Manski and Caplan
By Arnold Kling
I just got around to reading Charles Manski on “Genes, Eyeglasses, and Social Policy.” Manski is dismissive of heritability studies, and I am curious how Bryan would react, given the importance he places on heritability studies for his argument that parents should relax. Manski quotes Arthur Goldberger’s sarcastic comment,
Now suppose that the entire population lacks eyeglasses. Then the heritability of effective quality of sight is one. What does this imply about the usefulness of distributing eyeglasses as a treatment for nearsightedness? Nothing, of course.
What I believe Manski wants to argue is that high heritability of IQ does not mean that IQ is untreatable, just as high heritability of nearsightedness in a population without eyeglasses does not mean that nearsightedness is untreatable.
What I would counter is that high heritability of a trait may not tell us the effectiveness of treatments that have yet to be discovered. However, it does tell us that the existing treatments in a population make little difference.
As an aside, the eyeglass example is peculiar in that people seek finite absolute status rather than relative status or maximum status. The ability of eygelasses to equalize vision across the population might disappear if parents of children with good vision sought “gifted and talented” eyeglasses to enhance their children’s eyesight even further.