Introduction: dissociations revisited

In this chapter we look at Christopher in comparison with other subjects who are atypical signers in order to see if the dissociations manifest in his case are sui generis or reflect deeper generalisations. The hope, of course, is that such generalisations will emerge and will also serve to corroborate the details of the model of the mind we sketch in the next chapter.

By way of background to the present discussion it is worth briefly summarising the dissociations Christopher showed. Most obviously, there is an asymmetry between his striking linguistic ability and his impaired general intelligence, as seen in his performance on tests of theory of mind and on visuo-motor tasks. He showed a further asymmetry between his near-perfect first language ability and his flawed second language learning prowess. This was most obvious in the contrast between his mastery of the lexical properties of his ‘second’ languages and his more limited abilities in coming to grips with the computational system: specifically, his remarkable skill in morphology vis-à-vis the plateau effects seen in his learning of the syntax. His apraxia and mild autism led us to expect a dissociation between his sign and his speech, and between his abilities in language and in gesture. Within BSL this translates into a contrast between his use of syntactic space versus his relatively poor use of topographic space, especially when these come together in the use of classifiers.