PhD ceremony Mr. T.O. Abuom: Verb and word order deficits in Swahili-English bilingual agrammatic speakers

PhD ceremony: Mr. T.O. Abuom, 11.00 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Verb and word order deficits in Swahili-English bilingual agrammatic speakers

Promotor(s): prof. Y.R.M. Bastiaanse

Faculty: Arts

Tom Abuom’s dissertation focuses on the patterns and severity of verb inflection and word-order deficits in Swahili-English bilingual individuals with agrammatism. Agrammatism, also known as agrammatic aphasia, is a language disorder caused by damage to areas of the brain involved in language processing, especially in the frontal regions of left hemisphere. Individuals with agrammatism (agrammatic speakers), especially monolinguals, are known to have difficulties with sentences that refer to a past event through verb inflection and sentences in derived word order. For instance, sentences such as (for time reference to the past) “yesterday, the man picked a flower” and (for derived order) “the girl is kissed by the boy” are more problematic than sentences such as (for time reference to the present) “Now the man is picking a flower” and (for base word order) “the boy is kissing the girl”.

This dissertation investigated how these difficulties are manifest in agrammatic speakers of a previously undescribed language, Swahili and who, furthermore, are bilinguals speaking two morphologically different languages. Swahili is a morphologically rich Bantu language whereas English is an impoverished Indo-European language. The results demonstrate significant effects of time reference (reference to a past event is impaired), word order (production and comprehension of derived order sentences is impaired) and embedding (production and comprehension of sentences with embedded clauses such as “the girl who is kissing the boy is tall” is impaired) on the performance patterns of bilingual agrammatic speakers across their two languages. The similar pattern of impairment in both languages (Swahili and English) irrespective of their morphological differences suggests the two languages are represented in shared processing regions of the bilingual brain. The results, further, demonstrate that bilingual Swahili-English agrammatic speakers are not clinically very different from monolingual agrammatic speakers in terms of how their language production and comprehension are affected following brain damage.