Diversity in the lexical and syntactic abilities of fluent aphasic speakers

In an earlier study by the authors, it was suggested that some fluent aphasic speakers exhibit subtle grammatical deficits. In this paper, how far lexical accessing problems might account for these deficits is considered. For this study, spontaneous speech data collected from two groups of aphasic speakers, Dutch and English, and from normal controls are analysed. As expected, differences are found between the aphasic and the control groups. The English aphasic group was significantly different from the control group on lexical and grammatical measures. There was a significant difference between the Dutch aphasic group and the normal controls for one lexical measure (types and tokens of nouns used) and for one grammatical measure, the proportion of embedded clauses used. The relationship between the aphasic speakers' grammatical and lexical abilities is explored by comparing the distribution of clausal structures with the frequency and diversity of verb and noun use. A number of dissociations are found between the grammatical and the lexical measures within the aphasic groups which suggests that difficulty with lexical accessing may not always account for the grammatical limitations of fluent aphasics.