Race and intelligence are broad terms with many meanings that are often used to describe and measure human beings. The possibility of a relationship between race and intelligence has been a topic of considerable speculation, study, and debate, especially since the 19th century. ^[1] The contemporary debate focuses on the nature, causes, and importance of racial and ethnic differences in intelligence test scores and other measures of cognitive ability.

In the centuries after 1500 when European explorers came into contact with peoples around the world they became aware of wide differences in culture, the use of technology and political organization. They assumed that those difference arose from differences in innate biological ability. European countries would soon colonize much of the rest of the world. The colonists justified their power with the belief that the native inhabitants were intellectually inferior. These beliefs were not formalized until the 19th and early 20th century when some scholars attempted to scientifically prove the inferiority of non-white races using various theories that are now referred to as scientific racism. Such theories became quite popular, justifying poor outcomes and the harsh treatment of "the inferior races." ^[2].The Eugenics movements in Europe and the US seized upon these theories and they were instrumental in the Nazi policies of racial purity.

The end of the second world war brought revelations of human experimentaion and the T-4 Euthanasia Programin which roughly 200,000 mentally and physically disabled Germans were killed, and about 400,000 sterilized. Consequently there was a backlash against studies involving group differences. 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. It is against this backdrop that the study of racial differences as a discipline was largely abandoned by many westernized countries ^[3].

The chief protagonist in the study of group differences after the second world war has been Arthur Jensen. Much of the research on intelligence currently cited is based on IQ testing in the United States. Modern theories and research on race and intelligence are often grounded in two controversial assumptions:

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

See also Race and Race and genetics

The existence or non-existence of race still remains a controversial subject. On one extreme there are those scholars who view race as a social construct with no biological basis. On the other hand there are scholars who believe that the major human populations not only differ in physical appearance but in other biological traits such as behaviour and intellect. The findings of the Human genome project indicate that the DNA of all humans is on 99.9 percent alike and that most of the genetic differences are found within population rather than between populations. However the 0.1% genetic difference is still the subject of much controversy with some claiming that it is significant enough to warrant a genetic classification of the human population.

There is no one accepted definition of intelligence and its nature is widely debated. In general it is a property of mind that encompasses many related abilities, such as the capacities to reason, plan, solve problems, think abstractly, comprehend ideas and language, and learn. The major controversy regarding intelligence is how effectively it can be measured.

In this regard the most important theories are related to the general intelligence factor or g factor. The idea behind the g factor it is that a child who does well in one subject for example math will tend to do well in another such as vocabulary. Scholars view these intelligences to be highly correlated. By usinge factor analysis to measure the correlation between the various intelligences they can arrive at a single number g that is representative of the person's intelligence. IQ tests are considered the best measure of the g factor. Intelligence measured by IQ tests is the single most effective predictor of child's later performance in school and on the job. It also predicts many other aspects of wellbeing, including a person's chances of divorcing, dropping out of high school, being unemployed or having illegitimate children.

Other scholars are critical of the g factor. Stephen Jay Gould referred to it as statistical hocus pocus. He is quoted as saying "Mental ability tests measure differences in tasks that will soon be performed for all of us by computational agents. Such abilities probably have nothing to do with genius."

Other scholars view IQ tests and the g factor as a very narrow view of intelligence that does not represent the full complexities of the human brain which is still far from being fully understood. They argue that differences in test scores do not represent the overall difference in intelligence between individuals or groups since many other cognitive abilities that are under voluntary control by the brain are left out of pencil and paper tests. Psychologist Howard Gardner says there are multiple forms of intelligence, which he calls multiple intelligences not often captured by regular IQ tests. Multiple Intelligences can include the following: linguistic; logical-mathematical; spatial; bodily-kinesthetic; musical; naturalistic; interpersonal and intrapersonal. This raises the possibility that there it may not be possible to construct a single meaningful ordering on intelligence.

His theory is also based on the study of autistic savants who on one hand have severely impaired social skills and the other hand have some unusual ability, in the case of prodigous savants that ability exceeds the abilities of most humans. Though only a few prodigious savants exist, there presence has created difficulties in defining what intelligence is. Scholars such as Gardner question whether the g factor is a biological reality since it entails that all forms of intelligence, such as verbal or mathematical be correlated. However savants may exhibit super human skills in one area such as arithmetic or calendric calculation and be mentally retarded in others.

Triarchic theory of intelligence is another theory that was formulated by Robert J. Sternberg which suggests that there are three forms of intelligence, analytical, practical and creative. He contends that IQ tests only capture analytical intelligence and not practical or creative intelligence.

The scope of recent work in the study of racial difference is at present largely restricted to the United States. Many other countries have historically not collected information on race.

In France for example it is illegal to collect any information on race. The French ideal of "liberty, equality, fraternity" considers all people should be equally French with no differentiation ^{[4] [5]}. any. However the issues of discrimination against minority groups has resulted in calls for racial demographics to be included to highlight possible racial discrepancies.

Latin american countries have only recently began to collect racial demographics to highlight possible discrimination against its black and Native american population. However the populations in latin America are highly admixed and race and class are constructed differently. For example in Brazil racial categories are based on physical appearance rather than ancestry. Consequently full siblings may belong to different "racial categories" ^[6].

Asian countries though ethnically very diverse are racially homogeneous. Asian cultures tend to value hard work rather than innate talent. For example Howard Gardner noted Americans believe that if they do not do well, it is because they lack talent and ability; Asians believe it is because they did not work hard enough. A Japanese saying has it, Fail with five hours sleep, pass with four. Consequently not much emphasis is placed on IQ studies as in the United States ^[3]

Literacy rates in developing countries are relatively low compared to developed nations though the gap may be narrowing. Consequently policy in developing countries is directed more at improving literacy and providing basic education than trying to boost IQ scores. For example only 61% of India's population of 1 billion are literate. However India's intellectuals are important contributors to global science and technology.

In contrast to Latin America multiracial populations the United states has maintained a bifurcated racial system of blacks and whites. The United States is unique among many countries in that for the last four centuries it has maintained two distinct endogamous populations that live side by side in several cities ^[6]. The US also accurate racial demographics demographic data. Since IQ tests were adopted by the army in 1917 the US has close to 100 years of race and IQ test

The modern controversy surrounding intelligence and race focuses on the results of IQ studies conducted during the 20th century, mainly in the United States and some other industrialized nations. In almost every testing situation where tests were administered and evaluated correctly, the mean IQ of Blacks was approximately one standard deviation below that of Whites. Attempted world-wide compilations of average IQ by race generally place Ashkenazi Jews at the top, followed by East Asians, Whites, Hispanics, Sub-Saharan Africans and Australian Aborigines (See IQ and the Wealth of Nations for an attempted compilation of average IQ for different nations and a discussion of associated measurement problems). The IQ scores vary greatly among different nations for the same group. Blacks in Africa score much lower than Blacks in the US. However contrary to indications from the IQ and the Wealth of Nations study, the majority of blacks enrolled in Ivy League Universities in the US are either from Africa or the Caribbean. Notable examples include Barack Obama and his father Obama Sr. The chairperson of the sociology department at Harvard University stated:

Since they come from majority-black countries, they are less psychologically handicapped by the stigma of race.

Thus this is seen as evidence that racial prejudice combined with the status of being a minority that has been excluded from society does have a significant effect on academic achievement ^{[7] [8]}.However, according to the African-American economist Thomas Sowell racism and the legacy of slavery do not stand up under scrutiny of historical facts as explanations to the IQ disparity between Blacks and Whites. He argues that the dysfunctional black culture is the reason for the low IQ and poor academic performance of black Americans. ^[9].

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 (Roth et al. 2001). 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 students in 10th grade, and Asian students in 8th grade; Hispanic students do only slightly better than Blacks. Whether the gaps are narrowing or not is debated.

The consensus among intelligence researchers is that IQ differences between individuals of the same race reflect (1) real, (2) functionally/socially significant, and (3) substantial differences in the general intelligence factor. ^{[10] [11] [12] [13] [14] [15] [16] [17] [18] [19]} A consensus also exists for the view that average IQ differences between races reflect (1) real and (2) significant differences in the same g factor.^{[ citation needed]} However, it is a matter of debate whether IQ differences between races in the U.S. are (3a) entirely environmental or (3b) partly genetic. Several published consensus statements agree that the large differences between the average IQ scores of Blacks and Whites in the U.S. cannot be attributed to biases in test construction, nor can they be explained just by simple differences in socio-economic status, however they are still well with in the range that may be attributed to other environmental factors. The debate over causal explanations focuses predominately on the IQ gaps seen in developed countries. There is a consensus that IQ in developing countries is depressed due at least in part to poor health and nutrition.

The Nature versus Nurture debate over the black white gap in the US centers on the relative contribution of environment and genes. Scholars such as Jensen, Rushton and the authors of the Bell curve propose a genetic hypothesis, whereas other scholars believe that environmental factors are at play.

The genetic hypothesis which posits that the 15 point IQ difference between blacks and whites is largely due to genetic factors. Rushton and Jensen examined 10 categories of research evidence from around the world to contrast "a hereditarian model" (50% genetic-50% cultural) and a culture-only model (0% genetic-100% cultural). In the article "Thirty Years of Research on Race Differences in Cognitive Ability" published in the APA journal Psychology, Public Policy and Law they cite the following evidence to support the hereditarian model: ^{[20] [21]}

• 1)The Worldwide Pattern of IQ Scores. East Asians average higher on IQ tests than Whites, both in the U. S. and in Asia, even though IQ tests were developed for use in the Euro-American culture. Around the world, the average IQ for East Asians centers around 106; for Whites, about 100; and for Blacks about 85 in the U.S. and 70 in sub-Saharan Africa.

• 2)Race Differences are Most Pronounced on Tests that Best Measure the General Intelligence Factor (g). Black-White differences, for example, are larger on the Backward Digit Span test than on the less g loaded Forward Digit Span test.

• 3)The Gene-Environment Architecture of IQ is the Same in all Races, and Race Differences are Most Pronounced on More Heritable Abilities. Studies of Black, White, and East Asian twins, for example, show the heritability of IQ is 50% or higher in all races.

• 4)Brain Size Differences. Studies using magnetic resonance imaging (MRI) find a correlation of brain size with IQ of about 0.40. Larger brains contain more neurons and synapses and process information faster. Race differences in brain size are present at birth. By adulthood, East Asians average 1 cubic inch more cranial capacity than Whites who average 5 cubic inches more than Blacks.

• 5)Trans-Racial Adoption Studies. Race differences in IQ remain following adoption by White middle class parents. East Asians grow to average higher IQs than Whites while Blacks score lower. The Minnesota Transracial Adoption Study followed children to age 17 and found race differences were even greater than at age 7: White children, 106; Mixed-Race children, 99; and Black children, 89.

• 6) Racial Admixture Studies. Black children with lighter skin, for example, average higher IQ scores. In South Africa, the IQ of the mixed-race "Colored" population averages 85, intermediate to the African 70 and White 100.

• 7) IQ Scores of Blacks and Whites Regress toward the Averages of Their Race. Parents pass on only some exceptional genes to offspring so parents with very high IQs tend to have more average children. Black and White children with parents of IQ 115 move to different averages--Blacks toward 85 and Whites to 100.

• 8) Race Differences in Other "Life-History" Traits. East Asians and Blacks consistently fall at two ends of a continuum with Whites intermediate on 60 measures of maturation, personality, reproduction, and social organization. For example, Black children sit, crawl, walk, and put on their clothes earlier than Whites or East Asians.

• 9) Race Differences and the Out-of-Africa theory of Human Origins. East Asian-White-Black differences fit the theory that modern humans arose in Africa about 100,000 years ago and expanded northward. During prolonged winters there was evolutionary selection for higher IQ created by problems of raising children, gathering and storing food, gaining shelter, and making clothes.

• 10) Culture-only theories do not explain the highly consistent pattern of race differences in IQ, especially the East Asian data. No interventions such as ending segregation, introducing school busing, or "Head Start" programs have reduced the gaps as culture-only theory would predict.

Regarding the IQ gaps in the U.S., it has also been suggested that Black culture disfavors academic achievement and fosters an environment that is damaging to IQ (Boykin, 1994). Likewise, it is argued that a persistence of racism reinforces this negative effect. John Ogbu (1978, 1994) has developed a hypothesis that the condition of being a "caste-like minority" affects motivation and achievement, depressing IQ. Many anthropologists have argued that intelligence is a cultural category; some cultures emphasize speed and competition more than others, for example. Even proponents of the view that the IQ gap is caused partly by genetic differences recognize that non-genetic factors are likely involved. Non-genetic biological factors that affect IQ have been proposed. 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. The Flynn effect is often cited as evidence that average IQ scores have changed greatly and rapidly, for reasons poorly understood, noting that average IQ in the US may have been below 75 before the start of this effect, and thus some argue that the IQ gap between races could change in the future or is changing, especially if the effect started earlier for Whites.

Some researchers argue that the IQ gap is partly genetic. To support these claims, they most often cite: (1) worldwide Black-White-East Asian differences in IQ, reaction time, and brain size; (2) correlation between the extent to which IQ subtests measure g, the magnitude of Black-White-East Asian average IQ differences on those subtests (called Spearman's hypothesis), and measures of those subtests' heritability; and (3) the rising heritability of IQ with age (within races) and the disappearance by adulthood of shared environmental effects on IQ (e.g., family income, education, and home environment). Critics argue that there are counter-arguments to these arguments, and present results they see as contradicting a genetic explanation (which in turn are criticized by those arguing for a genetic role), such as studies on ancestry, adoption, and cross-fostering. For example, skin color among US blacks has an extremely low correlation (r=0.17) with IQ. ^[22] However, a 2002 study ^[23] relates that skin colour is not a reliable indicator to ancestry in some cases, prompting one of the researchers, Sergio Pena, to say: "There is wide agreement among anthropologists and human geneticists that, from a biological standpoint, human races do not exist", and further: "Our study makes clear the hazards of equating colour or race with geographical ancestry and using interchangeably terms such as white, Caucasian and European on one hand, and black, Negro or African on the other, as is often done in scientific and medical literature." ^[24]

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

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. ^[25] Another peer-reviewed paper, Intelligence, Human Capital, and Economic Growth: An Extreme-Bounds Analysis, finds a strong connection between intelligence and economic growth. ^[26] It has been argued that East Asian nations underachieve compared to IQ scores.

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. ^[27] However,psychologist John Philippe Rushton suggests these environmental differences may operate in part by selecting for higher levels of IQ ^[28] There is no evidence to suggest that such selective forces occur in regards to IQ. Consensus at the American Psychological Association is that a partly genetic hypothesis is as of now, inadequate in explaining differences in IQ among population groups. ^[29]

See also The genome and intelligence

Some scholars have proposed that in order to make a racial hypothesis about intelligence the genes for intelligence need to be identified along with their frequencies in the various populations. However recent studies attempting to find regions in the genome relating to intelligence have had little success. A recent study used several hundred people in two groups, one with a very high IQ, average 160, and a control group with an average IQ of 102. The study used 1,842 DNA markers and put them through a five step inspection process to eliminate false positives. By the fifth step the study could not find a single gene that was related to intelligence. Critics of these studies say the failure to find a specific gene associated with intelligence is indicative of the complex nature of intelligence. They contend that intelligence is probably under the influence of several genes. Some estimate that as much as 40% of the genome may contribute to intelligence. ^[30]

Recently scientists at the University of Chicago identified two genes, microcephalin and ASPM. Mutations in these genes are associated with brain size abnormality, microcephaly . The normal variants are found at high frequencies in Asian and European populations but they are not found among Sub-Saharan Africans. The scientists stated that microcephalin may have arisen some 37,000 ago coinciding with upper paleolithic transitions in Europe. They also stated that a variant of APSM arose about 5,800 years ago roughly correlating with the development of written language, spread of agriculture and development of cities. They thus believe these two genes conferred some cognitive abilities upon Asians and Europeans. ^[31] These studies have been criticized saying it was far from clear that the new alleles conferred any cognitive advantage or had spread for that reason.

Other scholars have criticized the University of Chicago scientists because they made claims about these genes without undertaking any direct experimentation to test their hypothesis on increased intelligence and brain size. Subsequently when these experiments were done, no relationship was found between these genes and intelligence or brain size. ^{[32] [33]}

In the US, Critics of these studies also say that as long as social and environmental disparities between the races exist it will be impossible to scientifically test whether there are any genetic differences in IQ between the various populations. They propose that if the historical effects of poverty and social bigotry were eliminated and differences in IQ between the races still persisted then there might be some utility in such research. ^[34]

Race and intelligence are sometimes portrayed as related in media. People of various races have been portrayed as more or less intelligent in media such as films, books, and newspapers. Likewise, reporting on research into race and intelligence has been criticized: either for giving scientific theories of race too much credit, or for rejecting the theories of some researchers in the name of racial harmony.

Critics of contemporary media have highlighted portrayals of minorities as less intelligent ^[35] (or in the case of Asians, on occasion more intelligent ^[36]) in films and movies. Entman and Rojeki assert that media images of Blacks may have profound effects on the perceptions by both Blacks and Whites about black intellectual potential. ^[37]

Even so-called positive images of Black people can lead to stereotypes about intelligence. In Darwin's Athletes: how sport has damaged Black America and preserved the myth of race John Hoberman writes that the prominence of African-American athletes encourages a de-emphasis on academic achievement in black communities. ^[38]Film director Spike Lee explains that these images have negative impacts "In my neighborhood, we looked up to athletes, guys who got the ladies, and intelligent people," said Lee. "[Now] If you're intelligent, you're called a white guy or girl." ^[39]

Blacks are not the only ethnic group in the US to be stereotyped as stupid. Shortly after the large waves of immigration in the 19th century and number of immigrant groups such as the Irish were stereotyped as being more closely related to apes or dogs and therefore intellectually inferior. ^[40] This changed after the definition of "white" was expanded to include the Irish. ^[41] Unlike other racial stereotypes of intelligence, the 19th century pseudo-scientific ideas about Irish stupidity and inferiority are not supported by most hereditarian proponents of modern race research^{[ citation needed]}. Other stereotypes, of Blacks, Jews and Asians endure to this day ^[42] as do the findings of Hereditarian researchers about these groups.

Other aspects of the media portrayal of race and intelligence include recent books asserting a genetic cause for group differences and surveys or consensus statements made by groups of scientists.

Theories of race and intelligence have been challenged on grounds of their utility. Critics want to know what purpose such research could serve and why it has been an intense an area of focus for a few researchers. Some defend the research, saying it has egalitarian aims or that it is pure science, others say that the true motivation for the research is the same as that of the eugenics movement and other forms of scientific racism. ^{[43] [44]} Even supporters of intelligence research have described such research as analogous to "working with dynamite" or "dangerous play" in sports. ^[45]

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

Sociologist and demographer Reanne Frank says that some race and intelligence research has been abused "The most malignant are the "true believers," who subscribe to the typological distinctions that imply hierarchical rankings of worth across different races. Although this group remains small, the members' work is often widely publicized and well known (e.g., Herrnstein and Murray 1994; Rushton 1991)" ^[46]

Proponents of genetic explanations of race/IQ correlation have often been criticized both of scientific misconduct and of their intimate links with groups that have historic ties to Nazis and eugenics of the early 19th century, such as the Pioneer Fund. The Pioneer Fund has been characterized by the Southern Poverty Law Center as a hate group.

Proponents of genetic explanations of race/IQ correlation have in turn accused their critics of suppressing scientific debate in the name of political correctness. They claim harassment and interference with both their work and funding.

See also: Intelligence and public policy

Public policy implications of IQ and race research are one of the greatest sources of controversy surrounding this issue. Regardless of the source of the gap, most educators agree that it must be addressed. They often advocate equitable funding for education. ^{[47] [48]}

Some proponents of a genetic interpretation of the IQ gap, such as Rushton and Jensen 2005a harvnb error: no target: CITEREFRushton_and_Jensen2005a ( help) and Gottfredson 2005b harvnb error: no target: CITEREFGottfredson2005b ( help), have sometimes argued that their interpretation does not in itself demand any particular policy response: while a conservative/ libertarian commentator ^[49] may feel the results justify, for example, reductions in affirmative action, a liberal commentator may argue from a Rawlsian point of view (that genetic advantages are undeserved and unjust) for substantial affirmative action. ^[50] Since all races have representatives at all levels of the IQ curve, this means any policy based on low IQ affects members of all races.

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 health care, nutrition, regulation of environmental toxins, and geographic distribution of diseases and control strategies between the developing world and developed nations have all been subjects of policies or policy recommendations (see Health and intelligence).

Finally, Gregory Stock, writes that 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. ^[51]