The critique of the genetics of complex social outcomes is partly well-founded, insofar as social outcomes sometimes have unreliable relations with cognitive traits. But the correct conclusion is not to dismiss the entire field altogether. Rather, the implication is to redirect geneticists' attention to the stable cognitive phenotypes that are natural candidates for genetic analysis.
Thomas & Karmiloff-Smith (T&K-S) claim that “Residual Normality” is a priori unlikely, that is, that specific cognitive deficits should not exist in developmental disorders. Here I review evidence that a specific cognitive deficit is at the core of developmental dyslexia and I provide a possible neurological account thereof.