For the purposes of looking at the second question (from the first post), “Does this make you think that differences among IQ scores between races are genetic?,” let’s accept that the answer to the first question, “What does it mean to say IQ test scores are largely genetic?” is that something called heritability is high for IQ test scores.
In the USA we see persistent large differences in average IQ test score exist between racial groups.
Why? (asking for audience input)
But no environmental factor, or composite of factors, seems to be associated strongly with the group average differences (Flynn 2007; but see Fryer and Levitt 2004).
This has led some researchers to make a two-part argument: the high heritability of IQ test scores within racial groups coupled with a failure of environmental hypotheses to account for the group differences supports—or lends plausibility to—explanations of mean differences in terms of genetic factors (even if these factors have yet to be elucidated) (e.g., Jensen in Miele 2002, 111ff).
Does this seem plausible to you? (waiting for audience input)
Consider this additional information.
Flynn ( 1994) has pointed to large gains in average IQ test score between generations in developed countries (now called the Flynn effect).
No environmental factor, or composite of factors, such as diet or years of education, has been shown to be associated strongly with the generational differences.
Now bring in the two-part argument: the high heritability of IQ test scores within groups coupled with a failure of environmental hypotheses to account for the group differences supports—or lends plausibility to—explanations of mean differences in terms of genetic factors.
If we look at each generation as a distinct group, the two-part argument means we should favor explanations of generational differences in terms of genetic factors, yet the change in gene frequencies in a human population over one generation is negligible.
Conclusion? The logic of the two-part argument must be flawed and must be put aside.
That leaves us still having to explain large differences between generations—or racial groups—in a highly heritable trait. That ” IQ paradox” is a discussion for another time.
Flynn, J.R.: 1994, IQ Gains over Time, in R. J. Sternberg (ed.), Encyclopedia of Human Intelligence, Macmillan, New York, pp. 617-623.
Flynn, J.R.: 2007, What is Intelligence? : Beyond the Flynn Effect. Cambridge University Press, Cambridge.
Fryer, R. and Levitt, S.: 2004, Understanding the Black-White Test Score Gap in the First Two Years of School. The Review of Economics and Statistics, 86(2), 447-464.
Miele, F.: 2002, Intelligence, Race, and Genetics: Conversations with Arthur Jensen, Westview Press, Boulder, CO.