This study examined the association between task-based language instruction and critical thinking development among tertiary English language learners through systematic analysis of scholarly writing. Using the University of Pittsburgh English Language Institute Corpus (PELIC), we analyzed 3,500 essays from 1,000 international students across five proficiency levels (2015–2020). Critical thinking was operationalized through argumentation complexity, counterargument independence, evaluative language density, and evidence integration quality. Four pedagogical task types—argumentative essays, analytical reports, reflective writing, and problem-solving exercises—were analyzed for cognitive complexity, openness, interactional demands, and authenticity. Statistical analysis employed hierarchical linear modeling, growth curve analysis, and moderation analysis. Results showed argumentative tasks produced the strongest critical thinking improvements ( d = 0.78), while analytical essays enhanced logical reasoning ( d = 0.65). Cognitive complexity emerged as the most potent predictor, explaining 31% of variance ( R 2 = .31), followed by task openness ( R 2 = .24). Longitudinal analysis revealed non-linear developmental patterns best captured by quadratic growth models (ΔAIC = −45). Cultural background significantly moderated outcomes, with East Asian students showing steady incremental progress while Middle Eastern students exhibited more heterogeneous developmental trajectories, potentially reflecting diverse rhetorical traditions within this broad regional category. These findings provide correlational evidence supporting task-based pedagogical approaches for critical thinking development, suggesting that cognitive complexity and specific design features are associated with improved learning outcomes across diverse student populations. As this study employs an observational design, these associations should be interpreted as suggestive rather than causal.
X. H. Zhang (Thu,) studied this question.