Comprehension of lexical subcategory distinctions by aphasic patients: proper/common and mass/count nouns

Previous research has found that agrammatic Broca aphasic patients have particular difficulty using determiners like "a" and "the" for the purposes of sentence comprehension. In this study, we test whether or not such difficulty extends to the level where lexical subcategories are distinguished by these articles. The absence or presence of a determiner distinguishes proper from common nouns (e.g., "ROSE" vs. "A ROSE"), and mass from count nouns (e.g., "GLASS" vs. "A GLASS"). Groups of agrammatic Broca and fluent aphasic subjects were required to point to one of two pictures in response to a sentence such as "Point to the picture of rose" or "Point to the picture of a rose". Sentences were presented in either printed or spoken form. Results indicated that for the agrammatic Broca patients, printed presentation yielded significant improvement over spoken presentation only for the proper noun/common noun distinction. Performance was significantly poorer for the mass noun/count noun distinction as compared to the proper/common distinction for these patients, and mass nouns proved particularly difficult. Interpretable patterns were not observed on either subcategory distinction for the fluent aphasic subjects. Current theories of agrammatism cannot fully explain these data. An independent explanation is offered that suggests proper noun/common noun is a universal semantic distinction. On the other hand, the mass noun/count noun distinction is more purely syntactic, and thus is particularly difficult for agrammatic Broca patients.