The Bell Curve

The Bell Curve

Company type	Book
Industry	Publishing
Founded	1994
Founder	Richard J. Herrnstein, Charles Murray

The Bell Curve: Intelligence and Class Structure in American Life is a 1994 publication authored by psychologist Richard J. Herrnstein and political scientist Charles Murray. The book posits that both genetic inheritance and environmental influences shape human intelligence, which in turn serves as a more reliable indicator than parental socioeconomic status for predicting outcomes such as earnings, occupational success, nonmarital childbirth, and criminal behavior. The authors argue that an emerging "cognitive elite" with superior intelligence is becoming increasingly segregated from those with average or lower cognitive abilities, thereby deepening social stratification within the United States.

This work remains a source of intense controversy, especially due to its exploration of purported connections between race and intelligence and the policy recommendations derived from these claims. The authors assert that genetic factors partially explain average differences in intelligence quotient (IQ) scores among racial and ethnic groups—a position that has since been widely discredited by the scientific community. A notable portion of the book’s references originate from proponents of racial hygiene, supported by the white supremacist group Pioneer Fund and published in its associated periodical Mankind Quarterly. These affiliations have led many critics to classify the book’s conclusions as pseudoscience.

Upon publication, the book ignited extensive discourse and prompted numerous critical analyses, many of which were collected in The Bell Curve Debate.

Synopsis

Released in 1994, The Bell Curve by Richard Herrnstein and Charles Murray examines the distribution of intelligence across American society, explores its implications, and suggests social policies responsive to these findings. The title alludes to the bell-shaped curve representing the normal distribution of IQ scores within large populations.

Introduction

The authors provide an overview of intelligence research history, tracing developments from Francis Galton through contemporary studies, with emphasis on Spearman’s concept of a general intelligence factor (g factor) and early associations between IQ testing and racial politics. They identify the 1960s as a pivotal era when societal issues began to be attributed more to external circumstances rather than inherent individual differences—an egalitarian perspective they argue fails to account for biologically based cognitive diversity.

They present six fundamental premises they regard as largely uncontested within technical circles:

1. A general cognitive ability factor exists that varies among individuals.
2. Standardized educational assessments measure this factor to some extent; IQ tests do so with greater precision.
3. IQ scores align closely with common understandings of intelligence.
4. IQ results remain relatively consistent throughout much of an individual’s lifespan.
5. Properly conducted IQ testing does not exhibit systematic bias against social, economic, ethnic, or racial groups.
6. Cognitive ability has a significant heritable component, estimated between 40% and 80%.

The authors warn against drawing conclusions about individuals based solely on group data (ecological fallacy) and stress that intelligence represents only one valuable human trait, which is frequently given disproportionate emphasis.

Part I. The Rise of a Cognitive Elite

Herrnstein and Murray describe a transformation in 20th-century America, where social standing shifted from being primarily influenced by family background to being largely determined by intellectual capability. Factors contributing to this change include expanded college enrollment, more effective identification of cognitive talent, and the stratification of educational institutions. They suggest that technological progress generated sufficient demand for highly skilled workers, resulting in the formation of a cognitive elite whose success increasingly depends on intelligence rather than race, gender, or socioeconomic class—an outcome facilitated by accessible education and anti-discrimination policies. Cognitive ability is identified as the most reliable predictor of employee productivity.

The authors assert that the growing premium placed on intelligence has produced a wealthier, more socially separated cognitive elite within the United States.

Part II. Cognitive Stratification and Social Outcomes

This segment connects intellectual capacity with patterns of social behavior, proposing that higher intelligence forecasts favorable life results, while lower intelligence is linked to adverse behaviors. Herrnstein and Murray maintain that cognitive ability offers a more accurate explanation for group disparities in social outcomes than socioeconomic status, a factor they believe has been underemphasized.

Their study utilizes data from the National Longitudinal Survey of Labor Market Experience of Youth (NLSY), concentrating on non-Hispanic white participants to isolate the effects of cognition from racial or ethnic influences.

Their findings reveal that IQ scores surpass parental socioeconomic status in forecasting adult outcomes such as poverty incidence, school dropout rates, unemployment duration, marital stability, reliance on welfare, criminal activity, and voter turnout.

All individuals in the NLSY were assessed using the Armed Services Vocational Aptitude Battery (ASVAB), whose scores show a strong correlation (.81) with earlier IQ tests. Herrnstein and Murray argue that IQ/AFQT measures are superior predictors of life trajectories compared to social class background, and adjusting for IQ significantly diminishes racial-ethnic disparities in outcomes.

Economic and social correlates associated with IQ

IQ Range	<75	75–90	90–110	110–125	>125
Percentage of US population	5	20	50	20	5
Married by age 30 (%)	72	81	81	72	67
Men out of labor force >1 month/year (%)	22	19	15	14	10
Men unemployed >1 month/year (%)	12	10	7	7	2
Divorce rate within five years (%)	21	22	23	15	9
Mothers with children in lowest IQ decile (%)	39	17	6	7	–
Mothers with illegitimate births (%)	32	17	8	4	2
Living below poverty line (%)	30	16	6	3	2
Men ever incarcerated (%)	7	7	3	1	0
Mothers receiving chronic welfare (%)	31	17	8	2	0
High school dropout rate (%)	55	35	6	0.4	0
Affirmative response on "Middle Class Values Index" (%)	16	30	50	67	74

Percentages represent proportions within each IQ category among non-Hispanic white individuals meeting various economic and social criteria.

Part III. The National Landscape

This part explores cognitive ability variations and corresponding social behaviors across ethnic groups. Herrnstein and Murray report that Asian Americans exhibit higher average IQ scores than white Americans, who themselves score above black Americans. They argue that the black-white difference is not attributable to test bias, noting that IQ assessments do not underestimate black individuals’ academic or occupational performance and that the gap is more pronounced on culturally neutral test items. Adjusting for socioeconomic factors does not fully close this gap; however, it appears to be decreasing over time.

The authors emphasize that high within-group heritability of IQ does not confirm genetic causes for between-group differences. They review evidence supporting partial genetic contributions—such as Spearman's hypothesis—alongside environmental influences like the Flynn effect’s generational IQ gains. Their conclusion suggests both genetic and environmental factors likely play roles in racial disparities but refrain from specifying their relative weights.

Regardless of underlying causes, they stress the importance of treating all individuals equally.

Repeating their analysis from Part II with NLSY data comparing whites to blacks and Hispanics, they find that controlling for IQ accounts for many observed racial differences in social outcomes.

They also note how higher fertility rates among lower-IQ groups and immigration patterns may reduce average national cognitive ability levels.

Finally, using NLSY evidence, they demonstrate a clear inverse correlation between IQ scores and prevalence of social problems.

Living Together

The final section explores the significance of cognitive ability in relation to key social challenges facing the United States.

After examining efforts to experimentally enhance intelligence, the authors determine that existing techniques produce only limited improvements.

They express disapproval of the homogenization of general and secondary education but advocate for the continuation of gifted education. Their analysis of affirmative action in academic and workplace settings prioritizes equal opportunity rather than equal results.

Herrnstein and Murray offer a bleak forecast for the nation’s trajectory: an intellectual elite progressively segregates itself while those with lower cognitive abilities experience deteriorating living conditions. Their proposed solution envisions a society that acknowledges cognitive diversity, assigns meaningful roles to all individuals, and is underpinned by robust local communities alongside universally upheld ethical standards.

Policy recommendations

The authors contend that the average genetic IQ in America is on the decline due to reproductive trends—namely, fewer children among higher-IQ individuals, shorter generational spans among lower-IQ populations, and immigration patterns favoring groups with lower measured intelligence. They caution that this could lead to a cognitively divided society adopting a conservative model similar to Latin American countries and evolving into a "custodial state," thereby eroding traditional American values such as individualism and equal rights.

They also predict a rise in totalitarianism, arguing that maintaining America’s legacy of individual freedoms and equal rights will become increasingly difficult if a large segment of the population remains dependent on government support indefinitely. To counter this, they suggest abolishing welfare policies they believe incentivize higher birth rates among economically disadvantaged women.

Reception

The Bell Curve generated widespread media interest but was initially distributed only to select reviewers, delaying comprehensive public critiques. Stephen Jay Gould, in his review for The New Yorker, challenged the book’s originality and data integrity, accusing the authors of selective fact presentation, statistical misapplication, and neglecting the broader implications of their conclusions.

In 1995, Jim Naureckas of Fairness and Accuracy in Reporting observed that media frequently accepted the book’s foundational assumptions despite intense criticism. The Brookings Institution noted that much attention was given to the race-intelligence debate while other elements were overlooked; it recognized both significant analytical shortcomings and some valuable points.

Over time, more rigorous critiques surfaced. Writing for Slate, Nicholas Lemann identified numerous flaws including faulty logic, incorrect citations, and mathematical errors—all seemingly supporting the authors’ arguments. Many of these criticisms were gathered in the volume The Bell Curve Debate.

Lack of peer review

Before publication, Herrnstein and Murray chose not to submit their manuscript for peer review, a process widely regarded as crucial for scholarly validation. This decision was interpreted as weakening the book’s academic credibility. Nicholas Lemann also pointed out the absence of galley proofs—a common practice that allows reviewers and journalists to prepare informed responses prior to release.

"Mainstream Science on Intelligence" declaration

In 1994, a statement titled "Mainstream Science on Intelligence" was published in The Wall Street Journal, endorsing various perspectives presented in The Bell Curve. This declaration, authored by Linda Gottfredson, an educational psychology professor at the University of Delaware, was circulated among 131 intelligence research specialists. Of those contacted, 52 endorsed the statement, 48 explicitly declined to sign, and 31 did not reply.

Donald Campbell, a former president of the American Psychological Association, observed that only ten of the endorsers were recognized experts in intelligence measurement. Additionally, the Southern Poverty Law Center noted that 20 signatories, including Gottfredson herself, had received financial support from the Pioneer Fund, an organization associated with white supremacist funding.

The scientific community has subjected both the content and the interpretation of this statement to significant scrutiny and criticism.

APA task force report

Following the debate sparked by The Bell Curve, the American Psychological Association's Board of Scientific Affairs established a task force led by Ulric Neisser to evaluate the research within the book while excluding its policy suggestions. The resulting document, Intelligence: Knowns and Unknowns, was published in 1995 and appeared in American Psychologist in 1996.

Concerning racial disparities in IQ scores, the APA task force determined:

In January 1997, American Psychologist featured eleven critical commentaries responding to this report.

Stephen Jay Gould's critique

Stephen Jay Gould contended that The Bell Curve relies on four fundamental assumptions about intelligence that lack sufficient support and are largely inaccurate:

1. Intelligence can be quantified by a single numerical value.
2. Intelligence enables a straightforward linear ranking of individuals.
3. Genetic factors predominantly determine intelligence.
4. Intelligence remains essentially fixed over time.

During a 1995 interview with Frank Miele for Skeptic, co-author Murray denied subscribing to these assumptions.

James Heckman's critique

Nobel Prize-winning economist James Heckman challenged two principal premises of the book: that the general intelligence factor (g) accounts for correlations among test scores and societal achievements, and that g is immutable. His reexamination revealed inconsistencies:

1. Factors influencing wages differ from those affecting test scores; explaining either requires more than just g.
2. Social outcomes depend on variables beyond g, many of which can be modified.

Murray countered by asserting that these critiques mischaracterize the book’s position, which does not claim that IQ or g are completely fixed or exclusive determinants of outcomes.

In a 2005 interview, Heckman acknowledged that The Bell Curve broke social taboos by addressing ability differences as predictors of socioeconomic status and praised its role in bringing attention to this topic. Nevertheless, he maintained that the authors exaggerated heredity’s influence on intelligence disparities.

Noam Chomsky's critique

In 1995, cognitive scientist Noam Chomsky disputed the book's assertion that IQ heritability is approximately 60%, arguing this figure is misleading because heritability estimates do not necessarily indicate genetic causation. He illustrated his point with an analogy involving women wearing earrings:

Chomsky concluded that evidence supporting a genetic basis for IQ differences is minimal and that environmental factors exert a more substantial influence.

Ned Block's Critique

Philosopher Ned Block highlighted a confusion in the book between genetic determination and heritability. Genetic determination refers to traits directly encoded by genes, whereas heritability quantifies how much genetic differences contribute to trait variation within a population. For instance, the number of fingers is genetically fixed but shows low heritability due to environmental influences; conversely, wearing earrings exhibits high heritability without any genetic basis. Block argued that while IQ is heritable, it is not genetically predetermined. He also faulted the twin studies cited for inadequately separating environmental influences, pointing out that twins often share similar racial and social contexts.

Psychologist Sidney Segalowitz concurred with the critique of twin studies, asserting they do not provide reliable estimates of heritability and labeling Murray’s approach as methodologically flawed.

Analytical Techniques

In Inequality by Design, Claude S. Fischer, Michael Hout, Martín Sánchez Jankowski, Samuel R. Lucas, Ann Swidler, and Kim Voss reexamined socioeconomic status effects using the same variables as The Bell Curve but applied different weighting schemes. Their analysis revealed that Herrnstein and Murray’s adjustment of IQ scores—specifically removing educational influences—artificially inflated IQ's capacity to predict poverty by as much as 61% among whites and 74% among blacks. They concluded that the book’s claim that IQ forecasts poverty better than socioeconomic status is largely an artifact of its statistical methodology.

In 1995, economist Sanders Korenman and sociologist Christopher Winship from Harvard challenged Herrnstein and Murray’s handling of measurement errors and their omission of critical family background factors such as single-parent households. Their findings suggested that parental family background might rival or surpass IQ in determining adult socioeconomic outcomes.

The volume Intelligence, Genes, and Success: Scientists Respond to The Bell Curve offers an in-depth examination of the relationships between genetics and intelligence, the plasticity of cognitive ability, educational influences, links between intelligence and earnings or meritocracy, racial health disparities, and implications for public policy. It contends that much public debate was polemical and overlooked the nuanced scientific and statistical foundations underlying the book’s conclusions.

Use of the Armed Forces Qualification Test

William J. Matthews pointed out that a portion of The Bell Curve's analysis depends on the Armed Forces Qualification Test (AFQT), which was originally developed to forecast military training outcomes rather than directly assess IQ. The AFQT includes components such as trigonometry.

James J. Heckman noted that the AFQT mainly predicts success in military schooling and functions more as an achievement test measuring accumulated knowledge rather than pure cognitive ability. He criticized Herrnstein and Murray for excluding a timed numerical operations subtest—the strongest AFQT predictor of earnings—from their composite score because it correlated weakly with other subtests. This selective inclusion raises concerns about the validity of a unidimensional intelligence model and suggests potential bias in their empirical work.

Janet Currie and Duncan Thomas (1999) provided evidence indicating that AFQT scores may reflect familial socioeconomic background more than innate intelligence, demonstrating the fragility of Herrnstein and Murray’s conclusions once socioeconomic variations are accounted for.

Cognitive Stratification and the "Cognitive Elite" Notion

The concept of a cognitive elite has attracted considerable skepticism. Frank Wilson dismissed The Bell Curve's claims regarding intelligence-driven social stratification as cultural myth rather than fact. Nicholas Lemann characterized the cognitive elite idea as a sociological stereotype employed more for political purposes than grounded in reality.

Research by Charles R. Tittle and Thomas Rotolo found that increased use of written IQ-like tests for job screening strengthens correlations between IQ and income, implying that IQ may capture test-taking skills leveraged by status groups to maintain exclusivity rather than innate ability alone.

Min-Hsiung Huang and Robert M. Hauser tested Herrnstein and Murray’s cognitive sorting hypotheses using General Social Survey data spanning 1974 to 1994 but found no empirical support. Their analyses indicated less concentration of high-IQ individuals in specific occupations than claimed by Herrnstein and Murray, attributing observed occupational shifts primarily to growth in highly educated professions rather than cognitive stratification.

Noam Chomsky (1972) criticized Herrnstein’s meritocracy concept by challenging assumptions that occupational choices are purely economically motivated and pay strictly reflects individual contribution. He argued existing inequalities shape compensation systems to uphold social hierarchies rather than reward merit.

Race and Intelligence

The book’s discussion on racial disparities in IQ has been highly contentious. The authors assert it is "highly likely" that both genetic and environmental factors influence racial differences but acknowledge this remains an unsettled debate.

Economist Thomas Sowell commended certain aspects of the book but reproached its approach to race and IQ malleability, noting historical evidence showing European immigrant groups initially scored below average on mental tests—a fact Herrnstein and Murray dismissed as mere "folklore."

Stephen Jay Gould’s 1996 updated edition of The Mismeasure of Man directly contested many assertions about race and intelligence from the book, emphasizing that heritability estimates do not establish genetic causation for group differences.

Psychologist David Marks argued that the ASVAB test used correlates closely with literacy measures rather than general intelligence.

Anthropologist Melvin Konner criticized The Bell Curve as politically motivated pseudo-science linking genetics with racial IQ disparities without sufficient evidence, highlighting African Americans’ improved outcomes under enriched environmental conditions.

The 2014 textbook Evolutionary Analysis by Herron and Freeman refutes what it terms the "Bell Curve fallacy," underscoring that heritability estimates cannot determine causes behind group mean differences absent controlled environmental experiments—which are impossible with human subjects.

Rutledge M. Dennis maintains media summaries from studies like Jensen's work and The Bell Curve portray minorities as biologically inferior, providing justification for systemic disenfranchisement.

Journalist Charles Lane noted many scholars cited in the book also contributed to Mankind Quarterly, a publication associated with white supremacist ideology. Murray responded by emphasizing the diversity of scholarly sources cited, including numerous articles published in leading peer-reviewed journals.

Steven Fraser’s edited volume The Bell Curve Wars critiques the book’s research methods, biases, and policy proposals, describing it as an amalgamation of disreputable race theorists’ ideas combined with eugenicist thought.

Accusations of Racism

Since The Bell Curve reports statistically lower average intelligence among blacks compared to whites, critics warn that its findings could be misused by extremists to rationalize hate crimes or genocide. Much referenced research received funding from the Pioneer Fund, which has been accused of promoting scientific racism; however, Murray disputed this characterization.

Evolutionary biologist Joseph L. Graves labeled The Bell Curve an example of racist science due to unsupported assertions, biased data interpretation favoring predetermined hypotheses, omission of contradictory evidence or theories, alongside policy recommendations aligned with racist agendas.

Eric Siegel argued that by failing to clarify why racial IQ differences are investigated, the book implicitly endorses prejudice by suggesting race predicts individual capabilities.

Howard Gardner accused the authors of engaging in "scholarly brinkmanship," presenting extreme positions without fully endorsing them but encouraging readers toward harsh conclusions.

New York Times columnist Bob Herbert described the work as "racial pornography disguised as serious scholarship," equating it with a refined form of racial slur.

See also

• Human Diversity (2020) by Charles Murray