Agrammatic aphasic production and comprehension of unaccusative verbs in sentence contexts

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Abstract

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.

Section snippets

Subjects

Aphasic subjects. Eight English-speaking agrammatic aphasic subjects (two females and six males; mean age=58.8 years) participated in the study. They were recruited from the subject pool of the Northwestern University Aphasia and Neurolinguistics Research Laboratory. All subjects were right-handed, with the exception of two males, and had at least a high-school education (mean=17 years). None of the subjects had a history of prior neurological disease, drug or alcohol abuse, psychiatric

Results

Mean percentage correct performance of subjects on comprehension and production tasks is shown in Table 2. A repeated measures three-way ANOVA revealed significant differences between the two tasks and between the two sentence types: subjects performed better on the comprehension task than on the production task (F(1,11)=11.562, p=0.006). They also showed better performance on unergative sentences than on unaccusatives (F(1,11)=11.957, p=0.005). There were also significant interaction effects

Discussion

Results from this study examining production of intransitive verbs in sentences were consistent with previous studies by Thompson, 2003, Kegl, 1995 showing that unaccusative intransitive verbs are selectively disrupted in agrammatic aphasic subjects. Specifically, as with single verbs, sentences involving unaccusative verbs presented production difficulty for agrammatic aphasic subjects, while those involving unergatives did not. This finding supports Kegl's Syntactically Enriched Verb Entry

Conclusion

Results of this study provide further evidence that agrammatic aphasic subjects have selective impairment in production of verbs, and that the complexity of the verbs' argument structure accounts for the impoverished sentence production observed in these subjects. Unaccusative verbs have a more complex argument structure than unergative verbs in terms of the type of argument, and thus present agrammatic subjects with more difficulty in sentence production. This difficulty, however, does not

Acknowledgments

This research was supported by the National Institute of Health grant DCo 1948. The authors acknowledge Mike Dickey, Yasmeen Faroqi-Shah, Steven Fix and Naomi Hashimoto for their assistance with data collection and analysis. We also thank William O’ Grady for his insightful comments on the earlier versions of this work. Our special thanks go to all individuals with aphasia who participated in this study.

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