Grammatical class in lexical production and morphological processing: Evidence from a case of fluent aphasia

We present the case of a fluent aphasic patient who is impaired at producin g nouns relative to verbs in picture naming, sentence completion, and sente nce generation tasks, but is better at both producing and comprehending con crete nouns than abstract nouns. Moreover, he displays a selective difficul ty in producing the plural forms of some nouns and pseudowords presented as nouns, but was able to produce the phonologically identical third-person s ingular forms of corresponding verb homonyms and of the same pseudowords pr esented as verbs. This pattern of performance casts doubt on the hypothesis that grammatical class effects are always epiphenomena of more general sem antic impairments that affect the naming of actions or of concrete objects, and suggests that these effects may arise instead from damage to syntactic processes pertaining specifically to the grammatical properties of words. We also discuss the implications of such damage for models of morphological processing.