The Bell Curve

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The Bell Curve
Cover of the first edition
Author Richard J. Herrnstein, Charles Murray
Subject Intelligence
Published 1994 (Free Press)
Media type Print (hardcover)
Pages 845
ISBN 0-02-914673-9
OCLC 30913157
305.9/082 20
LC Class BF431 .H398 1994

The Bell Curve: Intelligence and Class Structure in American Life is a 1994 book by American psychologist Richard J. Herrnstein (who died before the book was released) and American political scientist Charles Murray. Herrnstein and Murray's central argument is that human intelligence is substantially influenced by both inherited and environmental factors and is a better predictor of many personal dynamics, including financial income, job performance, birth out of wedlock, and involvement in crime than are an individual's parental socioeconomic status, or education level. They also argue that those with high intelligence, the "cognitive elite", are becoming separated from those of average and below-average intelligence.

The book was controversial, especially where the authors wrote about racial differences in intelligence and discussed the implications of those differences. The authors were reported throughout the popular press as arguing that these IQ differences are genetic. In fact, they wrote in chapter 13: "It seems highly likely to us that both genes and the environment have something to do with racial differences." The introduction to the chapter more cautiously states, "The debate about whether and how much genes and environment have to do with ethnic differences remains unresolved."

The book's title comes from the bell-shaped normal distribution of intelligence quotient (IQ) scores in a population.

Shortly after publication, many people rallied both in criticism and defense of the book. A number of critical texts were written in response to the work.


The Bell Curve, published in 1994, was written by Richard Herrnstein and Charles Murray to explain the variations in intelligence in American society, warn of some consequences of that variation, and propose social policies for mitigating the worst of the consequences. Many of the arguments put forth by the authors are controversial, ranging from the relationships between low measured intelligence and anti-social behavior, to a genetic component of the low observed test scores for African-American (compared to whites and East Asians). The book was heavily publicized as it was released, just after the death of Herrnstein. In the first several months of its release, 400,000 copies of the book were sold around the world. Hundreds of reviews and commentaries were written about the book soon after its publication. The Bell Curve argues that:

  1. Intelligence exists and is accurately measurable across racial, language, and national boundaries.
  2. Intelligence is one of, if not the most, important factors correlated to economic, social, and overall success in the United States, and its importance is increasing.
  3. Intelligence is largely (40% to 80%) heritable.
  4. No one has so far been able to manipulate IQ to a significant degree through changes in environmental factors—except for child adoption—and in the light of these failures, future successful manipulations are unlikely.
  5. The United States has been in denial of these facts. A better public understanding of the nature of intelligence and its social correlates is necessary to guide future policy decisions.

The book's argument is based on the authors' analysis of data compiled in the National Longitudinal Study of Youth (NLSY), a study conducted by the United States Department of Labor's Bureau of Labor Statistics tracking thousands of Americans starting in the 1980s. All participants in the NLSY took the Armed Services Vocational Aptitude Battery (ASVAB), a battery of ten tests taken by all who apply for entry into the armed services. (Some had taken an IQ test in high school, and the median correlation of the Armed Forces Qualification Test (AFQT) scores and those IQ test scores was .81). 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.

Economic and social correlates of IQ
IQ <75 75-90 90-110 110-125 >125
US population distribution 5 20 50 20 5
Married by age 30 72 81 81 72 67
Out of labor force more than 1 month out of year (men) 22 19 15 14 10
Unemployed more than 1 month out of year (men) 12 10 7 7 2
Divorced in 5 years 21 22 23 15 9
 % of children w/ IQ in bottom decile (mothers) 39 17 6 7 -
Had an illegitimate baby (mothers) 32 17 8 4 2
Lives in poverty 30 16 6 3 2
Ever incarcerated (men) 7 7 3 1 0
Chronic welfare recipient (mothers) 31 17 8 2 0
High school dropout 55 35 6 0.4 0
Scored "Yes" on "Middle Class Values Index"[c 1] 16 30 50 67 74
Values are the percentage of each IQ sub-population, among non-Hispanic whites only, fitting each descriptor. Herrnstein & Murray (1994) pp. 171, 158, 163, 174, 230, 180, 132, 194, 247-248, 194, 146, 264 respectively.

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Policy recommendations

The book argued the average genetic IQ of the United States is declining owing, to the tendency of the more intelligent to have fewer children than the less intelligent, the generation length to be shorter for the less intelligent, and the large-scale immigration to the United States of those with low intelligence. Discussing a possible future political outcome of an intellectually stratified society, the authors stated that they "fear that a new kind of conservatism is becoming the dominant ideology of the affluent – not in the social tradition of an Edmund Burke or in the economic tradition of an Adam Smith but 'conservatism' along Latin American lines, where to be conservative has often meant doing whatever is necessary to preserve the mansions on the hills from the menace of the slums below."[1] Moreover, they fear that increasing welfare will create a "custodial state" in "a high-tech and more lavish version of the Indian reservation for some substantial minority of the nation's population." They also predict increasing totalitarianism: "It is difficult to imagine the United States preserving its heritage of individualism, equal rights before the law, free people running their own lives, once it is accepted that a significant part of the population must be made permanent wards of the states."[2]

Herrnstein and Murray recommended the elimination of welfare policies that encourage poor women to have babies:

We can imagine no recommendation for using the government to manipulate fertility that does not have dangers. But this highlights the problem: The United States already has policies that inadvertently social-engineer who has babies, and it is encouraging the wrong women. "If the United States did as much to encourage high-IQ women to have babies as it now does to encourage low-IQ women, it would rightly be described as engaging in aggressive manipulation of fertility." The technically precise description of America's fertility policy is that it subsidizes births among poor women, who are also disproportionately at the low end of the intelligence distribution. We urge generally that these policies, represented by the extensive network of cash and services for low-income women who have babies, be ended. The government should stop subsidizing births to anyone rich or poor. The other generic recommendation, as close to harmless as any government program we can imagine, is to make it easy for women to make good on their prior decision not to get pregnant by making available birth control mechanisms that are increasingly flexible, foolproof, inexpensive, and safe.[3]

The book also argued for reducing immigration into the U.S. which was argued to lower the average national IQ. It also recommended against policies of affirmative action.


Media response

A 1995 article by Fairness and Accuracy in Reporting writer Jim Naureckas analyzed the media response. The Bell Curve received a great deal of media attention. He wrote "While many of these discussions included sharp criticisms of the book, media accounts showed a disturbing tendency to accept Murray and Herrnstein's premises and evidence even while debating their conclusions" and "their critics were sometimes identified with censorious political correctness". Naureckas criticized these assumptions, arguing that the book was part of a campaign to justify racism and against welfare and immigration.[4]

Peer review

An early criticism was that Herrnstein and Murray did not submit their work to peer review before publication.[5] Many scholarly reviews of the book arrived later as discussed below. Richard Lynn (1999) wrote that "The book has been the subject of several hundred critical reviews, a number of which have been collected in edited volumes".[6]

"Mainstream Science on Intelligence"

Fifty-two professors, most of them researchers in intelligence and related fields, signed an opinion statement titled "Mainstream Science on Intelligence"[7] endorsing a number of the views presented in The Bell Curve. The statement was written by psychologist Linda Gottfredson and published in The Wall Street Journal in 1994 and subsequently reprinted in Intelligence, an academic journal. Of the 131 who were invited by mail to sign the document, 100 responded, with 52 agreeing to sign and 48 declining. Eleven of the 48 dissenters claimed that the statement or some part thereof did not represent the mainstream view of intelligence.[7]

APA 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.[8] In their final report, titled Intelligence: Knowns and Unknowns,[9] some of the task force's findings supported or were consistent with statements from The Bell Curve. They agreed that:

  • IQ scores have high predictive validity for individual differences in school achievement.
  • IQ scores have predictive validity for adult occupational status, even when variables such as education and family background have been statistically controlled.
  • There is little evidence to show that childhood diet influences intelligence except in cases of severe malnutrition.

Regarding Murray and Herrnstein's claims about racial differences and genetics, the APA task force stated:

There is certainly no such support for a genetic interpretation...It is sometimes suggested that the Black/White differential in psychometric intelligence is partly due to genetic differences (Jensen, 1972). There is not much direct evidence on this point, but what little there is fails to support the genetic hypothesis.

Regarding statements about other explanations for racial differences, the APA task force stated [emphasis added]:

The differential between the mean intelligence test scores of Blacks and Whites (about one standard deviation, although it may be diminishing) does not result from any obvious biases in test construction and administration, nor does it simply reflect differences in socio-economic status. Explanations based on factors of caste and culture may be appropriate, but so far have little direct empirical support. There is certainly no such support for a genetic interpretation. At present, no one knows what causes this differential.

The APA journal that published the statement, American Psychologist, subsequently published eleven critical responses in January 1997.

Critical response

The Nobel-Memorial-Prize-winning economist James Heckman considers two assumptions made in the book to be questionable: that g accounts for correlation across test scores and performance in society, and that g cannot be manipulated. Heckman's reanalysis of the evidence used in The Bell Curve found contradictions:

  1. The factors that explain wages receive different weights than the factors that explain test scores. More than g is required to explain either.
  2. Other factors besides g contribute to social performance, and they can be manipulated.[10]

In response, Murray argued that this was a straw man and that the book does not argue that g or IQ are totally immutable or the only factors affecting outcomes.[11]

In a 2005 interview, Heckman praised The Bell Curve for breaking "a taboo by showing that differences in ability existed and predicted a variety of socioeconomic outcomes" and for playing "a very important role in raising the issue of differences in ability and their importance" and stated that he was "a bigger fan of [The Bell Curve] than you might think." However, he also maintained that Herrnstein and Murray overestimated the role of heredity in determining intelligence differences.[12]

Michael Hout of the University of California, Berkeley, along with five colleagues, recalculated the effect of socioeconomic status, using the same variables as The Bell Curve, but weighting them differently. They found that if IQ scores are corrected, as Herrnstein and Murray did, to eliminate the effect of education, the ability of IQ to predict poverty can be made to look dramatically overstated, by as much as 61 percent for whites and 74 percent for blacks. According to Hout et al., Herrnstein and Murray's finding, that IQ predicts poverty much better than socioeconomic status does, is substantially a result of the way they handled the statistics.[13]

In August 1995, at the National Bureau of Economic Research economist Sanders Korenman and Harvard University sociologist Christopher Winship found certain errors in Herrnstein's methodology. Korenman and Winship concluded:"... there is evidence of substantial bias due to measurement error in their estimates of the effects of parents' socioeconomic status. In addition, Herrnstein and Murray's measure of parental socioeconomic status (SES) fails to capture the effects of important elements of family background (such as single-parent family structure at age 14). As a result, their analysis gives an exaggerated impression of the importance of IQ relative to parents' SES, and relative to family background more generally. Estimates based on a variety of methods, including analyses of siblings, suggest that parental family background is at least as important, and may be more important than IQ in determining socioeconomic success in adulthood."[14]

Author's follow-up

After two decades since publication, Charles Murrary asserted that the book's claims on IQ and its main arguments have been vindicated and not overturned by events and subsequent research in social science, neuroscience, and genetics. He noted critics still focus on the book's subtopic of race and intelligence, going so far as to say that it can be used to justify fascism, racism, or eugenics. He charged that those that engage in such criticisms are engaged in "Intellectual McCarthyism".[15]


Further reading

External links

Responses to The Bell Curve


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  1. page 518.
  2. page 526.
  3. pp. 548–49.
  4. Racism Resurgent:How Media Let The Bell Curve's Pseudo-Science Define the Agenda on Race by Jim Naureckas January/February 1995
  5. Arthur S. Goldberger and Charles F. Manski (1995) "Review Article: The Bell Curve by Herrnstein and Murray", Journal of Economic Literature, 36(2), June 1995, pp. 762–76. "HM and their publishers have done a disservice by circumventing peer review. ...a process of scientific review is now under way. But, given the process to date, peer review of The Bell Curve is now an exercise in damage control...."
  6. Richard Lynn (1999) The Attack on The Bell Curve Personality and Individual Differences 26, pp. 761–65
  7. 7.0 7.1 Gottfredson, Linda S. (1997). "Mainstream Science on Intelligence (editorial)" (PDF). Intelligence. 24: 13–23. ISSN 0160-2896. doi:10.1016/s0160-2896(97)90011-8. 
  8. See: The APA 1996 Intelligence Task Force Report.
  9. Neisser, Ulric; Boodoo, Gwyneth; Bouchard, Thomas J., Jr.; Boykin, A. Wade; Brody, Nathan; Ceci, Stephen J.; Halpern, Diane F.; Loehlin, John C.; Perloff, Robert; Sternberg, Robert J.; Urbina, Susana (1996). "Intelligence: Knowns and Unknowns" (PDF). American Psychologist. 51 (2): 77–101. doi:10.1037/0003-066X.51.2.77. 
  10. Heckman, James J. (1995). "Lessons from the Bell Curve". Journal of Political Economy. 103 (5): 1091–1120. doi:10.1086/262014. .
  11. August 1995 letter exchange in Commentary magazine
  12. Interview with James Heckman. Douglas Clement. June 2005. The Region.
  13. Inequality by Design:Cracking the Bell Curve Myth Claude S. Fischer, Michael Hout, Martín Sánchez Jankowski, Samuel R. Lucas, Ann Swidler, and Kim Vos
  14. Korenman, Sanders and Winship, Christopher, "A Reanalysis of The Bell Curve" (August 1995). NBER Working Paper Series, Vol. w5230, 1995.
  15. An Open Letter to the Virginia Tech Community. Charles Murray. March 2016. AEIdeas