Lexical selection in Mandarin-English bilingual speakers

Lee, Yun-Wei and Casaponsa, Aina and Rebuschat, Patrick (2025) Lexical selection in Mandarin-English bilingual speakers. PhD thesis, Lancaster University.

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Abstract

The ongoing debate in bilingualism research revolves the inhibition towards the nontarget language and the required speed to switch to another language. This inhibition has been investigated through various switching-paradigm, whereby suggesting the importance of language proficiency and use. However, given the growing body of bilingual speakers from different background, it is crucial to tap into the magnitude of inhibition and its dynamic nature within different language contexts and exposure. In the current thesis, I examined how language context affects the need of inhibition and how flexibly can bilingual speakers adapt themselves to optimise their language switching efficiency. In Study 1, Mandarin-English bilinguals completed language-switching tasks in different language contexts: (1) “L1-predominant” (most trials named in L1), (2) “L2- predominant” (most trials named in L2) and (3) “Mixed” (trials named half in L1 and half in L2). Based on our findings, I confirmed that switch cost asymmetry does not necessarily emerge during switching, and that the pattern of switch cost can also be modulated by the type of production process. In the production process with pictures named in either language (i.e., top-down processing), the degree of inhibition is dynamic and dependent on the predominant language. In Study 2, I then tested whether this switch cost pattern (asymmetry in the L1- predominant not in L2-predominant) would also emerge in other production-based tasks (here, reading aloud) or whether it was constrained to picture naming. Mandarin ChineseEnglish bilinguals were asked to read aloud Chinese characters and English words. The procedure was otherwise identical, including the context manipulation, but pictures were replaced with words. In contrast to study 1, I did not observe the asymmetry in both contexts. Study 3 tested whether the switch cost patterns (asymmetry in the L1-predominant, not in L2-predominant) would also emerge when participants could prepare for the target language (here, 250ms). Mandarin-English bilinguals saw a cue 250ms before the onset of the target pictures. The context manipulation remained the same. Here, I found different that magnitude of asymmetry was absent in both contexts. Study 4 was set out to investigate the brain activity before speech onset. The results showed that switching to L2 requires greater cognitive demands than switching to L1. To this end, I provide direct evidence with dynamics of inhibition, and importantly the anticipatory ability of the bilingual brain. This suggests that future work should continue to explore the language production processes in bilingual speakers. In summary, the results presented in this thesis demonstrated the flexibility of bilingual speakers when they switch languages. Furthermore, the effect of language context plays a role in bilingual language switching.