Generative AI (GenAI) is increasingly used in academic writing, yet its effects on students' writing self-efficacy remain contingent on how assistance is configured. This pilot study investigates how ideation-level, sentence-level, full-process, and no AI support differentially shape undergraduate writers' self-efficacy using a 2 by 2 experimental design with Korean undergraduates completing argumentative writing tasks. Results indicate that AI assistance does not uniformly enhance self-efficacy full AI support produced high but stable self-efficacy alongside signs of reduced ownership, sentence-level AI support led to consistent self-efficacy decline, and ideation-level AI support was associated with both high self-efficacy and positive longitudinal change. These findings suggest that the locus of AI intervention, rather than the amount of assistance, is critical in fostering writing self-efficacy while preserving learner agency.

翻译：生成式人工智能（GenAI）在学术写作中的应用日益广泛，但其对学生写作自我效能感的影响仍取决于辅助方式的配置。本试点研究采用2×2实验设计，以韩国本科生完成议论文写作任务为对象，探究构思层面、句子层面、全流程及无AI支持四种模式如何差异化影响写作者的自我效能感。结果表明：AI辅助并非统一提升自我效能感——全流程AI支持虽产生较高但稳定的自我效能感，同时伴随自主性降低的迹象；句子层面AI支持导致自我效能感持续下降；而构思层面AI支持则与高自我效能感及积极的纵向变化相关。这些发现表明，AI干预的着力点（而非辅助量）对于在保持学习者能动性的同时培养写作自我效能感至关重要。