The breakdown of functional categories in Greek aphasia: Evidence from agreement, tense, and aspect

Abstract

Background: Verbal inflectional errors are among the most prominent characteristics of aphasic nonfluent speech. Several studies have shown that such impairment is selective: subject–verb agreement is relatively intact while tense is severely impaired. A number of researchers view the deficit as structural and attribute errors to a breakdown of functional categories and their projections. Agrammatic individuals are thought to produce trees that are intact up to the Tense node and “pruned” from this node up. Aims: The present study investigates (a) the relative sensitivity of functional categories related to verbal inflection in Greek aphasia and the systematicity thereof; and (b) the relation between patterns of impairment in production and grammaticality judgements. Method & Procedures: We present results from a sentence completion and a grammaticality judgement task with seven Greek‐speaking aphasic individuals and seven control participants matched for age and education. Materials were constructed to assess three functional categories: subject–verb agreement, tense, and aspect. Eight verbs were used, balancing estimated familiarity and regularity of aspectual conjugation. Outcomes & Results: A great variability was observed among participants in overall performance but the pattern of performance was quite systematic. The results indicated that inflectional morphemes are not all impaired to the same degree in Greek aphasia. In both tasks, as a group, patients made more errors in aspect than in agreement. The group differences between tense and the other two conditions did not reach statistical significance. Moreover, a comparison of individual aphasic performance in the three functional categories indicated that in every case in which statistically significant differences were observed among the three functional categories, agreement was found to be less impaired than tense, aspect, or both. Conclusions: These findings do not support a global impairment of inflectional morphemes in aphasia but support a selective one and, in particular, a dissociation between agreement, on the one hand, and tense and/or aspect, on the other hand. Moreover, our findings do not support a hierarchical account along the lines of Friedmann and Grodzinsky (1997 Friedmann, N. and Grodzinsky, Y. 1997. Tense and agreement in agrammatic production. Pruning the syntactic tree.. Brain & Language, 56: 71–90. [Crossref] , [Google Scholar]) but are compatible with Chomsky's (2000 Chomsky, N. 2000. “Minimalist inquiries: The framework.”. In Step by step, Edited by: Martin, R, Michaels, D and Uriagereka, J. 89–155. Cambridge, MA: MIT Press. [Google Scholar]) Minimalist Program and with Wenzlaff and Clahsen's (2004 Wenzlaff, M. and Clahsen, H. 2004. Tense and agreement in German agrammatism.. Brain & Language, 89: 57–68. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) tense underspecification theory.