Yet More on the Heritability and Malleability of IQ

Yet More on the Heritability and Malleability of IQ: "So: Do I really believe that the heritability of IQ is zero? Well, I hope by this point I've persuaded you that's not a well-posed question. What I hope you really want to ask is something like: Do I think there are currently any genetic variations which, holding environment fixed to within some reasonable norms for prosperous, democratic, industrial or post-industrial societies, would tend to lead to differences in IQ? There my answer is 'yes, of course'. I've mentioned phenylketonuria and hypothyroidism already, and many other in-born errors of metabolism also lead to cognitive deficits, including lower IQ, at least in certain environments. More interestingly, conditions like Williams's Syndrome, Downs's Syndrome, etc., are genetically caused, and lead to reasonably predictable patterns of cognitive deficits, affecting different abilities in different ways. In many of these cases, it seems very likely (but is not yet established) that these variants cause problems with the signaling pathways which set how gene expression responds to environmental cues. Manipulating those signaling pathways during the right time windows would change what kind of mind the organism has later. The fact that different genetic disorders lead to different patterns of cognitive deficits, rather than just generally making people duller all around, suggests ways of disentangling which ge"