Research has suggested that bilinguals often demonstrate advantages over monolinguals in additional language learning. However, this appears less evident among Chinese Tibetan bilinguals, who are labeled as underachievers in English (L3) learning. This study investigated how L2 Chinese proficiency and L3 motivation shaped 450 Tibetan secondary school students' L3 English achievement, adopting a concurrent mixed-methods design informed by the theoretical framework of Motivational Self System. Structural equation modelling results showed that L2 Chinese proficiency was a positive predictor of L3 English achievement. Among the motivational variables, the L3 Learning Experience had a positive predictive effect, Ought to L3 Self had a negative effect, and Ideal L3 Self was not a significant predictor. Interview results supported these findings and revealed that the L3 Learning Experience had facilitative and constraining effects on achievement, the Ought to L3 Self was associated with diminished engagement, and the Ideal L3 Self rarely translated into language success. Additionally, L2 Chinese exerted both enabling and limiting effects, which were not fully within learners' conscious awareness. The pedagogical implications of this study are discussed.
Yang et al. (Thu,) studied this question.