Saturday, November 27, 2010

The Bell Curve redivivus

Someone responded to my note with the following:

On 11/26/10 10:01 PM, Billy Blogblather wrote:

Assumptions [made by the authors of the Bell Curve]

Much of the criticism of The Bell Curve has focused on potential flaws in the basic assumptions made at the beginning of the book. William J. Matthews and Stephen Jay Gould list four basic assumptions of The Bell Curve:

  1. Intelligence must be reducible to a single number.
  2. Intelligence must be capable of rank ordering people in a linear order.
  3. Intelligence must be primarily genetically based.
  4. Intelligence must be essentially immutable.

According to Gould, if any of these premises are false, then their entire argument disintegrates (Gould, 1994).  Similarly, in "Science" in the service of Racism, C. Loring Brace writes that The Bell Curve makes six basic assumptions at the beginning of the book:

  1. Human Cognitive ability is a single general entity, depictable as a single number.
  2. Cognitive ability has a heritability of between 40 and 80 percent and is therefore primarily genetically based.
  3. IQ is essentially immutable, fixed over the course of a life span.
  4. IQ tests measure how "smart" or "intelligent" people are and are capable of rank ordering people in a linear order.
  5. IQ tests can measure this accurately.
  6. IQ tests are not biased with regard to race ethnic group or socioeconomic status.

Brace proceeds to argue that there are faults in every one of these assumptions."

Lawrence replies (I believe to the foregoing), but in any case, he dismisses them with
'Yeah, yeah. I read the criticisms at the time, but unlike most of the critics, I also read the book.'
Is it your claim that Stephen J. Gould and C. Loring Brace didn't read the book?

LAWRENCE RESPONDS: As to whether these critics have read The Bell Curve, I think they have read at least to page 23, for on pages 22 and 23 are the assumptions they denigrate. But when I read what Herrnstein and Murray wrote I can hardly recognize it in the critics’ rephrasing. Here is what Herrnstein and Murray actually wrote:

"Here are six conclusions regarding tests of cognitive ability, drawn from the classical tradition, that are by now beyond significant technical dispute:

1. There is such a thing as a general factor of cognitive ability on which human beings differ.

2. All standardized tests of academic aptitude or achievement measure this general factor to some degree, but IQ tests expressly designed for that purpose measure it most accurately.

3. IQ scores match, to a first degree, whatever it is that people mean when they use the word intelligent or smart in ordinary language.

4. IQ scores are stable, although not perfectly so, over much of a person's life.

5. Properly administered IQ tests are not demonstrably biased against social, economic, ethnic, or racial groups.

6. Cognitive ability is substantially heritable, apparently no less than 40 percent and no more than 80 percent.

We can see that Brace is a bit closer to what Herrnstein and Murray actually wrote, but why change it? What Herrnstein & Murray wrote sounds reasonable. What Brace wrote sounds less so, and what Matthews and Gould wrote sounds even less so. In any case drawing conclusions about the entire book based on the first 24 pages inclines me to think no, they didn't read the entire book, but that's just a guess.

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