History of the debate
(1857–1911), inventor of the first intelligence test
Claims of races having different intelligence were used to justify colonialism, slavery, racism, social Darwinism, and racial eugenics. Racial thinkers such as Arthur de Gobineau relied crucially on the assumption that black people were innately inferior to whites in developing their ideologies of white supremacy. Even enlightenment thinkers such as Thomas Jefferson, a slave owner, believed blacks to be innately inferior to whites in physique and intellect.
Early IQ testing
The first practical intelligence test was developed between 1905 and 1908 by Alfred Binet 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 (who introduced IQ scoring for the test results) and published under the name the Stanford–Binet Intelligence Scales. As Terman's test was published, there was great concern in the United States about the abilities and skills of recent immigrants. Different immigrant nationalities were sometimes thought to belong to different races, such as Slavs. A different set of tests developed by Robert Yerkes were used to evaluate draftees for World War I, and researchers found that people from southern and eastern Europe scored lower than native-born Americans, that Americans from northern states had higher scores than Americans from southern states, and that black Americans scored lower than white Americans. The results were widely publicized by a lobby of anti-immigration activists, including the New York patrician and conservationist Madison Grant, who considered the Nordic race to be superior, but under threat of immigration by inferior breeds. In his influential work, A Study of American Intelligence, psychologist Carl Brigham 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, states like Virginia enacted eugenic laws, such as its 1924 Racial Integrity Act, which established the one-drop rule 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 to test results (such as speaking English as a second language). By the mid-1930s, many United States psychologists adopted the view that environmental and cultural factors played a dominant role in IQ test results, among them Carl Brigham, who repudiated his own previous arguments on the grounds that he realized that the tests were not a measure of innate intelligence. Discussion of the issue in the United States also influenced German Nazi claims of the "Nordics" being a "master race", influenced by Grant's writings. As the 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, and Ruth Benedict and Gene Weltfish, did much to demonstrate the unscientific status of many of the claims about racial hierarchies of intelligence. Nonetheless, a powerful eugenics and segregation lobby funded largely by textile-magnate Wickliffe Draper continued to publicize studies using intelligence studies as an argument for eugenics, segregation, and anti-immigration legislation.
The Jensenism debates
As the de-segregation of the American South gained traction in the 1950s, the debate about black intelligence resurfaced. Audrey Shuey, funded by Draper's Pioneer Fund, published a new analysis of Yerkes' tests, concluding that blacks really were of inferior intellect to whites. This study was used by segregationists as an argument that it was to the advantage of black children to be educated separately from the superior white children. In the 1960s, the debate was further revived when William Shockley publicly defended the argument that black children were innately unable to learn as well as white children. Arthur Jensen stimulated scholarly discussion of the issue with his Harvard Educational Review article, "How Much Can We Boost IQ and Scholastic Achievement?" Jensen's article questioned remedial education for African-American children; he suggested their poor educational performance reflected an underlying genetic cause rather than lack of stimulation at home. Jensen continued to publish on the issue until his death in 2012.
The Bell Curve debate
Another revival of public debate followed the appearance of The Bell Curve (1994), a book by Richard Herrnstein and Charles Murray, who strongly emphasized the societal effects of low IQ (focusing in most chapters strictly on the non-Hispanic white population of the United States). In 1994, a group of 52 researchers (mostly psychologists) signed an editorial statement "Mainstream Science on Intelligence" in response to the book. The Bell Curve also led to a 1995 report from the American Psychological Association, "Intelligence: Knowns and Unknowns", acknowledging a difference between mean IQ scores of whites and blacks as well as the absence of any adequate explanation of it, either environmental or genetic. The Bell Curve prompted the publication of several multiple-author books responding from a variety of points of view. They include The Bell Curve Debate (1995), Inequality by Design: Cracking the Bell Curve Myth (1996) and a second edition of The Mismeasure of Man (1996) by Stephen Jay Gould. Jensen's last book-length publication, The g Factor: The Science of Mental Ability, was published a few years later in 1998.
The review article "Thirty Years of Research on Race Differences in Cognitive Ability" by Rushton and Jensen was published in 2005. The article was followed by a series of responses, some in support, some critical. Richard Nisbett, another psychologist who had also commented at the time, later included an amplified version of his critique as part of the book Intelligence and How to Get It: Why Schools and Cultures Count (2009). Rushton and Jensen in 2010 made a point-by-point reply to this thereafter. A comprehensive review article on the issue was published in the journal American Psychologist in 2012.
Some of the authors proposing genetic explanations for group differences have received funding from the Pioneer Fund, which was headed by Rushton until his death in 2012. The Southern Poverty Law Center lists the Pioneer Fund as a hate group, citing the fund's history, its funding of race and intelligence research, and its connections with racist individuals. Other researchers have criticized the Pioneer Fund for promoting scientific racism, eugenics and white supremacy.