How does mainstream science view intelligence testing?


This public statement, written and signed by 52 internationally known scholars, was published in the Wall Street Journal on December 13th, 1994 to clear up the major misconceptions the public has about intelligence testing. An alphabetical listing of the scholars and their home institutions are given at the end of the statement.

Many commentators have offered opinions about human intelligence that misstate current scientific evidence. Some conclusions dismissed in the media as discredited are actually firmly supported.

This statement outlines conclusions regarded as mainstream among researchers on intelligence; in particular, on the nature, origins, and practical consequences of individual and group differences in intelligence. Its aim is to promote more reasoned discussion of the vexing phenomenon that the research has revealed in recent decades. The following conclusions are fully described in the major textbooks, professional journals and encyclopedias in intelligence.

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, i.e. “catching on,” “making sense of things,” and “figuring out what to do.”

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. They do not measure creativity, character, personality, or other important differences among individuals, nor are they intended to.

While there are different types of intelligence tests, they all measure the same intelligence. Some use words or numbers and require specific cultural knowledge (like vocabulary). Others do not, and instead use shapes or designs and require knowledge of only simple, universal concepts (many/few, open/closed, up/down).

The spread of people along the IQ continuum, from low to high, can be represented well by the bell curve (in statistical jargon, the “normal curve”). Most people cluster around the average (IQ 100). Few are either very bright or very dull: About 3% of Americans score above IQ 130 (often considered the threshold for giftedness), with about the same percentage below IQ 70 (IQ 70-75 often being considered the threshold for mental retardation).

IQ is strongly related, probably more so than any other single measurable human trait, to many important educational, occupational, economic, and social outcomes. Its relation to the welfare and performance of individuals is very strong in some arenas in life (education, military training), moderate but robust in others (social competence), and modest but consistent in others (law-abidingness). Whatever IQ tests measure, it is of great practical and social importance.

A high IQ is an advantage in life because virtually all activities require some reasoning and decision-making. Conversely, a low IQ is often a disadvantage, especially in disorganized environments. Of course, a high IQ no more guarantees success than a low IQ guarantees failure in life. There are many exceptions, but the odds for success in our society greatly favor individuals with higher IQs.

The practical advantages of having a higher IQ increase as life settings become more complex (novel, ambiguous, changing, unpredictable, or multi-faceted). For example, a high IQ is generally necessary to perform well in highly complex or fluid jobs (the professions, management); it is a considerable advantage in moderately complex jobs (crafts, clerical and police work); but it provides less advantage in settings that require only routine decision making or simple problem solving (unskilled work).

Differences in intelligence certainly are not the only factor affecting performance in education, training, and highly complex jobs (no one claims they are), but intelligence is often the most important. When individuals have already been selected for high (or low) intelligence and so do not differ as much in IQ, as in graduate school (or special education), other influences on performance loom larger in comparison.

Certain personality traits, special talents, aptitudes, physical capabilities, experience, and the like are important (sometimes essential) for successful performance in many jobs, but they have narrower (or unknown) applicability or “transferability” across tasks and settings compared with general intelligence. Some scholars choose to refer to these other human traits as other “intelligences.”

Individuals differ in intelligence due to differences in both their environments and genetic heritage. Heritability estimates range from 0.4 to 0.8 (on a scale from 0 to 1), most thereby indicating that genetics plays a bigger role than does environment in creating IQ differences among individuals. (Heritability is the squared correlation of phenotype with genotype.) If all environments were to become equal for everyone, heritability would rise to 100% because all remaining differences in IQ would necessarily be genetic in origin.

Members of the same family also tend to differ substantially in intelligence (by an average of about 12 IQ points) for both genetic and environmental reasons. They differ genetically because biological brothers and sisters share exactly half their genes with each parent and, on the average, only half with each other. They also differ in IQ because they experience different environments within the same family.

That IQ may be highly heritable does not mean that it is not affected by the environment. Individuals are not born with fixed, unchangeable levels of intelligence (no one claims they are). 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 to raise low IQs permanently. Whether recent attempts show promise is still a matter of considerable scientific debate.

Genetically caused differences are not necessarily irremediable (consider diabetes, poor vision, and phenal ketonuria), nor are environmentally caused ones necessarily remediable (consider injuries, poisons, severe neglect, and some diseases). Both may be preventable to some extent.

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.

The following professors—all experts in intelligence and allied fields—have signed this statement:

Richard D. Arvey, University of Minnesota
Thomas J. Bouchard, Jr., University of Minnesota
John B. Carroll, Un. of North Carolina at Chapel Hill
Raymond B. Cattell, University of Hawaii
David B. Cohen, University of Texas at Austin
Rene V. Dawis, University of Minnesota
Douglas K. Detterman, Case Western Reserve Un.
Marvin Dunnette, University of Minnesota
Hans Eysenck, University of London
Jack Feldman, Georgia Institute of Technology
Edwin A. Fleishman, George Mason University
Grover C. Gilmore, Case Western Reserve University
Robert A. Gordon, Johns Hopkins University
Linda S. Gottfredson, University of Delaware
Robert L. Greene, Case Western Reserve University
Richard J.Haier, University of Callifornia at Irvine
Garrett Hardin, University of California at Berkeley
Robert Hogan, University of Tulsa
Joseph M. Horn, University of Texas at Austin
Lloyd G. Humphreys, University of Illinois at Urbana-Champaign
John E. Hunter, Michigan State University
Seymour W. Itzkoff, Smith College
Douglas N. Jackson, Un. of Western Ontario
James J. Jenkins, University of South Florida
Arthur R. Jensen, University of California at Berkeley
Alan S. Kaufman, University of Alabama
Nadeen L. Kaufman, California School of Professional Psychology at San Diego
Timothy Z. Keith, Alfred University
Nadine Lambert, University of California at Berkeley
John C. Loehlin, University of Texas at Austin
David Lubinski, Iowa State University
David T. Lykken, University of Minnesota
Richard Lynn, University of Ulster at Coleraine
Paul E. Meehl, University of Minnesota
R. Travis Osborne, University of Georgia
Robert Perloff, University of Pittsburgh
Robert Plomin, Institute of Psychiatry, London
Cecil R. Reynolds, Texas A & M University
David C. Rowe, University of Arizona
J. Philippe Rushton, Un. of Western Ontario
Vincent Sarich, University of California at Berkeley
Sandra Scarr, University of Virginia
Frank L. Schmidt, University of Iowa
Lyle F. Schoenfeldt, Texas A & M University
James C. Sharf, George Washington University
Herman Spitz, former director E.R. Johnstone Training and Research Center, Bordentown, N.J.
Julian C. Stanley, Johns Hopkins University
Del Thiessen, University of Texas at Austin
Lee A. Thompson, Case Western Reserve University
Robert M. Thorndike, Western Washington Un.
Philip Anthony Vernon, Un. of Western Ontario
Lee Willerman, University of Texas at Austin

Oh yeah I scored 126 [only] on the TA3! Woohoo I’m a member!


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