DeepSeek-Assisted EFL Writing: A Longitudinal Case Study of a Chinese High School Learner’s Writing Accuracy, Complexity, and Motivation

Abstract

—This longitudinal single-case study investigates the impact of DeepSeek, a Chinese-developed Large Language Model (LLM), on the English writing development and motivation of a Chinese EFL learner aged 15. Given the increasing importance of written communication in international professional contexts, particularly through email, improving writing proficiency has become a key objective for many Chinese EFL (English as a Foreign Language) students. With AI tools readily accessible to Chinese learners, they offer interactive feedback and writing assistance that may enhance both writing performance and learner engagement. This study examines changes in the learner’s writing complexity and accuracy through quantitative analysis, as well as shifts in motivation through qualitative data. The findings indicate that sustained use of DeepSeek contributed to improvements in written accuracy and linguistic complexity. In addition, the learner reported increased motivation, confidence, and engagement in the writing process due to the immediate feedback and collaborative interaction provided by the AI tool.