Parallel functional category deficits in clauses and nominal phrases: The case of English agrammatism

Abstract

Individuals with agrammatic aphasia exhibit restricted patterns of impairment of functional morphemes, however, syntactic characterization of the impairment is controversial. Previous studies have focused on functional morphology in clauses only. This study extends the empirical domain by testing functional morphemes in English nominal phrases in aphasia and comparing patients' impairment to their impairment of functional morphemes in English clauses. In the linguistics literature, it is assumed that clauses and nominal phrases are structurally parallel but exhibit inflectional differences. The results of the present study indicated that aphasic speakers evinced similar impairment patterns in clauses and nominal phrases. These findings are consistent with the Distributed Morphology Hypothesis (DMH), suggesting that the source of functional morphology deficits among agrammatics relates to difficulty implementing rules that convert inflectional features into morphemes. Our findings, however, are inconsistent with the Tree Pruning Hypothesis (TPH), which suggests that patients have difficulty building complex hierarchical structures.

Keywords: Agrammatic aphasia; Clause; Functional category; Nominal phrase.

Figures

Fig. 1

Selected slices from T1 MRI images of aphasic participants showing lesion sites. MRI scans were not available for the other five patients for health reasons.

Fig. 2

Mean response accuracy in clauses by condition, Experiment 1. Comp = the condition testing complementizers. Error bars represent standard errors (SE).

Fig. 3

Mean response accuracy in nominal phrases by condition, Experiment 2. Sg = the singular numeral, Pl = plural numerals. Error bars represent standard errors (SE).

Fig. 4

Mean response accuracy in clauses by condition, Experiment 3. Comp = the condition testing complementizers. Error bars represent standard errors (SE).

Fig. 5

Mean response accuracy in nominal phrases by condition, Experiment 4. Sg = the singular numeral, Pl = plural numerals. Error bars represent standard errors (SE).