Identifying ChatGPT-generated texts in EFL students’ writing: Through comparative analysis of linguistic fingerprints

The emergence of generative AI (GenAI) poses new challenges for L2 writing teachers. This study investigates the distinguishability of essays written by Japanese EFL learners from those generated by ChatGPT. Partially replicating Herbold et al. (2023), 140 first-year university students wrote essays and completed a survey on ChatGPT use. Among them, 125 wrote independently, 13 used ChatGPT for proofreading, and two asked ChatGPT to write the entire essay. To create a comparative dataset, 123 additional essays were generated by ChatGPT, imitating the two texts. The resulting 263 essays were then analyzed using the natural language processing (NLP) technique, including automated linguistic analysis and machine learning classification using random forest. The results reveal significant differences between human-written and ChatGPT-generated essays across all linguistic features, with the latter being easily identifiable. This study emphasizes the need for clear guidelines on the ethical use of AI in L2 writing, highlighting the potential risk of inappropriate AI use and the importance of fostering a mutual understanding of AI use with learners regarding responsible AI integration in academic work.