A theory of verb form use in the speech of agrammatic aphasics.

Previous descriptions of the use of grammatical markers associated with verbs in the speech of agrammatic patients are shown to be grammatically inadequate. A more appropriate grammatical description, defined in terms of the complexity of the derivational properties of verb forms and the complexity of the semantic notions that verb forms can express, is presented which can handle facts about English and Italian agrammatism. However, this type of description is shown to be incapable of accounting in a natural way for certain further facts about agrammatic productions in English and Italian which need to be explained. A psycholinguistic model compatible with the grammatical description is then presented to account for these facts. The model, an elaboration of M. Garrett's (1975, in G. Bower (ed.), Psychology of learning and motivation, New York: Academic Press, Vol. 9) model of normal sentence production, involves the accessing of two stores during syntactic processing--one containing phrase fragments, the other function words. Agrammatic patients are claimed to suffer from a specific inability to access these stores; the resulting agrammatic production system is shown to account for a wide range of facts about agrammatism.