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. A partial preliminary report of the data was presented at the “Science of Aphasia V” conference in Potsdam in 16–21 September 2004. An earlier version of this paper was presented at the Departmental Seminars of the Department of Language and Communication Science at City University (February 2005) and appeared at the Reading Working Papers in Linguistics 6 (2005). We thank two anonymous reviewers for comments on an earlier version of this paper as well as the two reviewers of Aphasiology for their useful comments and suggestions. We also thank speech pathologists M. Diamanti, A. Xofillis, and M. Moudouris for referring the patients. Note: All co‐authors have contributed equally to this article. 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) but are compatible with Chomsky's (2000) Minimalist Program and with Wenzlaff and Clahsen's (2004) tense underspecification theory.