Speech-language therapists are encountering an increasing number of bilingual children with suspected speech sound disorder of unknown origin (SSD). Accurate identification of bilingual children with SSD is a significant challenge because there is a lack of information about the characteristics that constitute typical phonological development in bilingual children. This doctoral thesis aims to provide clinically relevant information about phonological development in Korean-English bilingual (KEB) children. Using a cross-sectional design, single word speech samples were collected from 52 KEB children aged between 3;0 and 7;11 and analysed for phonetic inventories, segmental accuracy and the type of errors produced. The phonetic inventories, segmental accuracy and error productions in KEB children were compared to the available studies in monolingual English-speaking (ME) and monolingual Korean-speaking (MK) children. Twenty-three KEB children of these KEB children were followed up to supplement the findings of the cross-sectional study. Using a correlation study design, this doctoral thesis also examined the potential use of parental report as a tool for a universal speech screen to identify KEB children who require a full clinical assessment by a speech-language therapist. Phonological development in KEB children was qualitatively different from their monolingual counterparts. KEB children produced the type of errors that would be indicative of SSD in monolingual children. The qualitative differences in KEB children could be attributed to cross-linguistic interactions between two phonological systems. Cross-linguistic interactions reflect reorganisation of the two phonological systems wherein a dynamic process of re-specifying learned phonemes and their realisation rules for each language takes place. One manifestation of reorganisation was suggested to be prominent regressions during the course of phonological development. Clinically relevant information could not be obtained by comparing phonological skills and error productions of bilingual children to their monolingual counterparts. The findings in the correlational study mirrored the studies in phonological development in KEB children. A parent-rated measure based on monolingual children identified over 40% of the KEB children as needing a comprehensive clinical assessment by a speech-language therapist. What is considered the appropriate approach for monolingual children may not be applicable for bilingual children. This doctoral thesis suggests specific future research directions to build further evidence for how a universal speech screen may be implemented. This doctoral thesis presents a strong case against the use of available monolingual normative data to identify KEB children with SSD in clinical practice. Bilingual children should be considered fundamentally different from monolingual children in the use and development of their languages. Clinical implications for speech-language therapists working with KEB children with suspected SSD and directions for future research are further discussed.
|Qualification||Doctor of Philosophy|
|Award date||11 May 2016|
|Publication status||Unpublished - 2015|