  As to the first question, there seems to be no double dissociation.  First of all, WS individuals' language, while startling in contrast  with their level of mental retardation, is not normal; indeed, as we  have seen, it is indistinguishable on some tests from that of  language impaired individuals. In addition, as Thomas and  Karmiloff-Smith 2002, caution, it is not at all clear that one can  assume, in the case of a pervasive developmental disorder like  Williams syndrome, that apparently ‘intact’ competences  are a result of normal development of the underlying neurological and psychological structures. That is, given the known capacity of the  brain to compensate for deficits in one area by cobbling together a  solution in another, one cannot assume that there is a  ‘language module’ in WS patients which develops more or  less normally despite other cognitive systems' being massively  disrupted. Thomas and Karmiloff-Smith argue that the numerous  discrepancies between WS language development and that of normal  children suggests that this ‘residual normality’  assumption is misguided in this case, thus undermining the claim that what is spared in WS is ‘the language (or grammar)  module.’