Mainstream Science on Intelligence
Mainstream Science on Intelligence was a public statement issued by a group of academic researchers in fields associated with intelligence testing that claimed to present those findings widely accepted in the expert community. It was originally published in the Wall Street Journal on December 13, 1994 as a response to what the authors viewed as the inaccurate and misleading reports made by the media regarding academic consensus on the results of intelligence research in the wake of the appearance of The Bell Curve by Richard Herrnstein and Charles Murray earlier the same year. It was drafted by professor of psychology Linda Gottfredson, sent to 131 researchers, and signed by 52 university professors specializing in intelligence and related fields, including around one third of the editorial board of the journal Intelligence, in which it was subsequently reprinted in 1997. The 1997 editorial prefaced a special volume of Intelligence with contributions from a wide array of psychologists.
The letter to the Wall Street Journal set out 25 conclusions:
- "Intelligence is a very general mental capability ... it reflects a broader and deeper capability for comprehending our surroundings ..."
- "Intelligence, so defined, can be measured, and intelligence tests measure it well. They are among the most accurate (in technical terms, reliable and valid) of all psychological tests and assessments."
- "While there are different types of intelligence tests, they all measure the same intelligence."
- "The spread of people along the IQ continuum ... can be represented well by the ... ‘normal curve'."
- "Intelligence tests are not culturally biased"
- "The brain processes underlying intelligence are still little understood"
- "Members of all racial-ethnic groups can be found at every IQ level"
- "The bell curve for whites is centered roughly around IQ 100; the bell curve for American blacks roughly around 85; and those for different subgroups of Hispanics roughly midway between those for whites and blacks. The evidence is less definitive for exactly where above IQ 100 the bell curves for Jews and Asians are centered"
- "IQ is strongly related, probably more so than any other single measurable human trait, to many important educational, occupational, economic, and social outcomes ... Whatever IQ tests measure, it is of great practical and social importance"
- "A high IQ is an advantage because virtually all activities require some reasoning and decision-making"
- "The practical advantages of having a higher IQ increase as life’s settings become more complex"
- "Differences in intelligence certainly are not the only factor affecting performance in education, training, and complex jobs ... but intelligence is often the most important"
- "Certain personality traits, special talents, [etc] are important ... in many jobs, but they have narrower (or unknown) applicability or ‘transferability’ across tasks and settings compared with general intelligence"
- "Heritability estimates range from 0.4 to 0.8 ... indicating genetics plays a bigger role than environment in creating IQ differences"
- "Members of the same family also tend to differ substantially in intelligence"
- "That IQ may be highly heritable does not mean that it is not affected by the environment ... IQs do gradually stabilize during childhood, however, and generally change little thereafter"
- "Although the environment is important in creating IQ differences, we do not know yet how to manipulate it"
- "Genetically caused differences are not necessarily irremediable"
- "There is no persuasive evidence that the IQ bell curves for different racial-ethnic groups are converging"
- "Racial-ethnic differences in IQ bell curves are essentially the same when youngsters leave high school as when they enter first grade ... black 17-year-olds perform, on the average, more like white 13-year-olds"
- "The reasons that blacks differ among themselves in intelligence appear to be the same as those for why whites ... differ among themselves"
- "There is no definitive answer as to why bell curves differ across racial-ethnic groups. The reasons for these IQ differences between groups may be markedly different from the reasons for why individuals differ among themselves within any particular group"
- "Racial-ethnic differences are somewhat smaller but still substantial for individuals from the same socio-economic backgrounds"
- "Almost all Americans who identify themselves as black have white ancestors – the white admixture is about 20% ... research on intelligence relies on self-classification into distinct racial categories"
- "The research findings neither dictate nor preclude any particular social policy, because they can never determine our goals. They can, however, help us estimate the likely success and side-effects of pursuing those goals via different means."
History of the statement
In an article describing the background of the statement, Linda Gottfredson explains how she was prompted to write it by what she considered to be "outdated, pseudoscientific notions of intelligence" promoted by many critics of The Bell Curve in the controversy that followed the publication of the book. She contacted David Brooks at the Wall Street Journal, who was willing to publish a short statement signed by experts describing what is considered mainstream in the study of intelligence. Gottfredson drafted the statement, had it vetted by several leading researchers, and finally solicited signatures for it from experts in several disciplines, including anthropology, behavior genetics, mental retardation, neuropsychology, sociology, and various specialties in psychology. The experts invited to sign the statement were given no opportunity to revise it, nor was anyone told who else had been invited or who had already given his or her signature.
The invitation to sign was sent to 131 researchers, of whom 100 responded by the deadline. The signature form asked whether the respondent would sign the statement, and if not, why. 52 respondents agreed to sign, while 48 did not. 38 supplied an explanation for their refusal, with 11 explicitly disagreeing that it represented the mainstream (or at least disagreeing with some of the claims in it), another 11 saying they did not know whether it did, and the rest citing various other reasons, including the fear of jeopardizing their position or project.
Response and criticism
Intelligence is a very general mental capability that, among other things, involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly, and learn from experience. It is not merely book-learning, a narrow academic skill, or test-taking smarts. Rather, it reflects a broader and deeper capability for comprehending our surroundings "catching on," "making sense" of things, or "figuring out" what to do.
Gottfredson (1997b) describes intelligence in her own article in the same volume less broadly as "the ability to deal with complexity." However, the article by Carroll (1997b), one of the signatories of the statement, reviewed the numerous attempts in the academic literature to define what was meant by intelligence and found that there was no agreement. He cites experts as describing intelligence as "the total intellectual repertoire of behavioral responses," "some general property or quality ... of the brain," "reaction-time and physiological measures," "many different information-processing abilities" and "the rate with which learning occurs or the time required for learning." Plomin & Petrill (1997c) in the same volume describe intelligence as what is measured by intelligence tests: "What we mean by intelligence is general cognitive functioning (g) as assessed in the psychometric tradition of a general factor derived from a battery of diverse cognitive ability tests."
conclusions regarded as mainstream among researchers on intelligence, in particular, on the nature, origins, and practical consequences of individual and group differences in intelligence.
Schlinger claims that, "With a few exceptions, the list of cosigners reads like a Who's Who of those theorists (e.g., Thomas J. Bouchard, Jr., John B. Carroll, Raymond B. Cattell, Hans Eysenck, Linda S. Gottfredson, Seymour W. Itzkoff, Arthur R. Jensen, Robert Plomin, J. Philippe Rushton and Vincent Sarich) who have continued Spearman's tradition of factor analyzing intelligence test scores to generate a theory of general intelligence — g — and some of whom (e.g., Thomas J. Bouchard, Robert Plomin) believe that behavior genetic research supports the conclusion that g is highly heritable, and others of whom (e.g., Arthur Jensen, J. Philippe Rushton, Seymour Itzkoff) have written highly emotionally charged articles arguing that the research supports the conclusion that group differences on intelligence tests reflect genetic differences."
Intelligence tests are not culturally biased against American blacks, or other native-born, English-speaking peoples in the U.S. Rather IQ scores predict equally accurately for all such Americans, regardless of race or class
is not accepted by some prominent researchers in psychometrics who have pointed out the problems with using tests on population groups with a substantively different cultural background from those for whom the test was originally designed.
Harrington (1997) gives a point-by-point analysis of the conclusions of the letter. He points out that the validity of tests is claimed as a property of the tests, rather than how or where they are used. He queried the claims about there being no cultural bias; and that intelligence was a key factor determining fitness in human evolution, something that he argued was inconsistent with the claims on heritability, if the geneticist's version of evolution was being used. For him heritability was phylogenetic, not ontogenetic as their letter suggested. He pointed out that the use of the term race differed from the way geneticists classify population groups. Regarding the assertion that IQ research does not preclude or dictate any particular social policy, Harrington comments that the views of Charles Murray on social policy have been referenced by US Congressmen.
In a posthumous article in 1996, Donald T. Campbell, a former president of the American Psychological Association, included his own analysis of the Wall Street Journal statement, previously drafted as a letter to that newspaper. Campbell first remarked that:
Of the 52 signatories, there were 10 whom I would regard as measurement experts. I do not have a list of those who were asked to sign and refused, but I know they included Lee Cronbach, Robert Sternberg, and myself.
He remarked that the rhetorical organization of points in the statement, inadvertently or deliberately, seemed to him to build up to the conclusion that the black-white racial gap had a genetic cause. He pointed out that already at point 5, no provision had been allowed for differences in educational opportunity. Later on in point 14, he judged that the statements on heritability had been made without mentioning that it was based on twin studies, where environmental opportunities had been excluded as possible factors. In point 23, he pointed out that it was not possible to compare children of black and white parents that were "equally" educated, because in these circumstances the opportunities in the quality of education, both before and at college, would differ. On point 25, Campbell remarked that Jensen had himself published policy recommendations concerning rote learning.
Alderfer (2003) analysed the editorial as one of five responses to The Bell Curve, a book which he viewed as "an attempt to influence both psychological knowledge and U.S. politics". He concluded that some of the responses, including the editorial, "fell far short of providing a critical analysis of the book's racially biased argument and did little to reduce the misleading picture of race and IQ that the book promulgated." More specifically, Alderfer criticized the failure of the psychologists to recognize the effect of such a book on race relations in the US; as well as their failure to discuss the third and last part of the book on the implications for social policy. He wrote that, "Some psychologists said they wanted to keep themselves out of the emotional turmoil that had been generated by publication of the Bell Curve ... They might also have wanted to preserve the neutrality of psychology as a science. When examined in the contemporary racial context, however, their action was neither scientifically nor politically neutral. Essentially, they took a stand by not taking a stand. Their stand was not to become involved in how their expertise might be used to affect people's lives ...they missed an opportunity to caution their readers about regressive forces affecting U.S. race relations and to locate the book within that context. They did not fully use the authority based on their expertise to prevent harm."
- History of the race and intelligence controversy
- Intelligence: Knowns and Unknowns
- Race and intelligence
- Snyderman and Rothman (study)
- Alderfer, C.P. (2003), "The science and nonscience of psychologists' responses to The Bell Curve", Professional psychology, research and practice 34: 287–293, doi:10.1037/0735-7028.34.3.287
- Armour-Thomas, Eleanor (2003), Assessment of psychometric intelligence for racial and ethnic minorities, Handbook of racial and ethnic minority psychology (ed. Guillermo Bernal), SAGE, pp. 357–374, ISBN 0-7619-1965-1
- Campbell, Donald T. (1996), "Unresolved Issues in Measurement Validity : An Autobiographical Overview", Psychological Assessment 8: 363–368, doi:10.1037/1040-3522.214.171.1243
- Carroll, J. B. (1997a), "Psychometrics, intelligence, and public perception", Intelligence 24: 25–52, doi:10.1016/S0160-2896(97)90012-X
- Gottfredson, Linda S. (1997), "Mainstream Science on Intelligence (editorial)" (PDF), Intelligence 24: 13–23, doi:10.1016/S0160-2896(97)90011-8
- Gottfredson, Linda S. (1997b), "Why g matters: The complexity of everyday life", Intelligence 24: 79–132, doi:10.1016/S0160-2896(97)90014-3
- Harrington, Gordon M. (1997), "Psychological testing, IQ, and evolutionary fitness", Genetica 99: 113–123, doi:10.1007/bf02259515
- Hauser, Robert M. (2010), "Causes and Consequences of Cognitive Functioning Across the Life Course" (PDF), Educational Researcher 9: 95–109, doi:10.3102/0013189x10363171 (2009 AERA distinguished lecture)
- Laosa, Luis M. (1996), "Intelligence testing and social policy", Journal of Applied Developmental Psychology 17: 155–173, doi:10.1016/S0193-3973(96)90023-4
- Plomin, R.; Petrill, S. A. (1997c), "Genetics and intelligence: What’s new?", Intelligence 24: 53–77, doi:10.1016/s0160-2896(97)90013-1
- Schlinger, Henry D. (2003), "The myth of intelligence" (PDF), The psychological record 53: 15–32