Judgment of functional morphology in agrammatic aphasia

Abstract

Individuals with agrammatic Broca's aphasia show deficits in production of functional morphemes like complementizers (e.g., that and if) and tense and agreement markers (e.g., –ed and –s), with complementizers often being more impaired than verbal morphology. However, there has been comparatively little work examining patients’ ability to comprehend or judge the grammaticality of these morphemes. This paper investigates comprehension of complementizers and verb inflections in two timed grammaticality-judgment experiments. In Experiment 1, participants with agrammatic Broca's aphasia and grammatical-morphology production deficits ( n=10) and unimpaired controls ( n=10) heard complement clause sentences, subject relative clause sentences, and conjoined sentences. In Experiment 2, the same participants heard sentences with finite auxiliaries, sentences with finite main verbs, and sentences with uninflected verbs. Results showed above-chance accuracy in aphasic participants’ judgments for complementizer sentences in Experiment 1, but chance performance for verb inflections in Experiment 2. This pattern held regardless of whether the verb inflections were affixes or free-standing auxiliaries. Implications of these results for theories of agrammatic morphological impairments, including feature underspecification accounts [Wenzlaff, M., & Clahsen, H. (2004). Tense and agreement in German agrammatism. Brain and Language, 89, 57–68; Burchert, F., Swoboda-Moll, M., & De Bleser, R. (2005a). Tense and agreement dissociations in German agrammatic speakers: Underspecification vs. hierarchy. Brain and Language, 94, 188–199] and hierarchical structure-based accounts [Friedmann, N., & Grodzinsky, Y. (1997). Tense and agreement in agrammatic production: Pruning in the syntactic tree. Brain and Language, 56, 397–425; Izvorski, R., & Ullman, M. (1999). Verb inflection and the hierarchy of functional categories in agrammatic anterior aphasia. Brain and Language, 69, 288–291], are discussed.