This project pertains to the longitudinal dynamic relationship among linguistic performance constructs, such as complexity, accuracy, fluency, and lexis (CAFL) across contexts through a cross-sectional quantitative analysis of corpus and experimental data. Taking a usage-based perspective and drawing on dynamic systems theory (Verspoor & Behrens, 2011), this study explores the dynamic relationship among CAFL constructs to unfold developmental trajectories in English as an L2. Additionally, taking one component of CAFL, syntactic complexity development in the form of subordination, this study looks for empirical evidence for systematicity of interlanguage. By the same token, it aims to create a computerized model to predict L2 performance over CAFL measures in light of different language modalities (e.g., written and spoken), task types, contexts, and proficiency levels.