The developmental dynamics of complexity, accuracy, and fluency in advanced Chinese EFL learners’ oral production

The study traced the development and interactions of complexity, fluency, and accuracy (CAF) in the oral production of six advanced Chinese EFL learners over a semester, adopting a Complex Dynamic Systems Theory perspective. Employing six progressive-sensitive CAF indices, we examined group-level trajectories as well as individual variation and variability. CAF development at the group level was asynchronous and non-linear, characterized by distinct trends. Specifically, lexical diversity displayed a fall-rise pattern, shifting from a decline to an increase. In contrast, overall syntactic complexity declined. Accuracy progressed with an overall improvement, while fluency demonstrated a decreasing trend. Individually, the interactional patterns diverged further: fluency and syntactic complexity often supported each other while accuracy competed with either syntactic complexity or fluency. The developmental paths and interactions were influenced by cognitive trade-offs, learners’ L2 proficiency, educational context, and fatigue. These findings corroborate CDST tenets that L2 oral development is non-linear and adaptive, implying the need for pedagogical approaches that accommodate individual variability through targeted instruction and feedback.