The dynamics of changes in linguistic complexity and writing scores in timed argumentative writing among beginning-level EFL learners

Abstract This study investigates longitudinal changes in linguistic complexity and holistic scores in EFL timed argumentative writing among beginning-level learners using Complex Dynamic Systems Theory. It also explores relationships among linguistic complexity over time and with writing scores. Over nine months, 42 Japanese EFL learners completed six timed essays. Linguistic complexity was assessed through lexical, phraseological, and syntactic features. Findings indicate linear growth in writing scores, lexical sophistication, and noun phrase (NP) complexity, alongside stable phrasal complexity and non-linear subordination. Interrelated growth patterns included connections between lexical sophistication and phrasal complexity, and phraseological complexity and subordination. Competitive dynamics were observed between lexical diversity and NP complexity, and phraseological complexity and phrasal sophistication. Linear associations emerged between writing scores and lexical sophistication or syntactic complexity, while a non-linear relationship occurred with phraseological sophistication. This study illuminates the intricate dynamics of linguistic complexity and L2 writing scores among beginning-level learners in argumentative writing.