This study examined the read speech of vowel length contrasts produced by Cantonese-English-German trilinguals, comparing their performance with that of Mandarin-English-German trilinguals, Cantonese-English bilinguals, native English speakers, and native German speakers. Acoustic and statistical analyses of vowel quality and duration across the first language (L1), second language (L2), and third language (L3) yielded several key findings. First, Cantonese-speaking trilinguals were more nativelike than the Mandarin-speaking trilinguals in both the L2 and L3, indicating that the L1 exerts a sustained influence across the multilingual system. Second, Cantonese-English-German trilinguals differed from Cantonese-English bilinguals in the L2 but not the L1, suggesting that reverse transfer from the L3 more strongly affects the L2 than the L1. Finally, individuals who produced larger quality contrasts in L2 vowel length distinctions also demonstrated greater quality contrasts in comparable L3 vowels, whereas those who produced larger duration contrasts in the L1 exhibited reduced duration contrasts in analogous L3 vowels, indicating that L1-L3 and L2-L3 bidirectional interactions emerge among phonetically similar vowels. The study highlights the dynamicity of the multilingual phonological system.
Zhu et al. (Tue,) studied this question.