Differential diagnosis of phonological disorder in two bilingual children acquiring Italian and English

The need to differentially diagnose children with speech disorder is widely accepted, although how to do this remains controversial. One differential diagnostic framework proposes four subgroups of speech disorder. Investigating the error patterns of bilingual children will validate the existence of subgroups. The subgroups are differentiated in terms of their surface speech error patterns which are thought to reflect different underlying deficits in the speech processing chain. If this hypothesis is true, then bilingual children with speech disorder should show the same type of speech error patterns in each of their languages. The two case studies reported here describe the error patterns of two bilingual 4 year old children who spoke English and Italian. Their disorders were of unknown aetiology. One child presented with an inconsistent phonological system in both languages. The second child made errors that indicated a delay of her phonological development in both languages. The results of their phonological assessments are discussed in terms of current theories about bilingual development and differential diagnosis of phonological disorders. The study identifies the clinical implications for speech-language pathologists.