First-language use in English interlanguage: a multi-CEFR-level spoken learner corpus analysis of Taiwanese learners

Abstract This study explores the phenomenon of Chinese-English code-switching in interviews with 116 Taiwanese learners across proficiency levels within the Common European Framework of Reference ( CEFR ; Council of Europe. 2020. Common European Framework of Reference for Languages: Learning, teaching, assessment companion volume . Strasbourg: Council of Europe Publishing). The learner corpus data were extracted from the Taiwanese sub-corpus (Huang, Lan-fen. 2014. Constructing the Taiwanese component of the Louvain International Database of Spoken English Interlanguage (LINDSEI) . Taiwan Journal of TESOL 11(1). 31–74) of the Louvain International Database of Spoken English Interlanguage ( LINDSEI ; Gilquin, Gaëtanelle, de Cock Sylvie & Sylviane Granger (eds.). 2010. LINDSEI Louvain International Database of Spoken English Interlanguage . Handbook and CD-ROM . Louvain-la-Neuve: Presses universitaires de Louvain) and its expanded data (Huang, Lan-fen & Tomáš Gráf. 2021. Expanding LINDSEI to spoken learner English from several L1s across CEFR levels. Corpora 16(2). 271–285). The analysis of relative code-switching frequencies revealed a consistent decline from A1 to C1, indicating that as proficiency increased, L1 use declined. Kruskal-Wallis tests presented clear evidence of a difference between higher (B2 and above) and lower (B1 and below) levels. The functions of Chinese use were explored and interpreted on the basis of empirical evidence within their immediate context, following the taxonomy of linguistic functions proposed by Kaneko, Tomoko. 2009. Use of mother tongue in English-as-a-foreign-language speech by Japanese university students. Gakuen 822. 25–41. By analysing a CEFR -rated Taiwanese learner corpus, this study provides practical insights showing how L1 use evolves with proficiency. It also proposes alternatives: English expressions and appropriate communication strategies to address referential code-switching, which probably stems from learners’ limited proficiency. These findings yield practical suggestions and linguistic examples to support English language teachers working with Chinese-speaking learnerss.