expert community...
" 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
General intelligence factor
The g factor, where g stands for general intelligence, is a statistic used in psychometrics to model the mental ability underlying results of various tests of cognitive ability...
(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
Armed Services Vocational Aptitude Battery
The Armed Services Vocational Aptitude Battery is a multiple choice test, administered by the United States Military Entrance Processing Command, used to determine qualification for enlistment in the United States armed forces...
, SAT
SAT
The SAT Reasoning Test is a standardized test for college admissions in the United States. The SAT is owned, published, and developed by the College Board, a nonprofit organization in the United States. It was formerly developed, published, and scored by the Educational Testing Service which still...
, GRE
Graduate Record Examination
The Graduate Record Examinations is a standardized test that is an admissions requirement for many graduate schools in the United States, in other English-speaking countries and for English-taught graduate and business programs world-wide...
, GMAT and LSAT. International student assessment tests that have been used include the Trends in International Mathematics and Science Study
Trends in international mathematics and science study
The Trends in International Mathematics and Science Study is an international assessment of the mathematics and science knowledge of fourth- and eighth-grade students around the world...
, Programme for International Student Assessment
Programme for International Student Assessment
The Programme for International Student Assessment is a worldwide evaluation in OECD member countries of 15-year-old school pupils' scholastic performance, performed first in 2000 and repeated every three years...
, and Progress in International Reading Literacy Study. Other variables with much lower correlations such as brain size and reaction time have also been used.
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. et all (2005) argue that the overwhelming portion of the literature correlating race with identity has tacitly adopted folk definitions of race. The American Anthropological Association
American Anthropological Association
The American Anthropological Association is a professional organization of scholars and practitioners in the field of anthropology. With 11,000 members, the Arlington, Virginia based association includes archaeologists, cultural anthropologists, biological anthropologists, linguistic...
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, including anthropology in some other nations, 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
C. Loring Brace
C. Loring Brace is an anthropologist at the University of Michigan. He considers the attempt "to introduce a Darwinian outlook into biological anthropology" to be his greatest contribution to the field of anthropology.-Life and work:...
and Jonathan Kaplan and geneticist Joseph Graves, have argued that while there 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 therefore 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. Weiss and Fullerton have noted that if one sampled only Icelanders, Mayans and Maoris, three distinct clusters would form and all other populations could be described as being composed of admixtures of Maori, Icelandic and Mayan genetic materials. Kaplan 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
Earl Hunt
Earl Hunt is the name of:*Earl B. Hunt, American psychologist and computer scientist*Earl Gladstone Hunt, Jr. , American Methodist pastor and evangelist...
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.
US test scores
Rushton and Jensen (2005 and 2010) write that in the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, 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 deviation
Standard deviation
Standard deviation is a widely used measure of variability or diversity used in statistics and probability theory. It shows how much variation or "dispersion" there is from the average...
s (SDs). 15% to 20% of the black IQ distribution exceeds the white median IQ, so many blacks obtain scores above the white average. The black-white IQ difference is largest on those tests that best represent the general intelligence factor
General intelligence factor
The g factor, where g stands for general intelligence, is a statistic used in psychometrics to model the mental ability underlying results of various tests of cognitive ability...
g. The 1996 APA report "Intelligence: Knowns and Unknowns
Intelligence: Knowns and Unknowns
Intelligence: Knowns and Unknowns was a 1995 report issued by a Task Force created by the Board of Scientific Affairs of the American Psychological Association.- Background :...
" and the 1994 statement "Mainstream Science on Intelligence
Mainstream Science on Intelligence
Mainstream Science on Intelligence was a public statement issued by a group of academic researchers in fields allied to intelligence testing that claimed to present those findings widely accepted in the expert community...
" 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
Graduate Record Examination
The Graduate Record Examinations is a standardized test that is an admissions requirement for many graduate schools in the United States, in other English-speaking countries and for English-taught graduate and business programs world-wide...
(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 agree 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 argues that this has stalled and that there has been no further narrowing for people born after the late 1970s. He 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 Prize
Nobel Prize
The Nobel Prizes are annual international awards bestowed by Scandinavian committees in recognition of cultural and scientific advances. The will of the Swedish chemist Alfred Nobel, the inventor of dynamite, established the prizes in 1895...
s and 25% of the Turing Award
Turing Award
The Turing Award, in full The ACM A.M. Turing Award, is an annual award given by the Association for Computing Machinery to "an individual selected for contributions of a technical nature made to the computing community. The contributions should be of lasting and major technical importance to the...
s. 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
Ashkenazi intelligence
Whether Ashkenazi Jews have higher intelligence than other ethnic groups has been an occasional subject of scientific controversy. The 2005 paper "Natural History of Ashkenazi Intelligence" by Cochran, Hardy, and Harpending, argued on the basis of inherited diseases and the peculiar economic...
.
The racial groups studied in the United States and Europe are not necessarily a random sample
Random sample
In statistics, a sample is a subject chosen from a population for investigation; a random sample is one chosen by a method involving an unpredictable component...
of the populations in other parts of the world. Therefore, results from data in the US and Europe do not necessarily apply to the rest of the world.
International comparisons
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
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. FlynnJames R. Flynn
James Robert Flynn PhD FRSNZ , aka Jim Flynn, Emeritus Professor of Political Studies at the University of Otago in Dunedin, New Zealand, researches intelligence and has become well known for his discovery of the Flynn effect, the continued year-after-year increase of IQ scores in all parts of the...
, 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
A 1996 report by the American Psychological AssociationAmerican Psychological Association
The American Psychological Association is the largest scientific and professional organization of psychologists in the United States. It is the world's largest association of psychologists with around 154,000 members including scientists, educators, clinicians, consultants and students. The APA...
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
Nicholas Mackintosh
Nicholas John Mackintosh, FRS is a British experimental psychologist and author, specializing in intelligence, psychometrics and animal learning.-Career:...
in his 1998 book IQ and Human Intelligence, and by a 1999 literature review by Robert Brown et al.
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
Alexander Luria
Alexander Romanovich Luria was a famous Soviet neuropsychologist and developmental psychologist. He was one of the founders of neuropsychology and the jointly led the Vygotsky Circle.- Biography :...
concluded that it was impossible to devise an IQ test to assess peasant communities in Russia because taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
was alien to their way of reasoning.
Stereotype threat
Stereotype threatStereotype threat
Stereotype threat is the experience of anxiety or concern in a situation where a person has the potential to confirm a negative stereotype about their social group. First described by social psychologist Claude Steele and his colleagues, stereotype threat has been shown to reduce the performance of...
is the fear that one's behavior will confirm an existing stereotype
Stereotype
A stereotype is a popular belief about specific social groups or types of individuals. The concepts of "stereotype" and "prejudice" are often confused with many other different meanings...
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.
A 2009 meta-analysis by Jelte Wicherts found evidence of significant publication bias in 55 studies of stereotype threat and its effect on IQ, in which those that found a strong effect were more likely to be published than those that did not. Reviewing both published and unpublished studies, Wicherts found that stereotype threat did not have an effect on all test-taking settings in which a difference in average scores is observed between races, and therefore was not an adequate explanation for the racial IQ gap.
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.Rushton and Jensen argue that controlling for SES only reduces the black-white gap by a third or 5 points. If there are racial genetic differences, then this figure is overstated since part of the differences in parental SES are due to differences in parental IQ. Furthermore, they argue, an environment-only explanation predicts that the IQ gap would be smaller at higher levels of parental SES since these children would be less exposed to the environmental factors lowering IQ. However, the gap is actually larger at higher parental SES levels. They also point to studies finding higher average IQ for East Asians, American Indians, and Inuit with similar or worse SES than blacks. Comparing black and white children in terms of socioeconomic indicators found that the black children from the best areas and schools (those producing the highest average scores) still average slightly lower on IQ than the white children with the worst socioeconomic factors.
Health and nutrition
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
exposure, breast feeding, and nutrition
Nutrition
Nutrition is the provision, to cells and organisms, of the materials necessary to support life. Many common health problems can be prevented or alleviated with a healthy diet....
can significantly affect cognitive development and functioning. For example, iodine deficiency causes a fall
Cretinism
Cretinism is a condition of severely stunted physical and mental growth due to untreated congenital deficiency of thyroid hormones usually due to maternal hypothyroidism.-Etymology and use of cretin:...
, 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 of the possible prenatal and perinatal detrimental environmental factors.
The Copenhagen consensus
Copenhagen Consensus
Copenhagen Consensus is a project that seeks to establish priorities for advancing global welfare using methodologies based on the theory of welfare economics. It was conceived and organized by Bjørn Lomborg, the author of The Skeptical Environmentalist and the then director of the Danish...
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
Iodine deficiency
Iodine is an essential trace element; the thyroid hormones thyroxine and triiodotyronine contain iodine. In areas where there is little iodine in the diet—typically remote inlandareas where no marine foods are eaten—iodine deficiency gives rise to...
. 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, and Thornhill (2009) argue that "From an energetics standpoint, a developing human will have difficulty building a brain and fighting off infectious disease
Infectious disease
Infectious diseases, also known as communicable diseases, contagious diseases or transmissible diseases comprise clinically evident illness resulting from the infection, presence and growth of pathogenic biological agents in an individual host organism...
s at the same time, as both are very metabolically costly tasks" and that differences in prevalence of infectious diseases (such as malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...
) 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, and Thornhill (2011) 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 talentedGifted education
Gifted education is a broad term for special practices, procedures and theories used in the education of children who have been identified as gifted or talented...
educational programs was influenced in part by the students' ethnicity.
The Abecedarian Early Intervention Project
Abecedarian Early Intervention Project
The Carolina Abecedarian Project was a controlled experiment that was conducted in 1972 in North Carolina, United States, by the Frank Porter Graham Child Development Institute to study the potential benefits of early childhood education for poor children to enhance school readiness...
, 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 a study by Ramey and colleagues, 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 logographicLogogram
A logogram, or logograph, is a grapheme which represents a word or a morpheme . This stands in contrast to phonograms, which represent phonemes or combinations of phonemes, and determinatives, which mark semantic categories.Logograms are often commonly known also as "ideograms"...
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 American Indians 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 optimismEffort optimism
Effort optimism is the confidence that acquiring the skills valued by majority society, such as those skills measured by IQ tests, is worthwhile...
", 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
Inequality by Design: Cracking the Bell Curve Myth
Inequality by Design: Cracking the Bell Curve Myth is a book by Claude S. Fischer, Michael Hout, Martín Sánchez Jankowski, Samuel R. Lucas, Ann Swidler, and Kim Voss...
(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
Peruvians in Japan
There were estimated to be 60,000 Peruvians in Japan . Roughly half are themselves descendants of earlier Japanese immigrants to Peru, while the rest are of other ethnicities.-Migration history:...
and Brazilians
Brazilians in Japan
There is a significant community of Brazilians in Japan, consisting largely but not exclusively of Brazilians of Japanese ethnicity.-Migration history:...
in Japan, Burakumin
Burakumin
are a Japanese social minority group. The burakumin are one of the main minority groups in Japan, along with the Ainu of Hokkaidō, the Ryukyuans of Okinawa and Japanese residents of Korean and Chinese descent....
in Japan, Australian Aborigines
Australian Aborigines
Australian Aborigines , also called Aboriginal Australians, from the latin ab originem , are people who are indigenous to most of the Australian continentthat is, to mainland Australia and the island of Tasmania...
, Romani in Czechoslovakia, Maori in New Zealand, Afro-Brazilian
Afro-Brazilian
In Brazil, the term "preto" is one of the five categories used by the Brazilian Census, along with "branco" , "pardo" , "amarelo" and "indígena"...
s, Indigenous Brazilians, Pardo
Pardo
In Brazil, Pardo is a race/colour category used by the Brazilian Institute of Geography and Statistics in Brazilian censuses. It is a Portuguese word that encompasses various shades of brown, but is usually translated as "grayish-brown"...
s and Rural Exiles
Rural exodus
Rural flight is a term used to describe the migratory patterns of peoples from rural areas into urban areas.In modern times, it often occurs in a region following the industrialization of agriculture when fewer people are needed to bring the same amount of agricultural output to market and related...
(as, but not limited to, people from Northeast
Northeast Region, Brazil
The Northeast Region of Brazil is composed of the following states: Maranhão, Piauí, Ceará, Rio Grande do Norte, Paraíba, Pernambuco, Alagoas, Sergipe and Bahia, and it represents 18.26% of the Brazilian territory....
in Brasília
Brasília
Brasília is the capital city of Brazil. The name is commonly spelled Brasilia in English. The city and its District are located in the Central-West region of the country, along a plateau known as Planalto Central. It has a population of about 2,557,000 as of the 2008 IBGE estimate, making it the...
, São Paulo
São Paulo
São Paulo is the largest city in Brazil, the largest city in the southern hemisphere and South America, and the world's seventh largest city by population. The metropolis is anchor to the São Paulo metropolitan area, ranked as the second-most populous metropolitan area in the Americas and among...
and Rio de Janeiro
Rio de Janeiro
Rio de Janeiro , commonly referred to simply as Rio, is the capital city of the State of Rio de Janeiro, the second largest city of Brazil, and the third largest metropolitan area and agglomeration in South America, boasting approximately 6.3 million people within the city proper, making it the 6th...
metropolitan areas, and including a minority of poors of European descent
White Brazilian
White Brazilians make up 48.4% of Brazil's population, or around 92 million people, according to the IBGE's 2008 PNAD . Whites are present in the entire territory of Brazil, although the main concentrations are found in the South and Southeastern parts of the country...
) in Brazil, Afrikaners in South Africa, Catholics in North Ireland, Irish and Scottish in Great Britain, Flemish
Flemish
Flemish can refer to anything related to Flanders, and may refer directly to the following articles:*Flemish, an informal, though linguistically incorrect, name of any kind of the Dutch language as spoken in Belgium....
in Belgium, Arabs and Sephardi Jews
Sephardi Jews
Sephardi Jews is a general term referring to the descendants of the Jews who lived in the Iberian Peninsula before their expulsion in the Spanish Inquisition. It can also refer to those who use a Sephardic style of liturgy or would otherwise define themselves in terms of the Jewish customs and...
in Israel, and Dalit
Dalit
Dalit is a designation for a group of people traditionally regarded as Untouchable. Dalits are a mixed population, consisting of numerous castes from all over South Asia; they speak a variety of languages and practice a multitude of religions...
, 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 et al. have argued that this is a misrepresentation of the studies and that also the early testing support a high average Jewish IQ.
Hereditarians reply 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, Charles 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 Jews (Torah studyTorah study
Torah study is the study by Jewish people of the Torah, Hebrew Bible, Talmud, responsa, rabbinic literature and similar works, all of which are Judaism's religious texts...
) as well as Chinese (Confucianism
Confucianism
Confucianism is a Chinese ethical and philosophical system developed from the teachings of the Chinese philosopher Confucius . Confucianism originated as an "ethical-sociopolitical teaching" during the Spring and Autumn Period, but later developed metaphysical and cosmological elements in the Han...
and the Imperial examination
Imperial examination
The Imperial examination was an examination system in Imperial China designed to select the best administrative officials for the state's bureaucracy. This system had a huge influence on both society and culture in Imperial China and was directly responsible for the creation of a class of...
system).
Black subculture
Flynn has argued for importance of continued intellectual stimulation in order to sustain IQ. He writes, citing other authors, that "many black people have not signed up for the 'great mission' of the white middle class – the constant quest to stimulate intellectual growth and get their child into Harvard or Oxbridge. Rather than a 'hothouse' approach', they favour a 'natural growth' view: give a child food and love, and all will be well." There is a black teenage subculture of "Dressing sharply, sexual conquests, hanging out, drugs, hip-hop and atypical speech all crowd out more cognitively demanding pursuits."JR Harris suggested in The Nurture Assumption
The Nurture Assumption
The Nurture Assumption: Why Children Turn Out the Way They Do is a book written by Judith Rich Harris, with a foreword by Steven Pinker, originally published 1998 by the Free Press, which published a revised edition in 2009. It has been published in at least 20 languages...
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
Hereditarians argue that there is a substantial (50–80% in the US according to Rushton and Jensen) genetic contribution to the IQ gaps. Non-hereditarians argue that the genetic contribution to the gaps (not to individual IQ) is nil.Evolutionary theories
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 BraceC. Loring Brace
C. Loring Brace is an anthropologist at the University of Michigan. He considers the attempt "to introduce a Darwinian outlook into biological anthropology" to be his greatest contribution to the field of anthropology.-Life and work:...
has argued that such a clinal distribution in the trait is not possible, 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. Jensen points out that larger and more complex brains are very metabolically expensive, so they evolve only when they provide a strong selective advantage. According to Jensen, as early humans migrated out of Africa, the need to adapt to colder climates created a stronger selective pressure for intelligence in Europe and Asia than existed in Africa. J. Philippe Rushton carries this idea a step further in Race, Evolution, and Behavior
Race, Evolution, and Behavior
Race, Evolution, and Behavior: A Life History Perspective is a controversial book written by J...
, proposing that human groups differ in intelligence due to r/K selection theory
R/K selection theory
In ecology, r/K selection theory relates to the selection of combinations of traits in an organism that trade off between quantity or quality of offspring...
, 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
Joseph L. Graves
Joseph L. Graves, Jr. is Associate Dean for Research and Professor of Biological Studies at the Joint School for Nanoscience and Nanoengineering which is jointly administered by North Carolina Agricultural and Technical State University and UNC Greensboro...
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.
Race and genetics
The decoding of the human genomeHuman genome
The human genome is the genome of Homo sapiens, which is stored on 23 chromosome pairs plus the small mitochondrial DNA. 22 of the 23 chromosomes are autosomal chromosome pairs, while the remaining pair is sex-determining...
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 lineage
Lineage (evolution)
An evolutionary lineage is a sequence of species, that form a line of descent, each new species the direct result of speciation from an immediate ancestral species. Lineages are subsets of the evolutionary tree of life. Lineages are often determined by the techniques of molecular systematics.-...
s, 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
Gregor Mendel
Gregor Johann Mendel was an Austrian scientist and Augustinian friar who gained posthumous fame as the founder of the new science of genetics. Mendel demonstrated that the inheritance of certain traits in pea plants follows particular patterns, now referred to as the laws of Mendelian inheritance...
"common garden" 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 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
Robert Plomin
Robert Plomin is an American psychologist best known for his work in twin studies and behavior genetics. Plomin has made two of the most important discoveries in that field. First, he has shown the importance of non-shared environment, a term that he coined to refer to the environmental reasons...
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
American Psychologist
The American Psychologist is the official academic journal of the American Psychological Association. It contains archival documents and articles covering current issues in psychology, the science and practice of psychology, and psychology's contribution to public policy...
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 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".
Heritability within and between groups
Heritability
The Heritability of a population is the proportion of observable differences between individuals that is due to genetic differences. Factors including genetics, environment and random chance can all contribute to the variation between individuals in their observable characteristics...
is defined as the proportion of interindividual variance
Variance
In probability theory and statistics, the variance is a measure of how far a set of numbers is spread out. It is one of several descriptors of a probability distribution, describing how far the numbers lie from the mean . In particular, the variance is one of the moments of a distribution...
in a trait
Trait (biology)
A trait is a distinct variant of a phenotypic character of an organism that may be inherited, environmentally determined or be a combination of the two...
which is attributable to genotype
Genotype
The genotype is the genetic makeup of a cell, an organism, or an individual usually with reference to a specific character under consideration...
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).
Hereditarians 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
Feedback
Feedback describes the situation when output from an event or phenomenon in the past will influence an occurrence or occurrences of the same Feedback describes the situation when output from (or information about the result of) an event or phenomenon in the past will influence an occurrence or...
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.
Hereditarians argue that the same group differences are repeated worldwide, both when comparing regions and when comparing the different groups in the same region, and that non-hereditarians have particular difficulty explaining the higher results for East Asians compared to whites.
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 argues that if the average racial IQs are different, then due to regression toward the meanRegression toward the mean
In statistics, regression toward the mean is the phenomenon that if a variable is extreme on its first measurement, it will tend to be closer to the average on a second measurement, and—a fact that may superficially seem paradoxical—if it is extreme on a second measurement, will tend...
the average IQs of relatives to blacks and whites with the same IQ should be different. He argues that studies confirm this. Nisbett (2009) agrees that this seems to be the case but he sees this as a weak argument since this effect would also be expected from environmental factors depressing average black IQ more than average white IQ. Rushton and Jensen have replied that the results are seen for siblings who should have a very similar environment, that relatives of those scoring low regress upwards, and that, when looking at the magnitude of regression, the results are as predicted by a partial genetic hypothesis. Rushton agrees that these results could also be explained without a genetic contribution, but he argues that such an explanation would be contrived.
Gradual gap appearance
Fryer and 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
Minnesota Transracial Adoption Study
The Minnesota Transracial Adoption Study examined the IQ test scores of 130 black/interracial children adopted by advantaged white families. The aim of the study was to determine the contribution of environmental and genetic factors to the poor performance of black children on IQ tests as compared...
(1976) examined the IQ test scores
Intelligence quotient
An intelligence quotient, or IQ, is a score derived from one of several different standardized tests designed to assess intelligence. When modern IQ tests are constructed, the mean score within an age group is set to 100 and the standard deviation to 15...
of 122 adopted children and 143 nonadopted children reared by advantaged white families. The children were restudied ten years later. Nisbett has criticized the study for a number of weaknesses that are acknowledged by the authors. Rushton and Jensen have criticized this and argued for the significance of this study.
| Minnesota Transracial Adoption Study Tested at age 7 and follow-up at age 17 | ||||
| Biological parents | Number of children | Age 7, average IQ | Age 17, average IQ | |
|---|---|---|---|---|
| Black-black | 21 | 95 | 89 | |
| Black-white | 55 | 110 | 99 | |
| White-white | 16 | 118 | 106 | |
| Asian or indigenous American | 12 | 101 | 96 | |
| Biological children | 104 | 116 | 109 | |
Three other studies found opposing evidence with none finding higher intelligence in white children than in black children. Rushton and Jensen have criticized some of them for being small and all of them for, unlike the Minnesota Transracial Adoption Study, not measuring IQ after puberty
Puberty
Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...
since, they argued, the importance of the family environment is shown to decline with age. Nisbett has argued that there is significant heritability at age seven which makes the absence of differences quite telling.
Moore (1986) compared black and mixed-race children adopted by either black or white middle-class families in the US. There was no difference in IQ between black and mixed-race children, whether raised by black or white families. Moore also 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. The study was criticized by Rushton and Jensen for 20-25% of the "blacks" being North Africans and that the African Americans were an elite group because the Army General Classification Test
Army General Classification Test
The Army General Classification Test has a long history that runs parallel with research and means for attempting the assessment of intelligence or other abilities....
excluded 30% of African Americans tested compared to 3% of whites. Nisbett writes that Flynn has argued that the army testing could not have produced more than a 3 IQ point advantage for the African Americans soldiers compared to the general African Americans population and that the North Africans would change the results only by a small amount.
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 | |
|---|---|---|---|
| Moore (1986) Tested at age 7-10 | |||
| Black-black, interracial adoption | 17 | 102.9 | |
| Black-white, interracial adoption | 6 | 105.7 | |
| Black-black, transracial adoption | 9 | 118.0 | |
| Black-white, transracial adoption | 14 | 116.5 | |
| Eyferth (1961) 1/3 tested at age 5–10, 2/3 at age 10-13 | |||
| Black-white | 98 | 96.5 | |
| White-white | 83 | 97.2 | |
| Tizard et al. (1972) Tested at age 2–5, results for the only test out of four finding significant differences | |||
| Black-black | 15 | 105.7 | |
| Black-white | 15 | 109.8 | |
| White-white | 25 | 101.3 | |
Rushton and Jensen point to 3 adoption studies of East Asian children which in all cases scored significantly above the national averages in the US and Belgium although none had control groups from other races.
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
John C. Loehlin
John Clinton Loehlin is an American behavior geneticist and psychology and computer science professor emeritus. Loehlin has served as president of the Behavior Genetics Association and of the Society for Multivariate Experimental Psychology....
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. This study based its estimates of ancestry on self-reporting by the subjects in interviews. Mackenzie (1984) has criticized this study for comparing its sample group to a group that was not representative of the national average. More recent studies have compared IQ to ancestry estimates based on skin color, and found a correlation of 0.1-0.15 between lighter skin color and higher IQ. Nisbett considers this correlation too low to be significant, while Arthur Jensen has argued that because skin color is a highly imprecise measure of ancestry, no correlation higher than 0.2 could be expected if the hereditarian hypothesis is correct. 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 type
Blood type
A blood type is a classification of blood based on the presence or absence of inherited antigenic substances on the surface of red blood cells . These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system...
s 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. Such experiments have never been published, although the requirements for such a study have been discussed in the academic literature.
Brain size
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 ImagingMagnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
(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. A study on twins
Twin study
Twin studies help disentangle the relative importance of environmental and genetic influences on individual traits and behaviors. Twin research is considered a key tool in behavioral genetics and related fields...
showed that frontal gray matter
Gray Matter
"Gray Matter" is a short story by Stephen King, first published in the October 1973 issue of Cavalier magazine, and later collected in King's 1978 collection Night Shift. It is set in the same area as King's novel Dreamcatcher.-Setting:...
volume also was correlated with g
General intelligence factor
The g factor, where g stands for general intelligence, is a statistic used in psychometrics to model the mental ability underlying results of various tests of cognitive ability...
and highly heritable. A related MRI study has reported that the correlation between brain size (reported to have a heritability
Heritability
The Heritability of a population is the proportion of observable differences between individuals that is due to genetic differences. Factors including genetics, environment and random chance can all contribute to the variation between individuals in their observable characteristics...
of 0.85) and g is 0.4, and that correlation is mediated entirely by genetic factors.
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".
Proponents of both the environmental and hereditarian perspective believe that this variation is relevant to the racial IQ gap, although they disagree as to its cause. Ulric Neisser
Ulric Neisser
Ulric Neisser is an American psychologist and member of the National Academy of Sciences. He is a faculty member at Cornell University. In 1995, he headed an American Psychological Association task force that reviewed The Bell Curve and related controversies in the study of intelligence. The task...
, The Chair of the APA's Task Force on intelligence, acknowledges the brain size difference, but points out that brain size is known to be influenced by environmental factors such as nutrition, and that this fact has been demonstrated experimentally in rats. He thus believes that data on brain size cannot be considered strong evidence for a genetic component to the IQ difference. Rushton and Jensen disagree, citing several studies of malnourished East Asians showing that they have larger brains than whites, and studies demonstrating the brain size difference at birth and prenatally just a few weeks after conception. They argue that correcting for brain size between blacks and whites does not eliminate the IQ gap, which means that factors other than brain size contribute to intelligence differences; however, matching blacks and whites for IQ eliminates the difference in average brain size, suggesting that brain size is still a contributing factor.
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. Rushton argues that a 1994 MRI study in the UK on Africans and West Indians compared to Caucasians support his view although he acknowledges that the study provided no details on how, or if, the samples had been matched for age, sex, or body size.
Mental chronometry
Mental chronometryMental chronometry
Mental chronometry is the use of response time in perceptual-motor tasks to infer the content, duration, and temporal sequencing of cognitive operations....
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
Hans Eysenck
Hans Jürgen Eysenck was a German-British psychologist who spent most of his career in Britain, best remembered for his work on intelligence and personality, though he worked in a wide range of areas...
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. A 2007 study found Statistical mediation
Mediation (Statistics)
In statistics, a mediation model is one that seeks to identify and explicate the mechanism that underlies an observed relationship between an independent variable and a dependent variable via the inclusion of a third explanatory variable, known as a mediator variable...
between reaction time tests and a traditional IQ test, in that controlling for race differences on the RT tasks resulted in the race difference on the IQ test no longer being significant. Jensen has argued that since the black-white difference in RT tasks has a rank-order correlation
Spearman's rank correlation coefficient
In statistics, Spearman's rank correlation coefficient or Spearman's rho, named after Charles Spearman and often denoted by the Greek letter \rho or as r_s, is a non-parametric measure of statistical dependence between two variables. It assesses how well the relationship between two variables can...
with the tasks' g-loadings, this is evidence for the validity of Spearman's hypothesis
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...
.
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 a 1993 study by Jensen and Whang in which a group of Chinese Americans had longer reaction times than a group of European Americans, despite having higher IQs. Nisbett also mentions a pair of studies by Flynn and Deary 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. In a 2010 review of Nisbett's book, Rushton and Jensen argue that Nisbett has underestimated the strength of reaction time's correlation with IQ, and the degree to which differences in reaction time are due to g.
Significance of group differences
A significant part of the debate following The Bell CurveThe Bell Curve
The Bell Curve is a best-selling and controversial 1994 book by the Harvard psychologist Richard J. Herrnstein and political scientist Charles Murray...
concerned the significance of the group differences in IQ for the future achievements of the groups in the US. The book argued for the importance of IQ for factors such as future educational achievements, employment
Employment
Employment is a contract between two parties, one being the employer and the other being the employee. An employee may be defined as:- Employee :...
, income
Income
Income is the consumption and savings opportunity gained by an entity within a specified time frame, which is generally expressed in monetary terms. However, for households and individuals, "income is the sum of all the wages, salaries, profits, interests payments, rents and other forms of earnings...
, divorce
Divorce
Divorce is the final termination of a marital union, canceling the legal duties and responsibilities of marriage and dissolving the bonds of matrimony between the parties...
rates, and crime
Crime
Crime is the breach of rules or laws for which some governing authority can ultimately prescribe a conviction...
. The book's critics argued that it overstated the importance of IQ.
Earl Hunt
Earl B. Hunt
Earl B. Hunt is an American psychologist specializing in the study of human and artificial intelligence. Within these fields he has focused on individual differences in intelligence and the implications of these differences for the roles people play within a high-technology society...
discusses the relationship between cognitive ability, job performance and income in his 2011 book Human Intelligence. According to Hunt, cognitive test scores have a predictive validity of 0.3 to 0.6 for job performance, and also influence income. Hunt states that racial gaps exist in job performance and income, and that the gaps in job performance are about what would be predicted based on the correlation between cognitive test scores and performance. However, he also mentions that according to a 1997 study, the variation in income associated with test scores is less than the authors of The Bell Curve claimed it was.
Lynn in the 2008 book The Global Bell Curve
The Global Bell Curve
The Global Bell Curve: Race, IQ, and Inequality Worldwide is a book by Professor Richard Lynn, published by Washington Summit Publishers, June 2008...
, aiming to build on The Bell Curve, argues that group differences in IQ are an important explanation for different achievements for different groups worldwide. One example being that when East Asians arrived in Latin America as indenture
Indenture
An indenture is a legal contract reflecting a debt or purchase obligation, specifically referring to two types of practices: in historical usage, an indentured servant status, and in modern usage, an instrument used for commercial debt or real estate transaction.-Historical usage:An indenture is a...
d plantation workers as replacement for slaves, their descendents quickly became elite groups. Lynn argues that also environmental explanations are important, as well as non-IQ genetic group differences, such as average genetic group differences on personality variables.
The mainstream explanations of social scientists and historians for international inequality
International inequality
International inequality is inequality between countries . Economic differences between rich and poor countries are considerable...
, including the North-South divide
North-South divide
The north–south divide is a socio-economic and political division that exists between the wealthy developed countries, known collectively as "the north", and the poorer developing countries , or "the south." Although most nations comprising the "North" are in fact located in the Northern Hemisphere ,...
, is as the result of historical and political factors such as the heritage of colonialism
Colonialism
Colonialism is the establishment, maintenance, acquisition and expansion of colonies in one territory by people from another territory. It is a process whereby the metropole claims sovereignty over the colony and the social structure, government, and economics of the colony are changed by...
including conflicts and violence, discrimination
Discrimination
Discrimination is the prejudicial treatment of an individual based on their membership in a certain group or category. It involves the actual behaviors towards groups such as excluding or restricting members of one group from opportunities that are available to another group. The term began to be...
, economic exploitation by developed nations, and cultural factors such as work ethic
Work ethic
Work ethic is a set of values based on hard work and diligence. It is also a belief in the moral benefit of work and its ability to enhance character. An example would be the Protestant work ethic...
s, corruption
Political corruption
Political corruption is the use of legislated powers by government officials for illegitimate private gain. Misuse of government power for other purposes, such as repression of political opponents and general police brutality, is not considered political corruption. Neither are illegal acts by...
, and human capital
Human capital
Human capitalis the stock of competencies, knowledge and personality attributes embodied in the ability to perform labor so as to produce economic value. It is the attributes gained by a worker through education and experience...
theories where groups receive different education.
Policy relevance
Jensen and Rushton argue that the existence of biological group differences does not rule out, but removes part of the justification for, policies such as affirmative actionAffirmative action
Affirmative action refers to policies that take factors including "race, color, religion, gender, sexual orientation or national origin" into consideration in order to benefit an underrepresented group, usually as a means to counter the effects of a history of discrimination.-Origins:The term...
or redistribution in favor of the less successful group. They also argue for the importance of teaching not to stereotype
Stereotype
A stereotype is a popular belief about specific social groups or types of individuals. The concepts of "stereotype" and "prejudice" are often confused with many other different meanings...
from average differences, because of the significant overlap of people with varying intelligence between different races. Rushton, writing on the North African/South Asian average IQ, has argued that "Immigration
Immigration
Immigration is the act of foreigners passing or coming into a country for the purpose of permanent residence...
policy too, must be adjusted. Mass immigration from the region is very likely to lower the average IQ of the receiving Western countries, and consequently be dysfunctional."
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
Malnutrition
Malnutrition is the condition that results from taking an unbalanced diet in which certain nutrients are lacking, in excess , or in the wrong proportions....
, infectious diseases such as meningitis
Meningitis
Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
, parasites, and cerebral malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...
, in utero
In utero
In utero is a Latin term literally meaning "in the womb". In biology, the phrase describes the state of an embryo or fetus. In legal contexts, the phrase is used to refer to unborn children. Under common law, unborn children are still considered to exist for property transfer purposes.-See also:*...
drug
Drug
A drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...
and alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
exposure, newborn asphyxia
Asphyxia
Asphyxia or asphyxiation is a condition of severely deficient supply of oxygen to the body that arises from being unable to breathe normally. An example of asphyxia is choking. Asphyxia causes generalized hypoxia, which primarily affects the tissues and organs...
, low birth weight
Low birth weight
Low birth weight is defined as a birth weight of a liveborn infant of less than 2,500 g. regardless of gestational age-Causes:LBW is either the result of preterm birth or of the infant being small for gestational age , or a combination of...
, head injuries, and endocrine disorders.
Gregory Stock
Gregory Stock
Gregory Stock is a biophysicist, best-selling author, biotech entrepreneur, and the former director of the Program on Medicine, Technology and Society at UCLA’s School of Medicine...
argues that modern biotechnology
Biotechnology
Biotechnology is a field of applied biology that involves the use of living organisms and bioprocesses in engineering, technology, medicine and other fields requiring bioproducts. Biotechnology also utilizes these products for manufacturing purpose...
will allow parents to select desired genes in their children meaning "current debates about whether some of the differences among ethnic and racial groups are cultural or biological will soon become irrelevant, given the coming [malleability of biological traits]" He writes that such technology may allow parents to select intelligence or racially identifying traits (such as human skin color
Human skin color
Human skin color is primarily due to the presence of melanin in the skin. Skin color ranges from almost black to white with a pinkish tinge due to blood vessels underneath. Variation in natural skin color is mainly due to genetics, although the evolutionary causes are not completely certain...
; see gene SLC24A5
SLC24A5
Sodium/potassium/calcium exchanger 5 also known as solute carrier family 24 member 5 is a protein that in humans is encoded by the SLC24A5 gene that has a major influence on natural skin colour variation. The NCKX5 protein is a member of the potassium-dependent sodium/calcium exchanger family...
).
External links
- Intelligence: Knowns and Unknowns, a 1996 statement from the American Psychological AssociationAmerican Psychological AssociationThe American Psychological Association is the largest scientific and professional organization of psychologists in the United States. It is the world's largest association of psychologists with around 154,000 members including scientists, educators, clinicians, consultants and students. The APA...
. - Mainsteam Science on Intelligence, a statement signed by 52 researchers, published in the Wall Street Journal in 1994 and republished in the journal IntelligenceIntelligence (journal)Intelligence is a peer-reviewed academic journal of psychology that covers intelligence and psychometrics. It is published by Elsevier and the official journal of the International Society for Intelligence Research.The journal was established in 1977 and the editor in chief is Douglas K. Detterman...
in 1997. - 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 4Channel 4Channel 4 is a British public-service television broadcaster which began working on 2 November 1982. Although largely commercially self-funded, it is ultimately publicly owned; originally a subsidiary of the Independent Broadcasting Authority , the station is now owned and operated by the Channel...
public television station, featuring SomaliSomali peopleSomalis are an ethnic group located in the Horn of Africa, also known as the Somali Peninsula. The overwhelming majority of Somalis speak the Somali language, which is part of the Cushitic branch of the Afro-Asiatic language family...
-British journalist Rageh OmaarRageh OmaarRageh Omaar , is a Somali born British journalist and writer. His latest book Only Half of Me deals with the tensions between these two sides of his identity. He used to be a BBC world affairs correspondent, where he made his name reporting from Iraq...
- October 2009.