The book provides a systematic investigation of the dynamic trajectories in the oral language development of English as a foreign language (EFL) learners, integrating both inter-individual variation and intra-individual variability. It also identifies unobserved heterogeneity in oral language production.

Using longitudinal designs, comprehensive developmental data collection, and innovative analytic techniques, the study reveals distinct developmental trajectories in the oral language systems of EFL learners. It also examines the interactions among complexity, accuracy, and fluency (CAF), exploring the potential of complex dynamic systems theory (CDST)-inspired approaches to studying oral language development and their implications for teaching oral language to Chinese learners. In addition, by employing the novel growth mixture model (GMM) method, the study identifies salient developmental patterns of CAF within a larger population, thereby contributing to the generalizability of findings from CDST-based language development research.

This book will be valuable to students, researchers, and educational practitioners interested in oral language development and complex dynamic systems theory.

Hanjing Yu is an associate professor at School of Foreign Languages at Dalian University of Technology, China. Her research focuses on complex dynamic system theory and second language development.