Performance of adult aphasics on a sentence evaluation and revision task.

Adult aphasics completed a sentence evaluation and revision task to test some aspects of their linguistic competence. Grammatical and ungrammatical sentences served as the stimuli. Ungrammatical sentences were characterized by violations of syntactic or semantic structure, or both. Aphasics evaluated correctly the grammaticality of most stimulus sentences. Incorrect evaluations were associated with sentences characterized by violations of syntactic structure. Aphasics' revisions of sentences that they judged to be ungrammatical were in the direction of appropriate grammatical structures. Omission of morphological endings was the most frequent sentence revision error. Aphasics' errors on both tasks could be accounted for by performance deficits such as inattentiveness to syntactic detail, auditory perceptual impairments, and inefficient lexical retrieval. These findings lend support to the argument that aphasia is best characterized as a performance rather than competence disruption.