Causal inference is a fundamental goal of many research endeavors, including scholarship in the field of language education and learning. Randomized controlled trials are considered an ideal design to test causal claims, but not all claims can be subjected to experimental treatment due to ethical and practical constraints. In this article, we…

This study examined the relationship between complexity, accuracy and fluency (CAF), using longitudinal data. Conducted from the perspective of complex dynamic systems theory (CDST), this research adopted four CAF general measures to track the development of five Chinese undergraduates' English speech over a 15-week period. LOWESS graphs supported…

In this article, we highlight the important achievements of the editors and contributors in this special issue. We argue that this collection of studies on individual differences (IDs) advances the field in terms of theoretical diversification, methodological improvement, and pedagogical innovation. We also contend that a renewed interest in ID…