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The connection between race and intelligence has been a subject of debate in both popular science and academic research since the inception of intelligence testing in the early twentieth century, particularly in the United States. Intelligence quotient (IQ) tests performed in the US have consistently demonstrated a significant degree of variation between different racial groups, with the average score of the African American population being significantly lower - and that of the Asian American population being significantly higher - than that of the White American population. At the same time, there is considerable overlap between these group scores, and members of each racial group can be found at all points on the IQ spectrum. Similar findings have been reported for related populations around the world, most notably in Africa, though these are generally considered far less reliable due to the relative paucity of test data and the difficulties inherent in the cross-cultural comparison of intelligence test scores.

There are no universally accepted definitions of either race or intelligence in academia, and the discussion of their connection involves the results of multiple disciplines, including biology, anthropology, sociology, and psychology. Many factors that could potentially influence the development of intelligence have been advanced as possible causes of the racial IQ gap which, though subject to variation over time, has remained relatively stable since IQ testing began. It is generally agreed that environmental and/or cultural factors affect individual IQ scores, and it is widely assumed that most or all of the racial IQ gap is attributable to such factors, though none are conclusively supported by direct empirical evidence.

Far more controversial is the claim put forward by several psychologists, including Arthur Jensen, J. Philippe Rushton and Richard Lynn, that a significant portion of the racial IQ gap has an ultimately genetic origin. This claim has not been accepted by the wider academic community and has been met with widespread disapproval in the popular media. The American Psychological Association has concluded that the racial IQ gap is not the result of bias in the content or administration of tests, but that no adequate explanation of it has so far been given.

History

The idea that there are differences in the brain structures/sizes of different racial groups, and that these differences explain varying rates of intelligence, was widely held and studied during the 19th and early 20th centuries. Francis Galton spurred interest in the study of mental abilities, particularly as they relate to heredity and eugenics. Beginning in the 1930s, race difference research and hereditarianism—the belief that genetics are an important cause of differences in intelligence among human groups—began to fall out of favor in psychology and anthropology after major internal debates.

In 1937 the Pioneer Fund was set up by W.P. Draper with one of its two charitable purposes being to provide aid for "study and research into the problems of heredity and eugenics in the human race ... and ... into the problems of race betterment with special reference to the people of the United States". From the 1980s onwards the Pioneer Fund has funded research conducted on race and intelligence from the hereditarian point of view.

A controversial article by Arthur Jensen promoting the hereditarian point of view triggered the modern debate in 1969. Many authors disputed Jensen's conclusions, most prominently Stephen Jay Gould in The Mismeasure of Man, first published in 1981. William Shockley, Nobel laureate in physics, became one of Jensen's most vocal supporters.

Richard Herrnstein and Charles Murray wrote in The Bell Curve: "The debate about whether and how much genes and environment have to do with ethnic differences remains unresolved. The universality of the contrast in nonverbal and verbal skills between East Asians and European whites suggests, without quite proving, genetic roots."

The American Anthropological Association argues that "differentiating species into biologically defined "races" has proven meaningless and unscientific as a way of explaining variation (whether in intelligence or other traits)."

The American Psychological Association's Board of Scientific Affairs in 1995 established a task force which produced a report, "Intelligence: Knowns and Unknowns" The psychology association report authors wrote that IQ scores have high predictive validity for individual differences in school achievement, for adult occupational status, even when variables such as education and family background have been statistically controlled, and they said individual differences in intelligence are substantially influenced by genetics (75% in adults). The APA report confirmed the existence of racial IQ differences, while remaining agnostic about their underlying causes:

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 socio-economic 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.

Group differences

Intelligence is most commonly measured using IQ tests. These tests are often geared to measure the psychometric variable g (for general intelligence factor). Other tests that measure g (e.g, the Armed Forces Qualifying Test, SAT, GRE, GMAT and LSAT) also serve as measures of cognitive ability. Several conclusions about these types of tests are now largely accepted:

• IQ scores measure many of the qualities that people mean by intelligent or smart.
• IQ scores are fairly stable over much of a person's life.
• IQ tests predict school and job performance to a degree that does not significantly vary by socio-economic or racial-ethnic background.
• Intelligence is ].
• Family environment and community culture affect IQ, more so in children then in adults.

Test scores

Most of the evidence of intelligence differences between racial groups is based on studies of IQ test scores, almost always using self-reported racial data. Such self-reports are surprisingly accurate. There are observed differences in average test score achievement between racial groups, which vary depending on the populations studied and the type of tests used. In the United States, self-identified Blacks and Whites have been the subjects of the greatest number of studies. Black-White average IQ differences appear to increase with age, reaching an average of nearly 17 points by age 24, which is slightly more than 1 standard deviation.

Gaps are seen in other tests of cognitive ability or aptitude, including university admission exams, military aptitude tests and employment tests in corporate settings.

The IQ distributions of other racial and ethnic groups in the United States are less well studied. Amerindians populations, including Arctic Natives, tend to score worse on average than White populations but better on average than Black populations. East Asian populations score higher on average than White populations in the United States as they do elsewhere.

Racial differences in IQ scores are observed around the world. One meta-analysis estimates East Asians (105), Whites (102), Amerindians (87), Non-Bushmen sub-Saharan Africans (67). International achievement test scores, including TIMSS and PISA, have also been used to estimate average IQ worldwide with similar results where data is available.

Debate overview

Many factors, both genetic and environmental, influence the intelligence of individuals. To the extent that racial groups are exposed to these factors to varying degrees, average IQs by race will differ as a result of these effects. Important topics include the environment, discrimination, and stereotype threat. Richard Nisbett, in replying to hereditarian arguments, structures the debate into 12 major areas.

Heritability

Imagine that the height of "ordinary genetically varied corn" is 100% heritable when grown in a uniform environment. Further imagine that two populations of corn are grown: one in a normal nutrient environment and the other in a deficient nutrient environment. Consequently, the average height of the corn grown in the deficient nutrient environment is less than the average height of the corn grown in the normal environment. In such a scenario, the within-group heritability of height is 100% in both populations, but the substantial difference between groups are due entirely to environmental factors. With respect to the Black-White IQ gap, Jensen suggests that effects associated with racism (both overt and institutionalized racism) might be X-factors. Flynn believes that attributing the B-W gap to the effects of racism is incorrect, because the most plausible ways in which discrimination could affect IQ are themselves common environmental factors. These may include psychological effects such as stereotype threat; biological effects such as poor nutrition, health care and living close to toxic environments; and educational effects such as a lack of good schools. Instead, Flynn and his colleague William Dickens have developed more complicated models to explain the black-white gap in terms of environmental factors. One initial motivation of the Dickens-Flynn theory was Flynn's observation that IQ test scores have been rising over time in countries around the world – termed the Flynn effect. Flynn and others believe an explanation for the Flynn effect may elucidate the cause of the B-W gap. Jensen and others disagree.

Much of the research on this topic has been conducted by Arthur Jensen and James Flynn. Flynn and Jensen consider two general classes of environmental factors: common environmental factors, which vary both within and between groups; and X-factors, which vary between groups but not within groups. Flynn explains in Race, IQ and Jensen (1980) why common environmental factors are inadequate as an explanation for the IQ gap:

After all, if an environmental factor is potent enough to account for the 15-point performance gap between black and white, and if it varies much from person to person within the black population, it would be extremely odd if it accounted for none of the variable performance within the black population! And if it did, it would of course increase the role of environmental factors in explaining IQ variance and thus lower the h2 (within-group heritability) estimate for blacks. If we seize on SES (socio-economic status) as a between-population explanation, who can deny that there are large differences in SES within black America; if we seize on education, who can deny that blacks differ significantly in terms of quality of education?

The alternative to common environmental factors is the hypothesis that the racial IQ gap can be accounted for by X-factors: factors which vary between groups but not within groups. Jensen and Flynn agree that no X-factors have yet been identified that could account for the racial IQ gap. Jensen believes that under these circumstances, the “default hypothesis” should be that the differences in average IQ between races is caused by the same factors that cause within-group variance in IQ, while Flynn believes that the racial IQ gap is caused by X-factors that have yet to be discovered.

Score convergence

The overall average Black-White gap has reduced by one third over the course of the 20th century. For example, the black men inducted into the US armed forces during World War II averaged about 1.5 standard deviations below their white counterparts. This improvement is also reflected in Black-White differences on school achievement tests, which have shrunk from about 1.2 to about 0.8 standard deviations. However, these improvements may have stalled for people born after the early 1970s.

Test bias

Modern IQ tests are unbiased.

The Flynn effect describes an increase in average IQ test scores over the last century. Similar improvements have been reported for other cognitions such as semantic and episodic memory. The effect has been observed in most parts of the world at different rates. The Flynn effect is named for James R. Flynn, who did much to document it and promote awareness of its implications. The effect increase has been continuous and approximately linear from the earliest years of testing to the present.

This means, given the same test, the mean performance of Blacks today could be higher than the mean for Whites in 1920, though the gains causing this appear to have occurred predominantly in the lower half of the IQ distribution. If an unknown environmental factor can cause changes in IQ over time, then contemporary differences between groups could also be due to an unknown environmental factor.

Nichols (1987) critically summarized the argument as follows:

1. We do not know what causes the test score changes over time.
2. We do not know what causes racial differences in intelligence.
3. Since both causes are unknown, they must, therefore, be the same.
4. Since the unknown cause of changes over time cannot be shown to be genetic, it must be environmental.
5. Therefore, racial differences in intelligence are environmental in origin.

Dickens (2005) states that "Although the direct evidence on the role of environment is not definitive, it mostly suggests that genetic differences are not necessary to explain racial differences. Advocates of the hereditarian position have therefore turned to indirect evidence ... The indirect evidence on the role of genes in explaining the Black-White gap does not tell us how much of the gap genes explain and may be of no value at all in deciding whether genes do play a role. Because the direct evidence on ancestry, adoption, and cross-fostering is most consistent with little or no role for genes, it is unlikely that the Black-White gap has a large genetic component."

African ancestry

African Americans typically have ancestors from both Africa and Europe, with, on average, 20% of their genome inherited from European ancestors. Several studies performed without the use of DNA-based ancestry estimation attempted to correlate estimates of African or European ancestry with IQ. These studies have been variously regarded as inconclusive, supportive of an environmental interpretation, or supportive of a hereditarian interpretation. These studies are generally criticized for using unreliable methods to estimate ancestry and for their small sample sizes.

African IQ

The very low IQ scores reported for sub-Saharan African populations are especially controversial.

g loading

The general intelligence factor (abbreviated g) is a controversial construct used in the field of psychology (see also psychometrics) to quantify what is common to the scores of all intelligence tests. It was discovered in 1904 by Charles Spearman and subsequently developed in a theory in 1923.

Spearman, who was an early psychometrician, found that schoolchildren's grades across seemingly unrelated subjects were positively correlated, and proposed that these correlations reflected the influence of a dominant factor, which he termed g for "general" intelligence. He developed a model where all variation in intelligence test scores can be explained by two factors. The first is the factor specific to an individual mental task: the individual abilities that would make a person more skilled at one cognitive task than another. The second is g, a general factor that governs performance on all cognitive tasks.

Across a battery of tests, the size of the Black-White gap is correlated with the extent to which the tests measure g.

Nesbitt writes:

Herrnstein and Murray (1994) and Rushton and Jensen (2005) argue that because blacks and whites differ more in their performance on items and subtests that have higher g loadings (correlations with the g factor), this is evidence of the biological, genetic nature of the black white difference in IQ.

Nesbitt finds this argument unpersuasive, noting that

The g loadings of subtests do not differ that much, the g loading of a particular subtest cannot be construed as evidence about the degree to which the subtest measures strictly biological or hereditary differences as opposed to environmentally produced differences, and the scores for blacks have improved almost as much on a g-weighted IQ test as on a non-g-weighted test.

Inbreeding depression

Inbreeding depression is reduced fitness in a given population as a result of breeding of related individuals. It is often the result of a population bottleneck. In general, the higher the genetic variation within a breeding population, the less likely it is to suffer from inbreeding depression. Inbreeding depression seems to be present in most groups of organisms. Although severe inbreeding depression in humans seems to be highly uncommon and not widely known, there have been several cases of apparent forms of inbreeding depression in human populations.

Brain physiology

Much of the research into the neuroscience of intelligence has involved indirect approaches, such as searching for correlations between psychometric test scores and variables associated with the anatomy and physiology of the brain. Historically, research was conducted on non-human animals or on postmortem brains. More recent studies have involved non-invasive techniques such as MRI scans as they can be conducted on living subjects. MRI scans can be used to measure the size of various structures within the brain, or they can be used to detect areas of the brain that are active when subjects perform certain mental tasks.

Within human populations, studies have been conducted to determine whether there is a relationship between brain size and a number of cognitive measures. Studies have reported correlations that range from 0 to 0.6, with most correlations 0.3 or 0.4.

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.

In a study of the head growth of 633 term-born children from the Avon Longitudinal Study of Parents and Children cohort, it was shown that prenatal growth and growth during infancy were associated with subsequent IQ. The study’s conclusion was that the brain volume a child achieves by the age of 1 year helps determine later intelligence.

Many MRI volumetric analyses have shown that on average, the brains of people identifying themselves as African-American are 5% smaller than the brains of people identifying themselves as White and 6% smaller than people identifying themselves as Asian.

The average brain volumes (in cm) are approximately 1,268 (Blacks), 1,362 (Whites), and 1,415 (East Asians).

Reaction time

Reaction time is the elapsed time between the presentation of a sensory stimulus and the subsequent behavioral response. RT is often used in experimental psychology to measure the duration of mental operations, an area of research known as mental chronometry. In psychometric psychology it is considered to be an index of speed of processing. That is, it indicates how fast the thinker can execute the mental operations needed by the task at hand. In turn, speed of processing is considered an index of processing efficiency. The behavioral response is typically a button press but can also be an eye movement, a vocal response, or some other observable behavior.

Regression toward the mean

Regression toward the mean refers to the phenomenon that a variable that is extreme on its first measurement will tend to be closer to the center of the distribution on a later measurement. To avoid making wrong inferences, the possibility of regression toward the mean must be considered when designing experiments and interpreting experimental, survey, and other empirical data in the physical, life, behavioral and social sciences.

Adoption studies

The Minnesota Transracial Adoption Study examined the IQ test scores of 130 black/interracial children adopted by advantaged White families. The aim of the study was to determine the contribution of genetic factors to the poor performance of black children on IQ tests as compared to White children. The following table provides a summary of the results.

Policy relevance

In response to criticism that their conclusions would have a negative effect on society if they were to gain wide acceptance, Jensen and Rushton have justified their research in this area as being necessary to answer the question of how much racism should be held responsible for ethnic groups' unequal performance in certain areas. They maintain that when racism is blamed for disparities which are the result of biological differences, the result is mutual resentment, and unjustified punishment of the more successful group. They state:

he view that one segment of the population is largely to blame for the problems of another segment can be even more harmful to racial harmony, by first producing demands for compensation and thereby inviting a backlash. Equating group disparities in success with racism on the part of the more successful group guarantees mutual resentment. As overt discrimination fades, still large racial disparities in success lead Blacks to conclude that racism is not only pervasive but also insidious because it is so unobservable and "unconscious." Whites resent that nonfalsifiable accusation and the demands to compensate blacks for harm they do not believe they caused.

See also

• Health and intelligence
• Environment and intelligence
• Ashkenazi intelligence
• The Bell Curve (1994)
• Intelligence: Knowns and Unknowns (1996)
• IQ and Global Inequality (2006)
• The Mismeasure of Man (1981)
• Mainstream Science on Intelligence (1994; 1997)
• Race Differences in Intelligence (2006)
• Survey of Expert Opinion on Intelligence and Aptitude Testing (1987)

Notes

1. ^ Neisser, U., Boodoo, G., Bouchard, T. J. Jr., Boykin, A. W., Brody, N., Ceci, S. J.; et al. (1996). "Intelligence: Knowns and unknowns" (PDF). American Psychologist. 51: 77–101. {{cite journal}}: Explicit use of et al. in: |author= (help)CS1 maint: multiple names: authors list (link) "African American IQ scores have long averaged about 15 points below those of Whites, with correspondingly lower scores on academic achievement tests. In recent years the achievement-test gap has narrowed appreciably. It is possible that the IQ-score differential is narrowing as well, but this has not been clearly established. The cause of that differential is not known; it is apparently not due to any simple form of bias in the content or administration of the tests themselves. The Flynn effect shows that environmental factors can produce differences of at least this magnitude, but that effect is mysterious in its own right. Several culturally-based explanations of the Black/White IQ differential have been proposed; some are plausible, but so far none has been conclusively supported. There is even less empirical support for a genetic interpretation. In short, no adequate explanation of the differential between the IQ means of Blacks and Whites is presently available."
2. Samuel George Morton (1839). Crania Americana; or, A Comparative View of the Skulls of Various Aboriginal Nations of North and South America: To which is Prefixed An Essay on the Varieties of the Human Species. J. Dobson. {{cite book}}: Unknown parameter |city= ignored (|location= suggested) (help)
3. Robert Bennett Bean (1906). "Some racial peculiarities of the Negro brain". American Journal of Anatomy. 5: 353–432. doi:10.1002/aja.1000050402.
4. F. P. Mall (1909). "On several anatomical characters of the human brain, said to vary according to race and sex, with especial reference to the weight of the frontal lobe". American Journal of Anatomy. 9: 1–32.
5. Tucker, William H. (2002), The Funding of Scientific Racism: Wickliffe Draper and the Pioneer Fund, University of Illinois Press, pp. 43, 180–181, ISBN 0252027620
6. Lynn, Richard (2001), The science of human diversity: a history of the Pioneer Fund, University Press of America, ISBN 076182040X
7. Jensen, Arthur (1969). "How Much Can We Boost IQ and School Achievement?". Harvard Educational Review. 39: 1–123. "So all we are left with are various lines of evidence, no one of which is definitive alone, but which, viewed all together, make it a not unreasonable hypothesis that genetic factors are strongly implicated in the average Negro-white intelligence difference. The preponderance of the evidence is, in my opinion, less consistent with a strictly environmental hypothesis than with a genetic hypothesis, which, of course, does not exclude the influence of environment or its interaction with genetic factors."
8. Gould, Stephen Jay (1996). The Mismeasure of Man. Sagebrush Education Resources. ISBN 0613181301.
9. Shirkin, Joel N. (2006), Broken Genius: The Rise and Fall of William Shockley, Creator of the Electronic Age, Macmillan, ISBN 1403988153
10. ^ Richard J. Herrnstein; Charles Murray (1994). The Bell Curve: Intelligence and Class Structure in American Life. New York: Free Press. ISBN 0-02-914673-9.
11. American Anthropological Association (1994), Statement on "Race" and Intelligence, retrieved March 31, 2010
12. David J. Bartholomew (2004). Measuring Intelligence: Facts and Fallacies. Cambridge University Press. ISBN 0521544785.
13. Ian J. Deary (2001). Intelligence: A Very Short Introduction. Oxford University Press. ISBN 0192893211.
14. N. J. Mackintosh (1998). IQ and Human Intelligence. Oxford University Press. ISBN 019852367X.
15. ^ Earl Hunt and Jerry Carlson (2007). "Considerations Relating to the Study of Group Differences in Intelligence". Perspectives on Psychological Science. 2 (2): 194-213."Nevertheless, self-identification is a surprisingly reliable guide to genetic composition. Tang et al. (2005) applied mathematical clustering techniques in order to sort genomic markers for over 3,600 people in the United States and Taiwan into four groups. There was almost perfect agreement between cluster assignment and individuals’ self-reports of racial/ethnic identification as White, Black, East Asian, or Latino."
16. James R. Flynn (2007). What Is Intelligence? Beyond the Flynn Effect. Cambridge University Press. ISBN 0521880076.
17. ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi: 10.1111/j.1744-6570.2001.tb00094.x, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi= 10.1111/j.1744-6570.2001.tb00094.x instead.
18. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1080/00207596608247156, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1080/00207596608247156 instead.
19. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1080/00207596808246642, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1080/00207596808246642 instead.
20. "We should accept, then, without further ado that there is a difference in average IQ between blacks and white." Mackintosh (1998), page 150.
21. ^ Lynn, R. and Vanhanen, T. (2002). IQ and the wealth of nations. Westport, CT: Praeger. ISBN 0-275-97510-X
22. ^ Lynn, R. (2006). Race Differences in Intelligence: An Evolutionary Analysis. Washington Summit Books. {{cite book}}: Unknown parameter |isbd= ignored (help)
23. Lynn, R. (1991). "Race Differences in Intelligence: A Global Perspective" (PDF). Mankind Quarterly. 31: 255–296. {{cite journal}}: Cite has empty unknown parameter: |month= (help)
24. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi: 10.1016/j.paid.2005.10.004, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi= 10.1016/j.paid.2005.10.004 instead.
25. Rindermann, H. (2006). What do international student assessments measure?. Psychologische Rundschau, 57, 69–86.
26. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1016/j.intell.2007.09.003, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1016/j.intell.2007.09.003 instead.
27. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi: 10.1016/j.intell.2006.06.001, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi= 10.1016/j.intell.2006.06.001 instead.
28. ^ Nisbett, Richard (2009). Intelligence and How to Get It: Why Schools and Cultures Count. W. W. Norton & Company. ISBN 0393065057.
29. Richard Nisbett (2005). "Heredity, environment, and race differences in IQ: A commentary on Rushton and Jensen (2005)" (PDF). Psychology, Public Policy, and Law. 11 (2): 302–310. doi:10.1037/1076-8971.11.2.302.
30. ^ J. Philippe Rushton and Arthur Jensen (2005). "Thirty Years of Research on Race Differences in Cognitive Ability" (PDF). Psychology, Public Policy, and Law. 11 (2): 235–294. doi:10.1037/1076-8971.11.2.235.
31. J. Philippe Rushton and Arthur R. Jensen (2005). "WANTED: More Race Realism, Less Moralistic Fallacy" (PDF). Psychology, Public Policy, and Law. 11 (2): 328–336. doi:10.1037/1076-8971.11.2.328.
32. J. Philippe Rushton and Arthur R. Jensen (2010). "Race and IQ: A theory-based review of the research in Richard Nisbett's Intelligence and How to Get It" (PDF). The Open Psychology Journal. 3: 9–35.
33. Flynn 1980, pg. 59-60
34. Flynn (1980) and Flynn (1999)
35. Reviewed in Neisser et al. (1996). Data from the NLSY as reported in figure adapted from Herrnstein and Murray (1994), p. 288.
36. Loehlin, J. C., Lindzey, G., & Spuhler, J. N. (1975). Race differences in intelligence. San Francisco, CA: W.H. Freeman.
37. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1016/j.intell.2006.07.004, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1016/j.intell.2006.07.004 instead.
38. "Despite widespread belief to the contrary, however, there is ample evidence, both in Britain and the USA, that IQ tests predict educational attaintment just about as well in ethnic minorities as in the white majority." Mackintosh (1998), page 174.
39. Rönnlund M, Nilsson LG. (2009). Flynn effects on sub-factors of episodic and semantic memory: parallel gains over time and the same set of determining factors. Neuropsychologia. 47(11):2174-80. doi:10.1016/j.neuropsychologia.2009.05.001 PMID 19056409
40. Nichols, R. C. (1987). Interchange: Nichols replies to Flynn. In S. Modgil & C. Modgil (Eds.), Arthur Jensen: Consensus and controversy (pp. 233–234). New York, NY: Falmer.
41. Genetic Differences and School Readiness Dickens, William T. The Future of Children - Volume 15, Number 1, Spring 2005, pp. 55-69
42. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1016/j.intell.2009.05.002, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1016/j.intell.2009.05.002 instead.
43. Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1016/j.intell.2009.09.009, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with |doi=10.1016/j.intell.2009.09.009 instead.
44. Cohen, Mark N. year = 2005. "Race and IQ Again: A Review of Race: The Reality of Human Differences by Vincent Sarich and Frank Miele" (PDF). Evolutionary Psychology. 3: 255-262. {{cite journal}}: Missing pipe in: |first= (help)CS1 maint: numeric names: authors list (link)
45. Jensen, Arthur (1998). The g Factor: The Science of Mental Ability. Westport, CT: Praeger Publishers. ISBN 0-275-96103-6.
46. S. F. Witelson, H. Beresh and D. L. Kigar (2006). "Intelligence and brain size in 100 postmortem brains: sex, lateralization and age factor". Brain. 129 (2). Oxford University Press: 386–398. doi:10.1093/brain/awh696.
47. Paul Thompson, Tyrone D. Cannon, Katherine L. Narr; et al. (2001). "Genetic influences on brain structure" (PDF). Nature Neuroscience. 4 (12): 1253–1258. {{cite journal}}: Explicit use of et al. in: |author= (help)CS1 maint: multiple names: authors list (link)
48. Danielle Posthuma, Eco J. C. De Geus, Wim F. C. Baare, Hilleke E. Hulshoff Pol, Rene S. Kahn and Dorret I. Boomsma (2002). "The association between brain volume and intelligence is of genetic origin". Nature Neuroscience. 5: 83–84. doi:10.1038/nn0202-83.{{cite journal}}: CS1 maint: multiple names: authors list (link)
49. Catharine R. Gale; et al. (2006). "The Influence of Head Growth in Fetal Life, Infancy, and Childhood on Intelligence at the Ages of 4 and 8 Years". PEDIATRICS. 118 (4): 1486–1492. doi:10.1542/peds.2005-262. {{cite journal}}: Explicit use of et al. in: |author= (help)
50. ^ Rushton, J. P. (1997). Cranial size and IQ in Asian Americans from birth to age seven. Intelligence, 25, 7–20.
51. The Chair of the APA’s Task Force on intelligence: Neisser, U. (1997). Never a dull moment. American Psychologist, 52, 79–81.
52. Rushton JP. Race, evolution, and behavior: a life history perspective. New Brunswick, NJ: Transaction 1995.
53. S. Scarr and R.A. Weinberg (1976). "IQ test performance of black children adopted by white families". American Psychologist. 31: 726–739.
54. R.A. Weinberg, S. Scarr and I. D. Waldman (1992). "The Minnesota Transracial Adoption Study: A follow-up of IQ test performance at adolescence". Intelligence. 16: 117–135.
55. I. D. Waldman, R.A. Weinberg and S. Scarr (1994). "Racial-group differences in IQ in the Minnesota Transracial Adoption Study: A reply to Levin and Lyn". Intelligence. 19: 29–44.
56. John Loehlin (2000). Robert Sternberg (ed.). Handbook of Human Intelligence. p. 185.
57. K. Eyferth (1961). "Leistungern verscheidener Gruppen von Besatzungskindern in Hamburg-Wechsler Intelligenztest für Kinder (HAWIK)". Archiv für die gesamte Psychologie. 113: 222–41.
58. EGJ Moore (1986). "Family socialization and the IQ test performance of traditionally and transracially adopted black children". Dev Psychol. 22: 317–326.

References

v t e Sex differences in humans
Biology	Sexual differentiation Disorders In research Physiology Dimorphism Scientific measures
Medicine and Health	Autoimmunity Life expectancy Mental disorders Autism Depression Schizophrenia Substance abuse Suicide Stroke care
Neuroscience and Psychology	Cognition Coping Emotional expression Aggression Emotional intelligence Empathy Gender empathy gap Intelligence Memory Narcissism Neurosexism Sexuality Age disparity in relationships Attraction Desire Fantasy Jealousy
Sociology	Crime Education in the U.S. Gender inequality Leadership Religion Social capital Social support Sociolinguistics Equality paradox

• Race and intelligence controversy
• Intelligence
• Race
• Scientific controversies