Selective treatment of regular versus irregular verbs in agrammatic aphasia: Efficacy data

Abstract

Background: Production of verb morphology, especially tense marking, is frequently impaired in persons with agrammatic aphasia. Very little research has examined theoretically driven treatments for verb morphology deficits in aphasia.

Aims: This study examined the relative efficacy of using regular (wash-washed, rob-robbed) versus irregular (drink-drank, keep-kept) verbs as stimuli to treat morphological impairments in individuals with aphasia. This comparison was motivated by differences in the lexical organisation of regular and irregular verbs proposed in psycholinguistic theory.

Methods & Procedures: A single-participant multiple-baseline design was used to examine treatment outcomes in six individuals with agrammatic aphasia. Participants received training to produce tense morphology using only either regular or irregular verbs, and the crucial outcome measure was generalisation to untrained past tense forms (regular to irregular and vice versa).

Outcomes & Results: All participants improved in the trained tenses and generalised to the production of regular tense morphology on untrained verbs. Generalisation to untrained irregular past tense was relatively modest, irrespective of whether regular or irregular verbs were trained.

Conclusions: The results replicate previous findings that verb morphology deficits respond to intervention, and extend the findings by suggesting that choice of stimuli may have consequences for generalisation effects. The implication for aphasia rehabilitation is that tense training using irregularly inflected verbs generalises to a greater variety of untrained verb inflections (including regular past) than does the use of regular verbs.

Keywords:

• Aphasia
• Brain damage
• Inflection
• Morphology
• Language production
• Treatment efficacy
• Verb

Acknowledgments

This project was supported by General Research Board award from the University of Maryland to YF-S. The author wishes to thank all the participants and their families for their participation and support for this research. Special thanks to students who helped with various stages of data collection and analyses (listed alphabetically): Heather Alexander, Sarah Camponeschi, Isabelle Dunn, Xiomy Esteban, Lauren Graham, Melissa Graham, Jessica Greenberg, Jen Maultasch, Rachel Mont, Monica Sampson, Mohan Singh, and Pascale St. Victor. Partial findings of this study were presented at the Clinical Aphasiology Conference (2008) and the Annual Convention of the American Speech Language and Hearing Association (2008).

Notes

¹ Exceptional situations where regular forms may be stored include very high frequency forms (Alegre & Gordon, 1999). Conversely, nonword past tense generation tasks suggest the existence of subregular schemas for irregular verbs that are partially based on phonological form (Bybee & Slobin, 1982; Stemberger, 2002).

² All participants were pre-tested for comprehension of temporal adverbs using a calendar pointing task, on which they had to identify yesterday, today, tomorrow, next month, etc.

³ Given that the primary purpose of the Faroqi-Shah (2008) study was to compare the relative efficacy of morphosemantic and morphophonological treatments, oral production was minimised for morphosemantic treatment to preclude any morphophonological practice. The same protocol was repeated for the current study although the lack of oral practice has no direct implications for the research questions in the current study. Fidelity with the treatment protocol between studies serves to replicate and extend the findings of Faroqi-Shah (2008).

⁴ In cases of zero-standard deviation during baseline, Busk and Serlin (1992) proposed calculation of standard deviation by combining baseline and follow-up scores if both phases have similar performance. Since P4 improved significantly following treatment, Busk and Serlin's condition for calculation of pooled standard deviation was not met.