An investigation into the influence of AI tools on syntactic maturation in EFL writers at selected Vietnamese universities

This study examines the influence of AI-assisted writing tools on the syntactic complexity and writing autonomy of Vietnamese EFL university students. Adopting a quasi-experimental design, the research compared 23 students from Dai Nam University who employed AI tools (e.g., Grammarly, QuillBot, ChatGPT) with 26 students from the Banking Academy of Vietnam who completed equivalent writing tasks without AI support. Quantitative analysis, conducted using the L2 Syntactic Complexity Analyzer (L2SCA), focused on four indices: Mean Length of T-unit (MLT), Clauses per Sentence (C/S), Complex Noun Phrases per Clause (CN/C), and Dependent Clauses per Clause (DC/C). Results showed that the AI-assisted group demonstrated greater gains across all indices, with increases in MLT and CN/C nearing statistical significance (p ≈ .05). Thematic analysis of reflective journals indicated a shift from AI reliance to more autonomous syntactic decision-making. These findings suggest that, when used reflectively, AI writing tools can support syntactic maturation and foster learner autonomy in EFL academic writing. Pedagogical implications for AI integration in non-native English contexts are discussed.