Functional category production and degrees of severity: findings from Chinese agrammatism

Abstract

ABSTRACT Background: People with agrammatism have profound deficits in producing functional categories. The Tree Pruning Hypothesis proposes that these deficits are attributed to the reduced ability to project higher nodes in the syntactic trees. However, it is not clear whether this theory can be used to account for the deficits of functional category production among Chinese-speaking agrammatic patients. Aims: The current study examined functional category deficits in Chinese-speaking agrammatic patients in relation to the degree of impairment severity in order to test the hierarchical nature of functional category deficits. Methods & Procedures: 21 Chinese-speaking patients with different degrees of severity and 10 non-brain-damaged controls participated in this study. The Chinese version of the Western Aphasia Battery and a picture description task were administered to examine the production of function words related to a Complementiser Phrase (CP), Tense Phrase (TP) and verb Phrase (vP). Outcomes and Results: The degrees of impairment severity had a significant influence on functional category deficits. All patients were relatively accurate at CP, regardless of their severity. The patients with severe aphasia had profound problems in both vP- and TP-related elements, whereas the patients with mild aphasia retained their ability to access to either. Specifically, the vP-related words were significantly more impaired than TP-related words. Conclusions: The asymmetrical deficits in functional category production suggest that the impairments might lie in the selection of lexical arrays at the vP phase, rather than functional categories per se. The findings provided the evidence for a lexically-based account for Chinese agrammatism.