Sentence comprehension in Swahili-English bilingual agrammatic speakers.

For this study, sentence comprehension was tested in Swahili-English bilingual agrammatic speakers. The sentences were controlled for four factors: (1) order of the arguments (base vs. derived); (2) embedding (declarative vs. relative sentences); (3) overt use of the relative pronoun "who"; (4) language (English and Swahili). Two theories were tested: the Trace Deletion Hypothesis (TDH; [Grodzinsky, Y. (1995). A restrictive theory of agrammatic comprehension. Brain and Language, 50, 27-51]) that assumes a representational deficit in agrammatic aphasia and the Derived Order Problem Hypothesis (DOP-H; Bastiaanse & Van Zonneveld, 2005), which is a processing account. Both theories have the same predictions for sentences in derived order. The difference is that the TDH predicts chance level performance for sentences in which the arguments are not in base order, whereas the DOP-H predicts poorer performance when processing demands increase. The results show that word order influences performance, in that sentences in which the arguments are in derived order are harder to comprehend than sentences in which the arguments are in base order. However, there is a significant interaction with the factor "embedding": sentences with an embedding are harder to comprehend than simple declaratives and this influence is larger in derived order sentences. There is no effect of language nor of the use of a relative pronoun. These results are correctly accounted for by the DOP-H.