Abstract
In second language acquisition research, the psychological factors associated with language learning have been a prominent focus. The affective turn in and introduction of positive psychology in this field have further boosted research on the roles of positive learner psychological factors (e.g. motivation) in performance (e.g. engagement). However, the theoretical lens for investigating these variables requires further clarification, and the roles of some variables (e.g. boredom) in language learning have been under-researched. Guided by this background, this study aims to explore the complex relationships between learners' basic psychological needs, self-determined motivation, boredom and behavioural engagement among 687 Chinese senior high school EFL learners from the perspective of self-determination theory (SDT). Quantitative data collection and analysis revealed that students' basic psychological needs directly predicted behavioural engagement. Basic psychological needs also indirectly predicted behavioural engagement through the simple mediation of boredom and the chain mediation of self-determined motivation and boredom. However, the simple mediation of self-determined motivation in the relationship between basic psychological needs and behavioural engagement was non-significant. The findings enrich the application of SDT in the language learning engagement research, providing valuable implications for teachers and educators.