Comprehension of contrastive stress by Broca's aphasics

Comprehension of stress as a determiner of reference for pronouns was compa red in eight patients with Broca's aphasia (BA) and five age-matched contro l subjects. The subjects were asked to Listen to sentences in which the str essed or unstressed condition of the pronoun was a critical criterion for t he establishment of reference. For each sentence, subjects were shown three pictures and asked to point to the correct referent of the pronoun. While the controls were nearly perfect in both the stressed and unstressed condit ions, BA patients were significantly worse than normals, showing chance per formance in both cases. However, a significant disparity was found in the B A patients' selection of the object NP as the referent under stressed and u nstressed conditions, indicating that BA subjects are, indeed, sensitive to the stress patterns of pronouns. It was thus hypothesized that the BA pati ents' chance performance was the result of an inability to implement their knowledge of stress during the processing of sentences involving discourse- related linguistic operations, such as the establishment of pronoun referen ce (Grodzinsky, Wexler, Chien, Marakovitz, & Solomon, 1993). To test this h ypothesis, a second experiment was conducted in which discourse-related ope rations were eliminated. In this second experiment, comprehension of stress by the same two groups was compared in tasks involving purely morphosyntac tic processes. The contrastive stress patterns of other wise homophonous co mpound nouns and adjectival phrases (e.g., BLACKboard, black BOARD), rather than those of pronouns, were examined. In this grammatically ''simpler'' e xperiment (i.e., without discourse-related operations), BA subjects scored significantly above chance in their comprehension of sentences involving co mpound nouns; unexpectedly, however, these same subjects did not show signi fi cantly above-chance performance in their comprehension of sentences cont aining adjectival phrases, Nevertheless, the results obtained in these two experiments seem to support the view that aphasic patients may have a lack of processing capacity, resulting in more errors during the processing of d iscourse-related linguistic constructions. (C) 1999 Academic Press.