Sentence production in Swahili–English bilingual agrammatic speakers

Abstract

Background: It has been argued that agrammatic speakers' production of sentences in derived order is impaired (The Derived Order Problem Hypothesis, DOP-H), and that the underlying deficit in bilingual individuals with agrammatic Broca's aphasia may cause different surface manifestations in the languages when they differ in terms of their grammatical morphology. The current study presents results of a study on sentence production in Swahili-English bilingual agrammatic speakers. The two languages, Swahili and English, differ significantly in terms of their verbal morphology.

Aims: The current study tested the production of sentences in base and derived orders of arguments in the two languages of Swahili-English bilingual agrammatic speakers.

Methods & Procedures: Eight agrammatic and eight non-brain damaged individuals participated in the study. A sentence elicitation test was used to examine the production of sentences in base and derived word orders in Swahili and English. The base order condition consisted of active and subject-cleft sentences, whereas the derived order condition tested passive and object-cleft sentences.

Outcomes & Results: The non-brain-damaged individuals performed at ceiling in both languages. The agrammatic speakers' results, however, show sentences in derived order condition and were more difficult to produce than those in base order, similarly across the two languages irrespective of their morphological differences. Moreover, the embedded sentences were also more difficult to produce than simple sentences for agrammatic speakers.

Conclusions: The current data partially support the DOP-H and provide new insight into sentence production deficit of bilingual individuals with agrammatic Broca's aphasia. The findings are discussed with respect to the theories of sentence production in agrammatic speakers.

Keywords:

• Bilingual aphasia
• Swahili
• Base order
• Derived order
• DOP-H
• Agrammatism

Acknowledgments

We would like to thank Emma Shah, the administration of the Aga Khan University hospital and all the agrammatic and non-brain-damaged individuals for their contribution towards the success of this study. We also thank Trevor Benjamin and all the anonymous reviewers for their comments on the previous version of this paper.

Notes

¹ In both Swahili and English, the passive sentence is not simply an inversion of the thematic roles, like in sentences with object scrambling: the verb morphology changes into [auxiliary + participle], and the Subject NP becomes a PP (by-phrase). Theories on how this derivation takes place differ largely. What is important for the current study is the fact that he thematic roles are not in base order.

² Ag = agent, V = verb, Th = theme.

³ The eight agrammatic participants had previously participated in a study on sentence comprehension a year earlier (Abuom et al., 2013).

⁴ The term “bilingual” has been used in this study to refer to all those people who use two or more languages or dialects in their everyday lives (Grosjean, 1994).