Race And Intelligence
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Discussions of race and intelligence – specifically, claims of differences in intelligence along racial lines – have appeared in both
popular science ''Popular Science'' (also known as ''PopSci'') is an American digital magazine carrying popular science content, which refers to articles for the general reader on science and technology subjects. ''Popular Science'' has won over 58 awards, incl ...
and
academic research Research is " creative and systematic work undertaken to increase the stock of knowledge". It involves the collection, organization and analysis of evidence to increase understanding of a topic, characterized by a particular attentiveness ...
since the modern concept of
race Race, RACE or "The Race" may refer to: * Race (biology), an informal taxonomic classification within a species, generally within a sub-species * Race (human categorization), classification of humans into groups based on physical traits, and/or s ...
was first introduced. With the inception of
IQ testing An intelligence quotient (IQ) is a total score derived from a set of standardized tests or subtests designed to assess human intelligence. The abbreviation "IQ" was coined by the psychologist William Stern for the German term ''Intelligenz ...
in the early 20th century, differences in average test performance between racial groups were observed, though these differences have fluctuated and in many cases steadily decreased over time. Further complicating the issue, modern science has shown race to be a
social construct Social constructionism is a theory in sociology, social ontology, and communication theory which proposes that certain ideas about reality, physical reality arise from collaborative consensus, instead of pure observation of said reality. The ...
rather than a biological reality, and
intelligence Intelligence has been defined in many ways: the capacity for abstraction, logic, understanding, self-awareness, learning, emotional knowledge, reasoning, planning, creativity, critical thinking, and problem-solving. More generally, it can b ...
has no undisputed definition. The validity of IQ testing as a metric for
human intelligence Human intelligence is the intellectual capability of humans, which is marked by complex cognitive feats and high levels of motivation and self-awareness. High intelligence is associated with better outcomes in life. Through intelligence, humans ...
is itself disputed. Today, the scientific consensus is that
genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar wor ...
does not explain differences in IQ test performance between groups, and that observed differences are environmental in origin.
Pseudoscientific Pseudoscience consists of statements, beliefs, or practices that claim to be both scientific and factual but are incompatible with the scientific method. Pseudoscience is often characterized by contradictory, exaggerated or unfalsifiable claim ...
claims of inherent differences in intelligence between races have played a central role in the history of
scientific racism Scientific racism, sometimes termed biological racism, is the pseudoscience, pseudoscientific belief that empirical evidence exists to support or justify racism (racial discrimination), racial inferiority, or racial superiority.. "Few tragedies ...
. The first tests showing differences in IQ scores between different population groups in the United States were the tests of
United States Army The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cla ...
recruits in
World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
. In the 1920s, groups of
eugenics Eugenics ( ; ) is a fringe set of beliefs and practices that aim to improve the genetic quality of a human population. Historically, eugenicists have attempted to alter human gene pools by excluding people and groups judged to be inferior or ...
lobbyists argued that these results demonstrated that
African Americans African Americans (also referred to as Black Americans and Afro-Americans) are an ethnic group consisting of Americans with partial or total ancestry from sub-Saharan Africa. The term "African American" generally denotes descendants of ens ...
and certain immigrant groups were of inferior intellect to
Anglo-Saxon The Anglo-Saxons were a Cultural identity, cultural group who inhabited England in the Early Middle Ages. They traced their origins to settlers who came to Britain from mainland Europe in the 5th century. However, the ethnogenesis of the Anglo- ...
white people White is a racialized classification of people and a skin color specifier, generally used for people of European origin, although the definition can vary depending on context, nationality, and point of view. Description of populations as ...
, and that this was due to innate biological differences. In turn, they used such beliefs to justify policies of
racial segregation Racial segregation is the systematic separation of people into race (human classification), racial or other Ethnicity, ethnic groups in daily life. Racial segregation can amount to the international crime of apartheid and a crimes against hum ...
. However, other studies soon appeared, contesting these conclusions and arguing instead that the Army tests had not adequately controlled for environmental factors, such as socioeconomic and educational inequality between black people and white people. Later observations of phenomena such as the
Flynn effect The Flynn effect is the substantial and long-sustained increase in both fluid and crystallized intelligence test scores that were measured in many parts of the world over the 20th century. When intelligence quotient (IQ) tests are initially standa ...
and disparities in access to
prenatal care Prenatal care, also known as antenatal care, is a type of preventive healthcare. It is provided in the form of medical checkups, consisting of recommendations on managing a healthy lifestyle and the provision of medical information such as materna ...
also highlighted ways in which environmental factors affect group IQ differences. In recent decades, as understanding of
human genetics Human genetics is the study of inheritance as it occurs in human beings. Human genetics encompasses a variety of overlapping fields including: classical genetics, cytogenetics, molecular genetics, biochemical genetics, genomics, population gene ...
has advanced, claims of inherent differences in intelligence between races have been broadly rejected by scientists on both
theoretical A theory is a rational type of abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with such processes as observational study or research. Theories may be ...
and
empirical Empirical evidence for a proposition is evidence, i.e. what supports or counters this proposition, that is constituted by or accessible to sense experience or experimental procedure. Empirical evidence is of central importance to the sciences and ...
grounds.


History of the controversy

Claims of differences in intelligence between races have been used to justify
colonialism Colonialism is a practice or policy of control by one people or power over other people or areas, often by establishing colonies and generally with the aim of economic dominance. In the process of colonisation, colonisers may impose their relig ...
,
slavery Slavery and enslavement are both the state and the condition of being a slave—someone forbidden to quit one's service for an enslaver, and who is treated by the enslaver as property. Slavery typically involves slaves being made to perf ...
,
racism Racism is the belief that groups of humans possess different behavioral traits corresponding to inherited attributes and can be divided based on the superiority of one race over another. It may also mean prejudice, discrimination, or antagonism ...
,
social Darwinism Social Darwinism refers to various theories and societal practices that purport to apply biological concepts of natural selection and survival of the fittest to sociology, economics and politics, and which were largely defined by scholars in We ...
, and racial
eugenic Eugenics ( ; ) is a fringe set of beliefs and practices that aim to improve the genetic quality of a human population. Historically, eugenicists have attempted to alter human gene pools by excluding people and groups judged to be inferior or ...
s. Racial thinkers such as
Arthur de Gobineau Joseph Arthur de Gobineau (; 14 July 1816 – 13 October 1882) was a French aristocrat who is best known for helping to legitimise racism by the use of scientific racist theory and "racial demography", and for developing the theory of the Ary ...
relied crucially on the assumption that black people were innately inferior to white people in developing their ideologies of
white supremacy White supremacy or white supremacism is the belief that white people are superior to those of other races and thus should dominate them. The belief favors the maintenance and defense of any power and privilege held by white people. White su ...
. Even Enlightenment thinkers such as
Thomas Jefferson Thomas Jefferson (April 13, 1743 – July 4, 1826) was an American statesman, diplomat, lawyer, architect, philosopher, and Founding Fathers of the United States, Founding Father who served as the third president of the United States from 18 ...
, a slave owner, believed black people to be innately inferior to white people in physique and intellect. At the same time, prominent examples of African-American genius such the
autodidact Autodidacticism (also autodidactism) or self-education (also self-learning and self-teaching) is education without the guidance of masters (such as teachers and professors) or institutions (such as schools). Generally, autodidacts are individua ...
and abolitionist
Frederick Douglass Frederick Douglass (born Frederick Augustus Washington Bailey, February 1817 or 1818 – February 20, 1895) was an American social reformer, abolitionist, orator, writer, and statesman. After escaping from slavery in Maryland, he became ...
, the pioneering sociologist W. E. B. Du Bois, and the poet
Paul Laurence Dunbar Paul Laurence Dunbar (June 27, 1872 – February 9, 1906) was an American poet, novelist, and short story writer of the late 19th and early 20th centuries. Born in Dayton, Ohio, to parents who had been enslaved in Kentucky before the American C ...
stood as high-profile counterexamples to widespread stereotypes of black intellectual inferiority.Stewart, Roderick M. 1999. "The Claims of Frederick Douglass Philosophically Considered." Pp. 155–56 in ''Frederick Douglass: A Critical Reader'', edited by B. E. Lawson and F. M. Kirkland. Wiley-Blackwell. . "Moreover, though he does not make the point explicitly, again the very fact that Douglass is ably disputing this argument on this occasion celebrating a select few's intellect and will (or moral character)—this fact constitutes a living counterexample to the narrowness of the pro-slavery definition of humans."


Early IQ testing

The first practical intelligence test was developed between 1905 and 1908 by
Alfred Binet Alfred Binet (; 8 July 1857 – 18 October 1911), born Alfredo Binetti, was a French psychologist who invented the first practical IQ test, the Binet–Simon test. In 1904, the French Ministry of Education asked psychologist Alfred Binet to ...
in France for school placement of children. Binet warned that results from his test should not be assumed to measure innate intelligence or used to label individuals permanently. Binet's test was translated into English and revised in 1916 by
Lewis Terman Lewis Madison Terman (January 15, 1877 – December 21, 1956) was an American psychologist and author. He was noted as a pioneer in educational psychology in the early 20th century at the Stanford Graduate School of Education. He is best known f ...
(who introduced IQ scoring for the test results) and published under the name
Stanford–Binet Intelligence Scales The Stanford–Binet Intelligence Scales (or more commonly the Stanford–Binet) is an individually-administered intelligence test that was revised from the original Binet–Simon Scale by Alfred Binet and Theodore Simon. The Stanford–Binet In ...
. In 1916 Terman wrote that Mexican-Americans, African-Americans, and Native Americans have a mental "dullness
hat A hat is a head covering which is worn for various reasons, including protection against weather conditions, ceremonial reasons such as university graduation, religious reasons, safety, or as a fashion accessory. Hats which incorporate mecha ...
seems to be racial, or at least inherent in the family stocks from which they come." The US Army used a different set of tests developed by
Robert Yerkes Robert Mearns Yerkes (; May 26, 1876 – February 3, 1956) was an American psychologist, ethologist, eugenicist and primatologist best known for his work in intelligence testing and in the field of comparative psychology. Yerkes was a pioneer ...
to evaluate draftees for World War I. Based on the Army's data, prominent psychologists and eugenicists such as Henry H. Goddard, Harry H. Laughlin, and Princeton professor
Carl Brigham Carl Campbell Brigham (May 4, 1890 – January 24, 1943) was an American eugenicist and professor of psychology at Princeton University's Department of Psychology and a pioneer in the field of psychometrics. He sat on the advisory council of t ...
wrote that people from southern and eastern Europe were less intelligent than native-born Americans or immigrants from the Nordic countries, and that black Americans were less intelligent than white Americans. The results were widely publicized by a lobby of anti-immigration activists, including the conservationist and theorist of
scientific racism Scientific racism, sometimes termed biological racism, is the pseudoscience, pseudoscientific belief that empirical evidence exists to support or justify racism (racial discrimination), racial inferiority, or racial superiority.. "Few tragedies ...
Madison Grant Madison Grant (November 19, 1865 – May 30, 1937) was an American lawyer, zoologist, anthropologist, and writer known primarily for his work as a eugenicist and conservationist, and as an advocate of scientific racism. Grant is less noted f ...
, who considered the so-called
Nordic race The Nordic race was a racial concept which originated in 19th century anthropology. It was considered a race or one of the putative sub-races into which some late-19th to mid-20th century anthropologists divided the Caucasian race, claiming th ...
to be superior, but under threat because of immigration by "inferior breeds." In his influential work, ''A Study of American Intelligence,'' psychologist
Carl Brigham Carl Campbell Brigham (May 4, 1890 – January 24, 1943) was an American eugenicist and professor of psychology at Princeton University's Department of Psychology and a pioneer in the field of psychometrics. He sat on the advisory council of t ...
used the results of the Army tests to argue for a stricter immigration policy, limiting immigration to countries considered to belong to the "Nordic race". In the 1920s, some US states enacted
eugenic Eugenics ( ; ) is a fringe set of beliefs and practices that aim to improve the genetic quality of a human population. Historically, eugenicists have attempted to alter human gene pools by excluding people and groups judged to be inferior or ...
laws, such as Virginia's 1924 Racial Integrity Act, which established the
one-drop rule The one-drop rule is a legal principle of racial classification that was prominent in the 20th-century United States. It asserted that any person with even one ancestor of black ancestry ("one drop" of "black blood")Davis, F. James. Frontlin" ...
(of '
racial purity The term racial hygiene was used to describe an approach to eugenics in the early 20th century, which found its most extensive implementation in Nazi Germany (Nazi eugenics). It was marked by efforts to avoid miscegenation, analogous to an animal ...
') as law. Many scientists reacted negatively to eugenicist claims linking abilities and moral character to racial or genetic ancestry. They pointed to the contribution of environment (such as speaking English as a second language) to test results. By the mid-1930s, many psychologists in the US had adopted the view that environmental and cultural factors played a dominant role in IQ test results. The psychologist Carl Brigham repudiated his own earlier arguments, explaining that he had come to realize that the tests were not a measure of innate intelligence. Discussions of the issue in the United States, especially in the writings of Madison Grant, influenced
German German(s) may refer to: * Germany (of or related to) ** Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ge ...
Nazi Nazism ( ; german: Nazismus), the common name in English for National Socialism (german: Nationalsozialismus, ), is the far-right totalitarian political ideology and practices associated with Adolf Hitler and the Nazi Party (NSDAP) in ...
claims that the "Nordics" were a "
master race The master race (german: Herrenrasse) is a Pseudoscience, pseudoscientific concept in Nazism, Nazi ideology in which the putative "Aryan race" is deemed the pinnacle of Race (classification of human beings), human racial hierarchy. Members wer ...
." As American public sentiment shifted against the Germans, claims of racial differences in intelligence increasingly came to be regarded as problematic. Anthropologists such as
Franz Boas Franz Uri Boas (July 9, 1858 – December 21, 1942) was a German-American anthropologist and a pioneer of modern anthropology who has been called the "Father of American Anthropology". His work is associated with the movements known as historical ...
,
Ruth Benedict Ruth Fulton Benedict (June 5, 1887 – September 17, 1948) was an American anthropologist and folklorist. She was born in New York City, attended Vassar College, and graduated in 1909. After studying anthropology at the New School of Social Re ...
, and
Gene Weltfish Gene Weltfish (born Regina Weltfish) (August 7, 1902 – August 2, 1980) was an American anthropologist and historian working at Columbia University from 1928 to 1953. She had studied with Franz Boas and was a specialist in the culture and histor ...
did much to demonstrate that claims about racial hierarchies of intelligence were unscientific. Nonetheless, a powerful eugenics and segregation lobby funded largely by textile-magnate
Wickliffe Draper Wickliffe Preston Draper (August 9, 1891 – 1972) was an American political activist. He was an ardent eugenicist and lifelong advocate of strict racial segregation. In 1937, he founded the Pioneer Fund for eugenics and heredity research; he l ...
continued to use intelligence studies as an argument for eugenics, segregation, and anti-immigration legislation.


The Pioneer Fund and ''The Bell Curve''

As the desegregation of the American South gained traction in the 1950s, debate about black intelligence resurfaced.
Audrey Shuey Audrey Mary Shuey (1900–1977) was an American psychologist and writer. She served as the Chair of the Department of Psychology at Randolph-Macon Women's College. Early life Audrey M. Shuey was born in 1900. Shuey took her B.A. at the University ...
, funded by Draper's
Pioneer Fund Pioneer Fund is an American non-profit foundation established in 1937 "to advance the scientific study of heredity and human differences". The organization has been described as racist and white supremacist in nature. One of its first projects w ...
, published a new analysis of Yerkes' tests, concluding that black people really were of inferior intellect to white people. This study was used by segregationists to argue that it was to the advantage of black children to be educated separately from the superior white children. In the 1960s, the debate was revived when
William Shockley William Bradford Shockley Jr. (February 13, 1910 – August 12, 1989) was an American physicist and inventor. He was the manager of a research group at Bell Labs that included John Bardeen and Walter Brattain. The three scientists were jointly ...
publicly defended the view that black children were innately unable to learn as well as white children.
Arthur Jensen Arthur Robert Jensen (August 24, 1923 – October 22, 2012) was an American psychologist and writer. He was a professor of educational psychology at the University of California, Berkeley. Jensen was known for his work in psychometrics an ...
expressed similar opinions in his ''
Harvard Educational Review The ''Harvard Educational Review'' is an academic journal of opinion and research dealing with education, associated with the Harvard Graduate School of Education, and published by the Harvard Education Publishing Group. The journal was establishe ...
'' article, " How Much Can We Boost IQ and Scholastic Achievement?," which questioned the value of
compensatory education Compensatory education offers supplementary programs or services designed to help children at risk of cognitive impairment and low educational achievement succeed. Children at risk of disadvantages Poor children do worse in school than their well ...
for African-American children. He suggested that poor educational performance in such cases reflected an underlying genetic cause rather than lack of stimulation at home or other environmental factors. Another revival of public debate followed the appearance of ''
The Bell Curve ''The Bell Curve: Intelligence and Class Structure in American Life'' is a 1994 book by psychologist Richard J. Herrnstein and political scientist Charles Murray, in which the authors argue that human intelligence is substantially influenced by b ...
'' (1994), a book by
Richard Herrnstein Richard Julius Herrnstein (May 20, 1930 – September 13, 1994) was an American psychologist at Harvard University. He was an active researcher in animal learning in the B. F. Skinner, Skinnerian tradition. Herrnstein was the Edgar Pierce Profess ...
and
Charles Murray Charles Murray may refer to: Politicians *Charles Murray, 1st Earl of Dunmore (1661–1710), British peer *Charles Murray (author and diplomat) (1806–1895), British author and diplomat *Charles Murray, 7th Earl of Dunmore (1841–1907), Scotti ...
that supported the general viewpoint of Jensen. A statement in support of Herrnstein and Murray titled "
Mainstream Science on Intelligence "Mainstream Science on Intelligence" was a public statement issued by a group of researchers of topics associated with intelligence testing. It was published originally in ''The Wall Street Journal'' on December 13, 1994, as a response to criticis ...
," was published in ''
The Wall Street Journal ''The Wall Street Journal'' is an American business-focused, international daily newspaper based in New York City, with international editions also available in Chinese and Japanese. The ''Journal'', along with its Asian editions, is published ...
'' with 52 signatures. ''The Bell Curve'' also led to critical responses in a statement titled " Intelligence: Knowns and Unknowns" of the American Psychological Association and in several books, including ''
The Bell Curve Debate ''The Bell Curve Debate'' is a 1995 book edited by the historian Russell Jacoby and the writer Naomi Glauberman. Summary A response to ''The Bell Curve'' (1994), by the psychologist Richard Herrnstein and the political scientist Charles Murra ...
'' (1995), '' Inequality by Design'' (1996) and a second edition of ''
The Mismeasure of Man ''The Mismeasure of Man'' is a 1981 book by paleontologist Stephen Jay Gould. The book is both a history and critique of the statistical methods and cultural motivations underlying biological determinism, the belief that "the social and economic ...
'' (1996) by
Stephen Jay Gould Stephen Jay Gould (; September 10, 1941 – May 20, 2002) was an American paleontologist, evolutionary biologist, and historian of science. He was one of the most influential and widely read authors of popular science of his generation. Gould sp ...
. Some of the authors proposing genetic explanations for group differences have received funding from the
Pioneer Fund Pioneer Fund is an American non-profit foundation established in 1937 "to advance the scientific study of heredity and human differences". The organization has been described as racist and white supremacist in nature. One of its first projects w ...
, which was headed by
J. Philippe Rushton John Philippe Rushton (December 3, 1943 – October 2, 2012) was a Canadian psychologist and author. He taught at the University of Western Ontario until the early 1990s, and became known to the general public during the 1980s and 1990s for resea ...
until his death in 2012. Arthur Jensen, who jointly with Rushton published a 2005 review article arguing that the difference in average IQs between blacks and whites is partly due to genetics, received $1.1 million from the Pioneer Fund. According to
Ashley Montagu Montague Francis Ashley-Montagu (June 28, 1905November 26, 1999) — born Israel Ehrenberg — was a British-American anthropologist who popularized the study of topics such as race and gender and their relation to politics and development. He ...
, "The University of California's Arthur Jensen, cited twenty-three times in ''The Bell Curve''s bibliography, is the book's principal authority on the intellectual inferiority of blacks." The
Southern Poverty Law Center The Southern Poverty Law Center (SPLC) is an American 501(c)(3) nonprofit legal advocacy organization specializing in civil rights and public interest litigation. Based in Montgomery, Alabama, it is known for its legal cases against white su ...
lists the Pioneer Fund as a
hate group A hate group is a social group that advocates and practices hatred, hostility, or violence towards members of a race (human classification), race, Ethnic group, ethnicity, nation, religion, gender, gender identity, sexual orientation, or any o ...
, citing the fund's history, its funding of race and intelligence research, and its connections with
racist Racism is the belief that groups of humans possess different behavioral traits corresponding to inherited attributes and can be divided based on the superiority of one race over another. It may also mean prejudice, discrimination, or antagonism ...
individuals. Other researchers have criticized the Pioneer Fund for promoting
scientific racism Scientific racism, sometimes termed biological racism, is the pseudoscience, pseudoscientific belief that empirical evidence exists to support or justify racism (racial discrimination), racial inferiority, or racial superiority.. "Few tragedies ...
,
eugenics Eugenics ( ; ) is a fringe set of beliefs and practices that aim to improve the genetic quality of a human population. Historically, eugenicists have attempted to alter human gene pools by excluding people and groups judged to be inferior or ...
and
white supremacy White supremacy or white supremacism is the belief that white people are superior to those of other races and thus should dominate them. The belief favors the maintenance and defense of any power and privilege held by white people. White su ...
.


Criticisms of ''race'' and ''intelligence'' as biologically defined concepts


Intelligence, IQ, ''g'' and IQ tests

The concept of intelligence and the degree to which intelligence is measurable are matters of debate. There is no consensus about how to define intelligence; nor is it universally accepted that it is something that can be meaningfully measured by a single figure. 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 by the same criteria in different societies. Consequently, some critics argue that it makes no sense to propose relationships between intelligence and other variables. Correlations between scores on various types of IQ tests led English psychologist
Charles Spearman Charles Edward Spearman, FRS (10 September 1863 – 17 September 1945) was an English psychologist known for work in statistics, as a pioneer of factor analysis, and for Spearman's rank correlation coefficient. He also did seminal work on mod ...
to propose in 1904 the existence of an underlying factor, which he referred to as "''g''" or "
general intelligence The ''g'' factor (also known as general intelligence, general mental ability or general intelligence factor) is a construct developed in psychometric investigations of cognitive abilities and human intelligence. It is a variable that summarizes ...
", a trait which is supposed to be innate. More recent proponents of this view include Arthur Jensen. This view, however, has been contradicted by a number of studies showing that education and changes in environment can significantly improve IQ test results. Other psychometricians have argued that, whether or not there is such a thing as a general intelligence factor, performance on tests relies crucially on knowledge acquired through prior exposure to the types of tasks that such tests contain. This means that comparisons of test scores between persons with widely different life experiences and cognitive habits do not reveal their relative innate potentials.


Race

The majority of anthropologists today consider race to be a sociopolitical phenomenon rather than a biological one,Templeton, A. (2016). EVOLUTION AND NOTIONS OF HUMAN RACE. In Losos J. & Lenski R. (Eds.), ''How Evolution Shapes Our Lives: Essays on Biology and Society'' (pp. 346-361). Princeton; Oxford: Princeton University Press. . That this view reflects the consensus among American anthropologists is stated in: See also: a view supported by considerable genetics research. The current mainstream view in the social sciences and biology is that race is a social construction based on folk ideologies that construct groups based on social disparities and superficial physical characteristics. state, "Race is a socially constructed concept, not a biological one. It derives from people's desire to classify." The concept of human "races" as natural and separate divisions within the human species has also been rejected by the
American Anthropological Association The American Anthropological Association (AAA) is an organization of scholars and practitioners in the field of anthropology. With 10,000 members, the association, based in Arlington, Virginia, includes archaeologists, cultural anthropologists, ...
. The official position of the AAA, adopted in 1998, is that advances in scientific knowledge have made it "clear that human populations are not unambiguous, clearly demarcated, biologically distinct groups" and that "any attempt to establish lines of division among biological populations sboth arbitrary and subjective." A more recent statement from the
American Association of Physical Anthropologists The American Association of Biological Anthropologists (AABA) is an international professional society of biological anthropologists, based in the United States. The organization publishes the ''American Journal of Physical Anthropology'', a pe ...
(2019) declares that "Race does not provide an accurate representation of human biological variation. It was never accurate in the past, and it remains inaccurate when referencing contemporary human populations. Humans are not divided biologically into distinct continental types or racial genetic clusters." In studies of human intelligence, race is almost always determined using self-reports rather than analyses of genetic characteristics. 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 disagreed, writing that "Nevertheless, self-identification is a surprisingly reliable guide to genetic composition," citing a study by . Sternberg and Grigorenko disputed Hunt and Carlson's interpretation of Tang's results as supporting the view that racial divisions are biological; rather, "Tang et al.'s point was that ancient geographic ancestry rather than current residence is associated with self-identification and not that such self-identification provides evidence for the existence of biological race." Anthropologist
C. Loring Brace Charles Loring Brace IV (December 19, 1930 – September 7, 2019) was an American anthropologist, Professor Emeritus at the University of Michigan's Department of Anthropology and Curator Emeritus at the University's Museum of Anthropological Arc ...
and geneticist Joseph Graves also disagree with the idea that cluster analysis and the correlation between self-reported race and genetic ancestry support the notion of biological races. They argue that while it is possible to find biological and genetic variation corresponding roughly to the groupings normally defined as races, this is true for almost all geographically distinct populations. The cluster structure of the genetic data is dependent on the initial hypotheses of the researcher and the populations sampled. When one samples continental groups, the clusters become continental; if one had chosen other sampling patterns, the clusters would be different. concludes that, while differences in particular allele frequencies can be used to identify populations that loosely correspond to the racial categories common in Western social discourse, the differences are of no more biological significance than the differences found between any human populations (e.g., the Spanish and Portuguese).


Group differences

The study of human intelligence is one of the most controversial topics in psychology, in part because of difficulty reaching agreement about the meaning of ''intelligence'' and objections to the assumption that intelligence can be meaningfully measured by IQ tests. Claims that there are innate differences in intelligence between racial and ethnic groups—which go back at least to the 19th century—have been criticized both for relying on specious assumptions and research methods and for serving as an ideological framework for discrimination and racism. In a 2012 study of tests of different components of intelligence, Hampshire et al. expressed disagreement with the view of Jensen and Rushton that genetic factors must play a role in IQ differences between races, stating that "it remains unclear, however, whether population differences in intelligence test scores are driven by heritable factors or by other correlated demographic variables such as socioeconomic status, education level, and motivation. More relevantly, it is questionable whether they opulation differences in intelligence test scoresrelate to a unitary intelligence factor, as opposed to a bias in testing paradigms toward particular components of a more complex intelligence construct." According to Jackson and Weidman,


Test scores

In the US, individuals identifying themselves as Asian generally tend to score higher on IQ tests than Caucasians, who tend to score higher than Hispanics, who tend to score higher than African Americans. Nevertheless, greater variation in IQ scores exists within each ethnic group than between them. A 2001
meta-analysis A meta-analysis is a statistical analysis that combines the results of multiple scientific studies. Meta-analyses can be performed when there are multiple scientific studies addressing the same question, with each individual study reporting me ...
of the results of 6,246,729 participants tested for cognitive ability or aptitude found a difference in average scores between black people and white people of 1.1
standard deviations In statistics, the standard deviation is a measure of the amount of variation or dispersion of a set of values. A low standard deviation indicates that the values tend to be close to the mean (also called the expected value) of the set, while ...
. Consistent results were found for college and university application tests such as the
Scholastic Aptitude Test The SAT ( ) is a standardized test widely used for college admissions in the United States. Since its debut in 1926, its name and scoring have changed several times; originally called the Scholastic Aptitude Test, it was later called the Schol ...
(N = 2.4 million) and
Graduate Record Examination The Graduate Record Examinations (GRE) is a standardized test that is an admissions requirement for many graduate schools in the United States and Canada and a few other countries. The GRE is owned and administered by Educational Testing Serv ...
(N = 2.3 million), as well as for tests of job applicants in corporate settings (N = 0.5 million) and in the military (N = 0.4 million). In response to the controversial 1994 book ''
The Bell Curve ''The Bell Curve: Intelligence and Class Structure in American Life'' is a 1994 book by psychologist Richard J. Herrnstein and political scientist Charles Murray, in which the authors argue that human intelligence is substantially influenced by b ...
'', the
American Psychological Association The American Psychological Association (APA) is the largest scientific and professional organization of psychologists in the United States, with over 133,000 members, including scientists, educators, clinicians, consultants, and students. It ha ...
(APA) formed a task-force of eleven experts, which issued a report " Intelligence: Knowns and Unknowns" in 1996. Regarding group differences, the report reaffirmed the consensus that differences within groups are much wider than differences between groups, and that claims of ethnic differences in intelligence should be scrutinized carefully, as such claims had been used to justify racial discrimination. The report also acknowledged problems with the racial categories used, as these categories are neither consistently applied, nor homogeneous (see also
race and ethnicity in the United States The United States has a Race (human categorization), racially and ethnic group, ethnically Multiculturalism, diverse population. At the federal level, race and ethnicity have been categorized separately. The most recent United States Census of ...
). In the UK, some African groups have higher average educational attainment and standardized test scores than the overall population. In 2010–2011, white British pupils were 2.3% less likely to have gained 5 A*–C grades at
GCSE The General Certificate of Secondary Education (GCSE) is an academic qualification in a particular subject, taken in England, Wales, and Northern Ireland. State schools in Scotland use the Scottish Qualifications Certificate instead. Private sc ...
than the national average, whereas the likelihood was 21.8% above average for those of
Nigerian Nigerians or the Nigerian people are citizens of Nigeria or people with ancestry from Nigeria. The name Nigeria was taken from the Niger River running through the country. This name was allegedly coined in the late 19th century by British jour ...
origin, 5.5% above average for those of
Ghanaian Ghana (; tw, Gaana, ee, Gana), officially the Republic of Ghana, is a country in West Africa. It abuts the Gulf of Guinea and the Atlantic Ocean to the south, sharing borders with Ivory Coast in Ghana–Ivory Coast border, the west, Burkina ...
origin, and 1.4% above average for those of Sierra Leonian origin. For the two other African ethnic groups on which data was available, the likelihood was 23.7% below average for those of Somali origin and 35.3% below average for those of Congolese origin. In 2014, Black-African pupils of 11 language groups were more likely to pass Key Stage 2 Maths 4+ in England than the national average. Overall, the average pass rate by ethnicity was 86.5% for white British (N = 395,787), whereas it was 85.6% for Black-Africans (N = 18,497). Nevertheless, several Black-African language groups, including
Yoruba The Yoruba people (, , ) are a West African ethnic group that mainly inhabit parts of Nigeria, Benin, and Togo. The areas of these countries primarily inhabited by Yoruba are often collectively referred to as Yorubaland. The Yoruba constitute ...
,
Igbo Igbo may refer to: * Igbo people, an ethnic group of Nigeria * Igbo language, their language * anything related to Igboland, a cultural region in Nigeria See also * Ibo (disambiguation) * Igbo mythology * Igbo music * Igbo art * * Igbo-Ukwu, a ...
,
Hausa Hausa may refer to: * Hausa people, an ethnic group of West Africa * Hausa language, spoken in West Africa * Hausa Kingdoms, a historical collection of Hausa city-states * Hausa (horse) or Dongola horse, an African breed of riding horse See also * ...
,
Akan Akan may refer to: People and languages *Akan people, an ethnic group in Ghana and Côte d'Ivoire *Akan language, a language spoken by the Akan people *Kwa languages, a language group which includes Akan *Central Tano languages, a language group w ...
, Ga, Swahili, Edo, Ewe,
Amharic Amharic ( or ; (Amharic: ), ', ) is an Ethiopian Semitic language, which is a subgrouping within the Semitic branch of the Afroasiatic languages. It is spoken as a first language by the Amharas, and also serves as a lingua franca for all oth ...
speakers, and English-speaking Africans, each had an average pass rate above the white British average (total N = 9,314), with the Hausa, Igbo, Yoruba, and Amhara having averages above 90% (N = 2,071). In 2017–2018, the percentage of pupils getting a strong pass (grade 5 or above) in the English and maths GCSE (in
Key Stage 4 Key Stage 4 (KS4) is the legal term for the two years of school education which incorporate GCSEs, and other examinations, in maintained schools in England normally known as Year 10 and Year 11, when pupils are aged between 14 and 16 by August 31. ...
) was 42.7% for whites (N = 396,680) and 44.3% for Black-Africans (N = 18,358).


Flynn effect and the closing gap

During the 20th century, raw scores on IQ tests were rising; this score increase is known as the "Flynn effect," named after James R. Flynn. In the United States, the increase was continuous and approximately linear from the earliest years of testing to about 1998 when the gains stopped and some tests even showed decreasing test scores. For example, the average scores of black people on some IQ tests in 1995 were the same as the scores of white people in 1945. As one pair of academics phrased it, "the typical African American today probably has a slightly higher IQ than the grandparents of today's average white American." Flynn has argued that, given that these changes took place between one generation and the next, it is highly unlikely that genetic factors could have accounted for the increasing scores, which must then have been caused by environmental factors. The importance of the Flynn effect in the debate over the causes of the black/white IQ gap lies in demonstrating that environmental factors may cause changes in test scores on the scale of 1 standard deviation. This had previously been doubted. A separate phenomenon from the Flynn effect has been the discovery that the IQ gap was gradually closing over the last decades of the 20th century, as black test-takers increased their average scores relative to white test-takers. For instance, Vincent reported in 1991 that the black–white IQ gap was decreasing among children, but that it was remaining constant among adults. Similarly, a 2006 study by Dickens and Flynn estimated that the difference between mean scores of black people and white people closed by about 5 or 6 IQ points between 1972 and 2002, a reduction of about one-third. In the same period, the educational achievement disparity also diminished. Reviews by Flynn and Dickens, Mackintosh, and Nisbett ''et al.'' accept the gradual closing of the gap as a fact.


Environmental influences on group differences in IQ


Health and nutrition

Environmental factors including childhood lead exposure, low rates of
breast feeding Breastfeeding, or nursing, is the process by which human breast milk is fed to a child. Breast milk may be from the breast, or may be expressed by hand or pumped and fed to the infant. The World Health Organization (WHO) recommends that brea ...
, and poor
nutrition Nutrition is the biochemical and physiological process by which an organism uses food to support its life. It provides organisms with nutrients, which can be metabolized to create energy and chemical structures. Failure to obtain sufficient n ...
are significantly correlated with poor cognitive development and functioning. For example, childhood exposure to lead, associated with homes in poorer areas, is associated with an average IQ drop of 7 points, and iodine deficiency causes a fall, on average, of 12 IQ points. Such impairments may sometimes be permanent, but in some cases they be partially or wholly compensated for by later growth. The first two years of life are critical for malnutrition, the consequences of which are often irreversible and include poor cognitive development, educability, and future economic productivity. The African American population of the United States is statistically more likely to be exposed to many detrimental environmental factors such as poorer neighborhoods (noise, crime, limited outdoor space, and other impoverishments), air pollution (diesel exhaust, smoke, industrial emissions, ultrafine particulates, etc.), subpar schools (insufficient funding, neglect, and disruption of schooling for myriad reasons), malnutrition (high levels of nutritionally bankrupt processed foods), and subpar prenatal and postnatal health care (inadequate funding). Mackintosh points out that, for American black people, infant mortality is about twice as high as for white people, and low birth weight is twice as prevalent. At the same time, white mothers are twice as likely to breastfeed their infants, and breastfeeding is directly correlated with IQ for low-birth-weight infants. In this way, a wide number of health-related factors which influence IQ are unequally distributed between the two groups. The
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, using cost–benefit analysis. It was conceived and organized around 2004 by Bjørn Lomb ...
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 is affected by
iodine deficiency Iodine deficiency is a lack of the trace element iodine, an essential nutrient in the diet. It may result in metabolic problems such as goiter, sometimes as an endemic goiter as well as congenital iodine deficiency syndrome due to untreated cong ...
. In developing countries, it is estimated that 40% of children aged four and under have
anaemia Anemia or anaemia (British English) is a blood disorder in which the blood has a reduced ability to carry oxygen due to a lower than normal number of red blood cells, or a reduction in the amount of hemoglobin. When anemia comes on slowly, th ...
because of insufficient iron in their diets. Other scholars have found that simply the standard of nutrition has a significant effect on population intelligence, and that the Flynn effect may be caused by increasing nutrition standards across the world. James Flynn has himself argued against this view. Some recent research has argued that the retardation caused in brain development by
infectious disease An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
s, many of which are more prevalent in non-white populations, may be an important factor in explaining the differences in IQ between different regions of the world. The findings of this research, showing the correlation between IQ, race and infectious diseases was also shown to apply to the IQ gap in the US, suggesting that this may be an important environmental factor. It is also suggested that "the Flynn effect may be caused in part by the decrease in the intensity of infectious diseases as nations develop." A 2013 meta-analysis by the World Health Organization found that, after controlling for maternal IQ, breastfeeding was associated with IQ gains of 2.19 points. The authors suggest that this relationship is causal but state that the practical significance of this gain is debatable; however, they highlight one study suggesting an association between breastfeeding and academic performance in Brazil, where "breastfeeding duration does not present marked variability by socioeconomic position." Colen and Ramey (2014) similarly find that controlling for sibling comparisons within families, rather than between families, reduces the correlation between breastfeeding status and WISC IQ scores by nearly a third, but further find the relationship between breastfeeding duration and WISC IQ scores to be insignificant. They suggest that "much of the beneficial long-term effects typically attributed to breastfeeding, per se, may primarily be due to selection pressures into infant feeding practices along key demographic characteristics such as race and socioeconomic status." Reichman estimates that no more than 3 to 4% of the black–white IQ gap can be explained by black–white disparities in low birth weight.


Education

Several studies have proposed that a large part of the gap can be attributed to differences in quality of education.
Racial discrimination Racial discrimination is any discrimination against any individual on the basis of their skin color, race or ethnic origin.Individuals can discriminate by refusing to do business with, socialize with, or share resources with people of a certain g ...
in education has been proposed as one possible cause of differences in educational quality between races. According to a paper by Hala Elhoweris, Kagendo Mutua, Negmeldin Alsheikh and Pauline Holloway, teachers' referral decisions for students to participate in gifted and talented educational programs were influenced in part by the students' ethnicity. The
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 poo ...
, an intensive early childhood education project, was also able to bring about an average IQ gain of 4.4 points at age 21 in the black children who participated in it compared to controls.
Arthur Jensen Arthur Robert Jensen (August 24, 1923 – October 22, 2012) was an American psychologist and writer. He was a professor of educational psychology at the University of California, Berkeley. Jensen was known for his work in psychometrics an ...
agreed that the Abecedarian project demonstrated that education can have a significant effect on IQ, but also declared his view that no educational program thus far had 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. A series of studies by
Joseph Fagan Joseph F. Fagan III (September 7, 1941 – August 10, 2013) was an American psychologist and the Lucy Adams Leffingwell Professor of psychology at Case Western Reserve University from 1990 until his death in 2013. Education Fagan received his B.A ...
and Cynthia Holland measured the effect of prior exposure to the kind of cognitive tasks posed in IQ tests on test performance. Assuming that the IQ gap was the result of lower exposure to tasks using the cognitive functions usually found in IQ tests among African American test takers, they prepared a group of African Americans in this type of tasks before taking an IQ test. The researchers found that there was no subsequent difference in performance between the African-Americans and white test takers. Daley and Onwuegbuzie conclude that Fagan and Holland demonstrate that "differences in knowledge between black people and white people for intelligence test items can be erased when equal opportunity is provided for exposure to the information to be tested". A similar argument is made by
David Marks David Lee Marks (born August 22, 1948) is an American guitarist who is best known for being an early member of the Beach Boys. While growing up in Hawthorne, California, Marks was a neighborhood friend of the original band members and was a freq ...
who argues that IQ differences correlate well with differences in literacy suggesting that developing literacy skills through education causes an increase in IQ test performance. A 2003 study found that two variables—stereotype threat and the degree of educational attainment of children's fathers—partially explained the black–white gap in cognitive ability test scores, undermining the hereditarian view that they stemmed from immutable genetic factors.


Socioeconomic environment

Different aspects of the socioeconomic environment in which children are raised have been shown to correlate with part of the IQ gap, but they do not account for the entire gap. According to a 2006 review, these factors account for slightly less than half of one standard deviation. Other research has focused on different causes of variation within low socioeconomic status (SES) and high SES groups.D. C. Rowe. (1994). ''The Limits of Family Influence: Genes, Experience and Behaviour''. Guilford Press. London In the US, among low SES groups, genetic differences account for a smaller proportion of the variance in IQ than among high SES populations. Such effects are predicted by the '' bioecological'' hypothesis—that genotypes are transformed into phenotypes through nonadditive synergistic effects of the environment. suggest that high SES individuals are more likely to be able to develop their full biological potential, whereas low SES individuals are likely to be hindered in their development by adverse environmental conditions. The same review also points out that adoption studies generally are biased towards including only high and high middle SES adoptive families, meaning that they will tend to overestimate average genetic effects. They also note that studies of adoption from lower-class homes to middle-class homes have shown that such children experience a 12 to 18 point gain in IQ relative to children who remain in low SES homes. A 2015 study found that environmental factors (namely, family income, maternal education, maternal verbal ability/knowledge, learning materials in the home, parenting factors, child birth order, and child birth weight) accounted for the black–white gap in cognitive ability test scores.


Test bias

A number of studies have reached the conclusion that IQ tests may be biased against certain groups. The validity and reliability of IQ scores obtained from outside 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. A 1996 report by the
American Psychological Association The American Psychological Association (APA) is the largest scientific and professional organization of psychologists in the United States, with over 133,000 members, including scientists, educators, clinicians, consultants, and students. It ha ...
states that intelligence can be difficult to compare across cultures, and notes that differing familiarity with test materials can produce substantial differences in test results; it also says that tests are accurate predictors of future achievement for black and white Americans, and are in that sense unbiased. The view that tests accurately predict future educational attainment is reinforced by
Nicholas Mackintosh Nicholas John Seymour Mackintosh, (9 July 1935 – 8 February 2015) was a British experimental psychologist and author, specialising in intelligence, psychometrics and animal learning. Education Mackintosh was born in London, the son of Ian Mac ...
in his 1998 book ''IQ and Human Intelligence'', and by a 1999 literature review by . James R. Flynn, surveying studies on the topic, notes that the weight and presence of many test questions depends on what sorts of information and modes of thinking are culturally valued. According to a 2008 article in the journal ''
Intelligence Intelligence has been defined in many ways: the capacity for abstraction, logic, understanding, self-awareness, learning, emotional knowledge, reasoning, planning, creativity, critical thinking, and problem-solving. More generally, it can b ...
'', a survey found that most researchers in the field of intelligence measurement do not believe there is robust evidence for the claim that IQ tests are racially or culturally biased. This finding is similar to that of a 2003 survey.


Stereotype threat and minority status

Stereotype threat Stereotype threat is a situational predicament in which people are or feel themselves to be at risk of conforming to stereotypes about their social group. It is theorized to be a contributing factor to long-standing racial and gender gaps in acad ...
is the fear that one's behavior will confirm an existing
stereotype In social psychology, a stereotype is a generalized belief about a particular category of people. It is an expectation that people might have about every person of a particular group. The type of expectation can vary; it can be, for example ...
of a group with which one identifies or by which one is defined; 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 who already score lower on average or are expected to score lower. Stereotype threat conditions cause larger than expected IQ differences among groups. Psychometrician
Nicholas Mackintosh Nicholas John Seymour Mackintosh, (9 July 1935 – 8 February 2015) was a British experimental psychologist and author, specialising in intelligence, psychometrics and animal learning. Education Mackintosh was born in London, the son of Ian Mac ...
considers that there is little doubt that the effects of stereotype threat contribute to the IQ gap between black people and white people. A large number of studies have shown that systemically disadvantaged minorities, such as the African American minority of the United States, generally perform worse in the educational system and in intelligence tests than the majority groups or less disadvantaged minorities such as immigrant or "voluntary" minorities. The explanation of these findings may be that children of caste-like minorities, due to the systemic limitations of their prospects of social advancement, do not have " effort optimism", i.e. they do not have the confidence that acquiring the skills valued by majority society, such as those skills measured by IQ tests, is worthwhile. They may even deliberately reject certain behaviors that are seen as "
acting white In the United States, acting white is a pejorative term, usually applied to black people, which refers to a person's perceived betrayal of their culture by assuming the social expectations of white society.
." Research published in 1997 indicates that part of the black–white gap in cognitive ability test scores is due to racial differences in test motivation. Some researchers have suggested that stereotype threat should not be interpreted as a factor in real-life performance gaps, and have raised the possibility of
publication bias In published academic research, publication bias occurs when the outcome of an experiment or research study biases the decision to publish or otherwise distribute it. Publishing only results that show a significant finding disturbs the balance o ...
.Pdf.
Other critics have focused on correcting what they claim are misconceptions of early studies showing a large effect. However, numerous
meta-analyses A meta-analysis is a statistical analysis that combines the results of multiple scientific studies. Meta-analyses can be performed when there are multiple scientific studies addressing the same question, with each individual study reporting me ...
and systematic reviews have shown significant evidence for the effects of stereotype threat, though the phenomenon defies over-simplistic characterization. For instance, one meta-analysis found that with female subjects "subtle threat-activating cues produced the largest effect, followed by blatant and moderately explicit cues" while with minorities "moderately explicit stereotype threat-activating cues produced the largest effect, followed by blatant and subtle cues". Some researchers have argued that studies of stereotype threat may in fact systematically under-represent its effects, since such studies measure "only that portion of psychological threat that research has identified and remedied. To the extent that unidentified or unremedied psychological threats further undermine performance, the results underestimate the bias."


Research into possible genetic influences on test score differences

Although IQ differences between individuals have been shown to have a large hereditary component, it does not follow that mean group-level disparities (between-group differences) in IQ necessarily have a genetic basis. The scientific consensus is that there is no evidence for a genetic component behind IQ differences between racial groups. Growing evidence indicates that environmental factors, not genetic ones, explain the racial IQ gap.


Genetics of race and intelligence

Geneticist
Alan R. Templeton Alan R. Templeton is an American geneticist and statistician at Washington University in St. Louis, where he is the Charles Rebstock emeritus professor of biology. From 2010 to 2019, he held positions in the Institute of Evolution and the Departm ...
argued that the question about the possible genetic effects on the test score gap 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. Templeton pointed out that racial groups neither represent sub-species nor distinct evolutionary lineages, and that therefore there is no basis for making claims about the general intelligence of races. He argued that, for these reasons, the search for possible genetic influences on the black–white test score gap is ''a priori'' flawed, because there is no genetic material shared by all Africans or by all Europeans. , on the other hand, argued that by using genetic cluster analysis to correlate gene frequencies with continental populations it might be possible to show that African populations have a higher frequency of certain genetic variants that contribute to differences in average intelligence. Such a hypothetical situation could hold without all Africans carrying the same genes or belonging to a single evolutionary lineage. According to Mackintosh, a biological basis for the observed gap in IQ test performance thus cannot be ruled out on ''a priori'' grounds. noted that "no genes related to difference in cognitive skills have across the various racial and ethnic groups have ever been discovered. The argument for genetic differences has been carried forward largely by circumstantial evidence. Of course, tomorrow afternoon genetic mechanisms producing racial and ethnic differences in intelligence might be discovered, but there have been a lot of investigations, and tomorrow has not come for quite some time now." concurred, noting that while several environmental factors have been shown to influence the IQ gap, the evidence for a genetic influence has been negligible. A 2012 review by concluded that the entire IQ gap can be explained by known environmental factors, and Mackintosh found this view to be plausible. More recent research attempting to identify genetic loci associated with individual-level differences in IQ has yielded promising results, which led the editorial board of ''
Nature Nature, in the broadest sense, is the physics, physical world or universe. "Nature" can refer to the phenomenon, phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. ...
'' to issue a statement differentiating this research from the "racist" pseudoscience which it acknowledged has dogged intelligence research since its inception. It characterized the idea of genetically determined differences in intelligence between races as definitively false.


Heritability within and between groups

Twin studies Twin studies are studies conducted on identical or fraternal twins. They aim to reveal the importance of environmental and genetic influences for traits, phenotypes, and disorders. Twin research is considered a key tool in behavioral genetics a ...
of intelligence have reported high heritability values. However, these studies have been criticized for being based on questionable assumptions. When used in the context of human
behavior genetics Behavioural genetics, also referred to as behaviour genetics, is a field of scientific research that uses genetic methods to investigate the nature and origins of individual differences in behaviour. While the name "behavioural genetics" ...
, the term "heritability" can be misleading, as it does not necessarily convey information about the relative importance of genetic or environmental factors on the development of a given trait, nor does it convey the extent to which that trait is genetically determined. Arguments in support of a genetic explanation of racial differences in IQ are sometimes fallacious. For instance, hereditarians have sometimes cited the failure of known environmental factors to account for such differences, or the high heritability of intelligence within races, as evidence that racial differences in IQ are genetic. Psychometricians have found 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. In biology heritability is defined as the ratio of variation attributable to genetic differences in an observable trait to the trait's total observable variation. The heritability of a trait describes the proportion of variation in the trait that is attributable to genetic factors within a particular population. 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. In psychological testing, heritability tends to be understood as the degree of correlation between the results of a test taker and those of their biological parents. However, since high heritability is simply a correlation between child and parents, it does not describe the causes of heritability which in humans can be either genetic or environmental. Therefore, a high heritability measure does not imply that a trait is genetic or unchangeable. In addition, environmental factors that affect all group members equally will not be measured by heritability, and the heritability of a trait may also change over time in response to changes in the distribution of genetic and environmental factors. High heritability does not imply that all of the heritability is genetically determined; rather, it can also be due to environmental differences that affect only a certain genetically defined group (indirect heritability). The figure to the right demonstrates how heritability works. In each of the two gardens the difference between tall and short cornstalks is 100% heritable, as cornstalks that are genetically disposed for growing tall will become taller than those without this disposition. But the difference in height between the cornstalks to the left and those on the right is 100% environmental, as it is due to different nutrients being supplied to the two gardens. Hence, the causes of differences within a group and between groups may not be the same, even when looking at traits that are highly heritable.


Spearman's hypothesis

Spearman's hypothesis states that the magnitude of the black–white difference in tests of cognitive ability depends entirely or mainly on the extent to which a test measures general mental ability, or ''g''. The hypothesis was first formalized by
Arthur Jensen Arthur Robert Jensen (August 24, 1923 – October 22, 2012) was an American psychologist and writer. He was a professor of educational psychology at the University of California, Berkeley. Jensen was known for his work in psychometrics an ...
, who devised the statistical "method of correlated vectors" to test it. If Spearman's hypothesis holds true, then the cognitive tasks that have the highest ''g''-load are the tasks in which the gap between black and white test takers are greatest. Jensen and Rushton take this to show that the cause of ''g'' and the cause of the gap are the same—in their view, genetic differences. acknowledges that Jensen and Rushton showed a modest correlation between ''g''-loading, heritability, and the test score gap, but does not agree that this demonstrates a genetic origin of the gap. Mackintosh argues that it is exactly those tests that Rushton and Jensen consider to have the highest ''g''-loading and heritability, such as the Wechsler test, that have seen the greatest increases in black performance due to the Flynn effect. This likely suggests that they are also the most sensitive to environmental changes, which undermines Jensen's argument that the black–white gap is most likely caused by genetic factors. Mackintosh also argues that Spearman's hypothesis, which he considers to be likely to be correct, simply shows that the test score gap is based on whatever cognitive faculty is central to intelligence, but does not show what this factor is. make the same point, noting also that the increase in the IQ scores of black test takers necessarily indicates an increase in ''g''. Flynn has criticized Jensen's basic assumption that confirmation of Spearman's hypothesis would support a partially genetic explanation for IQ differences. He argues that, no matter what the causes are of average group IQ differences, one would expect the differences to be greater for more complex tasks. Flynn thus sees the correlation between ''g''-loading and the test score gap to offer no clue to the cause of the gap.


Adoption studies

A number of IQ studies have been done on the effect of similar rearing conditions on children from different races. The hypothesis is that this can be determined by investigating whether black children adopted into white families demonstrated gains in IQ test scores relative to black children reared in black families. Depending on whether their test scores are more similar to their biological or adoptive families, that could be interpreted as supporting either a genetic or an environmental hypothesis. Critiques of such studies question whether the environment of black children—even when raised in white families—is truly comparable to the environment of white children. Several reviews of the
adoption study Adoption studies are one of the classic research methods of behavioral genetics and are an effective technique for assessing the interconnections of genetic and environmental variables in the elicitation of human qualities such as intelligence (IQ) ...
literature have suggested that it is probably impossible to avoid confounding biological and environmental factors in this type of study. Another criticism by is that adoption studies on the whole tend to be carried out in a restricted set of environments, mostly in the medium-high SES range, where heritability is higher than in the low-SES range. The
Minnesota Transracial Adoption Study The Minnesota Transracial Adoption Study examined the IQ test scores of 130 black or interracial children adopted by advantaged white families. The aim of the study was to determine the contribution of environmental and genetic factors to the poo ...
(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. The study found higher IQ for white people compared to black people, both at age 7 and age 17. Acknowledging the existence of confounding factors, Scarr and Weinberg, the authors of the original study, did not consider that it provided support for either the hereditarian or environmentalist view. Three other studies lend support to environmental explanations of group IQ differences: * studied the out-of-wedlock children of black and white soldiers stationed in Germany after World War II who were then raised by white German mothers in what has become known as the
Eyferth study The Eyferth study, conducted by German psychologist Klaus Eyferth, examined the IQs of white and racially-mixed children raised by single mothers in post-World War II West Germany. The mothers of the children studied were white German women, whi ...
. He found no significant differences in average IQ between groups. * studied black (West Indian), white, and mixed-race children raised in British long-stay residential nurseries. Two out of three tests found no significant differences. One test found higher scores for non-white people. * compared black and mixed-race children adopted by either black or white middle-class families in the United States. Moore observed that 23 black and interracial children raised by white parents had a significantly higher mean score than 23 age-matched children raised by black parents (117 vs 104), and argued that differences in early socialization explained these differences. Frydman and Lynn (1989) showed a mean IQ of 119 for Korean infants adopted by Belgian families. After correcting for the
Flynn effect The Flynn effect is the substantial and long-sustained increase in both fluid and crystallized intelligence test scores that were measured in many parts of the world over the 20th century. When intelligence quotient (IQ) tests are initially standa ...
, the IQ of the adopted Korean children was still 10 points higher than that of the Belgian children. Reviewing the evidence from adoption studies, Mackintosh finds that environmental and genetic variables remain confounded and considers evidence from adoption studies inconclusive, and fully compatible with a 100% environmental explanation. Similarly, Drew Thomas argues that race differences in IQ that appear in adoption studies are in fact an artifact of methodology, and that East Asian IQ advantages and black IQ disadvantages disappear when this is controlled for.


Racial admixture studies

Most people have ancestry from different geographical regions. In particular, 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, one might expect black people with a higher degree of European ancestry to score higher on IQ tests than black people with less European ancestry, because the genes inherited from European ancestors would likely include some genes with a positive effect on IQ. Geneticist
Alan Templeton Alan R. Templeton is an American geneticist and Statistics#Specialized disciplines, statistician at Washington University in St. Louis, where he is the Charles Rebstock emeritus professor of biology. From 2010 to 2019, he held positions in the Ins ...
has argued that an experiment based on the Mendelian "common garden" design, where specimens with different hybrid compositions are subjected to the same environmental influences, are the only way to definitively show a causal relation between genes and group differences in IQ. Summarizing the findings of admixture studies, he concludes that they have shown no significant correlation between any cognitive ability and the degree of African or European ancestry. Studies have employed different ways of measuring or approximating relative degrees of ancestry from Africa and Europe. Some studies have used skin color as a measure, and others have used blood groups. surveys the literature and argues that the blood groups studies may be seen as providing some support to the genetic hypothesis, even though the correlation between ancestry and IQ was quite low. He finds that studies by , Willerman, Naylor & Myrianthopoulos (1970) did not find a correlation between degree of African/European ancestry and IQ. The latter study did find a difference based on the race of the mother, with children of white mothers with black fathers scoring higher than children of black mothers and white fathers. Loehlin considers that such a finding is compatible with either a genetic or an environmental cause. All in all Loehlin finds admixture studies inconclusive and recommends more research. Reviewing the evidence from admixture studies considers it to be inconclusive because of too many uncontrolled variables. quotes a statement by to the effect that admixture studies have not provided a shred of evidence in favor of a genetic basis for the IQ gap.


Mental chronometry

Mental chronometry Mental chronometry is the scientific study of processing speed or reaction time on cognitive tasks to infer the content, duration, and temporal sequencing of mental operations. Reaction time (RT; sometimes referred to as "response time") is meas ...
measures the elapsed time between the presentation of a sensory stimulus and the subsequent behavioral response by the participant. This reaction time (RT) 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 Jürgen Eysenck (; 4 March 1916 – 4 September 1997) was a German-born British psychologist who spent his professional career in Great Britain. He is best remembered for his work on intelligence and personality, although he worked on other ...
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 a 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. Black–white differences in reaction time, however, tend to be small (average
effect size In statistics, an effect size is a value measuring the strength of the relationship between two variables in a population, or a sample-based estimate of that quantity. It can refer to the value of a statistic calculated from a sample of data, the ...
.18). 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. Responding to this argument in ''Intelligence and How to Get It'', Nisbett points to the study in which a group of Chinese Americans had longer reaction times than a group of European Americans, despite having higher IQs. Nisbett also mentions findings in and 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, and that average movement time is faster for black people than for white people. considers reaction time evidence unconvincing and comments that other cognitive tests that also correlate well with IQ show no disparity at all, for example the habituation/
dishabituation Dishabituation (or ''dehabituation'') is a form of recovered or restored behavioral response wherein the reaction towards a known stimulus is enhanced, as opposed to habituation. Initially, it was proposed as an explanation to increased response fo ...
test. He further comments that studies show that rhesus monkeys have shorter reaction times than American college students, suggesting that different reaction times may not tell us anything useful about intelligence.


Brain size

A number of studies have reported a moderate statistical correlation between differences in IQ and brain size between individuals in the same group. Some scholars have reported differences in average brain sizes between racial groups, although this is unlikely to be a good measure of IQ as brain size also differs between men and women, but without significant differences in IQ. At the same time newborn black children have the same average brain size as white children, suggesting that the difference in average size could be accounted for by differences in environment. Several environmental factors that reduce brain size have been demonstrated to disproportionately affect black children.


Archaeological data

Archaeological evidence does not support claims by Rushton and others that black people's cognitive ability was inferior to white people's during prehistoric times.


Policy relevance and ethics

The
ethics Ethics or moral philosophy is a branch of philosophy that "involves systematizing, defending, and recommending concepts of right and wrong behavior".''Internet Encyclopedia of Philosophy'' The field of ethics, along with aesthetics, concerns m ...
of research on race and intelligence has long been a subject of debate: in a 1996 report of the
American Psychological Association The American Psychological Association (APA) is the largest scientific and professional organization of psychologists in the United States, with over 133,000 members, including scientists, educators, clinicians, consultants, and students. It ha ...
; in guidelines proposed by Gray and Thompson and by Hunt and Carlson; and in two editorials in ''Nature'' in 2009 by Steven Rose and by Stephen J. Ceci and Wendy M. Williams. Steven Rose maintains that the history of
eugenics Eugenics ( ; ) is a fringe set of beliefs and practices that aim to improve the genetic quality of a human population. Historically, eugenicists have attempted to alter human gene pools by excluding people and groups judged to be inferior or ...
makes this field of research difficult to reconcile with current ethical standards for science. On the other hand, James R. Flynn 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 The Flynn effect is the substantial and long-sustained increase in both fluid and crystallized intelligence test scores that were measured in many parts of the world over the 20th century. When intelligence quotient (IQ) tests are initially standa ...
) would not have occurred. Jensen and Rushton argued that what they believe to be biological differences in intelligence between races raises questions about the worthiness of policies such as affirmative action and promotion of diversity. Many have argued for increased interventions in order to close the gaps. Flynn writes that "America will have to address all the aspects of black experience that are disadvantageous, beginning with the regeneration of inner city neighborhoods and their schools." Especially in developing nations, society has been urged to take on the prevention of cognitive impairment in children as a high priority. Possible preventable causes include
malnutrition Malnutrition occurs when an organism gets too few or too many nutrients, resulting in health problems. Specifically, it is "a deficiency, excess, or imbalance of energy, protein and other nutrients" which adversely affects the body's tissues a ...
,
infectious diseases An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
such as
meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or ...
,
parasites Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of lif ...
, cerebral
malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...
,
in utero ''In Utero'' is the third and final studio album by American rock band Nirvana. It was released on September 21, 1993, by DGC Records. After breaking into the mainstream with their second album, ''Nevermind'' (1991), Nirvana hired Steve Albini t ...
drug A drug is any chemical substance that causes a change in an organism's physiology or psychology when consumed. Drugs are typically distinguished from food and substances that provide nutritional support. Consumption of drugs can be via insuffla ...
and alcohol exposure, newborn
asphyxia Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects primarily the tissues and organs. There are many circumstances that can i ...
,
low birth weight Low birth weight (LBW) is defined by the World Health Organization as a birth weight of an infant of or less, regardless of gestational age. Infants born with LBW have added health risks which require close management, often in a neonatal intensi ...
, head injuries,
lead poisoning Lead poisoning, also known as plumbism and saturnism, is a type of metal poisoning caused by lead in the body. The brain is the most sensitive. Symptoms may include abdominal pain, constipation, headaches, irritability, memory problems, inferti ...
and
endocrine disorders Endocrine diseases are disorders of the endocrine system. The branch of medicine associated with endocrine disorders is known as endocrinology. Types of disease Broadly speaking, endocrine disorders may be subdivided into three groups: # Endocrin ...
.


See also

*
Behavioral epigenetics Behavioral epigenetics is the field of study examining the role of epigenetics in shaping animal (including human) behavior. It seeks to explain how nurture shapes nature, where nature refers to biological heredity and nurture refers to virtually ...
*
Melanin theory Melanin theory is a set of pseudoscientific claims made by some proponents of Afrocentrism, which holds that black people, including ancient Egyptians, have superior mental, physical, and paranormal powers because they have higher levels of mel ...
*
Model minority A model minority is a minority demographic (whether based on ethnicity, race or religion) whose members are perceived as achieving a higher degree of socioeconomic success than the population average, thus serving as a reference group to outgroup ...
*
Outline of human intelligence The following outline is provided as an overview of and topical guide to human intelligence: Human intelligence is, in the human species, the mental capacities to learn, understand, and reason, including the capacities to comprehend ideas, plan ...
*
Race and crime Race is one of the correlates of crime receiving attention in academic studies, government surveys, media coverage, and public concern. Research has found that social status, poverty, and childhood exposure to violent behavior are causes of the r ...


Sources


Notes


References


Bibliography

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Intelligence Intelligence has been defined in many ways: the capacity for abstraction, logic, understanding, self-awareness, learning, emotional knowledge, reasoning, planning, creativity, critical thinking, and problem-solving. More generally, it can b ...
Factors related to intelligence Human population genetics Scientific controversies Anthropology
Intelligence Intelligence has been defined in many ways: the capacity for abstraction, logic, understanding, self-awareness, learning, emotional knowledge, reasoning, planning, creativity, critical thinking, and problem-solving. More generally, it can b ...
Eugenics