The Bell Curve

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See normal distribution for the "bell curve" in statistics

The Bell Curve
Author:	Richard Herrnstein, Charles Murray
Publisher:	Free Press
Date:	September 1994
ISBN	ISBN 0029146739

The Bell Curve is a controversial best-selling book published in 1994 by Richard J. Herrnstein and Charles Murray exploring the role of intelligence in understanding social problems in America. The title is a reference to the bell-shaped graph of IQ scores (see normal distribution).

The book claims to chronicle the rise of a "cognitive elite", a social stratum of persons with high intelligence and an increasingly high chance of succeeding in life. Although the book primarily became famous for its discussion of race and intelligence, only Chapters 13 and 14 address the topic directly.

Within both the mainstream media and the scientific community, large numbers of people rallied to both support and criticize the book. Some critics denounced the book and its authors as supporting scientific racism.

1 Summary of contents
2 Responses
3 Miscellanea
4 Citations
5 External links
- 5.1 Arguments against The Bell Curve

Summary of contents

The Bell Curve is fairly large for a book of its popularity, weighing in at 845 pages in the first printing and 879 in the revised paperback form. Much of its material is technical and academic, but the book's statistical explanations are styled to appeal to a general audience. There are extensive notes, graphs, and tables.

The Bell Curve is divided into four sections.

Part I argues that social stratification on the basis of intelligence has been increasing since the beginning of the twentieth century.
Part II presents original research showing strong correlations between intelligence and various types of social performance.
Part III, by far the most controversial, examines what role IQ plays in contributing to social and economic differences between ethnic groups in America.
In Part IV, the authors discuss the implications of their findings for education and social policy in the United States.

Image:Charles Murray.gif

Charles Murray

Herrnstein and Murray in many ways follow in the footsteps of Harvard researcher Arthur Jensen. The authors report that estimates from psychometricians of the heritability of intelligence range from 40% to 80%. They report that there exist significant differences in measured intelligence between various ethnic groups. They argue that a better public understanding of the nature of intelligence and its social correlates is necessary to guide future policy decisions in America.

Herrnstein and Murray set out to prove that American society has become highly meritocratic: that wealth and other social outcomes are being distributed increasingly on the basis of individual talents (especially intelligence) and decreasingly on the basis of social class. Thus they argue, to the extent that intelligence is not amenable to easy environmental control, but rather is substantially heritable, genetic variance is increasingly contributing to social and economic differences among individuals.

Their evidence comes from an analysis of data compiled in the National Longitudinal Study of Youth (NLSY), a study conducted by the U.S. Department of Labor's Bureau of Labor Statistics tracking thousands of Americans starting in the 1980s. All participants in the NLSY took the Armed Forces Qualifying Test (AFQT), a measure of cognitive ability comparable to an IQ test. Participants were later evaluated for social and economic outcomes. In general, IQ/AFQT scores were a better predictor of life outcomes than social class background. Similarly, after statistically controlling for differences in IQ, many outcome differences between racial-ethnic groups disappeared. (see also Significance of group IQ differences)

Responses

Upon publication, The Bell Curve received a great deal of positive publicity, including cover stories in Newsweek ("the science behind [it] is overwhelmingly mainstream"), early publication (under protest by other writers and editors) by The New Republic by its editor-in-chief at the time Andrew Sullivan, and The New York Times Book Review (which suggested critics disliked its "appeal to sweet reason" and are "inclined to hang the defendants without a trial"). Early articles and editorials appeared in Time, The New York Times ("makes a strong case"), The New York Times Magazine, Forbes, the Wall Street Journal, and The National Review. It received a respectful airing on such shows as Nightline, the MacNeil/Lehrer NewsHour, the McLaughlin Group, Think Tank, PrimeTime Live, and All Things Considered. [1] The book sold over 300,000 copies in hardcover.

While the book's popularity was mostly propelled by its controversial claims regarding race and intelligence, both the accuracy of those claims and the qualifications of the authors soon came under attack. Dr. Herrnstein died before the book was released, leaving Charles Murray to do most of its public defense. Although Herrnstein was a prominent psychologist, Murray has a Ph.D. in political science with no formal credentials in psychometrics.

Some scientific response to The Bell Curve has been highly negative. Professor Craig T. Ramey said "Within the sophisticated research community, the opinion has been virtually unanimous that The Bell Curve was a primitive, oversimplistic and flawed analysis." Professor Michael Nunley wrote:

I believe this book is a fraud, that its authors must have known it was a fraud when they were writing it, and that Charles Murray must still know it's a fraud as he goes around defending it. [...] After careful reading, I cannot believe its authors were not acutely aware of [...] how they were distorting the material they did include.

Professor Leon Kamin, a critic of cognitive ability tests, said the book did "a disservice to and abuse of science." Professor Howard Gardner (who, like Kamin and some of the other critics, holds views which are criticized by Herrnstein and Murray) called the style of thought "scholarly brinkmanship":

Whether concerning an issue of science, policy, or rhetoric, the authors come dangerously close to embracing the most extreme positions, yet in the end shy away from doing so. Discussing scientific work on intelligence, they never quite say that intelligence is all important and tied to one's genes; yet they signal that this is their belief and that readers ought to embrace the same conclusions.

Economist and conservative writer Thomas Sowell, who is black, criticized some aspects of the book, claiming that the authors ignored data and failed to draw obvious conclusions from it that would have hurt their argument. But he nonetheless concluded that "The Bell Curve is a very sober, very thorough, and very honest book." [2]

In its defense, fifty-two professors, including researchers in the study of intelligence and related fields, signed a statement titled "Mainstream Science on Intelligence" supporting many of the scientific views reported in The Bell Curve. The statement was written by psychometrics researcher Linda Gottfredson and published in The Wall Street Journal in 1994 and later in the journal Intelligence. Many of the signers had previously made similar claims about race and intelligence and were cited as sources in the book.

Race and intelligence research is often considered a taboo subject. Charles Murray noted, for example, "Some of the things we read to do this work, we literally hide when we're on planes and trains". Critics have noted much of the work referenced by the Bell Curve was funded by the Pioneer Fund, which aims to advance the scientific study of heredity and human differences, and has been accused of promoting scientific racism. Critics argue the book was written to encourage politically-beneficial racism, citing Murray's book proposal which described the target audience as the "huge number of well-meaning whites who fear that they are closet racists, and this book tells them they are not. It's going to make them feel better about things they already think but do not know how to say." (New York Times Magazine, 10/9/94)

American Psychological Association task force report

In response to the growing controversy surrounding The Bell Curve, the American Psychological Association's Board of Scientific Affairs established a special task force to publish an investigative report on the research presented in the book. The full text of the report is available at a third-party website. [3]

Many of the task force's findings supported statements from The Bell Curve. They agreed that IQ scores have high predictive validity for individual (but not necessarily population) differences in school achievement. They also confirm the predictive validity of IQ for adult occupational status, even when variables such as education and family background have been statistically controlled. They agree that individual (again, not necessarily population) differences in intelligence are substantially influenced by genetics. Consistent with Herrnstein and Murray's findings, they state there is little evidence to show that childhood diet influences intelligence except in cases of severe malnutrition. They agree that there are no significant differences between the IQ scores of males and females. Perhaps most significantly, the APA task force agrees that there do exist large differences between the average IQ scores of blacks and whites, and that these differences cannot be attributed to biases in test construction, nor do they merely reflect differences in socio-economic status between the ethnic groups.

In determining the cause of these differences, the APA task force chose to emphasize environmental over genetic factors. While they admit there is no empirical evidence supporting it, they suggest that explanations based on social status and cultural differences may be possible. They stress that there is no definite evidence for the hypothesis that the black-white test score gap is a result of genetic differences between the groups, whereas Herrnstein and Murray argue that such a hypothesis is possible. Regarding genetic explanations for ethnic differences in intelligence, they conclude with the following statement: "There is not much direct evidence on this point, but what little there is fails to support the genetic hypothesis."

Stephen Jay Gould's criticisms

Perhaps the most prominent critic of The Bell Curve was the late Stephen Jay Gould, who in 1996 released a revised and expanded edition of his 1981 work The Mismeasure of Man intended to refute many of The Bell Curve's claims regarding race and intelligence. Specifically, Gould argues that the current evidence showing heritability of IQ does not indicate a genetic origin to group differences in intelligence. Murray claims that Gould misstated his claims; for instance, Gould says Murray boils down intelligence to a single factor while Murray denies making such a claim.

Arthur Jensen, Professor of Educational Psychology, University of California, Berkeley, responds to Gould's criticisms in a paper titled The Debunking of Scientific Fossils and Straw Persons.[4]

Other criticisms

A minority of critics have objected not only to Herrnstein and Murray's conclusions, but to their statistical methodology as well. The Sociology Department of the University of California, Berkeley published a critical analysis of The Bell Curve under the title Inequality by Design. The book reviews The Bell Curve's statistical analyses and claims that it contains technical errors and omissions. Another statistical critique of the book was published by James Heckman in 1995. Murray responded to a shorter version of Heckman's critique in an August 1995 letter exchange in Commentary magazine.

In Intelligence, Genes, and Success: Scientists Respond to The Bell Curve a group of social scientists and statisticians analyzes the genetics-intelligence link, the concept of intelligence, the malleability of intelligence and the effects of education, the relationship between cognitive ability, wages and meritocracy, pathways to racial and ethnic inequalities in health, and the question of public policy.

Another popular book written at least in part to refute some of The Bell Curve's claims is the Pulitzer Prize-winning Guns, Germs, and Steel: The Fates of Human Societies, by Jared Diamond. Diamond argues that the differences in technology produced by various races are the result of differences in factors like terrain or the availability of natural resources—not of differences in intelligence.

A recent paper in the Psychological Review, "Heritability Estimates Versus Large Environmental Effects: The IQ Paradox Resolved" presents a mechanism by which environmental effects on IQ may be magnified by feedback effects. This approach may provide a resolution of the contradiction between the viewpoint of The Bell Curve and its supporters, and the 'nurture' factors of IQ believed to exist by its critics.

Miscellanea

From 1986 to 1989, Murray was given an annual grant by the conservative Bradley Foundation of $90,000, rising to $113,000 by 1991, and then to $163,000 following publication of The Bell Curve.

According to an American Broadcasting Company news report, the Pioneer Fund contributed $3.5 million to researchers cited in The Bell Curve, and almost half of the research cited to support the most controversial racial conclusions of the book was paid for by the Pioneer Fund. [5]

Citations

Gottfredson, Linda S.; "Mainstream Science on Intelligence". Published in The Wall Street Journal, December 13, 1994, and also in Intelligence, January-February 1997.
Claude S. Fischer et al.; Inequality by Design: Cracking the Bell Curve Myth. Princeton University Press, 1996, ISBN 0691028982.
Bernie Devlin et al.; Intelligence, Genes, and Success: Scientists Respond to The Bell Curve. Copernicus Books, 1997, ISBN 0387949860.