Production latencies of morphologically simple and complex verbs in aphasia

Abstract

There are several accounts of why some individuals with post-stroke aphasia experience difficulty in producing morphologically complex verbs. Although a majority of these individuals also produce syntactically flawed utterances, at least two accounts focus on word-level encoding operations. One account proposes a difficulty with rule-governed affixation, predicting that verbs without affixes (stems and irregular past) should be produced with ease. The second account emphasises the contribution of phonological encoding, noting that morphological complexity is often confounded by phonological complexity. The present study investigated the effect of morphological complexity (presence vs. absence of affixes) on verb production when phonological complexity and lexical frequency was controlled. A novel delayed repetition paradigm was used, accuracy and latency of production were the dependent measures. Data from nine agrammatic aphasic and nine unimpaired participants revealed no effects of morphological complexity, but a significant effect of frequency on production latency. The results indicate that morphological complexity plays little role, if any, in production difficulty, at least for this experimental task and this group of non-apraxic agrammatic aphasic individuals. A difficulty in usage of contextually appropriate verb inflections, rather than in morphophonological encoding, is suggested.

• agrammatism
• dual route model
• phonology

Acknowledgements

This research is supported in part by an American Speech-Language Hearing Foundation award in 2001, and a Graduate Research Grant from Northwestern University in 2003 to the author, and by the National Institutes of Health (NIDCD) grant # DC-01948-13 to Cynthia K. Thompson. This research was completed as part of the first author's doctoral dissertation. Preliminary results of this study were presented at the Annual Meeting of the Academy of Aphasia at Vienna, Austria in 2003. The author wishes to thank Alyssa Maultasch and Emily Schuster for data analysis including latency timing and computing inter-rater reliability.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Notes

1. Normal vision is 20/20. 20/40 indicates that the person can read letters twice as large as those on the 20/20 line.

2. All participants were pre-tested for comprehension of temporal adverbs by asking them to point to yesterday, today, tomorrow, next month etc. on a calendar.

3. Simple present verbs (Verb+s) were not used because of noun-verb ambiguity (e.g. cooks) and paucity of sufficient high frequency exemplars.

4. There were also 10 nouns matched in CV structure to a random set of stimuli (e.g. raft - wrapped). These served as fillers and were not matched for frequency of occurrence.