Race and intelligence: Difference between revisions
→Policy relevance: This seems to be generally supported. At least I'm not seeing many arguments against it. |
1)Removed material is cited and relevant 2)This addition is still being discussed and hasn't gained consensus. As per WP:BRD, let's please take it to the talk page. |
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There are no universally accepted definitions of either race or intelligence in academia, and many factors that could potentially influence the development of intelligence have been advanced to explain the racial IQ gap. [[Thomas_J._Bouchard,_Jr.|Thomas Bouchard]] and colleagues at the University of Minnesota expressed the view in 1990 that genetics is the primary factor in individual IQ scores, with environmental and cultural factors playing a smaller role.<ref> {{cite journal |author=Bouchard TJ, Lykken DT, McGue M, Segal NL, Tellegen A |title=Sources of human psychological differences: the Minnesota Study of Twins Reared Apart |journal=[[Science (journal)|Science]] |volume=250 |issue=4978 |pages=223–8 |year=1990 |month=October |pmid=2218526 |doi= |url=http://www.sciencemag.org/cgi/pmidlookup?view=long&pmid=2218526}}</ref> On the other hand, Bouchard and colleagues argue that "even highly heritable traits can be strongly manipulated by the environment, so heritability has little if anything to do with controllability."<ref>{{cite journal | author = Johnson, Wendy; Turkheimer, Eric; Gottesman, Irving I.; Bouchard Jr., Thomas | year = 2009 | title = Beyond Heritability: Twin Studies in Behavioral Research. | journal = Current Directions in Psychological Science | volume = 18 | issue = 4 | pages = 217–220 | doi = doi: 10.1111/j.1467-8721.200}}</ref> [[J. Philippe Rushton]] and [[Arthur Jensen]] wrote in 2005 that a variety of studies from around the world show that between 50-80% of the White-Black IQ gap is attributed to genetics,<ref name="30years">{{cite journal |author = J. Philippe Rushton and Arthur Jensen |title = Thirty Years of Research on Race Differences in Cognitive Ability |journal = Psychology, Public Policy, and Law |volume = 11 | number = 2 |pages = 235–294 |year = 2005 |url = http://psychology.uwo.ca/faculty/rushtonpdfs/PPPL1.pdf |doi = 10.1037/1076-8971.11.2.235 }}</ref> evoking a point-by-point response from [[Richard_E._Nisbett|Richard E. Nisbett]] in 2009.<ref name="Nisbett2009Appendix" /> The controversial view that a significant portion of the racial IQ gap is ultimately of genetic origin has been advanced by academics such as Jensen, Rushton, [[Richard Lynn]], and [[Hans Eysenck]]. The claim that the IQ gap has a genetic component met with widespread criticism in the popular media, particularly after the publication of "[[The Bell Curve]]." |
There are no universally accepted definitions of either race or intelligence in academia, and many factors that could potentially influence the development of intelligence have been advanced to explain the racial IQ gap. [[Thomas_J._Bouchard,_Jr.|Thomas Bouchard]] and colleagues at the University of Minnesota expressed the view in 1990 that genetics is the primary factor in individual IQ scores, with environmental and cultural factors playing a smaller role.<ref> {{cite journal |author=Bouchard TJ, Lykken DT, McGue M, Segal NL, Tellegen A |title=Sources of human psychological differences: the Minnesota Study of Twins Reared Apart |journal=[[Science (journal)|Science]] |volume=250 |issue=4978 |pages=223–8 |year=1990 |month=October |pmid=2218526 |doi= |url=http://www.sciencemag.org/cgi/pmidlookup?view=long&pmid=2218526}}</ref> On the other hand, Bouchard and colleagues argue that "even highly heritable traits can be strongly manipulated by the environment, so heritability has little if anything to do with controllability."<ref>{{cite journal | author = Johnson, Wendy; Turkheimer, Eric; Gottesman, Irving I.; Bouchard Jr., Thomas | year = 2009 | title = Beyond Heritability: Twin Studies in Behavioral Research. | journal = Current Directions in Psychological Science | volume = 18 | issue = 4 | pages = 217–220 | doi = doi: 10.1111/j.1467-8721.200}}</ref> [[J. Philippe Rushton]] and [[Arthur Jensen]] wrote in 2005 that a variety of studies from around the world show that between 50-80% of the White-Black IQ gap is attributed to genetics,<ref name="30years">{{cite journal |author = J. Philippe Rushton and Arthur Jensen |title = Thirty Years of Research on Race Differences in Cognitive Ability |journal = Psychology, Public Policy, and Law |volume = 11 | number = 2 |pages = 235–294 |year = 2005 |url = http://psychology.uwo.ca/faculty/rushtonpdfs/PPPL1.pdf |doi = 10.1037/1076-8971.11.2.235 }}</ref> evoking a point-by-point response from [[Richard_E._Nisbett|Richard E. Nisbett]] in 2009.<ref name="Nisbett2009Appendix" /> The controversial view that a significant portion of the racial IQ gap is ultimately of genetic origin has been advanced by academics such as Jensen, Rushton, [[Richard Lynn]], and [[Hans Eysenck]]. The claim that the IQ gap has a genetic component met with widespread criticism in the popular media, particularly after the publication of "[[The Bell Curve]]." |
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Other factors besides genetics and environment can affect IQ test results, such as the [[stereotype threat]], where it is found that performance of individuals on an IQ test can be significantly affected by changing their expectations right beforehand about how they should perform, or by giving them information which relates the test to a social [[stereotype]] that the test takers hold about themselves. In this manner, societal conditions can affect average IQ scores as a function of race whenever a stereotype exists about a race's intelligence, and the test takers are aware they are taking an intelligence test. <ref> Latent ability: Grades and test scores systematically underestimate the intellectual ability of negatively stereotyped students. Psychological Science, 20, 1132–1139.</ref> |
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A report issued by the [[American Psychological Association|APA]] in 1996 concluded that the racial IQ gap between African American and White Americans has remained relatively stable since IQ testing began<ref name="APA">{{cite journal |
A report issued by the [[American Psychological Association|APA]] in 1996 concluded that the racial IQ gap between African American and White Americans has remained relatively stable since IQ testing began<ref name="APA">{{cite journal |
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== |
== relevance== |
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:''See also: [[Intelligence_quotient#Positive_correlations_with_IQ]]'' |
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===IQ and social outcomes=== |
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Reviewing the literature on the effects of intelligence, the American Psychological Association has concluded that the characteristics measured by IQ tests predict many socially important outcomes, including educational performance, job performance, law abidingness and income, and they conclude that those characteristics are one of several factors influencing social outcomes, and that for school performance it may even be the strongest.<ref name="APA">{{cite journal|author = Neisser, U., Boodoo, G., Bouchard, T. J. Jr., Boykin, A. W., Brody, N., Ceci, S. J. et al.|title = Intelligence: Knowns and unknowns|journal = American Psychologist|volume = 51|pages = 77–101|year = 1996|url = http://www.psych.illinois.edu/~broberts/Neisser%20et%20al,%201996,%20intelligence.pdf}}"In summary, intelligence test scores predict a wide range of social outcomes with varying degrees of success. Correlations are highest for school achievement, where they account for about a quarter of the variance. They are somewhat lower for job performance, and very low for negatively valued outcomes such as criminality. In general, intelligence tests measure only some of the many personal characteristics that are relevant to life in contemporary America. Those characteristics are never the only influence on outcomes, though in the case of school performance they may well be the strongest."</ref> Regarding job performance, Frank Schmidt and John Hunter have stated that the validity of IQ as a predictor of job performance is above zero for all work studied to date, but varies with the type of job and across different studies, ranging from 0.2 to 0.6.<ref name="Schmidt98">{{cite journal |doi=10.1037/0033-2909.124.2.262 |title=The validity and utility of selection methods in personnel psychology: Practical and theoretical implications of 85 years of research findings. |year=1998 |last1=Schmidt |first1=Frank L. |last2=Hunter |first2=John E. |journal=Psychological Bulletin |volume=124 |pages=262}}</ref> Regarding academic achievement, Treena Eileen Rohde and Lee Anne Thompson write that general cognitive ability but not specific ability scores predict academic achievement, with the exception that processing speed and spatial ability predict performance on the SAT math beyond the effect of general cognitive ability.<ref>Treena Eileen Rohde and Lee Anne Thompson. (2007). Predicting academic achievement with cognitive ability, ''Intelligence'', '''35''', 83-92.</ref> |
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On the basis of this relationship, several scholars have concluded that the racial disparities in these areas are partly the result of the IQ gap.<ref name = "Gordon 1997">{{Cite doi | 10.1016/S0160-2896(97)90017-9}}</ref><ref name="Gottfredson 1997">{{Cite doi | 10.1016/S0160-2896(97)90014-3}} [http://www.udel.edu/educ/gottfredson/reprints/1997whygmatters.pdf ]</ref><ref>Jensen 1998, pg. 544-583</ref> Some have also argued that the causal relationship between these variables and IQ points in the opposite direction, meaning that high income and social status cause high IQ rather than the reverse,<ref name="bell myth">''[http://press.princeton.edu/chapters/s5877.html Inequality by Design: Cracking the Bell Curve Myth]'' by Claude S. Fischer, Michael Hout, Martín Sánchez Jankowski, Samuel R. Lucas, Ann Swidler, and Kim Vos. Page 191.</ref> or that IQ and social status both influence one another.<ref>Nisbett 2009</ref> |
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In [[The Bell Curve]], Murray and Herrnstein conclude that when Blacks and Whites are compared while adjusting for IQ, the difference in many social and economic variables shrinks or disappears. For example, controlling for IQ shrinks the income gap from thousands to a few hundred dollars, cuts differential poverty by about three-quarters and unemployment differences by half. At a given IQ level, the odds of having a college degree and working in a high-level occupation are higher for blacks than for whites.<ref name="The Bell Curve">{{cite book | last = Hernstein | first = Richard J. | authorlink = | coauthors = Charles Murray | year = 1994 | title = The Bell Curve: Intelligence and Class Structure in American Life | publisher = Free Press | location = New York | id = ISBN 0-02-914673-9}}</ref> Studies outside of ''The Bell Curve'' that have produced similar results are Nyborg and Jensen (2001)<ref name="Nyborg and Jensen, 2001">{{Cite doi| 10.1016/S0160-2896(00)00042-8}}</ref> and Kanazawa (2005).<ref name="Kanazawa 2005">{{Cite doi | 10.1016/j.joep.2004.05.001 }}</ref> Another study by Bowles and Gintis concluded that wealth, race and schooling are important to the inheritance of economic status, but IQ is not a major contributor. Since race, schooling and IQ are all correlated, the exact causal relationship between them is difficult to determine.<ref>{{cite journal | author = Bowles, S. and Gintis, H. | year = 2002 | month = Sum | title = The inheritance of inequality | journal = Journal of Economic Perspectives | volume = 16 | issue = 3 | pages = 3-30 | id = | url = http://www.umass.edu/preferen/gintis/intergen.pdf }}</ref> |
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Minority groups whose IQs are above the white average are often over-represented in high-paying professions. Examining this relationship, Nathanial Wehl has concluded that this over-representation is a consequence of their above-average IQ.<ref>{{cite journal | author = Weyl, Nathaniel | year = 1969 | month = | title = Some comparative performance indexes of American ethnic minorities | journal = Mankind Quarterly | volume = 9 | issue = | pages = 106-128 | doi = | url = }}</ref><ref>{{cite book | author = Weyl, Nathaniel | authorlink = | coauthors = | year = 1989 | month = | title = The Geography of American Achievement | chapter = | editor = | others = | edition = | pages = | publisher = Scott-Townsend | location = Washington, D.C. | id = | url = }}</ref> Cochran and Harpending have also made this proposal about [[Ashkenazi Jews]], which make up on 3% of the United States population but have won 27% of its Nobel prizes, which these authors attribute to them having an average IQ somewhere between one-half and one standard deviation above the White average.<ref>G. Cochran, J. Hardy, H. Harpending, [http://homepage.mac.com/harpend/.Public/AshkenaziIQ.jbiosocsci.pdf Natural History of Ashkenazi Intelligence], Journal of Biosocial Science 38 (5), pp. 659–693 (2006).</ref> (See "[[Ashkenazi intelligence]]".) The professions in which Asians and Ashkenazi Jews tend to be over-represented differ, and Richard Lynn has proposed that this difference is directly related to the fact that Ashkenazim tend to have above-average verbal and mathematical scores but below-average visuospatial scores, while for East Asians the opposite is the case.<ref>{{cite journal | author = Lynn, R. | year = 1991a | month = | title = Race Differences in Intelligence: A Global Perspective | journal = Mankind Quarterly | volume = 31 | issue = | pages = 255-296 | id = | url = http://www.mugu.com/cgi-bin/Upstream/People/Lynn/lynn-race-iq.html }}</ref> While acknowledging that East Asians have average IQs above the white average, the APA states that this group’s over-representation in high-paying professions is considerably greater than what could be predicted on the basis of IQ scores alone, so culture and temperament are likely to also be factors.<ref name="APA"></ref> |
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===Policy implications=== |
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{{Main|Intelligence and public policy}} |
{{Main|Intelligence and public policy}} |
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Because of the real-world effects associated with IQ, some scholars believe that addressing the racial IQ gap is a pressing social concern.<ref>{{Cite doi | 10.1037/0003-066x.59.1.7 }}: [http://www2.uni-jena.de/svw/igc/studies/ss03/sackitt_hardison_cullen_2004.pdf] "Sub-group differences in performance on high-stakes tests represent one of American society's most pressing social problems, and mechanisms for reducing or eliminating differences are of enormous interest" (p.11).</ref> One effort to address the IQ gap often advocated by educators is more equitable funding for education.<ref>[http://4909e99d35cada63e7f757471b7243be73e53e14.gripelements.com/.../2006_09_23BattleCreekEducation.ppt Achieving Equitable Education in Calhoun County]</ref><ref>[http://www.leaonline.com/doi/abs/10.1207/s15326993es4001_5 Educational Studies: A Journal of the American Educational Studies Association]</ref> Compensatory education programs have also been aimed at reducing achievement gaps between races, the most recent of which is the [[No Child Left Behind Act]],<ref name=autogenerated1>http://www.ed.gov/nclb/accountability/achieve/achievement_aa.html</ref> whose stated goal is to eliminate all racial achievement gaps by 2014.<ref>[http://www.chicagotribune.com/classified/realestate/chi-0211130369nov13,0,6024748.story Topic Galleries - chicagotribune.com<!-- Bot generated title -->]</ref> Arthur Jensen has argued that compensatory education programs as traditionally structured have a poor success rate,<ref>For the best-known example of this see Jensen 1969, which begins “Compensatory education has been tried and it apparently has failed.”</ref> and that in order to adequately address differences in educational outcomes, it is necessary to provide educational services that are tailored to each person's individual ability regardless of race.<ref>Frank Miele and Arthur Jensen. ''Intelligence, Race and Genetics: Conversations with Arthur R. Jensen''. Westview Press, 2002, pg. 178-179. "I have repeatedly emphasized, particularly in talks before educational organizations and in a recent publication, that quality education does not mean the very ''same'' program of instruction for every child, but equal opportunity for all children to receive a ''specific'' program tailored to their ''individual differences'' in general ability and in special aptitudes. I especially stress the words ''individual differences'' to emphasize that these differences cut across all racial, ethnic, and social class groups." (Emphasis in original.)</ref> |
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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 that result from biological differences, the result is mutual resentment, and unjustified punishment of the more successful group. They state: |
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As a result of the existence of racial gaps in average IQ, the [[US Supreme Court]] has ruled in the 1971 case [[Griggs v. Duke Power Co.]] that the use of IQ tests as a criteria for employment qualification was discriminatory even if no intentional discrimination was present.<ref> Griggs v. Duke Power Co. Findlaw Cases and Codes. [http://caselaw.lp.findlaw.com/scripts/getcase.pl?court=US&vol=401&invol=424]</ref> This case defined the U.S. policy of [[disparate impact]], by which corporate policies which adversely affect one gender or ethnic or religious group can be considered discriminatory even if they do not discriminate on the basis of gender, race or religion itself, unless such policies can be shown to be specifically related to job performance. This policy has been further defined by several additional laws and court cases, including the [[Civil Rights Act of 1991]] and the 2009 supreme court case [[Ricci v. DeStefano]], which ruled that [[disparate treatment]] on the basis for race was not permissible unless there was a strong basis of evidence that disparate impact would otherwise result.<ref>Ricci v. DeStefano. Finlaw Cases and Codes. [http://caselaw.lp.findlaw.com/scripts/getcase.pl?court=US&vol=000&invol=07-1428]</ref> |
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<blockquote> |
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⚫ | [T]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.<ref name="30years">{{cite journal |
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The social and scientific value of research about race and intelligence has also been questioned. Critics of research in this area have asserted that research in race and intelligence can never escape its association with the [[eugenics]] movement and [[scientific racism]] of the early 20th century, as well as that even modern research in this area is likely to be ideologically motivated.<ref>e.g., Sternberg, 2003, pp. 386–387</ref> In response to this and similar criticisms, Linda Gottfredson has argued that a genetic contribution to the IQ gap does not in itself demand any particular policy response: while a conservative/[[Libertarianism|libertarian]] commentator may feel the results justify, for example, reductions in [[affirmative action]], a [[Liberalism|liberal]] commentator may argue from a [[John Rawls|Rawlsian]] point of view (that genetic advantages are undeserved and unjust) for substantial affirmative action.<ref>Gottfredson 2005b</ref> Jensen and Rushton have also argued that their research in this area is necessary to answer the question of how much racism should be held responsible for ethnic groups' unequal performance in certain areas, since when racism is blamed for disparities that result from differences in mental ability, the result is mutual resentment, and unjustified punishment of the more successful group: |
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|author = J. Philippe Rushton and Arthur Jensen |
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⚫ | |||
|title = Thirty Years of Research on Race Differences in Cognitive Ability |
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The APA concludes their 1995 report ''Intelligence: Knowns and Unknowns'' with a statement that further research in this area is necessary because of its social and scientific importance, as well as a warning against anyone who would consider the debate over this topic fully resolved: |
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|journal = Psychology, Public Policy, and Law |
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<blockquote>In a field where so many issues are unresolved and so many questions unanswered, the confident tone that has characterized most of the debate on these topics is clearly out of place. The study of intelligence does not need politicized assertions and recriminations; it needs self-restraint, reflection, and a great deal more research. The questions that remain are socially as well as scientifically important. There is no reason to think them unanswerable, but finding the answers will require a shared and sustained effort as well as the commitment of substantial scientific resources. Just such a commitment is what we strongly recommend.<ref name="APA"></ref> </blockquote> |
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|volume = 11 |
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| number = 2 |
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|pages = 235–294 |
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|year = 2005 |
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|url = http://psychology.uwo.ca/faculty/rushtonpdfs/PPPL1.pdf |
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|doi = 10.1037/1076-8971.11.2.235 |
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}}</ref> |
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</blockquote> |
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==See also== |
==See also== |
Revision as of 18:38, 7 June 2010
This article's factual accuracy is disputed. (April 2010) |
Race and intelligence research investigates differences in the distributions of cognitive skills among human racial groups. Much of the debate in this area centers around questions of how intelligence is measured, and the relative influence that genetics and environment have on both intelligence and attempts to measure it. Debates in popular science and academic research over the possible relation between racial divisions and differences in intelligence originally began as a comparison of African Americans and Caucasians in the United States, but were later extended to other ethno-racial groups and regions of the world. In the US, intelligence quotient (IQ) test scores show statistical differences, with the average score of the African American population being lower - and that of the Asian American population being higher - than that of the White American population (based on the self-identification of those tested). These measured differences in the average value are typically fractions of a standard deviation, meaning that they only describe a shift in the center of the measured values, while the distribution is much broader and with considerable overlap between groups.
There are no universally accepted definitions of either race or intelligence in academia, and many factors that could potentially influence the development of intelligence have been advanced to explain the racial IQ gap. Thomas Bouchard and colleagues at the University of Minnesota expressed the view in 1990 that genetics is the primary factor in individual IQ scores, with environmental and cultural factors playing a smaller role.[1] On the other hand, Bouchard and colleagues argue that "even highly heritable traits can be strongly manipulated by the environment, so heritability has little if anything to do with controllability."[2] J. Philippe Rushton and Arthur Jensen wrote in 2005 that a variety of studies from around the world show that between 50-80% of the White-Black IQ gap is attributed to genetics,[3] evoking a point-by-point response from Richard E. Nisbett in 2009.[4] The controversial view that a significant portion of the racial IQ gap is ultimately of genetic origin has been advanced by academics such as Jensen, Rushton, Richard Lynn, and Hans Eysenck. The claim that the IQ gap has a genetic component met with widespread criticism in the popular media, particularly after the publication of "The Bell Curve."
Other factors besides genetics and environment can affect IQ test results, such as the stereotype threat, where it is found that performance of individuals on an IQ test can be significantly affected by changing their expectations right beforehand about how they should perform, or by giving them information which relates the test to a social stereotype that the test takers hold about themselves. In this manner, societal conditions can affect average IQ scores as a function of race whenever a stereotype exists about a race's intelligence, and the test takers are aware they are taking an intelligence test. [5]
A report issued by the APA in 1996 concluded that the racial IQ gap between African American and White Americans has remained relatively stable since IQ testing began[6], and concluded that the gap is not the result of "any obvious biases in the construction or administration of tests, nor does it simply reflect differences in socioeconomic status". A more recent 2006 study by Dickens et al. found that the gap has been closing by about 5 or 6 IQ points between 1972 and 2002[7].
History
The history of the race and intelligence controversy concerns the historical development of a debate, primarily in the United States, concerning possible explanations of group differences in scores on intelligence tests. Although it has never been disputed that there are systematic differences between average scores in IQ tests of different population groups, sometimes called "racial IQ gaps", there has been no agreement on whether this is mainly due to environmental and cultural factors, or whether some inherent hereditarian factor is at play, related to genetics.
In the late nineteenth and early twentieth century, group differences in intelligence were assumed to be due to race and, apart from intelligence tests, research relied on measurements such as brain size or reaction times. By the mid-1930s most psychologists had adopted the view that environmental and cultural factors played a dominant role.[8] In 1969 the Harvard Educational Review published a 125-page invited article by the educational psychologist Arthur Jensen reviving the hereditarian point of view; it concluded, "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".[9]: 82 Jensen's work, publicized by the Nobel laureate William Shockley, sparked controversy amongst the academic community and even led to student unrest.[10][11] A similar debate amongst academics followed publication in 1994 of The Bell Curve, a book by Richard Herrnstein and Charles Murray that argued in favor of the hereditarian viewpoint. It not only provoked the publication of several interdisciplinary books on the environmental point of view, some in popular science, but also led to a public statement from the American Psychological Association acknowledging a gap between average IQ scores of whites and blacks as well as the absence of any adequate explanation of it, either environmental or genetic.[12][13][14] The hereditarian line of research continues to be pursued by a group of researchers, mostly psychologists, some of whom are supported by the Pioneer Fund; these include Richard Lynn (global racial IQ gaps) and J. Philippe Rushton (brain size and racial IQ gaps), whose research had already been used in The Bell Curve.[10][15]
Hereditarianism and Environmental influence
In a review of the field, Hunt and Carlson[16] while arguing that "research on group differences in intelligence is scientifically valid and socially important" identify four contemporary positions on the topic of racial differences in intelligence:
- "There are differences in intelligence between races that are due in substantial part to genetically determined differences in brain structure and/or function (Rushton, 1995; Rushton & Jensen, 2005a)."
- "Differences in cognitive competencies between races exist and are of social origin (Ogbu, 2002; Sowell, 2005)."
- "Differences in test scores that are used to argue for differences in intelligence between races represent the inappropriate use of tests in different groups (Ogbu, 2002)."
- "There is no such thing as race; it is a term motivated by social concerns and not a scientific concept (Fish, 2004; Smedley & Smedley, 2005; Cooper, 2005; Sternberg, Grigorenko, & Kidd, 2005)."
Some scientists argue that the history of eugenics makes this field of research difficult to reconcile with current ethical standards for science.[17][18] Other scientists insist that, independent of ethical concerns, research into race and intelligence makes little sense because intelligence is poorly measured and because race is a social construction.[19] According to this view, intelligence is ill-defined and multi-dimensional, or has definitions that vary between cultures. This would make contrasting the intelligence of groups of people, especially groups that came from different cultures, dependent mainly on which culture’s definition of intelligence is being used. Moreover, this view asserts that even if intelligence were as simple to measure as height, racial differences in intelligence would still be meaningless since race exists only as a social construct, with no basis in biology.
Other scientists actively engaged in research in race and intelligence disagree with these criticisms.[20] For example, psychologist Richard Nisbett writes that:
Some laypeople I know — and some scientists as well — believe that it is a priori impossible for a genetic difference in intelligence to exist between the races. But such a conviction is entirely unfounded. There are a hundred ways that a genetic difference in intelligence could have arisen — either in favor of whites or in favor of blacks. The question is an empirical one, not answerable by a priori convictions about the essential equality of groups.[21]
Researchers fall into two groups: hereditarians and environmentalists. Both argue that, although race and intelligence are fuzzy concepts, they can be operationalized enough to draw conclusions about the connections, if any, between the two. Hereditarians argue that genetics explain a significant portion (approximately 50%) of the differences in measured intelligence among human races. Leading scholars of this view include Arthur Jensen, Philippe Rushton, Richard Herrnstein, Linda Gottfredson, Charles Murray and Richard Lynn. Environmentalists argue that the hereditarians are wrong, and that genetic differences are not an important cause of differences in measured intelligence among human races. Leading scholars of this view include Richard Lewontin, Stephen J. Gould, James Flynn, Richard Nisbett and Stephen Ceci. There are also other scientists who either take a more middle ground between these two viewpoints, or believe that there is currently not enough evidence to determine what part, if any, genetics plays in racial differences.[6]
According to Rushton and Jensen, the debate has remained unresolved for so long because of "the difficulty of the subject matter, the political issues associated with it and the emotions they arouse, and the different meta-theoretical perspectives of the experimental and correlational methodologies".[3] Contrasting these methodologies, they write that:
Hereditarian heuristics include constructing better tests, developing better techniques for measuring mental abilities, and discovering biological correlates (e.g., heritability, inbreeding depression and heterosis, brain size, brain metabolic rate, brain evoked potentials, brain imaging) of these tests. The process then involves examining the similarities of the scores among people whose varying degrees of genetic resemblance can be predicted from Mendelian theory (Fisher, 1918). [Environmentalist] heuristics include searching for the environmental factors that cause differences in intellectual performance and discovering the bias in existing tests. If two groups differ in mean IQ, [environmentalist] theorists conjecture either that the lower scoring group has been exposed to one or more deleterious experience or been deprived of some beneficial environmental stimuli or that the tests are not valid measures of their true ability. Compensatory training might be initiated and the hypothesis confirmed if the groups then obtain more nearly equal scores, or if less biased tests are developed on which the group differences are reduced but still predict outside criteria. Of course, these two programs overlap to some degree, and a given experiment might well combine elements of the heuristics of each.[3]
Current debate
After the publication of The Bell Curve, various books appeared discussing its findings critically, notably The Bell Curve Debate (1995), Inequality by Design: Cracking the Bell Curve Myth (1996) and a second edition of The Mismeasure of Man (1996) by Steven J. Gould. [22] There were also three books written from the hereditarian point of view: Why race matters: race differences and what they mean (1997) by Michael Levin; The g Factor: The science of mental ability (1998) by Jensen; and Intelligence; a new look by Hans Eysenck. Various other books of collected contributions appeared at the same time, including The black-white test gap (1998) edited by Christopher Jencks and Meredith Phillips, Intelligence, heredity and environment (1997) edited by Robert Sternberg and Elena Grigorenko.[23] A section in IQ and human intelligence (1998) by Nicholas Mackintosh discussed ethnic groups and Race and intelligence: separating science from myth(2002) edited by Jefferson Fish presented further commentary on The Bell Curve by anthropologists, psychologists, sociologists, historians, biologists and statisticians.[24]
In 2005 the debate gathered pace again with the publication, in the journal Psychology, Public Policy and Law of the American Psychological Association (APA), of a long lead article by Rushton and Jensen, reviewing 30 years of research on race differences in intelligence. They concluded that
the implication for public policy is that the discrimination model (i.e., Black-White differences in socially valued outcomes will be equal barring discrimination) must be tempered by a distributional model (i.e., Black-White differences reflect underlying group characteristics). Although the distributional model does not rule out affirmative action or compensation-type initiatives, it does reduce the impact of arguments in their favor based on an exclusive adherence to the discrimination model.
The article was followed by a series of responses, some in support, some critical.[25][26] Richard Nisbett, another psychologist who had also commented at the time, later included an amplified version of his commentary as part of the book Intelligence and How to Get It: Why Schools and Cultures Count (2010).
Nisbett summarises the findings of Rushton and Jensen as follows:[27]
- Since heritability of intelligence is high in the white population, the probability is high that a large portion of the black-white racial IQ gap is genetic in origin
- The gap is not caused by cultural differences, because culture-fair tests only increase the gap
- The average IQ of 70 for sub-Saharan Africans is lower than that of African Americans because 20% of the latters' gene pool is European
- Blacks score comparitively lower on questions with high general intelligence loadings, which are more affected by genetics
- Questions distinguishing "imbreeding depression" - low scores due to closely related parents - also distinguish the black-white racial gap
- Brain size is correlated to IQ and blacks have smaller brains than whites
- Speed of reaction is faster for those with higher IQs and whites have a higher speed of reaction to blacks
- The IQs of children of black parents with a high IQ regress to a lower mean than children of white parents with the same IQ, supporting a genetic explanation
- Interracial adoption studies support a genetic rather than an environmental explanation
During this period, the debate was tinged with controversy when two public figures repeated in interviews the claim of Lynn and Rushton that one of the main causes for poverty in Africa is the low average intelligence among sub-Saharan Africans. Following an interview in the monthly supplement of Helsingin Sanomat, Lynn's coauthor Tatu Vanhanen, a political scientist and father of the Prime Minister of Finland Matti Vanhanen, was investigated by the Finnish police between 2002 and 2004.[28] In 2007 James D. Watson, Nobel laureate in biology, gave a controversial interview to the Sunday Times Magazine during a book tour in the United Kingdom. This resulted in the cancellation of a Royal Society lecture, along with other public engagements, and his suspension from his administrative position at Cold Spring Harbor Laboratory. He subsequently cancelled the tour and resigned from his position.[29]
Subsequently Nature, which had commented during the Watson controversy, invited two editorials on the ethics of research in race and intelligence by Steven Rose (against) [30] and Stephen J. Ceci and Wendy M. Williams (for).[31] In the subsequent letters to Nature, the intelligence researcher James Flynn pointed out that had there been a ban on research on possibly poorly conceived ideas much valuable research on intelligence testing (including his own discovery of the Flynn effect) would not have occurred.[32]
Already in the 1996 report of the APA there had made comments on the ethics of research on race and intelligence.[33][16] Two further articles in 2004 by Gray and Thompson [34] and in 2007 by Hunt and Carlson[16] discussed different possible ethical guidelines.
Commentators have also argued that hereditarian psychologists have tacitly adopted folk definitions of race and heredity. Other common criticisms have centered on the problems that intelligence is poorly measured and that race is a social construct, not a biologically defined attribute. [35][36] According to this view, intelligence is ill-defined and multi-dimensional, or has definitions that vary between cultures. This would make contrasting the intelligence of groups of people, especially groups that came from different cultures, dependent mainly on which culture’s definition of intelligence is being used. Moreover, this view asserts that even if intelligence were as simple to measure as height, racial differences in intelligence would still be meaningless since race exists only as a social construct, with no basis in biology.
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:[6][37][38][39]
- 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 heritable.
- Family environment and community culture affect IQ, more so in children than 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. Self-reports have been shown to be reliable indicators of genetic race to the extent that they match up with genetic clusters derived from mathematical clustering techniques, but these techniques do not determine whether these clusters themselves have any relation to intelligence.[16] According to psychologist David Rowe, self-report is the preferred method for racial classification in studies of racial differences because classification based on genetic markers alone ignore the "cultural, behavioral, sociological, psychological, and epidemiological variables" that distinguish racial groups.[40]
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.[41] The Black-White IQ difference is largest on those tests that best represent the general intelligence factor g.[42] Using data primarily from the United States and Europe, Jensen and Rushton have estimated the average IQ of Blacks/Africans to be around 85; of whites/Europeans to be around 100, and of East Asians to be around 106.[3] Estimates from other researchers are more or less similar.[6][41] Gaps are also seen in other tests of cognitive ability or aptitude, including university admission exams, military aptitude tests and employment tests in corporate settings.[43]
The American Psychological Association has concluded that the racial IQ gap is not the result of a simple bias in the content or administration of tests, and the tests are equally valid predictors of achievement for Black and White Americans.[6] Arthur Jensen has found that when black and white individuals are matched for IQ, their relatives tend towards different means.[44][45]
The IQ distributions of other racial and ethnic groups in the United States are less well studied. The few Amerindian populations that have been systematically tested, including Arctic Natives,[46][47] tend to score worse on average than White populations but better on average than Black populations.[43] East Asian populations score higher on average than White populations in the United States as they do elsewhere.[16]
IQ differences outside of the USA
According to Richard Lynn and others, racial differences in IQ scores are observed around the world.[48][49] A commonly-cited review by Richard Lynn lists IQ scores for East Asians (105), Europeans (99), Inuit (91), Southeast Asians and Amerindians (87 each), Pacific Islanders (85), South Asians/North Africans (84), Non-Bushmen sub-Saharan Africans (67), Australian Aborigines (62) and Bushmen (54).[50][51][49][52][48]
This data is generally considered less accurate than data from the United States and Europe, in part because of the inherent difficulty of comparing IQ scores between cultures.[53][54]
Several researchers have argued that cultural differences limit the appropriateness of standard IQ tests in non-industrialized communities.[55][56] In the mid-1970s, for example, the Soviet psychologist Alexander Luria concluded that it was impossible to devise an IQ test to assess peasant communities in Russia because taxonomy was alien to their way of reasoning.[57]
Surveying the literature, Jelte Wicherts remarked that:
It is important to note that an observed IQ score does not necessarily equal a particular level of general intelligence or g (Bartholomew, 2004), as it is necessary to consider the issue of validity in interpreting an observed score as an indication of the position on a latent variable such as g. Several authors have questioned whether the IQ scores of Africans are valid and comparable to scores in western samples in terms of g ([Barnett and Williams, 2004], [Ervik, 2003], [Hunt and Carlson, 2007], [Hunt and Sternberg, 2006] and [Lane, 1994]). Some (e.g., Berry, 1974) reject the very possibility of obtaining a valid measure of g in Africa with western IQ tests, while others (e.g., [Herrnstein and Murray, 1994], [Lynn, 2006] and [Rushton and Jensen, 2005]) consider it relatively unproblematic. The psychometric issue of measurement invariance ([Mellenbergh, 1989] and [Millsap and Everson, 1993]) is crucial to the comparability of test scores across cultural groups in terms of latent variables, such as g. Alas, the number of studies addressing measurement invariance is small.[58]
Moreover, in a review of Lynn's book Race Differences in Intelligence (2006), where some of these findings are presented, Nicholas Mackintosh has also criticized Lynn for manipulation of data, and raised doubts about the reliability of his findings.[59][60]
Debate overview
Richard Nisbett,[4][61] in replying to hereditarian arguments,[9][50][3][62][63] structures the debate into several major areas.
Heritability within and between groups
There is consensus among intelligence researchers that IQ, like height, is significantly heritable within the same population.[6][64][65][66][67][68][69] However, there is debate over whether the IQ test differences between the racial groups are caused by genetic differences or by cultural or environmental factors. The following table shows the results of several studies examining the heritability of intelligence in African Americans:
Age | Mz —N | r | Dz-N | R | h' | c-h 2 | Reference | |
---|---|---|---|---|---|---|---|---|
1 | 4 | 60 | .77 | 84 | .52 | .50 | .56 | Loehlin et al., 1975 |
2 | 15 | 76 | .80 | 47 | .34 | .92 | 1.00 | Osborne, 1980 |
3 | 10-15 | 65 | .63 | 95 | .36 | .54 | .60 | Scarr, 1981 |
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?[71]
The alternative to common environmental factors is the hypothesis that the racial IQ gap can be accounted for by X-factors: factors that vary between groups but not within groups. A frequently-cited example of an X-factor from Richard Lewontin describes two populations of corn, one grown in a normal environment, and the other in a nutrient-deficient environment. The height of this corn is 100% heritable when grown in a uniform environment. Therefore, in such a scenario the within-group heritability of height is 100% in both populations, but the substantial differences between groups are due entirely to environmental factors. 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.[72]
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.[73] 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. Flynn claims that the Black-White gap has reduced throughout the 20th century[74]. However, Murray claims that these improvements may have stalled for people born after the early 1970s[75].
Flynn effect
Although modern IQ tests are unbiased,[76][dubious – discuss] average test scores over the last century have risen steadily around the world. This rise is known as the "Flynn effect," 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)[77] critically summarized the argument as follows:
- We do not know what causes the test score changes over time.
- We do not know what causes racial differences in intelligence.
- Since both causes are unknown, they must, therefore, be the same.
- Since the unknown cause of changes over time cannot be shown to be genetic, it must be environmental.
- 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."[78]
Spearman's hypothesis
Spearman's hypothesis asserts that group differences on intelligence test scores are caused primarily by group differences on the general intelligence factor (abbreviated g). The general factor is a statistical construct that measures what is common to the scores of all IQ test items. How well a person does on one IQ sub-test is usually correlated with how well he or she does on other sub-tests. This is the essence of g.
Jensen developed a statistical technique known as the method of correlated vectors to test Spearman's hypothesis. The idea is that a rank ordering of IQ sub-test items by g-loadings should correlate with the magnitude of the race difference on those items, if indeed g is their cause. For example, digit span backward is more g-loaded than is digit-span forward. And, the race difference on the former is about twice as large as the race difference on the latter.
Spearman's hypothesis is not without its critics. Psychologists Hunt and Carlson[16] write:
One of the most widely cited pieces of evidence (although not the only one) for biological differences in intelligence, sometimes referred to as Spearman's hypothesis (Jensen, 1998), rests on an indirect argument constructed from three facts. The first is that various IQ measures are substantially correlated, providing evidence for general intelligence. Although tests do vary in the extent of their g loading, factor structures are similar over several test batteries (Johnson, Bouchard, Krueger, McGue, & Gottesman, 2004). The second is that, within Whites, the g factor appears to have a substantial genetic component (see citations in Rushton & Jensen, 2005a). The third fact is that the g loadings of tests are substantially and positively correlated with the difference between the mean White and African American score on each subtest within a battery of tests. This analysis has been referred to as the "method of correlated vectors" (Jensen, 1998). Because it has also been well established that general intelligence has a substantial genetic component, results from the method of correlated vectors have been offered as putative evidence that the "default hypothesis" ought to be that about 50% of the variance in the African American versus White difference reflects genetic differences in a potential for intelligence (Jensen, 1998; Rushton and Jensen, 2005a).
They[16] further summarize criticisms of this position:
Technical objections have been made to the method of correlated vectors and to a somewhat stronger condition: that if the within-group correlations between measures are identical across groups, the between-group differences must arise from the same cause as the within-group correlations (Widaman, 2005). The essence of these objections is that the method of correlated vectors does not consider alternative hypotheses concerning the latent traits that might give rise to the observed difference in test scores. When a more appropriate method of analysis, multigroup confirmatory factor analysis, is applied, it has been found that Spearman's hypothesis (i.e., that the difference is due to differences in general intelligence) is only one of several models that could give rise to the observed distributions in test scores (Dolan, 2000). These findings render the method of correlated vectors ambiguous—which is not the same as saying that the Jensen-Rushton position is incorrect. Our point is that the argument for the default hypothesis is an indirect one. It would be far better if a direct causal argument could be made linking racial/ethnic genetic differences to studies of the development of the brain.
Variables potentially affecting intelligence in groups
The following factors have been suggested as explaining a portion of the differences in average IQ between races. These factors are not mutually exclusive with one another, and some may in fact directly contribute to others. For example, some or all of the differences in average brain size between races could be the result of nutritional factors,[79] and different geographic ancestry could also result in genetic differences.[80]
Socioeconomic environment
According to the report of a 1996 APA task force, socioeconomic factors (SES) cannot account for all of the observed racial-ethnic group differences in IQ. Their first reason for this conclusion is that that the black-white test score gap is not eliminated when individuals and groups are matched on SES. Second, attempts to exclude extreme conditions, nutritional and biological factors that may vary with SES have shown little effect on IQ. Third, the relationship between IQ and SES is not simply one in which SES determines IQ, but differences in intelligence, particularly parental intelligence, also cause differences in SES, making separating the two factors nearly impossible. Lastly, they argue that parameters of income and education alone fail to capture important categories of cultural experience that differ between racial and ethnic groups.[6]
Health and nutrition
Environmental factors including lead exposure[82], breast feeding[83], and nutrition[84][85] can significantly affect cognitive development and functioning. For example, iodine deficiency causes a fall, in average, of 12 IQ points [86]. Such impairments may sometimes be permanent, sometimes be partially or wholly compensated for by later growth. Comprehensive policy recommendations targeting reduction of cognitive impairment in children have been proposed.[87] The African American population of the United States is statistically more likely to be exposed to all of the possible prenatal and perinatal detrimental enviromental factors.[88][89]
Education
Although the test performance gaps between races persist even after adjusting for education level, several studies have proposed that a large part of the gap can be attributed to differences in quality of education.[90][91][92] Racial discrimination in education has been proposed as one possible cause of differences in educational quality between races.[93] According to a paper by Hala Elhoweris, Kagendo Mutua, Negmeldin Alsheikh and Pauline Holloway, teachers' referral decisions for students to participate in gifted and talented educational programs was influenced in part by the students’ ethnicity.[94]
Ellis Cose has suggested that special education programs can have a significant effect on raising the test scores of black students. In his book Intelligence can be Taught, Cose describes a program called SOAR implemented by Xavier University, which produced gains equivalent to 120 points on an SAT test. The Abecedarian Early Intervention Project, an intensive early childhood education project, was also able to cause an average IQ gain of 5 points in black children who participated in it, narrowing the IQ gap between them and whites from 15 points to 10.[95] Arthur Jensen has agreed that the Abecedarian project demonstrates that education can have a significant effect on IQ, but also points out that no educational program thus far has been able to reduce the B/W IQ gap by more than a third, so differences in education are unlikely to be its only cause.[96]
Nisbett argues that hereditarians Rushton and Jensen ignore early childhood development programs aside from Head Start. He points to work by Ramey and colleagues as an example, which found that 87% of children exposed to an educational intervention had IQs in the normal range compared to 56% of controls, and none of the intervention-exposed children were mildly retarded compared to 7% of controls. Nisbett also lists five other successful intervention studies, noting that they can be effective at any age.[61]: 304–5
Molecular genetics
The decoding of the human genome has enabled scientists to search for sections of the genome that contribute to cognitive abilities. Intelligence is both a quantitative and polygenic trait. This means that intelligence is under the influence of several genes, possibly several thousand. The effect of most individual genetic variants on intelligence is thought to be very small, well below 1% of the variance in g. Current studies using Quantitative trait loci have yielded little success in the search for genes influencing intelligence. Robert Plomin is confident that QTLs responsible for the variation in IQ scores exist, but due to their small effect sizes, more powerful tools of analysis will be required to detect them.[97] Others assert that no useful answers can be reasonably expected from such research before an understanding of the relation between DNA and human phenotypes emerges.[89] Some researchers have expressed reluctance to investigate possible links between genes and intelligence, due to the controversy it can produce.[98]
A 2005 literature review article on the links between race and intelligence in American Psychologist stated that no gene has been shown to be linked to intelligence, "so attempts to provide a compelling genetic link of race to intelligence are not feasible at this time".[99]. Several candidate genes have been proposed to have a relationship with intelligence. [100][101] However, a review of candidate genes for intelligence published in 2009 by Deary et al. failed to find evidence of an association between these genes and general intelligence, stating "there is still almost no replicated evidence concerning the individual genes, which have variants that contribute to intelligence differences".[102] A few genetic disorders such as congenital myopia and torsion dystonia have been found to be associated with higher intelligence among members of the same population, as well as being more prevalent among racial groups with higher average IQs, and some researchers have proposed that the unequal distribution between groups of both IQ and these disorders is influenced by the same genes.[103][104]
The theory that genetic differences contribute to the difference in average IQ between races has been criticized for this lack of direct evidence, and the fact that it must therefore rely on indirect evidence instead.[105] Supporters of a partially genetic basis for the IQ gap have asserted that despite this, such a model is able to provide a more parsimonious explanation for the IQ gap than one which does not involve genetic factors, because it does not rely on the existence of undiscovered environmental X-factors that affect IQ variance between races but not within them. In The g Factor, Arthur Jensen also asserts that this theory is able to make specific predictions about future results, while explanations for the IQ gap that rely on unknown environmental factors are not empirically testable or falsifiable.[106]
Geographic ancestry
African Americans typically have ancestors from both Africa and Europe, with, on average, 20% of their genome inherited from European ancestors.[107] 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 found that mixed-race individuals tended to have IQs intermediate between those of unmixed blacks and whites, with a correlation of 0.17 between the estimated degree of difference in ancestry and the size of the difference in average IQ.[108][109][49] These studies have been criticized for their imprecise method of estimating ancestry, which was based primarily on skin tone, as well as for their small sample sizes.[citation needed] Charges of data manipulation have also appeared [60].
Rowe (2005) and others have suggested using DNA-based methods to reproduce these studies with reliable estimates of ancestry. Such experiments have never been published, although the requirements for such a study have been discussed in the academic literature.[110]
Stereotype threat
Stereotype threat is the fear that one's behavior will confirm an existing stereotype of a group with which one identifies; this fear may in turn lead to an impairment of performance.[111] Testing situations that highlight the fact that intelligence is being measured tend to lower the scores of individuals from racial-ethnic groups that already score lower on average. Stereotype threat conditions cause larger than expected IQ differences among groups but do not explain the gaps found in non-threatening test conditions.
A 2009 meta-analysis by Jelte Wicherts found evidence of significant publication bias in 55 studies of stereotype threat and its effect on IQ, in which those that found a strong effect were more likely to be published than those that did not. Reviewing both published and unpublished studies, Wicherts found that stereotype threat did not have an effect on all test-taking settings in which a difference in average scores is observed between races, and therefore was not an adequate explanation for the racial IQ gap.[112]
Brain size
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.[113] Within human populations, studies conducted to determine whether there is a relationship between brain size and a number of cognitive measures have "yielded inconsistent findings with correlations from 0 to 0.6, with most correlations 0.3 or 0.4."[114] A study on twins showed that frontal gray matter volume also was correlated with g and highly heritable.[115] 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.[116]
Several studies have reported that races overlap significantly in brain size but differ in average brain size. The magnitude of these differences varies depending on the particular study and the methods used. The majority of studies have been based on external head measurement, while only a few studies have involved the more accurate MRI techniques. In general, these studies have reported that East Asians have on average a larger brain size than Whites who have on average a larger brain size than Blacks.[117][118][119][120] Other researchers have also found variation in average brain size between human groups, but concluded that this variation should be viewed as being based on biogeographic ancestry and independently of “race”.[121][122]
Proponents of both the environmental and hereditarian perspective believe that this variation is relevant to the racial IQ gap, although they disagree as to its cause. Ulric Neisser, The Chair of the APA’s Task Force on intelligence, acknowledges the brain size difference, but points out that brain size is known to be influenced by environmental factors such as nutrition, and that this fact has been demonstrated experimentally in rats. He thus believes that data on brain size cannot be considered strong evidence for a genetic component to the IQ difference.[79] Rushton and Jensen disagree, citing several studies of malnourished East Asians showing that they have larger brains than Whites, and studies demonstrating the brain size difference at birth and prenatally just a few weeks after conception. According Rushton and Jensen, correcting for brain size between Blacks and Whites does not eliminate the IQ gap, which means that factors other than brain size contribute to intelligence differences; however, matching Blacks and Whites for IQ eliminates the difference in average brain size, suggesting that brain size is still a contributing factor.[123][124]. According to an analysis by Jelte Wicherts, if race differences in brain size are genetic in origin, they still leave 91-95% of racial IQ gap unaccounted for.[125]
Processing efficiency
Reaction time (RT) is the elapsed time between the presentation of a sensory stimulus and the subsequent behavioral response by the participant. 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, RT is considered to be an index of speed of processing. That is, RT 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.
Scores on many but not all RT tasks tend to correlate with scores on paper and pencil IQ tests. This is especially true for so-called elementary cognitive tasks (ECTs). These require participants to perform trivially simple cognitive tasks, like deciding which of two briefly-presented lines is longer (the inspection time task), or which of three lighted buttons is farthest away from the other two (the odd man out task).
Most people can perform ECTs with near 100% accuracy, but individual differences in RT on these tasks are large and correlate well with IQ scores. Jensen (2001) argues that ECTs could replace traditional IQ tests as measures of intelligence, because the former are measured on a ratio scale whereas IQ tests only rank people on an ordinal scale. Jensen has invented a Jensen box to present ECT task stimuli to participants in a precise, standardized fashion.
Not all RT tasks, however, are good measures of intelligence. In general, RT on tasks that take between 200 milliseconds and 2 seconds to perform tend to correlate well with IQ. Tasks that most people can do faster than 200 milliseconds generally measure the efficiency of sensory processes (seeing, hearing) rather than intelligence. Tasks that take longer than about two seconds typically allow for strategic differences among people that cloud any relationship between RT and IQ (for these tasks, accuracy—versus speed—is likely more related to IQ).
Reaction time best predicts IQ test scores when participants perform many trials (i.e., 100s) of the same ECT. Aggregating average reaction times across different ECTs also produces significantly larger RT/IQ correlations. In many studies, the within person variability of RT is also a strong predictor of IQ. Participants showing relatively large RT differences from trial to trial tend to score lower on IQ tests than do participants who do not deviate much in their reaction time from trial to trial. Finally, the slowest trials for any person tend to better predict that person's IQ relative to either his or her average or fastest response.
Although the literature on RT is vast, far less research has looked at race differences on RT as a potential explanation for the race/IQ gap. The general pattern, however, is that race differences exist on ECT performance, and that these differences are in line with those found on traditional IQ tests. For example, a recent study in the journal Intelligence looked at race differences on the Wonderlic Personnel Test (a traditional paper and pencil IQ test) and performance on two ECTs (an inspection time and choice reaction time task). A black/white difference was found on the Wonderlic, and both ECTs. Statistical mediation was found in that controlling for race differences on the ECTs resulted in the race difference on the Wonderlic no longer being significant.
Some studies have found that movement time, the measure of how long it takes a person to move a finger after taking the decision to do so, correlate just as well with IQ as processing time does (a weak correlation of about .20) and that Blacks generally have faster movement times than whites.[126]
Caste-like minorities
A large number of studies have shown that systemically disavantaged minorities, such as the African American minority of the United States generally perform worse in the educational system and in intelligence tests than the majority groups or less disadvantaged minorities such as immigrant or "voluntary" minorities.[6] The explanation of these findings may be that children of caste-like minorities, due to the systemic limitations of their prospects of social advancement, do not have "effort optimism", i.e. they do not have the confidence that aquiring the skills valued by majority society, such as those skills measured by IQ tests, is worthwhile.[127][128][129]
This argument is also explored in the book Inequality by Design: Cracking the Bell Curve Myth (1996) which argues that it is not lower average intelligence that leads to the lower status of racial and ethnic minorities, it is instead their lower status that leads to their lower average intelligence test scores. To substantiate this claim, the book presents a table comparing social status or caste position with test scores and measures of school success in several countries around the world.[130] The authors note, however, that the comparisons made in the table do not represent the results of all relevant findings, nor do they reflect the fact that the tests and procedures varied greatly from study to study. The comparison of Jews and Arabs, for example, is based on a news report that, in 1992, 26% of Jewish high school students passed their matriculation exam, majority of whom were Ashkenazi Jews, as opposed to 15% of Arab students.[130]
Rearing conditions
Several studies have been done on the effect of different rearing conditions on black children. 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.[131]
Biological parents | Number of children | Initial testing | 10-year follow-up |
---|---|---|---|
Minnesota Transracial Adoption Study initially tested at age 7[132] | |||
Black-black | 21 | 91.4 | 83.7 |
Black-white | 55 | 105.4 | 93.2 |
White-white | 16 | 111.5 | 101.5 |
Biological children | 101 | 110.5 | 105.5 |
Studies by Moore, Eyferth, and Tizard have examined intellegence of the children of black and white parents in uniform environments. Moore examined children adopted by white parents in America, Eyferth studied the children of black and white GIs raised by white German mothers in occupied Germany, and Tizard studied West Indian children raised in British long-stay residential nurseries. None of studies found evidence of higher intellegence in white children than in black children, though none followed up the children at later ages.
Moore compared black and mixed-race children adopted by either black or white families. Unlike in the Weinberg, et al study, there was no difference in IQ between black and mixed-race children, whether raised by black or white families. Moore also observed that 23 black and interracial children raised by white parents had a significantly higher mean score than 23 age-matched children raised by black parents (117.1 vs 103.6), and argued that differences in early socialization explained these differences. Moore concluded that there is superiority of the mixed-race children over the black children and that the entire difference between the iQs of black and white at the time of the study could be accounted for by environmental factors associated with race.
The Eyferth study was criticized by Rushton and Jensen for the relatively high proportion of North Africans and the rigorous selection process of the military, but Flynn argued that the black and white soldier IQ gap was similar the general population.[61] The data is summarised below:
Biological parents | Number of children | Initial testing | 10-year follow-up |
---|---|---|---|
Moore (1986)[133] initially tested at age 7–10 | |||
Black-black | 9 | 108.7 | not done |
Black-white | 14 | 107.2 | not done |
Eyferth (1961)[134] initially tested at age 5–13 | |||
Black-white | 171 | 96.5 | not done |
White-white | 70 | 97.2 | not done |
Tizard et al (1972)[135] initially tested at age 2-5 | |||
Black-black | 31 | 103.1 | not done |
Black-white | 43 | 104.8 | not done |
White-white | 75 | 100.0 | not done |
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 that result from biological differences, the result is mutual resentment, and unjustified punishment of the more successful group. They state:
[T]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.[3]
See also
- Ashkenazi intelligence
- Health and intelligence
- Environment and 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
- ^ Bouchard TJ, Lykken DT, McGue M, Segal NL, Tellegen A (1990). "Sources of human psychological differences: the Minnesota Study of Twins Reared Apart". Science. 250 (4978): 223–8. PMID 2218526.
{{cite journal}}
: Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link) - ^ Johnson, Wendy; Turkheimer, Eric; Gottesman, Irving I.; Bouchard Jr., Thomas (2009). "Beyond Heritability: Twin Studies in Behavioral Research". Current Directions in Psychological Science. 18 (4): 217–220. doi:doi: 10.1111/j.1467-8721.200.
{{cite journal}}
: Check|doi=
value (help)CS1 maint: multiple names: authors list (link) - ^ a b c d e f 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. Cite error: The named reference "30years" was defined multiple times with different content (see the help page).
- ^ a b Nisbett, Richard (2009). Intelligence and How to Get It: Why Schools and Cultures Count. W. W. Norton & Company. ISBN 0393065057.
- ^ Latent ability: Grades and test scores systematically underestimate the intellectual ability of negatively stereotyped students. Psychological Science, 20, 1132–1139.
- ^ a b c d e f g h 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." Cite error: The named reference "APA" was defined multiple times with different content (see the help page). - ^ William T. Dickens and James R. Flynn (2006). "Black Americans Reduce the Racial IQ Gap: Evidence from Standardization Samples". Psychological Science. 16 (10): 825–924.It is often asserted that blacks have made no IQ gains on whites, despite relative environmental gains, and that this adds credibility to the case that the black/white IQ gap has genetic origins. Until recently, there have been no adequate data to measure black IQ trends. We analyze data from nine standardization samples for four major tests of cognitive ability. These suggest that blacks have gained 5 or 6 IQ points on non-Hispanic whites between 1972 and 2002. Gains have been fairly uniform across the entire range of black cognitive ability.
- ^ Benjamin, Ludy T. (2006), Brief History of Modern Psychology, Wiley-Blackwell, pp. 188–191, ISBN 140513206X
- ^ a b 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."
- ^ a b Tucker, William H. (2002), The Funding of Scientific Racism: Wickliffe Draper and the Pioneer Fund, University of Illinois Press, ISBN 0252027620
- ^ Wooldridge, Adrian (1995), Measuring the Mind: Education and Psychology in England c.1860-c.1990, Cambridge University Press, ISBN 0521395151
- ^ Mackintosh, N.J. (1998), IQ and Human Intelligence, Oxford University Press, ISBN 019852367X
- ^ Maltby, John; Day; Macaskill, Ann (2007), Personality, Individual Differences and Intelligence, Pearson Education, ISBN 0131297600
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ignored (help) - ^ Hothersall, David (2003), History of Psychology (4th ed.), McGraw-Hill, pp. 440–441, ISBN 0072849657
- ^ See:
- Maltby, John; Day; Macaskill, Ann (2007), Personality, Individual Differences and Intelligence, Pearson Education, pp. 334–347, ISBN 0131297600
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ignored (help) - Fish, Jefferson M., ed. (2002), Race and Intelligence: Separating Myth from Reality, Laurence Erlbaum Associates, pp. 57–94, ISBN 0-8058-3757-4, Chapter 3, "The Misuse of Life History Theory: J. P. Rushton and the Pseudoscience of Racial Hierarchy" by Joseph L. Graves
- Sternberg, Robert J.; Kaufman, James C., eds. (2001), The evolution of intelligence, Routledge, pp. 14, 19, ISBN 080583267X, Chapter 2, "Evolutionary Psychology", by James B. Grossman and James Kaufman
- Maltby, John; Day; Macaskill, Ann (2007), Personality, Individual Differences and Intelligence, Pearson Education, pp. 334–347, ISBN 0131297600
- ^ a b c d e f g 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 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." Cite error: The named reference "Hunt and Carlson" was defined multiple times with different content (see the help page).
- ^ American Anthropological Association (1994), Statement on "Race" and Intelligence, retrieved March 31, 2010
- ^ Steven Rose (2009). "Darwin 200: Should scientists study race and IQ? NO: Science and society do not benefit". Nature. 457: 786–788. doi:10.1038/457786a.
- ^ Robert J. Sternberg, Elena L. Grigorenko, and Kenneth K. Kidd (2005). "Intelligence, Race, and Genetics" (PDF). American Psychologist. 60 (1): 46–59. doi:10.1037/0003-066X.60.1.46.
{{cite journal}}
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- ^ Nisbett (2009) p. 94
- ^ Matlby, Day & Macaskill (2007), p. 334-347
- ^ Fish (2002) p.1-28
- ^ Sternberg, Grigorenko & Kidd (2005) Intelligence, Race and Genetics
- ^ Benjamin (2003), p. 191
- ^ Rouvroy, Antoinette (2008), Human genes and neoliberal governance: a Foucauldian critique, p. 86, ISBN 0415444330
{{citation}}
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- ^ [1], Helsingin Sanomat
- ^ *Hunt-Grubbe, C. "The elementary DNA of dear Dr. Watson", Times Online, October 14, 2007. Retrieved October 24, 2007.
- Science always has and should be open to debate 2007-10-21
- James Watson's Disastrous Interview 2007-10-14
- Race remarks get Nobel winner in trouble, MSNBC and AP, October 18, 2007. Retrieved October 18, 2007.
- Syal, R. "Nobel scientist who sparked race row says sorry - I didn't mean it", Times Online, October 19, 2007. Retrieved October 24, 2007.
- "Museum drops race row scientist", BBC, October 18, 2007. Retrieved October 24, 2007.
- "Watson Returns to USA after race row", International Herald Tribune, October 19, 2007. Retrieved on November 10, 2007
- Watson, James (2007). "Blinded by Science. An exclusive excerpt from Watson's new memoir, Avoid Boring People: Lessons from a Life in Science". 02138 Magazine: 102. Retrieved 2007-11-28.
As we find the human genes whose malfunctioning gives rise to such devastating developmental failures, we may well discover that sequence differences within many of them also lead to much of the observable variation in human IQs. A priori, there is no firm reason to anticipate that the intellectual capacities of peoples geographically separated in their evolution should prove to have evolved identically. Our desire to reserve equal powers of reason as some universal heritage of humanity will not be enough to make it so.
{{cite journal}}
: Unknown parameter|month=
ignored (help) - "The complex James Watson": an article in the TLS by Jerry A. Coyne, December 12, 2007
- How to Avoid Boring People: Lessons from a Life in Science The Science Network interview with James Watson
- On Point "James Watson on how to climb the slippery double helix of life" - Tom Ashbrook talks to James Watson about his new memoir, "Avoid Boring People: Lessons from a Life in Science."
- van Marsh, A. "Nobel-winning biologist apologizes for remarks about blacks", CNN, October 19, 2007. Retrieved October 24, 2007.
- Watson, J.D. "James Watson: To question genetic intelligence is not racism", Independent, October 19, 2007. Retrieved October 24, 2007
- Cold Springs Harbor Laboratory. October 18, 2007. Statement by Cold Spring Harbor Laboratory Board of Trustees and President Bruce Stillman, Ph.D. Regarding Dr. Watson’s Comments in The Sunday Times on October 14, 2007. Press release. Retrieved October 24, 2007.
- Wigglesworth, K.DNA pioneer quits after race comments, L.A. Times, October 26th, 2007. Retrieved December 5th, 2007
- "Nobel prize-winning biologist resigns."", CNN, October 25, 2007. Retrieved on October 25, 2007.
- "DNA Pioneer Watson Resigns Amid Cloud of Scandal" by Malcolm Ritter AP 10/25/07 11:29 AM PhT
- Watson, J.Statement by James D. Watson "Retirement", "N Y Times", 25th October, 2007. Retrieved 5th December, 2007.
- ^ Steven Rose (2009). "Darwin 200: Should scientists study race and IQ? NO: Science and society do not benefit". Nature. 457: 786–788. doi:10.1038/457786a.
- ^ Ceci, S.J.; Williams, W.M. (2009), Darwin 200:Should scientists study race and IQ? Yes: the scientific truth must be pursued, vol. 457, p. 788
{{citation}}
: Text "journal" ignored (help) - ^ Flynn, James (2009), "Would you wish the research undone?" (PDF), Nature, 458: 146
- ^ American Anthropological Association (1994), Statement on "Race" and Intelligence, retrieved March 31, 2010
- ^ Gray, Jeremy R.; Thompson, Paul M. (2004), "Neurobiology of intelligence: science and ethics", Nature Reviews Neuroscience, 5: 471–482
{{citation}}
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(help) - ^ Fish (2002), pp. 95, 113
- ^ Robert J. Sternberg, Elena L. Grigorenko, and Kenneth K. Kidd (2005). "Intelligence, Race, and Genetics" (PDF). American Psychologist. 60 (1): 46–59. doi:10.1037/0003-066X.60.1.46.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ David J. Bartholomew (2004). Measuring Intelligence: Facts and Fallacies. Cambridge University Press. ISBN 0521544785.
- ^ Ian J. Deary (2001). Intelligence: A Very Short Introduction. Oxford University Press. ISBN 0192893211.
- ^ N. J. Mackintosh (1998). IQ and Human Intelligence. Oxford University Press. ISBN 019852367X.
- ^ Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1037/0003-066X.60.1.60, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with
|doi=10.1037/0003-066X.60.1.60
instead. - ^ a b James R. Flynn (2007). What Is Intelligence? Beyond the Flynn Effect. Cambridge University Press. ISBN 0521880076.
- ^ Jensen, A. R. (1985). The nature of the black white difference on various psychometric tests: Spearman's hypothesis. Behavioral and Brain Sciences, 8. 193-263.
- ^ a b 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. - ^ Jensen's study matched black and white children for IQ and compared the IQs of their siblings, and found that siblings of black children had on average lower IQ scores than siblings of white children, suggesting that the two populations were regressing towards the different population means shown by the IQ gap. For example, black children with an IQ of 120 would tend to have siblings with IQ's averaging 100, while white children with a 120 IQ would have siblings averaging close to 110. Jensen 1973, pg. 107–109
- ^ Jensen 1998, pg. 467–472 Further research by Jensen and other researchers using structural equation modeling concluded that a model in which genetic and environmental contributions to the IQ gap are in roughly equal proportions best fit the data. (Jensen 1998, pg. 464–467)
- ^ 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
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instead. - ^ 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. - ^ a b Lynn, R. and Vanhanen, T. (2002). IQ and the wealth of nations. Westport, CT: Praeger. ISBN 0-275-97510-X
- ^ a b c Lynn, R. (2006). Race Differences in Intelligence: An Evolutionary Analysis. Washington Summit Books.
{{cite book}}
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ignored (help) - ^ a b Herrnstein, Richard J. (1994). The Bell Curve: Intelligence and Class Structure in American Life. New York: Free Press. ISBN 0-02-914673-9.
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ignored (|author=
suggested) (help) Cite error: The named reference "The Bell Curve" was defined multiple times with different content (see the help page). - ^ Lynn, R. (1991). "Race Differences in Intelligence: A Global Perspective" (PDF). Mankind Quarterly. 31: 255–296.
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(help) - ^ 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. - ^ E. Hunt & W. Wittmann (2008). "National intelligence and national prosperity". Intelligence. 36 (1): 1–9.
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: Unknown parameter|month=
ignored (help) - ^ K. Richardson (2004). "Book Review: IQ and the Wealth of Nations". Heredity. 92 (4): 359–360. doi:10.1038/sj.hdy.6800418.
- ^ Irvine, S.H. (1983), "Where intelligence tests fail", Nature, 302: 371, doi:10.1038/302371b0
- ^ Human Abilities in Culture, Cambridge University Press, 1988, ISBN 0521344824
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ignored (help), a collection of articles by several authors discussing the limits of assessment by intelligence tests in different communities in the world. In particular, in "Testing Bushmen in the Central Kalahari", pages 453-486, Helmut Reuning describes the difficulties in devising and administering tests for Kalahari bushmen. - ^ Mackintosh, N.J. (1998), IQ and Human Intelligence, Oxford University Press, pp. 180–182, ISBN 019852367X
- ^ 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
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instead. - ^ In Mackintosh 2006, p. 94 , Mackintosh questioned Lynn's inference that Kalahari bushmen, with an allegedly average measured IQ of 54, have a mental age equivalent to an average European 8-year-old; and that an 8 year old European child would have no difficulty learning the skills required for surviving in the same desert environment. Mackintosh writes, "Can anyone seriously accept Lynn's conclusion that the majority of San Bushmen, whose average IQ is 54, are mentally retarded? Lynn sees no problem: an adult with an IQ of 54 has the mental age of an 8-year-old European, and 8-year-old European children would have no difficulty learning the skills needed to survive in the Kalahari desert"
- ^ a b Mackintosh, N.J. (2007), "Book review – Race differences in intelligence: An evolutionary hypothesis", Intelligence, 35: 94–96, doi:10.1016/j.intell.2006.08.001 a:"Much labour has gone into this book. But I fear it is the sort of book that gives IQ testing a bad name. As a source of references, it will be useful to some. As a source of information, it should be treated with some suspicion. On the other hand, Lynn's preconceptions are so plain, and so pungently expressed, that many readers will be suspicious from the outset." b:"A more egregious example is provided by his treatment of the Eyferth (1961) study of two groups of illegitimate children fathered by (mostly) American black and white servicemen and brought up by their (carefully matched) German mothers. Eyferth reported an average IQ of 96.5 for the mixed race children and of 97.2 for the whites. Lynn reduces the former number to 94 to compensate for use of an old test, and compares it, not with the score of the white sample, but with an average IQ of 100 for German children. He is thus able to conclude that the IQ of these mixed race children is half way between that of Americans and Africans. He derives the same conclusion from the Weinberg, Scarr, and Waldman (1992) transracial adoption study since, at the 10-year follow-up, the mixed race children had an average IQ of 94, mid-way between the 102 of the white children and the 89 of the black children. He omits to mention one of the more salient features of this follow-up, namely, that there had been substantial attrition in the white sample—with a loss of those children with lower IQ scores, resulting in an overestimate of the white group's IQ by some 6 points."
- ^ a b c 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.
- ^ 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.
- ^ 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.
- ^ R. J. Sternberg (2000) Handbook of Intelligence. Cambridge: Cambridge University Press
- ^ David J. Bartholomew (2004) Measuring Intelligence: Facts and Fallacies. Cambridge: Cambridge University Press
- ^ Ian J. Deary. (2001) Intelligence: A Very Short Introduction. Oxford: Oxford University Press
- ^ Gottfredson, L. S. (1997). Mainstream science on intelligence: An editorial with 52 signatories, history, and bibliography. Intelligence, 24(1), 13–23.
- ^ Robert Plomin, John C. DeFries, Gerald E. McClearn, and Peter McGuffin (2000) Behavioral Genetics. Worth Publishers; Fourth Edition edition
- ^ Brody, N. (1992). Intelligence (2nd ed.). San Diego, CA: Academic Press.
- ^ How Heritability Misleads about Race
- ^ Flynn 1980, pg. 59-60
- ^ Flynn (1980) and Flynn (1999)
- ^ Loehlin, J. C., Lindzey, G., & Spuhler, J. N. (1975). Race differences in intelligence. San Francisco, CA: W.H. Freeman.
- ^ William T. Dickens and James R. Flynn (2006). "Black Americans Reduce the Racial IQ Gap: Evidence from Standardization Samples". Psychological Science. 16 (10): 825–924.
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instead. - ^ "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.
- ^ 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.
- ^ Genetic Differences and School Readiness Dickens, William T. The Future of Children – Volume 15, Number 1, Spring 2005, pp. 55–69
- ^ a b Neisser, U. (1997). Never a dull moment. American Psychologist, 52, 79–81.
- ^ Lynn B. Jorde & Stephen P. Wooding (2004). Genetic variation, classification and “race”. Nature 36, 528-533
- ^ Reviewed in Neisser et al. (1996). Data from the NLSY as reported in figure adapted from Herrnstein and Murray (1994), p. 288.
- ^ Low-Level Lead Exposure, Intelligence and Academic Achievement: A Long-term Follow-up Study David C. Bellinger PhD, MSc1, Karen M. Stiles PhD, MN1, and Herbert L. Needleman MD1. Pediatrics Vol. 90 No. 6 December 1992, pp. 855–861
- ^ Caspi A, Williams B, Kim-Cohen J; et al. (2007). "Moderation of breastfeeding effects on the IQ by genetic variation in fatty acid metabolism". Proceedings of the National Academy of Sciences. 104 (47): 18860. doi:10.1073/pnas.0704292104. PMC 2141867. PMID 17984066.
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ignored (help) - ^ Nisbett 2009 p. 220
- ^ a b Cooper, Richard. (2005) Race and Genetics: Molecular Genetics as Deus ex Machina, American Psychologist, vol 60 no 1. pp. 71-76
- ^ Reading level attenuates differences in neuropsychological test performance between African American and White elders Jennifer J. Manly, Diane M. Jacobs, Pegah Touradji, Scott A. Small and Yaakov Stern
- ^ Acculturation, Reading Level, and Neuropsychological Test Performance Among African American Elders Jennifer J. Manly, Desiree A. Byrd, Pegah Touradji, Yaakov Stern
- ^ Cancellation test performance in African American, Hispanic, and white elderly Desiree A. Byrd, Pegah Touradji, Ming-Xin Tang and Jennifer J. Manly
- ^ When Are Racial Disparities in Education the Result of Racial Discrimination? A Social Science Perspective by Roslyn Arlin Mickelson University of North Carolina at Charlotte
- ^ Effect of Children's Ethnicity on Teachers' Referral and Recommendation Decisions in Gifted and Talented Programs Journal article by Negmeldin Alsheikh, Hala Elhoweris, Pauline Holloway, Kagendo Mutua; Remedial and Special Education, Vol. 26, 2005
- ^ Frances A. Campbell, Craig T. Ramey, Elizabeth Pungello, Joseph Sparling, and Shari Miller-Johnson. Early Childhood Education: Young Adult Outcomes From the Abecedarian Project. Applied Developmental Science 6 (2002): 42-57.
- ^ Frank Miele and Arthur Jensen. Intelligence, Race and Genetics: Conversations with Arthur R. Jensen. Westview Press, 2002, pg. 133.
- ^ Plomin, R; Kennedy, J; Craig, I (2005). "The quest for quantitative trait loci associated with intelligence". Intelligence. 34: 513. doi:10.1016/j.intell.2006.01.001.
- ^ Antonio Regalado. Scientist's Study Of Brain Genes Sparks a Backlash. The Wall Street Journal. June 16, 2006.
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instead. - ^ Janneke R Zinkstok, Odette de Wilde, Therese AMJ van Amelsvoort, Michael W Tanck, Frank Baas and Don H Linszen (2007). "Association between the DTNBP1 gene and intelligence: a case-control study in young patients with schizophrenia and related disorders and unaffected siblings". Behavioral and Brain Functions 3:19 doi:10.1186/1744-9081-3-19
- ^ Dick DM, Aliev F, Kramer J, Wang JC, Hinrichs A, Bertelsen S, Kuperman S, Schuckit M, Nurnberger J Jr, Edenberg HJ, Porjesz B, Begleiter H, Hesselbrock V, Goate A, Bierut L (2007). “Association of CHRM2 with IQ: converging evidence for a gene influencing intelligence.” Behavioral Genetics 37(2):265-72
- ^ Deary (2009). "Genetic foundations of human intelligence". doi:0.1007/s00439-009-0655-4.
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suggested) (help) - ^ G. Cochran, J. Hardy, H. Harpending, Natural History of Ashkenazi Intelligence, Journal of Biosocial Science 38 (5), pp. 659–693 (2006).
- ^ Mankind Quarterly, Vol. 49, No. 3-4 (Spring-Summer 2009)pp. 280-291
- ^ Genetic Differences and School Readiness Dickens, William T. The Future of Children - Volume 15, Number 1, Spring 2005, pp. 55-69
- ^ Jensen 1998, pg. 515-516
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instead. - ^ Lynn, R. (2002). Skin color and intelligence in African Americans. Population and Environment, 23, 365–375.
- ^ Rowe, D. C., & Rodgers, J. L. (2002). Expanding variance and the case of historical changes in IQ means: A critique of Dickens and Flynn (2001). Psychological Review, 109, 759 –763.
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instead. - ^ Aronson, Wilson, & Akert, 2005
- ^ Wicherts, Jelte M.; Cor de Haan (2009). "Stereotype threat and the cognitive test performance of African Americans". University of Amsterdam. [2]
- ^ 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.
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References