The Bell Curve

THE BELL CURVE….Yes, Andrew Sullivan should be ashamed for saying that The Bell Curve “still holds up.” It’s a pernicious book that misused its own statistics in an effort to convince the public that the longstanding gap in IQ scores between whites and blacks is an immutable genetic reality that needs to be accepted as a permanent fact of life ? a conclusion that’s not only wrong, but wrong even on the terms of the book’s own evidence.

Since everyone is talking about this, though, it’s worth pointing out that legitimate criticism of The Bell Curve sometimes morphs into pop debunkings of the entire subject of IQ, biology, and environment. With that in mind, if you’re interested in the consensus view of the psychology and psychometrics profession on the current state of IQ research, you might want to check out a summary report issued by the American Psychological Association in 1995 following the publication of The Bell Curve. With the caveat that it’s ten years old, it presents a reasonably concise summary of what the profession itself believes about IQ, how it’s measured, whether it matters, how it can be affected, and whether there are biological differences in IQ between genders and races.

For those who don’t want to read the entire report, however, here’s what it says on the key questions of genetics and race:

  • On genetics: “Across the ordinary range of environments in modern Western societies, a sizable part of the variation in intelligence test scores is associated with genetic differences among individuals….In childhood [heritability is] of the order of .45….by late adolescence [heritability] is around .75….Substantial environmental variance remains, but it primarily reflects within-family rather than between-family differences.”

  • On race: “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….”

Read the whole report for caveats and further detail, of course.