Agrammatic aphasic production and comprehension of unaccusative verbs in sentence contexts

This study examined the Argument Structure Complexity Hypothesis (ASCH, [J. Neuroling. 16 (2003) 151]), by investigating agrammatic aphasic comprehension and elicited production of two types of intransitive verbs (i.e. unergatives and unaccusatives) in sentence contexts. The ASCH attributes production difficulty frequently observed in agrammatic aphasia to the argument structure entries of verbs, stating that verbs with a more complex argument structure (in terms of the number and type of arguments) are more difficult for agrammatic aphasic patients to produce than those with a less complex argument structure. Results showed that eight agrammatic aphasic subjects had production difficulty with unaccusative verb sentences, as compared to unergatives, in the face of near-normal comprehension of both sentence types. These findings support the ASCH that predicts production difficulty with sentences involving unaccusatives with more complex argument structures. Error patterns observed also indicated successful lemma access in that the full array of verb argument structures were produced during sentence attempts, suggesting that complex argument structures hinder appropriate processing after the lemma level.