Multilingual Speech Acquisition by Vietnamese-English–Speaking Children and Adult Family Members

Purpose: This article presents a large-scale example of culturally responsive assessment and analysis of multilingual Vietnamese-English–speaking children and their family members using the VietSpeech Protocol involving (a) examining all spoken languages, (b) comparing ambient phonology produced by family members, (c) including dialectal variants in the definition of accuracy, and (d) clustering participants with similar language experience. Method: The VietSpeech participants ( N = 154) comprised 69 children (2;0–8;10 [years;months]) and 85 adult family members with Vietnamese heritage living in Australia. Speech was sampled using the Vietnamese Speech Assessment (Vietnamese) and the Diagnostic Evaluation of Articulation and Phonology (English). Results: Children's Vietnamese consonant accuracy was significantly higher when dialectal variants were accepted (percentage of consonants correct–dialect [PCC-D]: M = 87.76, SD = 8.18), compared to when only Standard Vietnamese was accepted as the correct production (percentage of consonants correct–standard [PCC-S]: M = 70.34, SD = 8.78), Cohen's d = 3.55 (large effect). Vietnamese voiced plosives, nasals, semivowels, vowels, and tones were more often correct than voiceless plosives and fricatives. Children's Standard Australian English consonant accuracy (PCC-S) was 82.51 ( SD = 15.57). English plosives, nasals, glides, and vowels were more often correct than fricatives and affricates. Vietnamese word-initial consonants had lower accuracy than word-final consonants, whereas English consonant accuracy was rarely influenced by word position. Consonant accuracy and intelligibility were highest for children with high proficiency in both Vietnamese and English. Children's consonant productions were most similar to their mothers' than other adults or siblings' productions. Adults' Vietnamese consonants, vowels, and tones were more likely to match Vietnamese targets than their children's productions. Conclusions: Children's speech acquisition was influenced by cross-linguistic, dialectal, maturational, language experience, and environmental (ambient phonology) factors. Adults' pronunciation was influenced by dialectal and cross-linguistic factors. This study highlights the importance of including all spoken languages, adult family members, dialectal variants, and language proficiency to inform differential diagnosis of speech sound disorders and identify clinical markers in multilingual populations. Supplemental Material: https://doi.org/10.23641/asha.23290055