Race and intelligence is a controversial area of intelligence research studying the nature, origins, and practical consequences of racial and ethnic group differences in intelligence test scores and other measures of cognitive ability.^[3]

This research is grounded in several controversial assumptions:

• the social categories of race and ethnicity are concordant with genetic categories, such as biogeographic ancestry.
• intelligence is measurable (see psychometrics) and is dominated by a unitary general cognitive ability.

Much of the evidence currently cited is based on IQ testing in the United States. While the distributions of IQ scores among different racial-ethnic groups overlap and often have a comparable range, groups differ in where their members cluster along the IQ scale.^[4] Similar clustering occurs with related variables, such as school achievement, reaction time, and brain size.^[5] Most variation in IQ in the U.S. occurs within individual families, not between races. However, even small differences in average IQ at the group level might theoretically have large effects on social outcomes. For example, a randomly selected group of Americans with an average IQ of 103 had a poverty rate 25% lower than a group with an average IQ of 100. Similar substantial correlations in high school drop-out rates, crime rates, and other outcomes have been measured.^[6]

Several hypotheses have been proposed to explain why average IQ varies among racial-ethnic groups. Certain environmental factors, such as nutrition, are thought to modulate IQ in children,^[7] and other influences have been hypothesized, including education level, richness of the early home environment, and other social, cultural, or economic factors. The primary focus of the scientific debate is whether group IQ differences also reflect a genetic component. Hereditarianism hypothesizes that a genetic contribution to intelligence could include genes linked to neuron structure or function, brain size or metabolism, or other physiological differences which could vary with biogeographic ancestry.

The findings of this field have engendered significant controversy. Media portrayal of the role of genetic and environmental factors in explaining individual and group differences in IQ has itself been studied (1988) and found to be misleading regarding mainstream expert opinion. Some critics examine the fairness and validity of cognitive testing and racial categorization, as well as the reliability of the studies and the motives of the authors, on both sides. This has included accusations that funding from the Pioneer Fund (which has funded all of the leading researchers of the hereditarian stance) supports only research that "tends to come out with results that further the division between races... by justifying the superiority of one race and the inferiority of another ^[8] On the other side, it is asserted that misguided political correctness has led to large-scale denial of recent developments in the human sciences.^[9] Some critics fear the misuse of the research, question its utility, or feel that comparing the intelligence of racial groups is itself unethical. The disparity in average IQ among racial groups does not mean that all members of one group are more intelligent than all members of another, nor that ranking group averages from "high" to "low" implies a moral ranking from "good" to "bad" or an overall ranking of "superior" to "inferior".^[10] The conclusion that racial groups vary in average IQ scores, and the hypothesis that a genetic component may be involved, have led to heated academic debates that have spilled over into the public sphere.

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Background information

Race

| See also: Race and multilocus allele clusters

Racial distinctions are generally made on the basis of skin color, facial features, inferred ancestry, national origin and self-identification. In an ongoing debate, some geneticists argue race is neither a meaningful concept nor a useful heuristic device,^[11] and even that genetic differences between groups are biologically meaningless,^[12] on the basis of that more genetic variation exists within such races than between them,^[13] and that racial traits overlap without discrete boundaries.^[14] Other geneticists, in contrast, argue that categories of self-identified race/ethnicity or biogeographic ancestry are both valid and useful,^[15] that these categories correspond with clusters inferred from multilocus genetic data,^[16] and that this correspondence implies that genetic factors might contribute to unexplained phenotypic variation between groups.^[17]

Worldwide, human populations are geographically bounded into five less than perfectly distinct continental areas: the Americas, Eurasia (including Europe, North Africa and West Asia), East Asia, Sub-Saharan Africa, and the Pacific Islands (including Australia).^[18] At least in the United States, self-identified racial labels correspond to geographic regions of genetic ancestry, with only a small number of individuals showing genetic cluster membership different from their self-identified race/ethnicity.^[19] People labeled Blacks have most of their ancestors from sub-Saharan Africa, Whites from Europe (and sometimes the Middle East and North Africa), and East Asians from the north-western Pacific Rim. Hispanics form a genetically diverse group that includes many recent U.S. immigrants of mixed ancestry, and are more often called an ethnic group.

It is well known that many alleles vary in frequency across (and within) human populations. Most of this variation is selectively neutral, but a significant number show evidence of recent positive selection.^[20] These include genes involved in brain development and other neuronal functions, which have variants that have spread to high frequencies under selective pressure and now occur in substantially different frequencies in different global populations.^[21] The actual functions of these genes, and their effect, if any, on IQ is unknown. (Discussed below.)

The political, social and cultural structure of the United States is still weighted by race. It was only in the 1960s that racial discrimination became illegal in many areas of public and private life, including employment and housing, and some consider discrimination to remain prevalent. The national and state governments of the United States employ racial categorization in the census, law enforcement, and innumerable other ways. Many political organizations intend to represent the interests of specific racial groups. See the articles Race and Race (U.S. Census) for further discussion.

Intelligence testing

Intelligence is most commonly measured using IQ tests. These tests are often geared to be good measures of the psychometric variable g (for general intelligence factor), and other tests that measure g (for example, the Armed Forces Qualifying Test and the SAT) also serve as measures of cognitive ability.

All such tests are often called "intelligence tests," though the use of the term "intelligence" is itself controversial. It is clear, however, that performance in these tests correlates with performance in similar life tasks (school grades and to a lower degree college grades). The correlation with many real-world results is lower. For example, while the correlation of IQ with job performance is strong, income is modestly correlated and accumulated wealth is only weakly correlated. The genetic transmission of wealth via IQ is near zero. As commonly used, "IQ test" denotes any test of cognitive ability, and "IQ" is used as shorthand for scores on tests of cognitive ability. Some critics question the validity of all IQ testing or claim that there are aspects of "intelligence" not reflected in IQ tests. Historically, criticisms of the validity of IQ testing focused primarily on questions of "test bias", which has many related meanings. Several conclusions about tests of cognitive ability are now largely accepted:

• IQ scores measure many, but not all of the qualities that people mean by intelligent or smart (for example, IQ does not measure creativity, wisdom, or personality)
• IQ scores are fairly stable over much of a person's life
• IQ tests are predictive of school and job performance, to a degree that does not significantly vary by socio-economic or racial-ethnic background
• For people living in the prevailing conditions of the developed world, cognitive ability is substantially heritable, and while the impact of family environment on the IQ of children is substantial, after adolescence this effect becomes difficult to detect.

See the articles Intelligence, IQ, and g for further discussion of the validity of these tests.

The contemporary debate: results and interpretations

The contemporary scholarly debate about race and intelligence involves both the relatively uncontroversial experimental results that indicate that average IQ test scores vary among racial groups, and the relatively more controversial interpretations of these IQ differences. In general, contemporary interpretations of the "IQ gap" can be divided into three broad categories:

1. "culture-only" or "environment-only" interpretations that posit overwhelmingly non-genetic causes (for example, socioeconomic inequality or minority group membership) that differentially affect racial groups;
2. "partly genetic" interpretations that posit an IQ gap between racial groups caused by approximately the same matrix of genetic and environmental forces that cause IQ differences among individuals of the same race;
3. "insufficient data": no meaningful interpretation can be made based on available evidence.

History

1850s to World War II

The scientific debate on the contribution of nature versus nurture to individual and group differences in intelligence can be traced to at least the mid-19th century.^[22] Charles Darwin wrote in his Descent of Man (VII, On the races of Man): "[T]he various [human] races, when carefully compared and measured, differ much from each other—as in the texture of hair, the relative proportions of all parts of the body, the capacity of the lungs, the form and capacity of the skull, and even the convolutions of the brain. But it would be an endless task to specify the numerous points of difference. The races differ also in constitution, in acclimatization and in liability to certain diseases. Their mental characteristics are likewise very distinct; chiefly as it would appear in their emotional, but partly in their intellectual faculties."

The writings of Sir Francis Galton, elaborating on the work of his cousin Darwin, spurred interest in the study of mental abilities, particularly as they relate to heredity and eugenics.

The fact that there are differences in the brain sizes and brain structures of different racial and ethnic groups was well known and widely studied during the 19th century and early 20th century.^[23] Average ethnic and racial group differences in IQ were first found due to the widespread use of standardized mental tests during World War I.

Beginning in the 1930s, race difference research and hereditarianism — the belief that genetics contribute to differences in intelligence among humans — began to fall out of favor in psychology and anthropology after major internal debates.^[24] In anthropology this occurred in part due to the advocacy of Franz Boas, who in his 1938 edition of The Mind of Primitive Man wrote, "there is nothing at all that could be interpreted as suggesting any material difference in the mental capacity of the bulk of the Negro population as compared with the bulk of the White population."^[25] The hereditarian position was greatly weakened by Boas' finding that cranial vault size had increased significantly in the U.S. from one generation to the next, because racial differences in such characteristics had been among the strongest arguments for a genetic role.

Post WWII and modern times

Inspired by the American eugenics movement, Nazi Germany implemented the T-4 Euthanasia Program in which roughly 200,000 mentally and physically disabled Germans were killed, and about 400,000 sterilized. Due in part to the association of hereditarianism with Nazi Germany, after the conclusion of World War II until the 1994 publication of The Bell Curve, it became largely taboo to suggest that there were racial or ethnic differences in measures of intellectual or academic ability and even more taboo to suggest that they might involve a genetic component.^[26]

In 1961, the psychologist Henry Garrett coined the term equalitarian dogma to describe the then politically fashionable view that there were no race differences in intelligence, or if there were, they were purely the result of environmental factors. Those who questioned these views often put their careers at risk.^[27]

The contemporary scholarly debate on race and intelligence may be traced to Arthur Jensen's 1969 publication in the Harvard Educational Review of "How Much Can We Boost IQ and School Achievement?"^[28] In this paper, he wrote on some of the major issues that characterize the partly genetic hypothesis of racial IQ differences, and on compensatory educational programs. Reports on Jensen's article appeared in Time, Newsweek, Life, U.S. News & World Report, and The New York Times Magazine.

Press attention returned to the issue of race and intelligence in 1994 with the publication of The Bell Curve, which included two chapters on the subject of racial difference in intelligence and related life outcomes. In response to The Bell Curve, Stephen Jay Gould updated The Mismeasure of Man in 1996.^[29] Among other things, he criticized the IQ test as a measure of intelligence, citing what he perceived as inherent racial and social biases as well as systematic flaws in the testing process.

The introduction of biomedicine tailored to the genetics and disease patterns of specific racial groups is currently one of the factors adding to the complexity and controversy of debates on race and science.^[30] The scholarly debate continues on the question of "whether the cause of group differences in average IQ is purely social, economic, and cultural or whether genetic factors are also involved".^[31]

Average gaps among races

The modern controversy surrounding intelligence and race focuses on the results of IQ studies conducted during the second half of the 20th century, mainly in the United States and some other industrialized nations.^[33]

Some other psychological traits have also been found to vary significantly in distribution,^[34] but variance in cognitive ability is seen as a more pressing phenomenon.^[35]

World-wide scores

The largest review of the global cognitive ability data is Richard Lynn's 2006 Race Differences in Intelligence, which organizes the data by nine global regions,^[36] surveying 620 published studies from around the world, with a total of 813,778 tested individuals. Lynn's meta-analysis lists East Asians (105), Europeans (99), Inuit (91), Southeast Asians and Amerindians each (87), Pacific Islanders (85), Middle Easterners (including South Asians and North Africans) (84), sub-Saharan Africans (67), and Australian Aborigines (62). Lynn has previously argued at length that nutrition is the best supported environmental explanation for variation in the lower range,^[37] and a number of other environmental explanations have been advanced (see below). Ashkenazi Jews score significantly higher than other groups (107-115) in the U.S. and Britain, but estimates of the average IQ of Ashkenazim in Israel may be somewhat closer to the European mean.^[38] In other data, Hispanics average 91 and African Americans average 87,^[39] though the latter is debated.^[2] Lynn's survey is an expansion by nearly four times of the data collected in his 2002 IQ and the Wealth of Nations with Tatu Vanhanen. IQatWoN, which dealt with the relationship between IQ and economic development, received strong criticism from some for both error and alleged bias, but has also been used as a source of IQ data and hypotheses in several peer-reviewed studies.^[40] Lynn argues the surveyed studies have high reliability in the sense that different studies give similar results, and high validity in the sense that they correlate highly with performance in international studies of achievement in mathematics and science and with national economic development.

Related groups sometimes vary greatly in IQ in different nations. Black Africans score much lower than blacks in the US, although Black Americans average about 7-20% European admixture.^[41] Some reports indicate that the black–white gap is smaller in the UK than in the U.S.^[42] Differences between groups of whites can also be seen, ranging to the low 90s in SE Europe (with a decrease also seen in brain size).^[43] In Israel, large gaps in test scores and achievement separate Ashkenazi Jews from other groups such as the Sephardi.^[44]

Brain size, employment tests, and school achievement

IQ has a moderate correlation with various measures of brain size and performance on elementary tests of response time.^[46] For example, a 2005 meta-analysis found that brain size correlates with IQ by a factor of approximately .40 among adults.^[47] Reaction times correlate with IQ by about .30 to .50.^[48] Studies have shown racial differences in both brain size^[49] and tests of response time.^[50] Cranial vault size and shape have changed greatly during the last 150 years in the US. These changes must occur by early childhood because of the early development of the vault. The explanation for these changes may be related to the Flynn effect.^[51]

Gaps are seen in other tests of cognitive ability or aptitude, including university admission exams such as the SAT and GRE, as well as employment tests for corporate settings and the military.^[52] Measures of school achievement correlate fairly well with IQ, especially in younger children. In the United States, achievement tests find that by 12th grade black students are performing on average only as well as white and Asian students in 8th grade; Hispanic students do only slightly better than blacks.^[53] However, the achievement gap in the U.S. has shrunk since the 1970s.

Cultural or genetic explanations?

Introduction

The most widely accepted view among intelligence researchers is that IQ differences among individuals of the same race reflect real, functionally/socially significant, and substantially genetic differences in the general intelligence factor, g. It is likewise widely believed that average IQ differences among races reflect real and significant differences in the same g factor.^[54] While these conclusions are largely beyond technical dispute, the nature of g is still an active area of research.

However, it is a matter of debate whether the causes of IQ differences among races are entirely environmental or partly genetic. Several published consensus statements agree that the large difference between the average IQ scores of Blacks and Whites in the U.S. cannot be attributed to biases in test construction,^[55] nor can simple differences in socio-economic status be the whole explanation.

It should be noted that most research has been done in the US and a few other developed nations (see above for worldwide data). That research cannot directly be generalized to the world as a whole.^{[citation needed]} Blacks in the US do not constitute a random sample of the original African population,^{[citation needed]} and environmental conditions differ among nations. IQ tests done in developing countries are likely to have been affected by conditions associated with poverty that are common in the developing world, such as nutritional deficiencies and the impact of diseases (for example, HIV, anemia or chronic parasites) that have been known to affect IQ test scores.^{[citation needed]}

The extent to which the IQ gap is caused by genetic or environmental factors is logically independent of the ability for intervention to reduce the gap. A genetic cause is not necessarily irremediable (e.g. diabetes, myopia, and phenylketonuria) and an environmental cause may not be remediable (e.g. accidents and some diseases). Based in part on this distinction, Template:A(Y)ref argue that determining the extent to which genes or environment cause the IQ gap is unimportant.^[56]

Cultural explanations

Although IQ is regarded as being highly heritable, this does not mean that IQ differences between racial groups are necessarily genetic in origin, because estimates of heritability are dependent on a given environment. For example, in schizophrenia, also regarded as being highly heritable, increased rates in second and third generation immigrants to Western European countries do not seem to be the result of increased genetic susceptibility, but another, as yet unidentified, environmental factor.

Regarding the IQ gaps in the U.S., it has also been suggested that African-American culture disfavors academic achievement and fosters an environment that is damaging to IQ.^[57] Likewise, it is argued that the persistence of negative racial stereotypes reinforces this effect. John Ogbu has developed a hypothesis that the condition of being a "caste-like minority" affects motivation and achievement, depressing IQ.^[58] Similarly, it's suggested reduced performance from "stereotype threat" could be a contributing factor.^[59] One author has attempted to itemize the many factors that constitute the differences in social and socioeconomic environments between blacks and whites.^[60]

Many anthropologists have argued that intelligence is a cultural category; some cultures emphasize speed and competition more than others, for example. Speculations about innate differences in intelligence between ethnic groups have occurred throughout history. Aristotle in the 4th century B.C. and Cicero in the 1rst. century B.C. disparaged the intelligence of the northern Europeans of the time, as did the Moors in Iberia in the 11th century. ^[61]

A number of environmental factors are agreed to be likely involved. In the developing world many factors can greatly decrease IQ scores. Examples include nutrition deficiencies in iodine and iron; certain diseases like malaria; unregulated toxic industrial substances like lead and mercury; and poor health care for pregnant women and infants. Also, in the developed world there are many biological factors that can affect IQ. Increased rates of low birth weight babies and lower rates of breastfeeding in Blacks as compared to Whites are some factors of many that have been proposed to affect the IQ gap.^[62]

The secular, international increase in test scores, commonly called the Flynn effect, is seen by Flynn and others as reason to expect the eventual convergence of average Black and White IQ scores. As demonstrated by Flynn, the average IQ scores in several countries have increased about 3 points per decade during the 20th century, which he and others attribute predominately to environmental causes.^[63] This means, given the same test, the mean Black American performance today could be higher than the mean White American performance in 1920, though the gains causing this appear to have occurred predominantly in the lower half of the IQ distribution.^[64] If changes in environment can cause such large changes in IQ over time, they argue, then contemporary differences between groups could also be due to an unknown environmental factor. On the supposition that the effect started earlier for Whites, because their social and economical conditions began to improve earlier than did those of Blacks, they anticipate that the IQ gap among races might change in the future or is even now changing. An added complication to this hypothesis is the question of whether the secular IQ gains can be predominately a change in real intelligence. Flynn's face-value answer to this question is "No",^[65] and other researchers have found reason to concur.^[66] Responding to such concerns, Template:AYref have proposed a solution which rests on genotype-environment correlation, hypothesizing that small initial differences in environment cause feedback effects which magnify into large IQ differences.^[67] Such differences would need to develop before age 3, when the Black-White IQ gap can be first detected.

Many studies that attempt to test for heritability find results that do not support the genetic hypothesis. They include studies on IQ and skin color,^[68] self-reported European ancestry,^[69] children in post WWII Germany born to Black and White American soldiers,^[70] blood groups,^[71] and mixed-race children born to either a Black or a White mother.^[72] Many intervention and adoption studies also find results that do not support the genetic hypothesis.^{[citation needed]} Non-hereditarians have argued that these are direct tests of the genetic hypothesis and of more value than indirect variables, such as skull size and reaction time.^[73] Hereditarians argue that these studies are flawed, or that they do support the partly-genetic hypothesis.^[74]

A recent theory hypothesizes that fluid cognition (gF') may be separable from general intelligence, and that gF' may be very susceptible to environmental factors, in particular early childhood stress. Some IQ tests, especially those used with children, are poor measures of gF', which means that the effect of the environment on intelligence regarding racial differences, the Flynn effect, early childhood intervention, and life outcomes may have been underestimated in many studies. The article has received numerous peer commentaries for and against.[14]

A recent, newly available, large, and nationally representative data set find only very small (0.06 SD between whites and blacks) racial differences on measures for mental function for children aged eight to twelve months. These differences disappear when controlling for a limited set of factors such as differences in SES. "These findings pose a substantial challenge to the simplest, most direct, and most often articulated genetic stories regarding racial differences in mental function." "To the extent that there are any genetically-driven racial differences in intelligence, these gaps must either emerge after the age of one, or operate along dimensions not captured by this early test of mental cognition."^[75]

Genetic explanations

Arthur Jensen and others have concluded that the US IQ gap is partially genetic. Rushton and Jensen argue that while plausible environmental explanation for the lower mean IQ in Blacks in the U.S. can be offered in many cases, these explanations are less capable of explaining the higher average IQ of East Asians than Whites. Under their interpretation of Lakatos's technical concept of research programs, Jensen and Rushton argue that the culture-only hypothesis is not "progressive" but "degenerating".^[76]

To support these claims, they most often cite four main lines of converging data:

1. Worldwide Black–White–East Asian differences in IQ, reaction time, and brain size. In the United States, Black-White IQ differences are observable at every age above 3 years, within every occupation or socioeconomic level, in every region of the country, and at every time since the invention of ability tests.^[77]
2. The magnitude of race differences on different IQ subtests correlates with the extent to which those subtests measures g,^[78] which also correlates with measures of the subtests heritability^[79]
3. The rising heritability of IQ with age (within all races; on average in the developed world heritability starts at 20% in infants, rises to 40% in middle childhood, and peaks at 80% in adulthood); and the virtual disappearance (~0.0) by adulthood of shared environmental effects on IQ (for example, family income, education, and home environment), making adopted siblings no more similar in IQ than strangers^[80]
4. US comparisons of both parents to children and siblings to each other finds regression to differing means for different races (85 for Blacks and 100 for Whites) across the entire range of IQs,^[81] despite the fact that siblings are matched for shared environment and genetic heritage, with regression unaffected by family socioeconomic status and generation examined^[82]

Template:A(Y)ref believe that the best explanation is that 50%-80% of the group differences in average US IQ is genetic.^[83] For fuller listings of evidence for the partly-genetic position, see Comparison of interpretations, Template:A(Y)ref, or this press release.

Other evidence, such as transracial adoption, certain racial admixture studies, behavior genetic modeling of group differences, "life-history" traits, and evolutionary explanations have also been proposed to indicate a genetic contribution to the IQ gaps and explain how these arose. Critics of this view, such as Robert Sternberg, argue that these studies are either flawed and thus inconclusive, or else that they support the culture-only hypothesis.^[84] For example, Template:AYref argue that the statistical methods linking the Black-White gap to g are insufficent.^[85]

Several recent studies have found some neuronal genes have variants that have spread to high frequencies under selective pressure and now occur in different frequencies in different global populations.^[21] Some of this selection occurred within the last 10,000 years.^[86] The cause of the selective sweep and the effects of these variants are generally not yet known, although some suspect that they could be related to intelligence.^[87] Although neurogenic diversity theoretically increases the chances of functional diversity, ultimately, very little is known about the actual impact of these variants, and the researchers caution that they may not have anything to do with cognition or intelligence at all.^[88]

Expert opinion

A survey was conducted in 1987 of a broad sample of 1,020 scholars (65% replied) in specialties that would give them reason to be knowledgeable about IQ (but not necessarily about race). The survey was given to members of the American Education Research Association, National Council on Measurement in Education, American Psychological Association, American Sociological Association, Behavior Genetics Association, and Cognitive Science Society. 52.9% of respondents supported the "partly genetic" position, 1.2% of respondents supported the "entirely genetic" position, 17.7% supported the "entirely environmental" position, and 28.2% responded that there was insufficient data "to support any reasonable opinion".^[89] Respondents on average called themselves slightly left of center politically, but political and social opinions accounted for less than 10% of the variation in responses.

According to the American Psychological Association's 1995 task force report on intelligence research:

It is sometimes suggested that the Black/White differential in psychometric intelligence is partly due to genetic differences (Jensen, 1972). There is not much direct evidence on this point, but what little there is fails to support the genetic hypothesis.^[46]

The APA journal that published the statement subsequently published eleven critical responses in 1997, most arguing that the report failed to examine adequately the evidence for partly-genetic explanations.^[90] Charles Murray, for instance, responded:

Actually, there is no direct evidence at all, just a wide variety of indirect evidence, almost all of which the task force chose to ignore.^[91]

The report did agree with many of the statements on intelligence made in the Bell Curve^[92] and concludes with a call for more reflection in debates on intelligence and for a "shared and sustained effort" in more research to answer the many unanswered questions that remain.^[93] Coming advances in genetics and genomics are expected to soon provide the ability to test hypotheses about group differences more rigorously than has as yet been possible.^[94]

Researchers who believe that there is no significant genetic contribution to race differences in intelligence include Template:AYref, Template:AYref, Template:AYref, Template:AYref, Template:AYref, Template:AYref, and Template:AYref. Some scientists who emphasize cultural explanations do not necessarily exclude a small genetic influence. Template:A(Y)ref suggests up to 20% genetic influence be included in the cultural explanation. Researchers who believe that there are significant genetic contributions to race differences in intelligence include Template:AYref, Template:AYref, Template:AYref, Template:AYref, Template:AYref, Template:AYref, Template:AYref, Template:AYref, Template:AYref, Template:AYref, Template:AYref, Template:AYref, Template:AYref, Template:AYref, and Template:AYref.

Significance of group IQ differences

See also: Practical importance of IQ

Within societies

Scope

The distribution of IQ scores among individuals of each race overlap substantially. In a random sample of equal numbers of US Blacks and Whites, Template:A(Y)ref estimates most variance in IQ would be unrelated to race or social class.^[95] The average IQ difference between two randomly paired people from the U.S. population is approximately 17 points, and this only increases to 20 points when the pair are black and white. When the pair are siblings, the average difference is still 12 points.

In essays accompanying the publication of The Bell Curve, Herrnstein and Murray argue that whether the cause of the IQ gap is partly genetic or entirely environmental does not really matter because that knowledge alone would not help to eliminate the gap and that knowledge should not impact the way that individuals treat one another. They argue that group differences in intelligence ought not to be treated as more important or threatening than individual differences, but suggest that one legacy of Black slavery has been to exacerbate race relations such that Blacks and Whites cannot be comfortable with group differences in IQ or any other traits.^[96]

Moreover, although it may appear paradoxical, an indirect goal of social egalitarianism is to raise the genetic contribution to intelligence to as high as possible, by minimizing environmental inequalities and any negatively IQ-impacting cultural differences.^[97] If such conditions were achieved, any remaining group (but not individual) IQ differences would then be 100% hereditary: the only remaining factor that could potentially contribute to race-based outcome differences.

Practical importance

The appearance of a large practical importance for intelligence makes some scholars claim that the source and meaning of the IQ gap is a pressing social concern.^[98] The IQ gap is reflected by gaps in the academic, economic, and social factors correlated with IQ.^[99] However, some dispute the general importance of the role of IQ for real-world outcomes, especially for differences in accumulated wealth and general economic inequality in a nation. (See "Practical importance of IQ".)

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

Small differences in IQ, while relatively unimportant at the level of an individual, could theoretically have large effects at a population level. As a demonstration of these possible effects, Template:A(Y)ref used a resampling technique to calculate that according to their model a 3-point drop in average IQ would have little effect on factors like marriage, divorce, or unemployment. However, according to their model, a drop in IQ from 100 to 97-points would increase poverty rates by 11% and the proportion of children living in poverty by 13%. All else being equal, according to their model, similar rises would occur in rates of children born to single mothers, men in jail, high school drop-out, and men prevented from working due to health-related problems. In contrast, according to their model, if average IQ were to increase 3-points to 103, poverty rates would fall 25%, children living in poverty would fall 20%, and high school drop-out rates would fall 28%.^[101]

Controlling for IQ

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

Another study found that wealth, race and schooling are important to the inheritance of economic status, but IQ is not a major contributor and the genetic transmission of IQ is even less important.^[102] Conversely, controlling for IQ in the above studies also reduces the apparent effect of wealth, race and schooling due to this same correlation.

White populations are not homogeneous groups regarding real-world outcomes. For example, in the U.S. 33.6% of persons with self-reported Scottish ancestry completed college, while only 16.7% of persons with self-reported French-Canadian ancestry have done so.^[103]

For additional discussion of the effects of controlling for group differences on a variety of outcomes and groups, see Template:AYref, and Template:AYref.

Between nations

Some people have attributed differential economic growth between nations to differences in the intelligence of their populations. One example is Richard Lynn's IQ and the Wealth of Nations. The book, is sharply criticized in the peer-reviewed paper The Impact of National IQ on Income and Growth.^[104] Another peer-reviewed paper, Intelligence, Human Capital, and Economic Growth: An Extreme-Bounds Analysis, finds a strong connection between intelligence and economic growth.^[105] It has been argued that East Asian nations underachieve compared to IQ scores. One suggested explanation is that verbal IQ is more important than visuospatial IQ.^[106]

Jared Diamond's Guns, Germs and Steel instead argues that historical differences in economic and technological development for different areas can be explained by differences in geography (which affects factors like population density and spread of new technology) and differences in available crops and domesticatable animals.^[107] However, these environmental differences may operate in part by selecting for higher levels of IQ^[108]

For high-achieving minorities

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

In the United States, Jews, Indians, Japanese, and Chinese earn incomes 1.72, 1.42, 1.32, and 1.12 times the American average, respectively.^[109] Jews and East Asians have higher rates of college attendance, greater educational attainment, and are many times overrepresented in the Ivy League and many of the United States' most prestigious schools,^[110] even though affirmative action discriminates against Asians in the admissions process (relative to Whites as well as to other minorities)^[111] At Harvard, for example, Asian American and Jewish students together make up 51% of the student body, though only constituting roughly 6% of the US population.^[112] In various Southeast Asian nations, Chinese control a majority of the wealth despite being a minority of the population and are resented by the majority, in some cases being the target of violence.^[113]

Achievement in science, a high-complexity occupation in which practitioners tend to have IQs well above average, also appears consistent with some group IQ disparity.^[114] Only 0.25% of the world population is Jewish, but Jews make up an estimated 28% of Nobel prize winners in physics, chemistry, medicine, and economics.^[115] In the U.S., these numbers are 2% of the population and 40% of winners.

Some studies have shown significant variation in IQ subtest profiles between groups. In one analysis of IQ studies on Ashkenazi Jews, for example, high verbal and mathematical scores, but average or below average visuospatial scores were found.^[116] In a separate study, East Asians demonstrated high visuospatial scores, but average or slightly below average verbal scores.^[117] The professions in which these populations tend to be over-represented differ, and some believe the difference is directly related to IQ subtest score patterns asserted to exist.^[118] The high visiuospatial/average to below average verbal pattern of subtest scores has also been asserted to exist in fully assimilated third-generation Asian Americans, as well as in the Inuit and Native Americans (both of Asian origin).^[119]

Public debate and policy implications

Media portrayal

Utility of research and racism

One criticism of race and intelligence research, regardless of whether racial differences are genetic or not, questions its utility. It's been argued that society might actually be better off "with an untruth: that there is no good reason for this [racial] inequality, and therefore society is at fault and we must try harder."^[120]

The Southern Poverty Law Center has stated: "Race science has potentially frightening consequences, as is evident not only from the horrors of Nazi Germany, but also from the troubled racial history of the United States. If white supremacist groups had their way, the United States would return to its dark days. In publication after publication, hate groups are using this 'science' to legitimize racial hatred."^[121]

Another cricism is that it "“causes major psychological harm to millions of black children and adults (with respect to self-esteem, career expectations, interracial relationships, etc.)".[15]

Some scientists, including W. D. Hamilton,^[122] considered by some to be one of the greatest evolutionary theorists of the 20th century,^[123] argue that suppressing race and intelligence research is actually more harmful than dealing with it honestly. Linda Gottfredson, a prominent professor who's work has been influential in U.S. workplace policy and who's also a Pioneer fund grantee argues:

Lying about race differences in achievement is harmful because it foments mutual recrimination. Because the untruth insists that differences cannot be natural, they must be artificial, manmade, manufactured. Someone must be at fault. Someone must be refusing to do the right thing. It therefore sustains unwarranted, divisive, and ever-escalating mutual accusations of moral culpability, such as Whites are racist and Blacks are lazy.^[124]

Steven Pinker argues that opposition to racism is based on moral, not scientific assumptions, and is not vulnerable to being disproved by bioscientific advances. "The case against bigotry is not a factual claim that humans are biologically indistinguishable. It is a moral stance that condemns judging an individual according to the average traits of certain groups...".^[125] Pinker suggests that intellectual life may not at present be prepared to deal with this area of inquiry.^[126]

Coming advances in genetics and genomics are expected to soon provide the ability to test hypotheses about group differences rigorously, whether between races, sexes, or other groups, in cognitive traits or temperament, musical or athletic talent, or in responses to biomedical treatments.^[17] Some scientists predict this will be the source of one of the biggest social and intellectual issues of the coming decades.^[127]

Accusations of bias

Steven Pinker argues a fear of the implications of the science of human nature ("mind, brain, genes, and evolution") has led to the perception that these are dangerous ideas.^[128] Pinker argues this has resulted in a denial of human nature in which "large swaths of the intellectual landscape have been reengineered to try to rule [...] hypotheses out a priori (race does not exist, intelligence does not exist, the mind is a blank slate inscribed by parents)." Scientists working in these areas have in the past been targets of censorship, violence, and comparisons to Nazis.^[129]

Pioneer Fund

One of the largest source of funding for proponents of the partly genetic interpretation,^[130] the Pioneer Fund, has been criticized^[131] as having a eugenic and racist political agenda, and has been characterized by the Southern Poverty Law Center as a "hate group," using the definition "attack[ing] or malign[ing] an entire class of people, typically for their immutable characteristics" and citing a claimed racist and Nazi-sympathizer history.^[132] Anti-racist Searchlight Magazine notes Pioneer head J. Phillipe Rushton has given a speech at an American Renaissance meeting that Searchlight describes as a "veritable 'who’s who' of American white supremacy."^[133] Prominent critic Ulric Neisser, who was the chairman of the APA's 1995 taskforce on intelligence research regards the fund as having had an ultimately positive effect.^[134] Some critics have found it significant that some of the prominent researchers advancing genetic explanations have also opposed affirmative action and school integration.^[135]

In the early 1990s, the University of Delaware imposed a "prohibition on the receipt of funding (by a faculty member) from the Pioneer Fund, amidst accusations that the Fund had a "history of supporting racism, anti-semitism and other discriminatory practices".[16] Grantee Linda Gottfredson fought a two-year battle with the university before it rescinded its prohibition, arguing that a ban on funding restricted academic freedom.[17]

There is no evidence that the Pioneer Fund has biased the research. However, one critic notes "The real question is not did the Pioneer Fund make you alter your scientific findings but why did the Pioneer Fund fund you?""It's not so much a question of whether or not they influence an individual scientist but rather the scientists they choose to fund in the first place, Weizmann added."[18]

Policy implications

See also: Intelligence and public policy

The public policy implications of IQ and race research are possibly the greatest source of controversy surrounding this issue. For example, the conservative policy recommendations of Herrnstein and Murray in The Bell Curve were denounced by many. Indeed, even proponents of a partly genetic interpretation of the IQ gap, such as Template:A(Y)ref and Template:A(Y)ref, argue that their interpretation does not in itself demand any particular policy response: while a conservative/libertarian commentator may feel the results justify reductions in affirmative action, a liberal commentator may argue from a Rawlsian point of view (that genetic advantages are undeserved and unjust) for substantial affirmative action.^[136] According to the "Mainstream Science on Intelligence"; statement published in Intelligence in 1997:

The research findings neither dictate nor preclude any particular social policy, because they can never determine our goals. They can, however, help us estimate the likely success and side-effects of pursuing those goals via different means.^[137]

While not specifically race-related, policies focused on geographical regions or nations may have disproportionate influences on certain racial groups and on cognitive development. Differences in healthcare, nutrition, regulation of environmental toxins, and geographic distribution of diseases and control strategies between the developing world and developed nations have all been subjects of policies or policy recommendations (see health and nutrition policies relating to intelligence).

Finally, germinal choice technology may one day be able to select or change directly alleles found to influence intelligence or racially identifying traits (such as skin color; see gene SLC24A5), making them susceptible to biotechnological intervention.^[138]

End material

See also

• Brain to body mass ratio
• Craniometry
• Hominid intelligence
• Neuroscience and intelligence
• Race and crime
• Sex and intelligence
• Scientific racism
• The Mismeasure of Man

Notes

References

External links

Collective Statements

• The Wall Street Journal: Mainstream Science on IntelligencePDF
• APA Task Force Examines the Knowns and Unknowns of Intelligence
• Statement on "Race" and Intelligence. American Anthropological Association. Adopted December 1994.

Review Papers

• June 2005 issue of Psychology, Public Policy, and Law, Vol. 11, No. 2.
  • Thirty Years of Research on Race Differences in Cognitive Ability J. Philippe Rushton & Arthur R. Jensen
  • There Are No Public-Policy Implications Robert J. Sternberg
  • What if the Hereditarian Hypothesis is True? Linda S. Gottfredson
  • Heredity, Environment, and Race Differences in IQ Richard E. Nisbett
  • The Cultural Malleability of Intelligence and Its Impact on the Racial/Ethnic Hierarchy Lisa Suzuki & Joshua Aronson
  • Wanted: More Race Realism, Less Moralistic Fallacy J. Philippe Rushton & Arthur R. Jensen
• Race, Genetics and IQ Richard E. Nisbett (PDF)
• The Inequality Taboo Charles Murray
• The Black-White Test Score Gap (1998) online (page-image) version of ISBN 0815746091

Others

• Crippled by Their Culture - Race doesn't hold back America's black rednecks. Nor does racism by Thomas Sowell
• Race and IQ: Part 1, Part 2, Part 3 by Thomas Sowell
• The Skeptic's Dictionary entry on IQ and race
• (Skeptic Magazine): Two book reviews, by Paul R. Gross and Alondra Oubre, of Sarich’s and Miele’s book, Race: The Reality of Human Differences
• Criticism on source material of Bell Curve book
• Poverty and Brain Development in Early Childhood 1999 report
• Miscellaneous articles by Richard Lynn et al.
• Are IQ Tests Biased?
• Scholars Provide an Overview of Explanations for Black-White Test Score Gap
• School Readiness: Closing Racial and Ethnic Gaps
• La Griffe du Lion - pseudonymously released statistical analyses on this and related subjects. (Review)
• A review of the field (Jan. 2006) Kohn, Marek, "This racist undercurrent in the tide of genetic research: As taboos fall away, there's a danger that denial of racial difference will be replaced with uncritical acceptance," The Guardian.
• "The Lessons of the Ashkenazim: Groups and Genes," Steven Pinker, June 2006, The New Republic.
• Are all races equally intelligent? -- Or: When is knowledge knowledge? by John J. Ray
• Black-White Gap in IQ Scores Closing, Study Finds

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