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== Background information == == Background information ==


'''Racial distinctions''' are most often made on the basis of skin color, facial features, ancestry, and national origin. Some scientists argue that common racial classifications are not meaningful, often on the basis of research indicating that more genetic variation exists within such races than between them. <!-- DEAD Link --> To define terms, racial labels most commonly used in the ] relate to genetic ancestry (Tang et al., 2005). People labeled '']'' have most of their ancestors from sub-Saharan Africa, '']'' from Europe, and '']'' from countries on the western side of the Pacific Rim. '']'', more often called an ] rather than a race, form a genetically diverse group that includes many recent Mexican, Puerto Rican, and Cuban immigrants to the United States having mixed Native American, African, and European ancestry. See the articles ] and ] for further discussion. Racial distinctions are often described in terms of skin color, facial features, ancestry, and national origin. Some scientists argue that common racial classifications are not meaningful, often on the basis of research indicating that more genetic variation exists within such races than between them. <!-- DEAD Link --> To define terms, racial labels most commonly used in the ] relate to genetic ancestry (Tang et al., 2005). People labeled black or African-American have most of their ancestors from sub-Saharan Africa, whites from Europe, and east asians from countries on the western side of the Pacific Rim. Hispanics, more often called an ] rather than a race, form a genetically diverse group that includes many recent Mexican, Puerto Rican, and Cuban immigrants to the United States having mixed Native American, African, and European ancestry. See the articles ] and ] for further discussion.


Attempts to measure '''intelligence''' most commonly employ IQ tests. In turn, IQ tests are generally geared to measure the ] variable '''''g'''''. Some question the validity of all IQ testing or claim that there are aspects of intelligence not reflected in IQ tests. See the articles ], ], and ] for further discussion on the validity of these tests. Attempts to measure intelligence most commonly employ IQ tests. In turn, IQ tests are generally geared to measure the ] variable ''g''. Some question the validity of all IQ testing or claim that there are aspects of intelligence not reflected in IQ tests. See the articles ], ], and ] for further discussion on the validity of these tests.


Some researchers have argued that '''race and intelligence''' research is fundamentally flawed. ] expressed this view in his ] book '']''. Tate & Audette (2001) argue that issues of "race" and "intelligence" are pseudo-questions because both concepts are arbitrary social constructions. Similarly, in a ] review paper Sternberg and colleagues question the basis of race and intelligence research{{ref|apa1}}: Some researchers have argued that race and intelligence research is fundamentally flawed. ] expressed this view in his ] book '']''. Tate & Audette (2001) argue that issues of "race" and "intelligence" are pseudo-questions because both concepts are arbitrary social constructions. Similarly, in a ] review paper Sternberg and colleagues question the basis of race and intelligence research{{ref|apa1}}:
<blockquote>In this article, the authors argue that the overwhelming portion of the literature on intelligence, race, and genetics is based on folk taxonomies rather than scientific analysis. They suggest that because theorists working on intelligence disagree as to what it is, any consideration of its relationships to other constructs must be tentative at best. They further argue that race is a social construction with no scientific definition. Thus, studies of the relationship between race and other constructs may serve social ends but cannot serve scientific ends.</blockquote> <blockquote>In this article, the authors argue that the overwhelming portion of the literature on intelligence, race, and genetics is based on folk taxonomies rather than scientific analysis. They suggest that because theorists working on intelligence disagree as to what it is, any consideration of its relationships to other constructs must be tentative at best. They further argue that race is a social construction with no scientific definition. Thus, studies of the relationship between race and other constructs may serve social ends but cannot serve scientific ends.</blockquote>
These views contrast with those expressed in "Intelligence: Knowns and Unknowns" {{ref|Neisser96}} a report from the ], and , a statement signed by 52 intelligence researchers meant to outline "conclusions regarded as mainstream among researchers on intelligence". These views contrast with those expressed in "Intelligence: Knowns and Unknowns" {{ref|Neisser96}} a report from the ], and , a statement signed by 52 intelligence researchers meant to outline "conclusions regarded as mainstream among researchers on intelligence".


⚫ The scholarly debate about race and intelligence involves both the relatively less controversial experimental results that indicate that average IQ test scores vary among racial groups, and the relatively more controversial interpretation of these IQ score differences. In general, interpretations of the "IQ gap" can be divided into two categories:
The debates described in the following article assume that IQ tests measure some interesting aspect of intelligence, and that some interesting information may be gained by studying racial group differences. For a critique of these assumptions, please see the previously mentioned articles.


* Environmental interpretations or causes such as ], ] level, access to ] or other environmental factors.
⚫ The scholarly debate about race and intelligence involves both the relatively less controversial experimental '''results''' that indicate that average IQ test scores vary among racial groups, and the relatively more controversial '''interpretation''' of these IQ score differences. In general, interpretations of the "IQ gap" can be divided into two categories:
⚫ * Partial genetic causes that posit an IQ gap between racial groups caused by approximately the same matrix of genetic and environmental forces that cause IQ differences among individuals of the same race.

# '''"culture-only"''' interpretations that posit environmental causes (e.g., ] or ] membership) that differentially affect racial groups; and
⚫ # '''"partly-genetic"''' interpretations that posit an IQ gap between racial groups caused by approximately the same matrix of genetic and environmental forces that cause IQ differences among individuals of the same race.


=== History === === History ===

] wrote on eugenics and psychometrics in the 19th century.]] ] wrote on eugenics and psychometrics in the 19th century.]]
The scientific debate on the contribution of ] to individual and group differences in intelligence can be traced to at least the mid-19th century (Degler, 1991; Loehlin, Lindzey, & Spuhler, 1975). The writings of Sir ], elaborating on the work of his cousin ], spurred interest in the study of mental abilities, particularly ] and ]. The scientific debate on the contribution of ] to individual and group differences in intelligence can be traced to at least the mid-19th century (Degler, 1991; Loehlin, Lindzey, & Spuhler, 1975). The writings of Sir ], elaborating on the work of his cousin ], spurred interest in the study of mental abilities, particularly ] and ].

Revision as of 04:30, 30 June 2005

Racial and ethnic groups in the U.S. show differences in average IQ test scores, but the distributions of IQ overlap greatly.

Race and intelligence refers to the controversy surrounding the findings of many studies that racial groups show differences in average intelligence quotient (IQ) test scores, and differences in other variables that correlate with IQ scores, such as school achievement, reaction time, or brain size.

These results have sparked public debates concerning not only the reliability of the studies and the motives of their authors, but also the validity and fairness of intelligence tests and racial categorization in general. The primary focus of the scholarly debate is the question of whether group differences in average intelligence are caused only by environmental factors (such as nutrition, the richness of the early home environment, and other social, cultural or economic factors) or whether there is also a genetic component that follows racial classifications.

Because it appears that intelligence is of great practical significance in modern society, some scholars claim that elucidating the source and meaning of the gap in measured IQs is a pressing social concern.

Background information

Racial distinctions are often described in terms of skin color, facial features, ancestry, and national origin. Some scientists argue that common racial classifications are not meaningful, often on the basis of research indicating that more genetic variation exists within such races than between them. To define terms, racial labels most commonly used in the United States relate to genetic ancestry (Tang et al., 2005). People labeled black or African-American have most of their ancestors from sub-Saharan Africa, whites from Europe, and east asians from countries on the western side of the Pacific Rim. Hispanics, more often called an ethnic group rather than a race, form a genetically diverse group that includes many recent Mexican, Puerto Rican, and Cuban immigrants to the United States having mixed Native American, African, and European ancestry. See the articles Race and Race (U.S. Census) for further discussion.

Attempts to measure intelligence most commonly employ IQ tests. In turn, IQ tests are generally geared to measure the psychometric variable g. Some question the validity of all IQ testing or claim that there are aspects of intelligence not reflected in IQ tests. See the articles Intelligence, IQ, and G theory for further discussion on the validity of these tests.

Some researchers have argued that race and intelligence research is fundamentally flawed. Stephen Jay Gould expressed this view in his 1981 book The Mismeasure of Man. Tate & Audette (2001) argue that issues of "race" and "intelligence" are pseudo-questions because both concepts are arbitrary social constructions. Similarly, in a 2005 review paper Sternberg and colleagues question the basis of race and intelligence research:

In this article, the authors argue that the overwhelming portion of the literature on intelligence, race, and genetics is based on folk taxonomies rather than scientific analysis. They suggest that because theorists working on intelligence disagree as to what it is, any consideration of its relationships to other constructs must be tentative at best. They further argue that race is a social construction with no scientific definition. Thus, studies of the relationship between race and other constructs may serve social ends but cannot serve scientific ends.

These views contrast with those expressed in "Intelligence: Knowns and Unknowns" a report from the American Psychological Association, and "Mainstream Science on Intelligence", a statement signed by 52 intelligence researchers meant to outline "conclusions regarded as mainstream among researchers on intelligence".

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

  • Environmental interpretations or causes such as Nutrition, Wealth level, access to Health care or other environmental factors.
  • Partial genetic causes that posit an IQ gap between racial groups caused by approximately the same matrix of genetic and environmental forces that cause IQ differences among individuals of the same race.

History

Sir Francis Galton wrote on eugenics and psychometrics in the 19th century.

The scientific debate on the contribution of nature versus nurture to individual and group differences in intelligence can be traced to at least the mid-19th century (Degler, 1991; Loehlin, Lindzey, & Spuhler, 1975). The writings of Sir Francis Galton, elaborating on the work of his cousin Charles Darwin, spurred interest in the study of mental abilities, particularly heredity and eugenics.

The fact that there are differences in the brain sizes and brain structures of different racial and ethnic groups was well known and widely studied during the 19th century and early 20th century (Bean, 1906; Broca, 1873; Mall, 1909; Morton, 1839; Pearl, 1934; Vint, 1934).

Average ethnic and racial group differences in IQ were first found with the widespread use of standardized mental tests in World War I.

Beginning in the 1930s, hereditarianism — the belief that genetics contribute to differences in intelligence among humans — began to fall out of favor, in part due to the advocacy of Franz Boas, who in his 1938 edition of The Mind of Primitive Man wrote

...there is nothing at all that could be interpreted as suggesting any material difference in the mental capacity of the bulk of the Negro population as compared with the bulk of the white population (Boas, 1938).

The hereditarian position was greatly weakened by Boas finding that cranial vault size had increased significantly in the U.S. from one generation to the next, because racial differences in such characteristics had been among the strongest arguments for a genetic role.

Eugenics was later adopted by the Nazi party as a justification for the systematic elimination of "parasitic" races such as Jews and Gypsies. (Note that the Ashkenazi Jewish population has significantly higher average IQ scores than other Whites.)

Due to the association of hereditarianism with Nazi Germany, after the conclusion of World War II until the 1994 publication of The Bell Curve, it became largely taboo to suggest that there were racial or ethnic differences in measures of intellectual or academic ability and even more taboo to suggest that they might involve a genetic component. (Garrett, 1961; Lynn, 2001, pp. xlv-liv).

In 1961, the psychologist Henry Garrett coined the term equalitarian dogma to describe the then politically fashionable view that there were no race differences in intelligence, or if there were, they were purely the result of environmental factors. Those who questioned these views often put their careers at risk (Lynn, 2001, pp. 67-69).

The contemporary scholarly debate on race and intelligence may be traced to Arthur Jensen's 1969 publication in the Harvard Educational Review of "How Much Can We Boost IQ and School Achievement?" In this paper Jensen concluded that:

(a) IQ tests measure socially relevant general ability; (b) individual differences in IQ have a high heritability, at least for the White populations of the United States and Europe; (c) compensatory educational programs have proved generally ineffective in raising the IQs or school achievement of individuals or groups; (d) because social mobility is linked to ability, social class differences in IQ probably have an appreciable genetic component; and tentatively, but most controversially, (e) the mean Black-White group difference in IQ probably has some genetic component (from Rushton & Jensen, 2005).

Reports on Jensen's article appeared in Time, Newsweek, Life, U.S. News & World Report, and The New York Times Magazine. Press attention returned to the issue of race and intelligence in 1994 with the publication of The Bell Curve (Herrnstein & Murray, 1994), which included two chapters on the subject of racial difference in intelligence and related life outcomes. In response to The Bell Curve, Stephen Gould updated The Mismeasure of Man, criticising many aspect of IQ research. Some IQ researchers have been accused of misrepresenting the available data, especially when trying to associate the results with various other claimed differences in personality and physical characteristics.

In 2005, the scholarly debate continues on the question of "whether the cause of group differences in average IQ is purely social, economic, and cultural or whether genetic factors are also involved" (Rushton & Jensen, 2005).

Moral criticism

A political motivation is frequently ascribed to researchers who work on questions of race and intelligence. Many have been described as racists. For example, psychologist Jerry Hirsch has claimed that Arthur Jensen has "avowed goals" that were "as heinously barbaric as were Hitler's and the anti-abolitionists" (Hunt, 1999). In turn, some researchers have questioned the political motivations of their critics, some of whom have been forced to apologize. More often the ad hominem criticisms are allowed (Gottfredson, 2005).

Another common criticism of race and intelligence research is that society would be better off not knowing if races differ in IQ, regardless of whether the cause were genetic or not. For example, Glazer (1994, p. 16) asked of race and intelligence research in The Bell Curve, "what good will come of it?" He adds:

Our society, our polity, our elites, according to Herrnstein and Murray, live with an untruth: that there is no good reason for this inequality, and therefore society is at fault and we must try harder. I ask myself whether the untruth is not better for American society than the truth.

More recently, Yale psychologist Robert Sternberg asked whether race and intelligence researchers Arthur Jensen and J. Philippe Rushton show "good taste" in their choice of research topics. Further, he questioned, "What good is research of the kind done by Rushton and Jensen supposed to achieve?" (Sternberg, 2005). Harvard University microbiologist Bernard Davis (1978) criticized this position as the "moralistic fallacy", implying it was the converse of the naturalistic fallacy. Some researchers in the field of race and intelligence argue that suppressing race and intelligence research is actually more harmful. For example, Gottfredson (2005) argues against the suggestion of a benevolent untruth:

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

Race in the United States

see also Race

The political, social and cultural structure of the United States is still explicitly conscious of race; legal equality of Whites and Blacks did not fully materialize until the 20th century. The national and state governments of the United States employ race in the census, law enforcement, and innumerable other ways. Many minority races have political organizations to represent their interests. Racial discrimination is illegal in many areas of public and private life, including employment.

Average intelligence gaps among races

The modern controversy surrounding intelligence and race focuses on the results of IQ studies conducted during the second half of the 20th century, mainly in the United States and some other industrialized nations. IQ studies outside these nations are few and small. It is uncertain what the average IQ or subgroup IQ tests scores would be with more complete studies in the developing world. IQ test scores in the developing world may be affected by factors less important in the developed world such as nutritional deficiencies. Most of the remainder of this article refers to studies attempting to explain race differences in IQ test scores in the US, and does not refer to the world as a whole.

IQ gap in the US

File:IQ-4races-rotate-highres.png
Approximate cumulative IQ distributions in the U.S. based on Wechsler Adult Intelligence Scale IQs for Whites (mean = 101.4, SD = 14.7) and Blacks (mean = 86.9, SD = 13.0) from (Reynolds, Chastain, Kaufman, & McLean, 1987, p. 330); distributions for Hispanics (mean = 91) and Asians (mean = 106) are less precise. Most reports estimate that the average IQ of Ashkenazi Jews (not shown) is greater than any other group.

In almost every testing situation where tests were administered and evaluated correctly, a difference of approximately one standard deviation was observed in the US between the mean IQ score of Blacks and Whites. In the United States, the mean IQ score among Blacks is approximately 85 and the mean IQ score among Whites is approximately 100; the mean IQ score of Hispanics is usually reported to be between the mean Black and White scores (Herrnstein and Murray report a mean "Latino" IQ of 89 in The Bell Curve). The mean score for people of East Asian and Jewish descent is usually higher than the mean score of Whites, but the extent of that difference is not precisely known. However, several studies place the median IQ of Ashkenazi Jews (who make up the overwhelming majority of American Jews) at approximately one standard deviation above the mean for other Whites, with the primary Jewish advantage in verbal reasoning and the East Asian advantage primarily in spatial reasoning. In The Bell Curve, Herrnstein and Murray report mean IQ scores for East Asians and Jewish Americans of 106 and 113, respectively.

Similar gaps are seen in other tests of cognitive ability or aptitude, including university admission exams such as the SAT and GRE as well as employment tests for corporate settings and the military (Roth et al. 2001).

Is the gap closing?

Richard Nisbett and others have argued that the Black-White gap on various ability tests has narrowed from the 1970s to the 1990s (Grissmer, 1994; Grissmer, Flanagan, & Williamson, 1998; Grissmer, Williamson, Kirby, & Berends, 1998; Hedges & Nowell, 1998; Nisbett, 1995, 1998, 2005). These tests include the Equality of Educational Opportunity (EEO) survey, the National Longitudinal Study, the High School and Beyond survey, the National Education Longitudinal Study, and the National Assessment of Educational Progress program (NAEP). The Journal of Blacks in Higher Education found that although the Black-White gap on the SAT declined from 1976-1988, it has been increasing since 1988. On the other hand, some studies find that the gap has been decreasing for the most of the 20th century and that this trend continued during the nineties.

Jensen (1998 pp. 375-376, 407-408, 494-495) has argued that the Black-White differences in g have not narrowed. In support of this claim, he presents evidence that, while there have been gains in measures of acquired competency such as scholastic achievement, these improvements do not indicate gains in g. Jensen also argues that Black-White differences in g seen in measures of reaction time have not narrowed. A meta-analysis by Roth et al. (2001) found a mean Black-White score difference of 1.1 standard deviations (6,246,729 samples; ranging from 0.38 to 1.46 depending on the g loading of the test). As to whether the IQ gap is narrowing, they speculated that any reduction was "either small, potentially a function of sampling error ... or nonexistent for highly g loaded" tests (Roth et al. 2001). Gottfredson (2005) agreed that the Black-White gap observed in the National Assessment of Educational Progress test has narrowed from 1.07 to 0.89 standard deviations. However, she then argues that reduction stopped by the mid-1980s and is compatible with stable group differences in g.

A large (21,260 children) and probably the most recent (1998) study found that the Black-White gap for young children in reading and math scores was much smaller than in earlier studies, and that all of the remaining difference could be explained by a few environmental factors. One possible explanation is that the Flynn effect started earlier for Whites but has now stopped, while continuing for Blacks. Reading and math scores are correlated with, but not substitutable for, IQ, so these findings alone may not indicate convergence in the IQ gap. Still, the correlation of IQ with grades is highest in elementary school (0.6 to 0.7; Jensen 1998), so convergence in scores may, in fact, indicate that the IQ gap is narrowing.

IQ gaps in other nations

Attempted compilations of average IQ by race generally place Ashkenazi Jews at the top, followed by East Asians, Whites, other Asians, Arabs and Blacks. See IQ and the Wealth of Nations for an attempted compilation of average IQ for different nations and a discussion of associated measurement problems.

The IQ scores vary greatly among different nations for the same group. Blacks in Africa score much lower than Blacks in the US. Some reports indicate that the Black-White gap is smaller in the UK than in the U.S.. Other examples are Jews who score much lower in developing nations and Koreans who score much lower in Japan. There are also other examples of IQ score differences between close neighbours in the same nation, for example between French vs. Flemish speakers in Belgium, Slovaks vs. Gypsies in Slovakia, Irish and Scottish vs. English in Great Britain, and white speakers of Afrikaans vs. white speakers of English in South Africa. The difference between the neighboring white Protestants and Catholics in Northern Ireland is as large as the differences between whites and blacks in the U.S.

There has been at least one comparative study on IQ scores in different European nations. The difference between the highest and lowest average national IQ scores were 8 points. There was a statistically insignificant correlation between the latitute of each country and its average IQ score as found by the study. The southern Europeans had a larger variation than the northern Europeans. The Norwegians had less than half of the variability of the white American population while Italians and Bulgarians had about 150%.

Hybrid vigor

Intelligence is associated with the degree of "hybrid vigor" (heterosis) manifested by offspring of cross-ethnic matings. Children of Japanese–Caucasian cross-ethnic matings score .26 SD higher on several cognitive tests than those from within-ethnic matings, despite having virtually identical parental educational and occupational backgrounds. The increase in scores tends to be higher on cognitive tests that are more g-loaded, suggesting that hybrid vigor improves g. Heterosis may be partially responsible for the Flynn effect.

School achievement gap

Measures of school achievement correlate fairly well with IQ, especially in younger children. The National Assessment of Educational Progress in the United States, find that by 12th grade Black students are performing on average only as well as White and Asian students in 8th grade; Hispanic students do only slightly better than Blacks. Closing this achievement gap is one of the aims of the No Child Left Behind act. The gap has been attributed to academic disengagement of Black students and parents and to environmental causes. The school achievement gap can potentially be explained by many environmental factors that do not affect IQ tests to a similar degree, like bias in those giving grades or constructing tests.

Attempts to redress the acheivement gap in the U.S. include Head Start and related early intervention programs. However, neither Head Start nor more intensive programs have been able to produce lasting gains in IQ or school achievement. However, the gains continued as long as the program continued. Lack of sufficient funding is often cited as a reason for the failure of Head Start programs to have lasting impact.

Reaction time

In 1991, Richard Lynn tested 1,468 9-year old children consisting of Blacks from South Africa, East Asians from Hong Kong and Japan, and Whites from Britain and Ireland. The content of the tests involved flipping a switch after one or more lights came on. Lynn found that the decision times (the time taken to make a decision about what to do) had a low correlation with IQ data on Raven's Progressive Matrices tests also administered during the same study, and that movement times (the time taken to execute the decision) did not show any correlation. He found that the Asians had the fastest decision times, followed by the Whites, and then by the Blacks. He also determined that the Black children had movement times that were substantially faster than those of Whites and Asians on certain tests. Studies have shown similar patterns in response time on tests of arithmetic and international studies confirm the trend.

Brain size

see also Craniometry, Neuroscience and intelligence

Modern studies using MRI imaging shows a weak to moderate correlation between brain size and IQ and have shown that brain size correlates with IQ by a factor of approximately .40 among adults.. The correlation between brain size and IQ seems to hold for comparisons between and within families., although one study found no correlation within family. A study on twins showed that frontal gray matter volume was correlated with g and highly heritable. A related study has reported that the correlation between brain size (reported to have a heritability of 0.85) and g is 0.4, and that correlation is mediated entirely by genetic factors. Note that none of the MRI studies have studied racial differences.

File:HRSM.png
Left to right: Brain weight distributions for Black women (μ=1158, σ=119), White women (μ=1252, σ=125), Black men (μ=1286, σ=138), and White men (μ=1392, σ=130). Drawn from Ho et. al (1980)

The order of group differences in average IQ tends to approximate the order of group differences in brain size and parallels the order of group differences in brain to body mass ratios and number of free neurons. Numerous historical and modern studies, using skull and head measurements, weighing of brains at autopsy, and more recently, magnetic resonance imaging report racial differences. These studies are usually accompanied by a great deal of controversy. The American Psychological Association's Task Force Report on Intelligence reports that with respect to "racial differences in the mean measured sizes of skulls and brains (with East Asians having the largest, followed by Whites and then Blacks)...there is indeed a small overall trend".

Cranial vault size and shape have changed greatly during the last 150 years in the US. These changes must occur by early childhood because of the early development of the vault. The explanation for these changes may be related to the Flynn effect.

Culture-only or partially-genetic explanation?

Main article: Race and intelligence (Culture-only or partially-genetic explanation)

The consensus among IQ researchers is that IQ differences between individuals of the same race reflect (1) real, (2) functionally/socially significant, and (3) substantially genetic differences in the g factor (general intelligence). A consensus also exists for the view that average IQ differences between races reflect (1) real and (2) significant differences in the same g factor (Gottfredson, 2005). However, it is a matter of debate whether IQ differences between races in the U.S. are (3a) entirely environmental or (3b) partly genetic. Several published consensus statements agree that the large differences between the average IQ scores of Blacks and Whites in the U.S. cannot be attributed to biases in test construction, nor can they be explained just by simple differences in socio-economic status.

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

Arthur Jensen and others have concluded that the IQ gap is partly genetic. They argue that while plausible environmental explanation for the lower mean IQ in Blacks in the U.S. can be offered in many cases, these explanations are less capable of explaining the higher average IQ of East Asians than Whites, and that overall the culture-only hypothesis is not "progressive" but "degenerating" (see Lakatos; Rushton & Jensen, 2005). To support these claims, they most often cite: (1) worldwide Black-White-East Asian differences in IQ, reaction time, and brain size; (2) correlation between the extent to which IQ subtests measure g, the magnitude of Black-White-East Asian average IQ differences on those subtests (called Spearman's hypothesis), and measures of those subtests' heritability; and (3) the rising heritability of IQ with age (within races) and the disappearance by adulthood of shared environmental effects on IQ (e.g., family income, education, and home environment). Other evidence, such as transracial adoption, racial admixture studies, "life-history" traits, and evolutionary explanations are also debated. The critics have counter arguments to all of this and a definite answer may not be possible until intelligence is directly linked to specific genes.

IQ, race, and public policy

There is substantial overlap in the distribution of IQ scores among individuals of each race. Jensen (1998, p. 357) estimates that in a random sample of equal numbers of US Blacks and Whites, most of variance in IQ would be unrelated to race or social class. The average IQ difference between two randomly paired people from the U.S. population, one Black and one White, is approximately 20 points. However, by the same method of calculation, the average difference between two random people is approximately 17 points, and the average difference between two siblings is 12 points.

The appearance of a large practical importance for intelligence makes some scholars claim that the source and meaning of the IQ gap is a pressing social concern. Two statistical effects interact to exacerbate IQ differences. First, there seem to be minimum statistical thresholds of IQ for many socially valued outcomes (e.g., high school graduation and college admission). Second, because of the shape of the normal distribution, only about 16% of the population is at least one standard deviation above the mean. Thus, although the IQ distributions for Blacks and Whites are largely overlapping, different IQ thresholds can have a significant impact on the proportion of Blacks and Whites above and below a particular cut-off. (See IQ for a discussion of its practical importance.)

Approximate IQ Distributions & Significance in the United States
IQ range Whites Blacks Black:White ratio Training prospects High school dropout Lives in poverty
<75 3.6% 18.0% ~5:1 simple, supervised work; eligible for government assistance 55% 30%
<90 21.9% 59.4% ~2:1 very explicit hands on training; IQ >80 for military training; no government assistance 35% 16%
>100 53.8% 15.7% ~1:3 written material plus experience 6% 6%
>110 27.9% 3.8% ~1:7 college format 0.4% 3%
>125 5.4% 0.2% ~1:32 independent, self-teaching 0% 2%
Based on Wechsler Adult Intelligence Scale IQs for Whites (mean = 101.4, SD = 14.7) and for Blacks (mean = 86.9, SD = 13.0) from (Reynolds, Chastain, Kaufman, & McLean, 1987, p. 330). Significance data is from Herrnstein & Murray (1994). Note that correlation is not causation. For example poverty can be both a cause and consequence of low IQ.

Real-world outcomes

The IQ gap is reflected by gaps in the academic, economic, and social factors correlated with IQ (Gordon 1997; Gottfredson 1997). For example, Murray (1998) argues from IQ variation among siblings (full brothers/sisters who grew up in the same home, where one of the sibling pairs has a normal range IQ) that IQ has a large effect on adult life outcomes. For example, Murray found that very bright siblings in the 90th+ centile of IQ earned $13,000 more in annual income (in 1993) compared to siblings in the 75–89th centile, who in turn earned $4,000 more than the normal siblings in the 25–74th centiles (Murray, 1998). Similarly. lower IQ sibling groups had lower average incomes. Rates of educational and occupational attainment were likewise stratified by IQ. The effects of IQ were nearly identical even among the "Utopian" subset of siblings that grew up in families not burdened by divorce or poverty. However, these differences are less impressive when considering that in 1993 the average family income was $61,800 while the average family income of the richest 10% was $172,400. (Note these income values are larger than those from Murray's study, possibly because these values include income other than wages. Murray found average family incomes at five IQ tiers of $53,000 for the top 10 percent of IQ, $45,000 for the next 15 percent, $37,000 for the middle 50 percent, $23,400 for the next 15 percent, and $12,000 for the bottom 10 percent.)

Small differences in IQ, while relatively unimportant at the level of an individual, would theoretically have large effects at a population level. Herrnstein and Murray (1994) calculate that a 3-point drop in average IQ would have little effect on factors like marriage, divorce, or unemployment. However, the drop from IQ 100 to 97 would increase poverty rates by 11 percent and the proportion of children living in poverty by 13 percent. All else being equal, similar rises would occur in rates of children born to single mothers, men in jail, high school drop-out, and men prevented from working due to health-related problems. In contrast, if average IQ were to increase 3-points to 103, poverty rates would fall 25 percent, children living in poverty would fall 20 percent, and high school drop-out rates would fall 28 percent.

Percentages of Blacks and Whites (Statistically Matched for IQ) in Educational and Social Outcomes
Condition (matching IQ) Blacks Whites
High school graduation (103) 91 89
College graduation (114) 68 50
High-level occupation (117) 26 10
Living in poverty (100) 14 6
Unemployed for 1 month or more (100) 15 11
Married by age 30 (100) 58 79
Unwed mother with children (100) 51 10
Has ever been on welfare (100) 30 12
Mothers in poverty receiving welfare (100) 74 56
Having a low birth-weight baby (100) 6 3
Average annual wage (100) $25,001 $25,546
from Herrnstein & Murray (1994), Chapter 14.

Studies from The Bell Curve and elsewhere indicate that controlling for IQ narrows, eliminates, or even reverses the Black-White gap in social and economic factors associated with IQ. After controlling for IQ, the probability of having a college degree or working in a high-IQ occupation is higher for Blacks than Whites. Controlling for IQ shrinks the income gap from thousands to a few hundred dollars. Controlling for IQ cuts differential poverty by about three-quarters and unemployment differences by half. However, controlling for IQ has little effect on differential marriage rates. For many other factors, controlling for IQ eliminates the differences between Whites and Hispanics, but the Black-White gap remains (albiet smaller).

However, IQ is only one of several factors that are important for economic outcomes. Personality, for example, and especially conscientiousness, may play a large role in economic outcomes. Some scholars dispute the importance of IQ test score results for real-world achievement. Some argue that the role of IQ gradually becomes weaker with age and after school. They cite evidence that IQ is correlated with early school grades but other factors explain most of the variance. Regarding economic inequality, one study found that if we could magically give everyone identical IQs, we would still see 90 to 95 percent of the inequality we see today. Another study found that wealth, race and schooling are important to the inheritance of economic status, but IQ is not a major contributor and the genetic transmission of IQ is even less important. Some argue that IQ scores are used as an excuse for not trying to reduce poverty or otherwise improve living standards for all. Claimed low intelligence has historically been used to justify the feudal system and unequal treatment of women.

Whites are not a homogeneous group regarding real-world outcomes. For example, in the U.S. 33.6% of persons with self-reported Scottish ancestry has completed college, while only 16.7% of persons with self-reported French-Canadian ancestry have done so.

Differences in intelligence have been used to explain differences in economic growth between nations. One example is IQ and the Wealth of Nations. The book, which has not been peer-reviewed, is sharply criticized in the peer-reviewed paper The Impact of National IQ on Income and Growth. It has been argued that East Asian nations underachieve compared to IQ scores. One suggested explanation is that verbal IQ is more important than spatial IQ. The book Guns, Germs and Steel instead argues that historical differences in economic and technological development for different areas can be explained by differences in geography, which affects factors like population density and spread of new technology, noting for instance that current IQ scores cannot explain why the world's first civilizations appeared along the river plains in the Middle East.

The book World on Fire notes the existence in many nations of successful minorities that have created and control a disproportionate share of the economy. Examples include Chinese in Southeast Asia; Whites, Indians, Lebanese and Ibo in Africa; Whites in Latin America; and Jews in Russia. These minorities are often resented and sometimes persecuted by the less successful majority.

In the United States, Jews, Japanese, and Chinese earn incomes 1.72, 1.32, and 1.12 times the American average, respectively (Sowell, 1981, p. 5). Jews and East Asians have higher rates of college attendance, greater educational attainment, and are many times overrepresented in the Ivy League and many of the United States' most prestigious schools (Sowell, pp. 7, 93) , even though affirmative action discriminates against East Asians in the admissions process. In various Southeast Asian nations, Chinese control a majority of the wealth despite being a minority of the population and are resented by the majority, and in some cases are the target of violence (Sowell, pp. 133-134; Purdey, 2002).

Achievement in science may be more closely associated with IQ than for example income, which may be greatly influence by inherited wealth, other personality characteristics, or even physical characteristics such as athletic ability or beauty. Only 0.25% of the world population are Jews, but 20–30% of all Nobel prize winners in physics, chemistry, and medicine are Jewish. A large scale decline in the number of Nobel prized awarded to Europe and similar increase in the number of prized awarded to the U.S. occurred at the same time as Nazi persecutions of Jews during the 1930s and the Holocaust during the 1940s.

Policy implications

The public policy implications of IQ and race research are possibly the greatest source of controversy surrounding this issue. For example, the conservative policy recommendations of Herrnstein and Murray in The Bell Curve were denounced by many. Indeed, even proponents of a partly-genetic interpretation of the IQ gap such as Rushton and Jensen (2005) and Gottfredson (2005) argue that their interpretation does not in itself demand any particular policy response. They argue instead that the primary determinant of policy conclusions from race and intelligence research will be political philosophy itself.

For example, while a conservative/libertarian commentator like Charles Murray may call for reductions in affirmative action, a liberal commentator may use the same evidence to argue from a Rawlsian point of view (that genetic advantages are undeserved and unjust) for substantial and permanent affirmative action (Gottfredson, 2005). This point of view was summarized in the "Mainstream Science on Intelligence" statement published in the Wall Street Journal in 1994:

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

All of the most cost effective methods to improve the world, according to the Copenhagen consensus, would probably also directly or indirectly raise IQ scores, especially providing micronutrients to pregnant women and children. Reducing malaria might also have a large effect because it affects 300–500 million persons each year, mostly children under the age of 5 in Africa, causing widespread anemia during a period of rapid brain development, and also direct brain damage from cerebral malaria to which children are more vulnerable.

Summary

The source of and meaning of the average IQ differences between groups is not known. Many theories have been proposed, but none are generally accepted. Most of the theories are supported by only indirect evidence. The cause may be environmental. Many attribute the difference primarily to cultural factors that disadvantage caste-like minorities. Many researchers in the field of intelligence suggest that the difference is partially genetic and partially environmental. Other observers suggest that the differences may be entirely environmental. The cause of the IQ gap may be identical to the cause of IQ differences between all individuals, or it may represent a race-specific effect. This is an active area of research. In general, simple correlations cannot decide the role of genetics. Advanced statistical methods are instead used with hotly debated results.

Biological differences in brain volume and reaction time, which show low to moderate correlations with IQ, are not by themselves evidence for genetic differences. Even if these differences or the average IQ test score gap indicate a gap in actual intelligence, this may be due to environmental differences in factors such as nutrition during pregnancy or early childhood which may produce such differences without any genetic cause.

Because the cause of the IQ gap is ultimately an empirical question, it should be possible to resolve this question in the future. Irrefutable direct evidence is currently lacking and may continue to be so until intelligence is mapped to specific genes.

Most research has been done in the US and a few other developed nations. That research cannot directly be generalized to the world as a whole. Blacks in the US do not constitute a random sample from Africa, and environmental conditions differ among nations. IQ tests done in developing countries are likely to have been affected by conditions associated with poverty that are common in the developing world, such as nutritional deficiencies (for instance, iodine deficiency is known to substantially affect intelligence and iodine is usually by law added to certain food products in developed nations but is deficient in hundreds of millions in the third world) and the impact of diseases (e.g., HIV, anemia or chronic parasites that may affect IQ test scores).

Finally, genetic engineering may soon be able to directly change the genetic determinants of intelligence. This change may make genetic intelligence and other genetic characteristics a matter of voluntary parental (or enforced governmental) decision. This could theoretically, in a single generation, dramatically increase human intelligence and make the current concept and discussion of race and possible associated characteristics obsolete.

Notes

  1. "Intelligence, Race, and Genetics," American Psychologist 60, no. 1 (January 2005): 46–51.
  2. Neisser et al. (1996)
  3. Min-Hsiung Huang and Robert M. Hauser, "Convergent Trends in Black-White Test-Score Differentials in the U.S.: A Correction of Richard Lynn1," University of Wisconsin–Madison, July 31, 2000.
  4. Roland G. Fryer Jr. and Steven D. Levitt, "Understanding the Black-White Test Score Gap in the First Two Years of School," The Review of Economics and Statistics 86, no. 2 (2004).
  5. IQ comments, Gene Expression, September 23, 2003.
  6. Myth: Some ethnic groups have genetically inferior IQ's.
  7. Nagoshi and Johnson (1986), p. 204
  8. Mingroni (2004)
  9. Ogbu (2003)
  10. Thernstrom and Thernstrom (2003)
  11. Jensen (1998)
  12. Richard Lynn, "Race Differences in Intelligence: A Global Perspective ," The Mankind Quarterly 31, no. 3 (1991): 255–96; Means for Progressive Matrices and 12 reaction time measures for 9-year-old children from five countries.
  13. Jensen, 1993; Jensen and Whang, 1994.
  14. See Shigehisa and Lynn (1991) for Japan; Chan and Lynn (1989) for Hong Kong and Britain; Lynn (1991) for Ireland; and Lynn and Holmshaw (1990) for South Africa.
  15. National Collaborative Perinatal Project, 1959-1974
  16. Joseph L Graves, "What a tangled web he weaves: Race, reproductive strategies and Rushton's life history theory," Anthropological Theory 2, no. 2 (2002): 131–54; Leonard Lieberman et al., "How 'Caucasoids' Got Such Big Crania and Why They Shrank," Current Anthropology 42 (2001): 69–95; Zack Cernovsky, "On the similarities of American blacks and whites: A reply to J.P. Rushton," Journal of Black Studies 25 (1995): 672.
  17. Harvey, Persaud, Ron, Baker, & Murray, 1994
  18. McDaniel, 2005
  19. Gignac et al. 2003; Jensen 1994; Jensen & Johnson 1994.
  20. Schoenemann et al. 2000
  21. Thompson et al. 2001
  22. Posthuma et al. 2002
  23. Neisser, 1997, p. 80
  24. Clarence C. Gravlee, H. Russell Bernard, and William R. Leonard, "Heredity, Environment, and Cranial Form: A Reanalysis of Boas’s Immigrant Data," American Anthropologist 105, no. 1 (2003); Clarence C. Gravlee, H. Russell Bernard, and William R. Leonard, "Boas’s Changes in Bodily Form: The Immigrant Study, Cranial Plasticity, and Boas’s Physical Anthropology," American Anthropologist 105, no. 2 (June 2003); R.L. Jantz and Lee Meadows Jantz, "Secular change in craniofacial morphology," American Journal of Human Biology 12, no. 3 (April 1999): 327–38; R.L. Jantz, "Cranial change in Americans: 1850–1975," Journal of Forensic Sciences 46, no. 4 (July 2001): 784–87.
  25. Joel Wiesen, "An Annotated List of Many Possible Reasons for the Black-White Mean Score Differences Seen With Many Cognitive Ability Tests: Notes to File," Applied Personnel Research, March 18, 2005.
  26. Greek IQ
  27. National Center for Health Statistics: Vital Statistics of the United States (1988).
  28. Scientific American, April 1996, p.25.
  29. "Fat, Fitness And Performance," Peak Performance; I.B. Helland et al., "Maternal supplementation with very-long-chain n-3 fatty acids during pregnancy and lactation augments children's IQ at 4 years of age," Pediatrics 111, no. 1 (January 2003): 39–44.
  30. "Myth: Social intervention cannot raise IQ; Intelligence Quotient, The Encyclopedia of Adoption.
  31. Papers relating to group difference in IQ test scores & Spearman's hypothesis.
  32. Joseph L. Graves, "What a tangled web he weaves: Race, reproductive strategies and Rushton's life history theory," Anthropological Theory 2, no. 2 (2002): 131–54; Leonard Lieberman et al., "How 'Caucasoids' Got Such Big Crania and Why They Shrank,"; Current Anthropology 42 (2001): 69–95; Zack Cernovsky, "On the similarities of American blacks and whites: A reply to J.P. Rushton," Journal of Black Studies 25 (1995): 672.
  33. Greek IQ
  34. Charles C. Roseman, "Detecting interregionally diversifying natural selection on modern human cranial form by using matched molecular and morphometric data" Proceedings of the national Academy of Sciences of the United States vol. 101 no. 35 (August 31, 2004):12824-12829.
  35. Gregory Cochran, Jason Hardy, Henry Harpending, "Natural History of Ashkenazi Intelligence," Journal of Biosocial Science (June 2005).
  36. See note 3 above.
  37. Arthur Hu's Index of Diversity, Scholastic Aptitude Test.
  38. "Myth: The black/white IQ gap is largely genetically caused.
  39. D.M. Ivanovic et al., "Nutritional status, brain development and scholastic achievement of Chilean high-school graduates from high and low intellectual quotient and socio-economic status," British Journal of Nutrition 87, no. 1 (January 2002): 81–92; D.M. Ivanovic et al., "Head size and intelligence, learning, nutritional status and brain development. Head, IQ, learning, nutrition and brain," Neuropsychologia 42, no. 8 (2004): 1118–31.
  40. Marinus H. van IJzendoorn, Femmie Juffer, and Caroline W. Klein Poelhuis, "Adoption and Cognitive Development: A Meta-Analytic Comparison of Adopted and Nonadopted Children’s IQ and School Performance," Psychological Bulletin 131, no. 2 (2005): 301–316.
  41. William T. Dickens, "Behavioral Genetics and School Readiness," The Future of Children 15, no. 1 (Spring 2005): 55–69; "Intelligence: Knowns and Unknowns," Report of a Task Force established by the Board of Scientific Affairs of the APA.
  42. IQ studies by year from IQ and the Wealth of Nations by Lynn & Vanhanen
  43. Abstracts from the Journal of American Indian Education 1987; Rhett Diessner and Jacqueline L. Walker, "A Cognitive Pattern of the Yakima Indian Students," Journal of American Indian Education 25, no. 2 (January 1986); "Smart Fraction Theory II: Why Asians Lag," La Griffe du Lion 6, no. 2 (May 2004).
  44. Zack Cernovsky, "On the similarities of American blacks and whites: A reply to J.P. Rushton," Journal of Black Studies 25 (July 1995): 672.
  45. Table 50 National Vital Statistics Reports Vol. 52, No. 10, December 17, 2003. CDC.
  46. "What's in a yam? Clues to fertility, a student discovers," Yale Medicin Summer 99
  47. William T. Dickens and James R. Flynn, "The IQ Paradox: Still Resolved," Psychological Review 109, no. 4 (2002).
  48. Richard Herrnstein and Charles Murray, "Race, genes and I.Q.—an apologia: the case for conservative multiculturalism," The New Republic 211, no. 11 (October 1994): 27.
  49. Charles Murray, Income Inequality and IQ (Washington, DC: American Enterprise Institute Press, 1998)
  50. Effective Federal Tax Rates: 1979-2001 Congressional Budget Office.
  51. Cary Cherniss, "Emotional Intelligence: What it is and Why it Matters" (Paper presented at the Annual Meeting of the Society for Industrial and Organizational Psychology, New Orleans, La., April 15, 2000).
  52. "What Can You Predict from an IQ Test Score?," Lefton Learning Community.
  53. Myth: IQ best predicts if you will succeed or fail in life.
  54. Samuel Bowles and Herbert Gintis, "The Inheritance of Inequality," Journal of Economic Perspectives 16, no. 3 (Summer 2002).
  55. Myth: Some ethnic groups have genetically inferior IQ's.
  56. Thomas Volken, "The Impact of National IQ on Income and Growth."
  57. "Smart Fraction Theory II: Why Asians Lag," La Griffe du Lion 6, no. 2 (May 2004).
  58. Falk, Gerhard. "American Jews"
  59. Jewish Nobel Prize Winners, JINFO.ORG.
  60. Wolfgang Jank, Bruce L. Golden, and Paul F. Zantek, "Old World vs. New World: Evolution of Nobel Prize Shares," University of Maryland (December 2004).
  61. "Mainstream Science on Intelligence," Wall Street Journal, December 13, 1994.

See also

References

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