Background
In the early part of the 20th century there was a widespread belief that the major component of human intelligence was determined by genetics rather than environmental influences. Diagnostic tests developed to determine a student’s readiness for instruction were repurposed into IQ tests designed to measure an individual’s innate intelligence determined by their genes. Those who believed that intelligence is an innate characteristic determined by an individual’s genetics, were called “hereditarians.” Those who believed that intelligence was predominantly a result of environmental influences such as family background and education were called “nurturists.”
During the mid 1960’s, social unrest infused with an anti-establishment sentiment was rumbling across America. Anti-war protests on college campuses against American involvement in Vietnam were among the early harbingers of growing social discontent. The Civil Rights Movement was gaining momentum and the quest for social equality was erupting in violence. Psychologists were arguing that the difference in IQ scores by race were a result of poverty and underfunded education. Attitudes began to shift away from the established view of intelligence as an inherited trait and IQ as a surrogate for intelligence. In her book A Century of IQ Testing, Elaine
Castles reflected on how this egalitarian movement had impacted the nature vs. nurture debate:*
As issues of equality and social justice rose to the forefront, environmental explanations for differences in IQ scores suddenly again became fashionable. The work of socially conscious and environmentally oriented psychologists like J. McVickers Hunt and Benjamin Bloom guided policy makers at the highest level.
The Publication of The Bell Curve
The controversy that began in the 1970s was reignited in 1994 with the publication of The Bell Curve: Intelligence and Class Structure in American Life, by Herrnstein and Murray. In this heavily-researched tome, the authors argued that IQ tests are an accurate measure of intelligence and that intelligence is a strongly heritable and immutable trait. Within a short time, the academics aligned themselves on one side or the other of the debate. Once again, it was the hereditarians vs. the nurturists. The hereditarians, including many behavioral geneticists and sociobiologists, used heritability analyses to support their claim that IQ tests are an effective measure of intelligence and that intelligence is mainly attributable to genetic factors. The nurturists, including many biologists and social scientists as well as several left-leaning activists, asserted that the assumptions underpinning heritability were flawed and, therefore, the conclusions were meaningless. Some critics of The Bell Curveperceived this publication not only as a shot across the bow of the nurturist ship, but as a racist act disguised as research.
At the height of what were called “the Bell Curve Wars,” the field of psychology was involved in a struggle to maintain its status as a legitimate science. Some hereditarians were perceived as racists and some left-leaning nurturists were seen as neo-Lysenkoists–denying any conclusions that suggest racial or gender differences. Many in the community of psychologists realized that it was time to retreat from politics and return to the original rationale for science–the unfettered quest for truth.
The Ultimate Impact of The Bell Curve
To mitigate the Bell Curve Wars, the American Psychological Association (APA) established a task force to gather consensus on what was known and what was unknown on the topic of human intelligence. In 1996, after two years of meetings, drafts, revisions, and circulation throughout the research community, the task force published Intelligence: Knowns and Unknowns. Acknowledging that the debate had been contaminated often with political ideologies, it stated:**
[An] unfortunate aspect of the [nature-nurture] debate was that many participants made little effort to distinguish scientific issues from political ones. Research findings were often assessed not so much on their merits or their scientific standing as on their supposed political implications. In such a climate, individuals who wish to make their own judgments find it hard to know what to believe.
The Bell Curve played a pivotal role in raising the red flag in academe, alerting the intellectual community to the dangers of allowing political opinion to distort objective scientific research. Studies, during the 1990’s, of identical twins raised separately from birth provided incontestable evidence of the strong role played by genetics in determining an individual’s cognitive strengths. The controversy referred to as “The Bell Curve Wars” reminds us of the danger in allowing political ideologies to undermine the objective approach to science.
* “As issues of equality and social justice …” found in Castles, Elaine E. 2012. Inventing Intelligence: How America Came to Worship IQ. Santa Barbara, CA: Praeger. pp. 113–114.
**Neisser, Ulric. et al. 1996. “Intelligence: Knowns and Unknowns”: a report published by the Board of Scientific Affairs of the American Psychological Association. American Psychologist. Vol. 51, No. 2. p. 77.
