The development of morphological error patterns of monolingual Dutch and bilingual Turkish-Dutch children with and without a Developmental Language Disorder
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Background: Morphology is often seen as a clinical marker (i.e. a characteristic point of difficulty) of Development Language Disorder (DLD) in monolingual children. Previous studies have reported overlap in the difficulties bilingual TD (Typical Development) children and monolingual children with DLD have with morphology. As a result, it is uncertain whether morphology can be used to help identify DLD in bilingual children. Aim: The aim of this thesis is to identify the effects of DLD and bilingualism on the development of the morphological error patterns of monolingual Dutch and bilingual Turkish-Dutch children with and without a Developmental Language Disorder. Method: Longitudinal data of Dutch monolingual and bilingual Turkish-Dutch children with and without DLD (n = 10 per group) between the ages of 5 to 7 years was collected during three yearly sessions. At each session, children’s spontaneous language was recorded during a semi-structured interview and narrative task. For each child, the morphological errors in verb inflection, determiners, adjectives, plural nouns and prepositions were coded based on error types (i.e. substitution, omission or other errors). Results: The absolute error numbers showed that the children with DLD were more likely than TD children to make omission errors rather than substitution errors in each session in the verb inflection and the noun phrase feature categories. However, this difference between TD and DLD were only consistently significant in the verb inflection category. The omissions to total errors proportions showed a number of longitudinal effects. There was a significant effect of bilingualism in children with DLD and a significant effect of DLD in bilingual children. The bilingual children with DLD had a larger decrease in omission proportions than the monolingual children with DLD over the course of the experiment. However, the bilingual group with DLD had consistently higher omission proportions than the bilingual TD group and the monolingual group with DLD. Conclusion: There is evidence that longitudinal error patterns involving verb inflection, noun phrase features and prepositions could help distinguish DLD from TD in bilingual children.