  Dissociations of language disorders acquired in adulthood (e.g.,  Broca's and Wernicke's aphasia) may tell us something about how  language is organized in the mature brain, but cannot tell us much  about how language is acquired or the role of innate knowledge in  that process — a fact that nativists about language generally  acknowledge. By contrast, language dissociations arising during  childhood are sometimes held to bear strongly on the question of  whether language is innate. Pinker (1994:297-314) articulates this  latter line of thought, arguing that there is a double dissociation  between ‘general intelligence’ and language in two  developmental disorders called Williams Syndrome (WS) and Specific  Language Impairment (SLI). People with WS have IQs well below the  normal range (50-60), yet are able to speak fluently and engagingly  about many topics. Those with SLI, by contrast, have normal  (≈90) non-verbal intelligence but speak effortfully and slowly, frequently making errors in their production and comprehension of  sentences and words. Pinker argues that there is a double  dissociation here, and that it supports the view that there is a  special ‘language acquisition device’ that is separable  from any general learning abilities children might possess. In  addition, following Gopnik 1990a,b, and Gopnik and Crago 1991, he  urges that the fact that the dissociation appears to concern aspects  of syntax in particular indicates that the language faculty in  question is the grammar faculty. Finally, and again following Gopnik, he argues that since SLI appears to run in families and, in at least  one case, displays a Mendelian inheritance pattern, what we have here is evidence not just of a ‘grammar faculty,’ but of a  ‘grammar gene.’