The Bell Curve Phenomenon

A momentous event in the perception of the role of intelligence in society occured with the publication of The Bell Curve by Herrnstein and Murray. The impact of the book is demonstrated by the rapid publication of a number of responses. A whole issue of The New Republic was devoted to the book, and two edited books of responses were quickly published. Some of the responses were largely political or emotional in character, but others attacked the book on scientific grounds. A closely reasoned attack appeared a year after these collections. The American Psychological Association also sponsored a report that although not directly a response to The Bell Curve was largely motivated by it.

Some of the main arguments of the book are that (i) conventional IQ tests measure intelligence, at least to a good first approximation; (ii) IQ is an important predictor of many measures of success in life, including school success, but also economic success, work success, success in parenting, avoidance of criminality, and avoidance of welfare dependence; (iii) as a result of this prediction, people who are high in IQ are forming a cognitive elite, meaning that they are reaching the upper levels of society, whereas those who are low in

IQ are falling toward the bottom; (iv) tests can and should be used as a gating mechanism, given their predictive success; (v) IQ is highly heritable and hence is passed on through the genes from one generation to the next, with the heritability of IQ probably in the 0.50.8 range; (vi) there are racial and ethnic differences in intelligence, with blacks in the United States, for example, scoring about one standard deviation below whites; (vii) it is likely, although not certain, that at least some of this difference between groups is due to genetic factors; and (viii) tests can and should be used as a gating mechanism, given their success.

Herrnstein and Murray attempted to document their claims using available literature and also their own analysis of the National Longitudinal Study of Youth data that were available to them. Although their book was written for a trade (popular) audience, it was unusual among books for such an audience in its use of fairly sophisticated statistical techniques.

It is not possible to review the full range of responses to Herrnstein and Murray. Among psychologists, there seems to be widespread agreement that the social policy recommendations of Herrnstein and Murray, which call for greater isolation of and paternalism toward those with lower IQs, do not follow from their data but rather represent a separate ideological statement. Beyond that, there is a great deal of disagreement regarding the claims made by these authors.

Our view is that it would be easy to draw much stronger inferences from the Herrnstein-Murray analysis than the data warrant and perhaps even than Herrnstein and Murray would support. First, Herrnstein and Murray acknowledge that, in the United States, IQ typically accounts only for approximately 10% of the variation, on average, in individual differences across the domains of success they survey. In other words, about 90% of the variation, and sometimes much more, remains unexplained.

Second, even the 10% figure may be inflated by the fact that U.S. society uses IQ-like tests to select, place, and, ultimately, to stratify students so that some of the outcomes that Herrnstein and Murray mention may actually be results of the use of IQ-like tests rather than results of individual differences in intelligence per se. For example, admission to selective colleges in the United States typically requires students to take either the SAT or the American College Test, both of which are similar (although not identical) to conventional tests of IQ. Admission to graduate and professional programs requires similar kinds of tests. The result is that those who do not test well may be denied access to these programs and to the routes that would lead them to job, economic, and other socially sanctioned forms of success in our society.

It is thus not surprising that test scores would be highly correlated with, for example, job status. People who do not test well have difficulty gaining access to high-status jobs, which in turn pay better than other jobs to which they might be able to gain access. If we were to use some other index instead of test scores (e.g., social class or economic class), then different people would be selected for the access routes to societal success. In fact, we do use these alternative measures to some degree, although less so than in the past.

Finally, although group differences in IQ are acknowledged by virtually all psychologists to be real, the cause of them remains very much in dispute. What is clear is that the evidence in favor of genetic causes is weak and equivocal. We are certainly in no position to assign causes at this time. Understanding of group differences requires further analysis and probably requires examining these differences through the lens of broader theories of intelligence.

Understanding And Treating Autism

Understanding And Treating Autism

Whenever a doctor informs the parents that their child is suffering with Autism, the first & foremost question that is thrown over him is - How did it happen? How did my child get this disease? Well, there is no definite answer to what are the exact causes of Autism.

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