The Impact of Using Grammarly on Complexity, Accuracy, Fluency, and Self-Efficacy in Iranian EFL Learners’ Argumentative Essay Writing

Articles in Press

Document Type : Research Paper

Authors

1 PhD Candidate at English language department, faculty of humanities, University of Guilan, Iran.

2 associate professor English language department, faculty of humanities, University of Guilan, Iran.

10.22111/ijals.2026.53481.2563

Abstract

Artificial intelligence (AI) is reshaping language education by offering real-time, personalized writing feedback. This study assessed the impact of Grammarly---an AI-powered writing assistant that utilizes advanced natural language processing and generative AI---on the complexity, accuracy, fluency (CAF), and self-efficacy of Iranian EFL students' argumentative writing. One hundred twenty high-intermediate learners from intact classes were screened for proficiency level via Oxford Quick Placement Test and then randomly divided into an experimental group (Grammarly, n=60) and a control group (conventional teacher feedback, n=60). Over 12 weeks, a period deemed necessary for the development of complex writing skills, the experimental group used Grammarly for automated feedback on grammar, vocabulary, and style during weekly writing tasks, while the control group received conventional teacher feedback. The analysis ANCOVA confirmed the Grammarly group achieved significantly greater gains than the control group. These gains were large and significant for complexity, accuracy, fluency, and self-efficacy (all p < .001), with the strongest effect for accuracy. These results align with the CAF framework, indicating AI tools excel most in rule-based domains (e.g., grammar) rather than procedural fluency. The findings underscore Grammarly's value in scaffolding grammatical competence and learner confidence, specifying that the tool is most effective for grammatical scaffolding.

Keywords

Iranian Journal of Applied Language Studies

Articles in Press, Accepted Manuscript
Available Online from 08 January 2026

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