Critical Thinking in a GenAI World: Evaluating the Efficacy of ChatGPT-Assisted Essay Writing in ESL Classrooms

Abstract

The brisk integration of Generative Artificial Intelligence (GenAI), particularly Large Language Models (LLMs) like ChatGPT, has fundamentally disrupted educational paradigms, specifically second language acquisition (SLA) and English as a Second Language (ESL) writing instruction. While GenAI tools offer unparalleled scaffolding for grammar, vocabulary generation, and structural organisation, their impact on higher-order cognitive skills remains highly contested. This study evaluates the empirical efficacy of ChatGPT-assisted essay writing in university-level ESL classrooms, focusing specifically on its effects on students’ critical thinking (CT) skills. Using a mixed-methods convergent parallel design over a 15-week academic semester, this study examined $N = 124$ undergraduate ESL students split into an experimental group (utilising ChatGPT as a structured co-writing and dialogue partner) and a control group (utilising conventional process-writing methodologies). Quantitative data were gathered using pre- and post-test assessments scored via a validated Critical Thinking Rubric (evaluating argument analysis, evidence evaluation, alternative perspectives, and bias recognition) along with automated linguistic analysis of student essays. Qualitative data were obtained via semi-structured focus group interviews and student reflective journals. The quantitative findings indicate that while the experimental group demonstrated significant improvements in surface-level linguistic accuracy, lexical density, and structural cohesion, their independent scores in evidence evaluation and independent thesis formulation were statistically lower than those of the control group when ChatGPT assistance was removed in unassisted proctored post-tests ($p < .05$). The qualitative thematic analysis revealed a phenomenon termed "cognitive outsourcing," where students routinely accepted AI-generated assertions without epistemological verification. However, a sub-cohort trained in aggressive prompt engineering and dialectical inquiry demonstrated elevated critical engagement. This paper proposes a “Dialectical AI-Scaffolding Framework” designed to shift ChatGPT from a product-generation tool to an intellectual sparring partner, ensuring that GenAI advances rather than compromises critical thinking in ESL pedagogy.