Nisbett claims that heredity is much less important for IQ than thought (see also counterclaims posted below).

Heredity, per se, is irrelevant to the argument.

The question is how much family environment and particularly effort matters. Nisbett's title ("schools and cultures") suggests that he is not arguing for parental input. The quote about parents' time suggests otherwise. Shea admits that Nibett admits that there are declining returns. The quote "smaller (but still potent) effects" is a substantive disagreement, but it's pretty weaselly. The question is not whether bad parenting is possible, but whether it is likely in the people Caplan addresses.

Added: Lots of people on this thread make the same error.