Investigating the dynamic relationship of lexical and syntactic complexity in L2 writing across proficiency levels: A CDST-inspired study

This study examines the development of lexical and syntactic complexity in L2 writing across five proficiency levels (ST2-ST6) of Chinese EFL learners. Analyzing 3423 essays from the Chinese Learner English Corpus (2003), we employed the Moving-Average Type-Token Ratio and Mean Dependency Distance to measure lexical and syntactic complexity, respectively. Results revealed significant, though non-linear, increase in both measures across proficiency levels. Syntactic complexity showed consistent growth, while lexical complexity plateaued at intermediate levels. A dynamic relationship analysis indicated periods of compensatory growth between lexical and syntactic complexity, particularly at lower proficiency levels. A combined complexity measure demonstrated an overall linear trend with significant non-linear components. These findings, interpreted through the lens of Complex Dynamic Systems Theory , suggest that L2 writing development involves intricate, sometimes competitive interactions between different levels of language proficiency. The study's outcomes have implications for language pedagogy, particularly in informing stage-appropriate instructional strategies and multi-dimensional assessment practices.