IQ: Viewpoints and Controversies

Cynthia Crosser. 21st Century Anthropology: A Reference Handbook. Editor: H James Birx. Volume 2. Thousand Oaks, CA: Sage Reference, 2010. 

All cultures value intelligence; however, definitions of what constitutes intelligence vary across cultures. The term intelligence quotient (IQ) was coined by German psychologist William Stern (1871-1938) in 1912. IQ tests measure specific skills and specific knowledge that have been used to represent overall intelligence. The exporting and translation of Western measurements of intelligence through IQ testing has influenced views of intelligence globally. In the West, IQ testing has generated controversy as beliefs and assumptions have been challenged. There are three major issues for IQ testing: the question of whether there is a single general intelligence or multiple intelligences, the nature-nurture debate, and the use of IQ tests in policy and legal decisions.

Western psychometric IQ testing is based on the assumption that humans have a general intelligence that can be measured quantitatively. However, this assumption is not universally accepted. Opposing theorists such as American psychologists Louis Thurstone (1887-1955) and Howard Gardner (b. 1943) claim that intelligence is really composed of discrete abilities and cannot be viewed as a single cognitive entity.

The nature-nurture debate has generated a great deal of controversy. While many researchers accept an interaction between genetics and heredity, others have taken more extreme positions. British psychologist Cyril Burt (1883-1971) used twin studies in the 1950s to claim that genetics play the only important role, while Canadian cultural psychologist John Berry (b. 1939) argued in 1974 that intelligence can be viewed only as a cultural construct.

The use of IQ tests for policy and legal decisions has been and continues to be highly controversial. IQ testing has been involved in the areas of education, employment, immigration, and law, this last with respect to sterilization. IQ testing continues to play a role in screening for special needs students and as a gatekeeper for programs for gifted students in the United States. Related standardized aptitude and achievement tests are used for admissions in higher education and for job placement in the military.

The General Intelligence Controversy

Views of intelligence are dependent on the metaphors and assumptions of a culture. The Western concept of a generalized measure of intelligence can be traced back to the ancient Greek philosopher Plato (427-347 BCE), who compared people’s intelligence to blocks of wax differing in size, hardness, moistness, and purity. The view of multiple intelligences can be traced back to the 18th-century German philosopher Immanuel Kant’s (1724-1804) portrayal of intelligence as a multifaceted structure. More recently, the emergence of psychology as an academic field has driven Western concepts of intelligence and the emergence of IQ testing.

IQ testing has two main branches of development, with one branch following the assumption of a general intelligence and the other advocating the view of multiple intelligences. The first branch has become accepted in educational psychology, and its assumptions are those that are widely used in screening students for special programs. The multiple intelligences view had been incorporated into educational curricula and is used in cross-cultural research.

Development of General Intelligence Testing

British biologist Francis Galton (1822-1911) was a 19th-century pioneer of mental testing research. Galton was influenced by the work of his cousin, Charles Darwin, and the philosophy of Wilhelm Wundt (1832-1920). Wundt’s psychological laboratory in Leipzig, Germany, studied the general principles of sensation, perception, and other mental processes using laboratory techniques that were state of the art for that time period. Galton believed that intelligence was a general inherited characteristic composed of an individual’s perceptual sensitivity and the capacity to exert effort. Galton assumed that this general mental ability could be objectively measured using tests for sensory discrimination and reaction times. Galton devised and ran tests to measure differences in the ability to discriminate differences in weight, tone, color, and other perceptual differences. His book Hereditary Genius: An Inquiry Into Its Laws and Consequences, which was published in 1869, influenced the thinking of subsequent researchers. Galton was the first researcher to use a normal distribution curve to map out differences in intelligence. This was an important contribution that is still utilized today.

Some of Galton’s beliefs have generated controversy, especially his assumptions that intelligence is biologically based and varies by race and social class. Galton believed that members of higher social classes should perform better on sensory-based intelligence tests. He coined the term eugenics, the practice of selective reproduction, as a way to improve mankind as a species.

In 1890, American psychologist James Cattell (1860-1944) proposed 50 tests, including tests for physical strength, movement speed, reaction time, and memory, which he believed would correlate with intelligence. He conducted large-scale testing of college students in an attempt to correlate his tests with each other and with measures of intelligence, such as college grades. The research did not produce the desired results. However, British psychologist Charles Spearman (1863-1945) believed that poor methodology was responsible for Cattell’s failure to show correlations among tests associated with intelligence.

Spearman was attracted to Galton’s concept of a general mental ability with a strong biological basis. In 1904, Spearman used factor analysis to postulate the existence of general intelligence as the correlation among all complex mental tests. He developed a two-factor theory of general (g) and specific (s) intelligence, with g describing the variance attributed to general intelligence and s describing the variance that is unique for each individual test. Because he was able to connect a theoretical construct with a mathematical correlation, Spearman’s work helped to establish a school of thought that assumes intelligence as a single mental reality with an inherited biological basis. This has given rise to the continued practice of measuring overall intelligence using tests believed to measure components of general intelligence. In addition to his impact on the field of intelligence, Spearman made important contributions to the field of statistics. Statistics continues to be used as an important tool in intellectual assessment.

Alfred Binet (1857-1911) and Theodore Simon (1863-1961) published the first modern intelligence test in L’année psychologique in 1905. The goal of their assessment scales was to identify children who would benefit from special education classes. Binet and Simon believed in a general intelligence based on higher-level judgment skills. The original Binet-Simon test was an untimed test administered individually by a trained examiner. The test consisted of a series of tasks of increasing difficulty. Binet and Simon believed that each task represented the normal level of performance for a given age. The highest level that a child successfully performed was designated as his or her mental age. The Binet-Simon test laid the foundation for all individually given IQ tests today.

American psychologist Henry Goddard (1866-1957) was the first to translate the Binet-Simon test into English, distributing thousands of copies throughout the United States for testing students in public schools. Goddard’s work was influential in advocating a strong heritability of intelligence. His book The Kallikak Family: A Study in the Heredity of Feeble-Mindedness, first published in 1912, argues for a strict genetic view of feeblemindedness (very low intelligence). Goddard also proposed the controversial solution of involuntary sterilization of the feebleminded to improve the intelligence of the American people.

Goddard was invited to test immigrants at Ellis Island in 1913. Using his version of the Binet-Simon intelligence test, Goddard concluded that the intelligence of the average steerage passenger was very low. Because the immigrants tested came from Southern and Eastern Europe, public perception of the people from these regions was negative. This negative view of the intelligence of immigrants from these countries influenced the establishment of immigration quotas.

American psychologist Lewis Terman (1877-1956) translated and adapted the revised Binet-Simon Intelligence Test Scales for use in the United States in 1916. Terman also incorporated the intelligence quotient that had been introduced by William Stern in 1912. Stern defined the intelligence quotient (IQ) as the ratio of the mental age and the chronological age multiplied by 100 (e.g., 10 years/8 years × 100 = 125). Terman called his new version the Stanford-Binet Intelligence Test Scales (SBITS). The SBITS is in its fifth revision and is still used today as a measure of general intelligence. It is not without controversy and has been criticized as culturally biased.

The United States entered World War I in 1917. During this critical time the military worked with psychologists to adapt the Stanford-Binet for group testing. In 1917, Robert Yerkes (1876-1956), head of the American Psychological Association, lobbied and received permission from the National Research Council to create a Committee on Psychology. As chair of this committee, Yerkes was responsible for bringing together psychologists (including Henry Goddard and Lewis Terman) to modify the SBITS for use by the U.S. Army. The army was interested in classifying recruits according to their mental abilities for job placement.

Yerkes’s group designed two multiple choice tests that could be administered to groups. The alpha test was given to literate recruits, and the beta test was given to recruits who could not read and write in English, if at all. The army tests are significant for two reasons. First, the change in format provided a model for group testing, and second, the results were interpreted to indicate that recent immigrants from Southern and Eastern Europe were of lower intelligence than immigrants from Western Europe, who tended to have been in the country longer. Although the results showed a strong correlation between years living in the United States and scores on the Army Beta test, this explanation was rejected by Yerkes in favor of a biological explanation.

David Wechsler (1896-1981), who had been involved with Army intelligence testing during World War I, published the Wechsler-Bellevue Intelligence Scales in 1939. Wechsler was influenced by Spearman’s work on generalized intelligence. His intelligence scales comprised the verbal and nonverbal factors believed to compose general intelligence. The Wechsler scales are performance tests that measure a person’s ability to complete a drawing or provide verbal definitions of orally presented words. Because Wechsler worked initially with adults, he rejected the concept of a mental age. He developed a point system that could be used effectively for both children and adults. Each subtest reflected an ability that expressed general intelligence. A major innovation came in 1949 with the introduction of the deviation IQ score. Wechsler scales yield IQ scores with a mean (or average) score of 100 and a standard deviation of 1.5. Individuals are compared to others their own age when computing the IQ score. The deviation score has replaced the mental age score as the standard way for measuring IQ. Tests derived from the original Wechsler intelligence tests are still used today.

Wechsler’s biggest contributions to the field of intelligence testing were his use of standardization sampling and normalizing procedures. However, despite these procedures, the Wechsler tests generated criticisms of cultural bias. Researchers looked for ways to get beyond the limitations of language problems and culture-specific knowledge. In 1936, John C. Raven (1902-1970) developed Raven’s Progressive Matrices Test, an untimed nonverbal assessment of abstract reasoning. To answer test questions, participants identify the missing segment necessary to complete a larger pattern. In 1940, Raymond Cattell (1905-1998) introduced the concept of the Culture-Fair Test. The purpose of this test is to avoid test bias based on linguistic skills and general knowledge. This was the first test designed to distinguish between genetic and environmental factors in intelligence. Both tests are still in use today in the United States and internationally. They have both generated criticisms that they are not free of cultural bias.

In the mid-1950s, English psychologist Cyril Burt (1883-1971) published a series of studies on monozygotic twins. Burt claimed that monozygotic twins reared together had an almost perfect correlation on tests of intellectual ability. He went on to claim that monozygotic twins reared apart showed only slightly less similarity on intellectual tests. Burt used his data to argue that the environment played no role in differences in intelligence and to argue for biological differences between social classes in Great Britain. Subsequent research has shown that Burt was careless or dishonest in reporting his data and that the correlations were lower than he reported. However, Burt’s work formed the basis of subsequent research by Arthur Jensen (b. 1923), who claimed in a 1969 article in the Harvard Educational Review that biological differences between individuals of different races are responsible for differences in IQ between white and African American students. Jensen’s article incited sharp reactions from the American Anthropological Society and the Society for the Psychological Study of Social Issues, a division of the American Psychological Association.

John L. Horn (1928-2006) and Raymond Cattell published several important articles on the theory of fluid and crystallized intelligence in 1966. This theory assumes the existence of a general entity of intelligence and divides it into a fluid general intelligence (fg) and crystallized general intelligence (cg). The former refers to the ability to draw inferences and understand relationships in new situations, while the latter refers to abilities dependent on knowledge and experience. In its simplest version, crystallized intelligence is said to increase over time, while fluid intelligence declines with age. This theory generated controversy because of test results indicating racial group differences in fluid intelligence.

American psychologist Richard Herrnstein (1930-1994) and political scientist Charles Murray (b. 1943) published The Bell Curve in 1994. This book claims that intelligence is one of the most important factors in socioeconomic success in the United States. It also claims that IQ plays a role in socioeconomic differences among races. Both the American Anthropological Association and the American Psychological Association responded to the controversy surrounding publication of The Bell Curve. In December 1994, the American Anthropological Association issued an official statement in response, disputing the existence of biological racial categories as a concept with any value for explaining human variation in intelligence or other traits. In 1996, the American Psychological Association published “Intelligence: Known and Unknowns” (Neisser et al., 1996). This paper acknowledges group differences between whites and African Americans, but claims that the reasons for these differences are unknown.

Development of Multiple Intelligences Testing

Although many researchers in the early 20th century believed that intelligence was a single biological entity, others challenged this view. American psychologist Louis Thurston (1887-1955) disputed the results of Spearman’s factor analysis. Thurston’s 1938 book Primary Mental Abilities proposed that intelligence is not a single factor. Thurston claimed that intelligence is composed of seven primary abilities or factors: word fluency, verbal comprehension, spatial processing, ability to perform numeric calculations, memory, induction, and perceptual speed. Thurston’s work in statistics has been disputed; however, it laid a foundation for the view that does not accept the concept of a general intelligence.

Canadian psychologist George A. Ferguson (b. 1914) published “On Transfer and the Abilities of Man” in 1956. Ferguson argued that culture plays a critical role in learning. Ferguson admitted that biology fixes limits for learning but disputed the idea that intelligence is biologically determined. He argued that society has an obligation to provide educational processes to improve outcomes for its people. Ferguson influenced the work of John Berry.

Canadian cultural psychologist John Berry (b. 1939) published the controversial book chapter “Radical Cultural Relativism and the Concept of Intelligence” in 1974. Berry rejected assumed universals across cultural systems, claiming that intelligence can only be understood as an indigenous construct within a cultural context. This work challenged the practice of using Western intelligence testing cross-culturally. In subsequent publications, Berry accepted biologically universal concepts such as memory but posited ecological influences as the most important factors in determining intelligence.

In 1974, American psychologist Leon Kamin (b. 1928) published The Science and Politics of IQ, in which he claimed that there was no evidence that IQ was heritable. Kamin’s book was instrumental in discrediting Cyril Burt’s research on identical twins reared apart. German-born psychologist Hans Eysenck (1916-1997), who had studied under Burt in London, challenged Kamin’s attack on Burt. However, Kamin’s criticism of Burt was followed by further examination, resulting in a general disbelief in Burt’s results. Kamin’s claim that there is no evidence for the genetic basis of intelligence remains controversial. However, his work has been influential on educational practices, such as tracking students by ability.

In 1977, two issues of the journal Principal were brought out in the book The Myth of Measurability. This book, edited by Paul L. Houts (b. 1937), the journal’s director of publications and editor, contains 29 papers that are highly critical of general tests for intelligence. The book includes articles dealing with issues of cultural bias and articles claiming that general intelligence does not exist. This controversial book encouraged the development of theories of multiple intelligences.

American paleontologist, evolutionary biologist, and historian of science Stephen J. Gould (1941-2002) published The Mismeasure of Man in 1981. Gould argued against the concepts of generalized intelligence, the heritability of intelligence, and the ranking of individuals by IQ. This book generated a great deal of controversy and there were claims that the book contained inaccuracies.

In 1983, American psychologist Howard Gardner (b. 1943) published Frames of Mind. Gardner reviewed the data in studies of intelligence using eight criteria for indicators of intelligence:

  1. Potential isolation by brain damage
  2. The existence of idiots savants, prodigies, and other exceptional individuals
  3. An identifiable core operation or set of operations
  4. A distinctive development history, along with a definable set of “end-state” performances
  5. An evolutionary history and evolutionary plausibility
  6. Support from experimental psychological tasks
  7. Support from psychometric findings
  8. Susceptibility to encoding in a symbol system

Gardner suggested the existence of seven separate intelligences: linguistic, logical-mathematical, musical, bodily-kinesthetic, spatial, interpersonal, and intrapersonal. This work played an important role in setting criteria that could be used to evaluate separate intelligences and has been incorporated into teaching methods. However, a way of assessing the individual intelligences has not be published or endorsed by Gardner.

Robert Sternberg (b. 1949) published Beyond IQ: A Triarchic Theory of Human Intelligence in 1985. Sternberg believes intelligence comprises three components: the analytical, the creative, and the practical. Sternberg believes intelligence must be translated into real-life success and is dependent on motivation, perseverance, and self-control. In 1991 he proposed the Sternberg Triarchic Abilities Test (STAT) to measure his theory of intelligence. Because the triarchic theory includes an assessment tool, it provides a possible alternative to IQ testing that assumes an overall general intelligence. This test is used in cross-cultural research.

Cultural Bias in Modern General Intelligence Tests

The existence of a general intelligence that drives the ability to reason, plan, problem solve, and think abstractly remains theoretically controversial. The main criticism of these tests has been that they are culturally biased. Cultural bias can be a problem for use internationally and for use with minority ethnic groups in the country that developed the test. An example of a culturally biased test item would be an analogy question involving snow given to young children in Hawai’i, who may have never experienced snow.

The Stanford-Binet V of 2003 is an IQ test that is used to assess individuals between the ages of 2 and 90. Some important characteristics of the original test have remained. The test is still untimed and given individually by a trained examiner. However, it has been altered so that verbal and nonverbal skills are weighted equally. Also, it is no longer based on mental age. Instead the deviation IQ measures a person’s performance relative to others of the same chronological age. The test has been statistically renormalized against a large population so that the results of individual assessments can be statistically compared with those of a large up-to-date base population. However, there is still some controversy as to the accuracy and cultural bias of the test.

The Wechsler Intelligence Scales include the Wechsler Adult Intelligence Scale (WAIS), Wechsler Intelligence Test for Children (WISC), and the Wechsler Preschool and Primary Scale of Intelligence (WPPSI). The WAIS IV of 2008 and the WISC IV of 2003 include a composite general intelligence score and subtests measuring verbal comprehension, perceptual reasoning, working memory, and processing speed. The WPPSI III of 2003 provides subtest scores in verbal and performance cognitive domains, and includes a composite general intelligence score. Although the tests have been modified and updated, there are still claims of cultural bias in the Wechsler Intelligence Scales.

Raven’s Progressive Matrices Test is an untimed nonverbal assessment of abstract reasoning. The test questions require the participant to identify the missing segment necessary to complete a larger pattern. Three versions of the test exist: Standard Progressive Matrices (all ages), Colored Progressive Matrices (children only), and Advanced Progressive Matrices (all ages with above-average intelligence). This test can be used for assessing individuals with language deficits. Because the test does not require competence in any language, it is useful internationally. This test has generated some controversy over its use in some third world countries, such as South Africa. It is claimed that cultural differences render the test inappropriate to some groups.

The theory of fluid and crystallized intelligence put forward by John Horn and Raymond Cattell was incorporated into the Kaufman Adolescent and Adult Intelligence Test (KAIT), first published in 1993. The fluid portion of the KAIT tests for the ability to decode picture-words and to solve logic problems. The crystallized portion tests comprehension of oral stories, words with double meanings, and definitions. The KAIT has been criticized for its lack of multicultural consideration.

Cultural Bias and Achievement Tests/Aptitude Tests

While intelligence tests are designed to measure general thinking abilities, achievement/aptitude tests are designed to test specific knowledge acquisition. However, standardized achievement/aptitude tests are highly correlated with IQ scores and are frequently included in the controversy of cultural bias. Examples include the Armed Services Vocational Aptitude Battery (ASVAB), the SAT (formerly Scholastic Aptitude Test or Scholastic Assessment Test), the Graduate Record Examination (GRE), and the Law School Admission test (LSAT).

The SAT, originally known as the Scholastic Aptitude Test, was first used in 1926 as a measurement of a student’s level of preparation for college work. The SAT was most recently updated in 2005, with the introduction of a writing section. The current version assesses critical reading, mathematics, and writing. Use of the test as an assessment of college preparedness is controversial because of charges that it is culturally biased. A 2006 USA Today article (Bruno, 2006) reported that many liberal arts colleges, including Bowdoin, Middlebury, Hamilton, and Bates, have made the SAT optional. The National Collegiate Athletic Association 2008 eligibility requirements for incoming Division I freshmen do not have a minimum SAT requirement. Instead, freshman eligibility is judged on a sliding scale incorporating both grade point average (GPA) and combined scores of the reading and mathematics sections of the SAT. A Division I incoming freshman with a GPA of 3.5 or over requires a combined mathematics and reading score of 400; a student with a GPA of 2.0 must have a combined score of 1010.

The ASVAB was introduced as an assessment tool in 1968 and was most recently updated in 2002. Although the official ASVAB site claims that the test is not an intelligence test, the test is used to sort individuals for military placement and as a tool for career placement in high schools. The ASVAB is controversial both because of charges that it is culturally biased and because the military uses it to recruit high school seniors who are given the test for occupational testing. The ASVAB tests knowledge in eight areas: general science, arithmetic reasoning, word knowledge, paragraph comprehension, mathematics knowledge, electronics information, auto and shop information, and mechanical comprehension.

A group called FairTest, first formed in 1985, monitors standardized tests for evidence of bias. This group tries to ensure that tests are reliable, valid, and used appropriately. FairTest has also been active in lobbying for more access to test data and the establishment of alternative testing procedures.

The Nature-Nurture Controversy

Most researchers accept that intelligence is based on both genetic and environmental factors. Some researchers have taken extreme positions, such as those mentioned above of British psychologist Cyril Burt and Canadian cultural psychologist John Berry.

Genetic Factors and Intelligence

Heritability of Intelligence

Heritability refers to the proportion of a characteristic that is attributable to genetic variance. It is a population concept that ranges from a proportion of 0.0 to 1.0. A heritability of .50 would indicate, on average, 50% of the individual differences that we observe in a trait or behavior are attributable to genetic individual differences in the population. It does not mean that 50% of any person’s trait or behavior is due to genes and the other 50% is due to environment. Heritability depends on the range of typical environments in the population that is studied. If the environment of the population is fairly uniform, then heritability can be high, but if the range of environmental differences is large, then heritability can be low.

According to a 1996 review of the literature on intelligence published by the American Psychological Association, the heritability of intelligence of varies with age. Research indicates that in children it is estimated to be about .45, while in adults it is estimated to be .75. This means that as children grow up, intelligence test scores tend to increasingly reflect their specific genes and individual experiences rather than differences among the families in which they were raised. The reasons for the shift are unknown. It should be noted that most of the available studies included in the review dealt with white Americans and that the lack of subjects from other cultural backgrounds in the study is a known limitation.

Twin Studies

Although Francis Galton did not originate the use of twin studies, he was the first researcher to make use of the genetic similarity between twins to study the nature-nurture question. The results of his study were published in an 1876 article, “The History of Twins as a Criterion of the Relative Powers of Nature and Nurture.” Unfortunately, the difference between monozygotic (identical) and dizygotic (fraternal) twins was not understood at that time, which limits the usefulness of his research.

Monozygotic twins have 100% genetic similarity, while dizygotic twins have approximately 50% genetic similarity. The most powerful type of twin study involves comparing adopted monozygotic twins reared separately with monozygotic twins reared in the same home. These studies assume that twins reared in the same home will experience the same environment, while twins reared apart will have different environments. Since ethics prevents twins being deliberately placed in extreme environments, the effects of environments that are radically different cannot really be tested.

The first well-known modern twin studies were performed by British psychologist Cyril Burt in the 1950s. Burt reported in several studies that monozygotic twins reared together had almost perfect correlations in intelligence tests and that monozygotic twins reared apart had only slightly less strong correlations. He used his test results to claim that biology is the only important factor in intelligence, as noted earlier. American psychologist Leon Kamin discredited Burt’s work in 1974. It is now believed that Burt was either extremely careless or dishonest in reporting his results. A literature review published in 1997 by Thomas Bouchard (b. 1937), director of the Minnesota Center for Twin and Adoption Research at the University of Minnesota, gives the average correlation of intelligence tests between identical twins reared apart as 75%.

Intelligence as a Cultural Construct

The strong view that John Berry posited in 1974 claims that intelligence can only be viewed as a cultural construct. In later publications with other researchers, Berry proposed the law of cultural differentiation or Ferguson’s law based on the following quote from Ferguson’s 1956 paper on cognitive transfer: “Cultural factors prescribe what shall be learned and at what age; consequently different cultural environments lead to the development of different patterns of ability.” This view of intelligence is controversial.

Researchers such as Hans Eysenck and Arthur Jensen, who believe that intelligence is the same cross-culturally, contest this view and believe that properly translated tools can be successfully used internationally. American psychologist Robert Sternberg has argued for a middle position, claiming that intelligence is the same across cultures but that the instruments of measurement are not. Sternberg believes that the components of intelligence are universal but that the types and items of knowledge vary across cultures.

A literature review by Sternberg in 2007 provides examples of modern views of intelligence in China and Africa. A 1994 study conducted in Taiwan argues that the Chinese conception of intelligence involves three factors: nonverbal reasoning ability, verbal reasoning ability, and rote memory. A 1997 study also conducted in Taiwan argues that the Chinese view of intelligence involves five factors: a general cognitive factor, interpersonal intelligence, intrapersonal intelligence, intellectual self-assertion, and intellectual self-effacement. A 1996 study of Chewa adults in Zambia claims that this group considers intelligence to consist of performance in three areas: social responsibilities, obedience, and cooperativeness. Sternberg’s review of the literature makes clear the need for more cross-cultural research on intelligence.

Intelligence and Gender

Before educational opportunities for women were equal to those for men, it was frequently assumed that males had intelligence that was superior to that of females. Modern research has not found significant gender effects for intelligence. Most research has found differences in patterns of mental abilities rather than differences in overall intelligence. Visual-spatial and mathematical abilities are generally superior for males, while verbal and memory abilities are generally higher for females.

However, some researchers are still pursuing this line of research. Canadian psychologist Phillipe Rushton (b. 1943) and other researchers used biological measures, such as head size, and academic achievement tests, such as the SAT, to claim that males have superior intelligence (Jackson & Rushton, 2006). The addition of the writing section to the SAT may address this issue, since females generally outperform males in language abilities.

Intelligence and Race

General intelligence tests in the United States consistently find group differences for race. Some researchers, such as Arthur Jensen and Phillipe Rushton, continue to argue that biological differences between races are responsible for group differences in intelligence test results. Other researchers, such as Leon Kamin, argue that environmental factors are responsible for group differences. The American Psychological Association acknowledges differences in group results but claims that the reasons are unknown. The American Anthropological Association claims that race is not a valid category.

The Bell Curve

American psychologists Richard Herrnstein (1930-1994) and political scientist Charles Murray (b. 1943) published The Bell Curve in 1994. This book claims that intelligence is one of the most important factors in socioeconomic success in the United States. It also claims that IQ plays a role in socioeconomic differences between races. Both the American Anthropological Association and the American Psychological Association responded to the controversy surrounding publication of The Bell Curve.

Official Statement of the American Anthropological Association

The American Anthropological Association released the following statement in December 1994 in response to the controversy surrounding the publication of The Bell Curve earlier that year:

The American Anthropological Association (AAA) is deeply concerned by recent public discussions which imply that intelligence is biologically determined by race. Repeatedly challenged by scientists, nevertheless these ideas continue to be advanced. Such discussions distract public and scholarly attention from and diminish support for the collective challenge to ensure equal opportunities for all people, regardless of ethnicity or phenotypic variation…,

WHEREAS all human beings are members of one species, Homo sapiens, and

WHEREAS, differentiating species into biologically defined “races” has proven meaningless and unscientific as a way of explaining variation (whether in intelligence or other traits),

THEREFORE, the American Anthropological Association urges the academy, our political leaders and our communities to affirm, without distraction by mistaken claims of racially determined intelligence, the common stake in assuring equal opportunity, in respecting diversity and in securing a harmonious quality of life for all people.

Literature Review From the American Psychological Association

The following quote is taken from a paper published by the American Psychological Association in 1995. Prompted by the public controversy surrounding the publication of The Bell Curve in 1994, this paper reviews the relevant literature on intelligence and summarizes important findings:

Differences in genetic endowment contribute substantially to individual differences in (psychometric) intelligence, but the pathway by which genes produce their effects is still unknown. The impact of genetic differences appears to increase with age, but we do not know why.

Environmental factors also contribute substantially to the development of intelligence, but we do not clearly understand what those factors are or how they work. Attendance at school is certainly important, for example, but we do not know what aspects of schooling are critical….

The differential between the mean intelligence test scores of Blacks and Whites (about one standard deviation, although it may be diminishing) does not result from any obvious biases in test construction and administration, nor does it simply reflect differences in socioeconomic status. Explanations based on factors of caste and culture may be appropriate, but so far have little direct empirical support. There is certainly no such support for a genetic interpretation. At present, no one knows what causes this differential.

Controversies in Group Results

Controversies in education, immigration, hiring practices, and reproductive freedom have all been affected by group results in general IQ tests. The manner in which the results affect society is influenced by views of the nature-nurture debate.

Policy and Legal Controversies in Education

Head Start

American educational researcher Benjamin Bloom (1913-1999) published Stability and Change in Human Characteristics in 1964. Bloom’s book rejects the view of biological determinism for intelligence and advocates the mastery of educational goals for all children. Bloom’s work was influential in the establishment of the Head Start program in 1964.

In 1969, Arthur Jensen, an educational psychologist at the University of California, Berkeley published the highly controversial article mentioned previously, “How Much Can We Boost IQ and Scholastic Achievement?” In this article, Jensen argues that programs such as Head Start, which were designed to promote school readiness by enhancing the social and cognitive development of children, could never succeed because of the heritability of IQ. Jensen claims that the lower IQ scores of African Americans are caused primarily by racial differences. The article led to protests outside his office in Berkeley and numerous publications disputing his claims. The Society for the Psychological Study of Social Issues, a division of the American Psychological Society, issued a five-page statement to news agencies outlining their disagreement with Jensen’s conclusions. The 1969 convention of the American Anthropological Society passed a resolution condemning him. The controversy surrounding Jensen brought to light the polarized views of the nature-nurture controversy and the way in which they impact views of educational policy.

In 2005, a review of the intelligence literature by Rushton and Jensen was published in Psychology, Public Policy, and Law. The authors defend Jensen’s original position on Head Start and argue for the abolishment of affirmative action. A reply by Robert Sternberg challenging this view was printed in the same journal issue (Sternberg, 2005).

Tracking and Special Education

The federal suit Hobson v. Hansen in 1967 had a huge impact on the use of group-administered IQ tests for school tracking. The Hobson case claimed that the tracking program then in place in the Washington, D.C., public schools violated Title VI of the Civil Rights act of 1964. The evidence in the case was based on the disproportionate number of African American children in the lower-ability tracks. Judge Skelly Wright ruled that the tests were racially biased. This ruling eliminated the tracking system in the D.C. public schools.

One of the most important legal cases involving education policy is Larry P. v. Wilson Riles. The parents of seven African American children brought suit against the State of California in November 1971, claiming that their children had been incorrectly placed in classes for the educable mentally retarded (EMR), based on the children’s scores on an IQ test. This suit claimed that the individually administered IQ test was culturally biased. During the course of the trial, Judge Robert Peckham granted a temporary injunction halting any future placement of African American children into EMR classes on the basis of intelligence tests. In 1979, Judge Peckham ruled that the tests were culturally biased. The verdict was upheld by the U.S. Court of Appeals for the Ninth Circuit in 1984. In 1992, a federal judge ruled that African American students could be given intelligence tests at the request of their parents.

Employment and IQ Testing

U.S. employers’ use of intelligence testing in hiring practices increased from 26% in 1940 to 63% in 1957. The federal government played a role in increasing employer testing by making intelligence tests available free of charge through the U.S. Employment Service, which was founded by the Wagner-Peyser Act of 1933. However, controversy over the use of intelligence testing in the workplace led to lawsuits.

The case of Griggs v. Duke Power Company set important precedent for the use of intelligence testing by employers. A group of African American employees brought suit against the power company, claiming that their rights were being violated under the Civil Rights Act of 1964. The company had a policy of requiring a high school diploma and a satisfactory intelligence score for certain jobs. The effect of the policy was to maintain the practice of segregation that had been in place prior to the passage of the Civil Rights Act. The U.S. Supreme Court ruled on March 8, 1971, that employers could use general intelligence test scores only in special circumstances. The ruling specified that high school diplomas and minimum scores on general intelligence tests could be used as job requirements only if they could be shown to significantly relate to job performance.

In 1989, the Committee on the General Aptitude Test Battery published Fairness in Employment Testing. This report deals with a proposal by the U.S. Department of Labor to promote use of the General Aptitude Test Battery throughout the U.S. Employment Service. The report concludes that test score adjustments are necessary for African Americans and Hispanics because of test bias.

The Law and Sterilization Based on IQ

The eugenics movement in the United States advocated for the use of compulsory sterilization of individuals with low intelligence or mental illness. Indiana became the first state to pass a compulsory sterilization law in 1907. California and Washington passed similar laws in 1909. In Buck v. Bell, the U.S. Supreme Court upheld the 1924 Virginia law requiring sterilization of the mentally retarded. The ruling on this case encouraged other states, and eventually 33 states passed compulsory sterilization laws. The Virginia law was repealed in 1974, following a national trend to discontinue the practice.

In Canada, the province of Alberta passed the Sexual Sterilization Act in 1928 (Grekul, Krahn, & Odynak, 2004). A four-member Alberta Eugenics Board was created to oversee approval of procedures. The Sterilization Act was used as a basis for compulsory sterilization of over 2,800 people between 1929 and 1972, when the act was repealed. Aboriginals were particularly targeted by the Alberta Eugenics Board. In 1995, Leilani Muir successfully sued the Alberta government for performing a wrongful sterilization on her in 1959, and she was awarded $740,000 in damages and $230,000 in legal costs. After Muir’s case was decided, a class action lawsuit on behalf of other sterilized individuals reached an out-of-court settlement with the government of Alberta. Approximately 700 people were awarded damages for wrongful sterilization.

After taking power in Germany, the Nazi government introduced the 1933 Law for the Prevention of Offspring with Hereditary Diseases. This law required all physicians to register every case of hereditary illness, including low IQ. Only women over the age of 45 were exempt, since they were considered too old to produce children. The law was used as a basis for the forced sterilization of over 400,000 people between 1934 and 1937.

IQ Testing and Immigration Policy

The public perception of immigrants from certain countries was influenced by Henry Goddard’s work on Ellis Island in 1913 and Robert Yerkes’s work on U.S. Army testing during World War I. Belief in the intellectual inferiority of certain peoples led to passage of the Immigration Restriction Act of 1924. This law introduced quotas for countries in Southern and Eastern Europe and eliminated immigration from Asia. This law remained in effect until passage of the Immigration and Nationality Act of 1965.


All cultures value intelligence. Western culture developed IQ testing that reflected the cultural values and scientific beliefs that were held at the time the tests were developed. Divergent beliefs and values are reflected in the controversies surrounding IQ testing. There are three major issues for IQ: the question of whether there is a single general intelligence or multiple intelligences, the nature-nurture debate, and the use of IQ tests in policy and legal decisions. The first of these three questions has not been answered. Instead the two views are reflected in different usages. General intelligence tests are used to screen for special education and as a gatekeeper for gifted programs in public schools. The theory of multiple intelligences has been incorporated into curriculum theory for teaching purposes and is used for cross-cultural research. Although most researchers accept that the interaction of genetics and environment determines intelligence, the topic still excites controversy. The use of group results for policy and legal decisions remains an important controversy. As recently as 2005, Rushton and Jensen advocated changing public policies, such as affirmative action, because African Americans’ scores on intelligence tests were lower than those of other groups.

Recent research has provided new insights about the views of intelligence in other cultures. Further cross-cultural research is needed to help answer the controversial issues in intelligence testing.