SENTENCE COMPLEXITY IN EFL LEARNERS’ WRITING: A SYNTACTIC ANALYSIS OF UNIVERSITY STUDENTS’ COMPOSITIONS

This quasi-experimental study investigates the impact of explicit instruction in critical thinking (CT) on the syntactic complexity of English as a Foreign Language (EFL) students' argumentative writing. Specifically, it explores whether teaching CT enhances the use of complex sentence types, namely compound, complex, and compound-complex sentences, as indicators of higher-order thinking skills (HOTS). Intact EFL classes (N = 100), randomly assigned to experimental and control groups, participated in a pre-test and post-test design. The experimental group received CT instruction embedded within their writing course, while the control group followed a standard curriculum. Syntactic complexity was measured using metrics such as Mean Length of Sentence (MLS), number of clauses per sentence, and frequency of complex sentence types (compound, complex, and compound-complex). Post-test results revealed that the experimental group significantly outperformed the control group in all complexity measures. Specifically, the experimental group demonstrated higher mean sentence length, t(98) = 8.87, p < .001, d = 1.78; more clauses per sentence, t(98) = 10.12, p < .001, d = 2.03; greater use of complex sentences, t(98) = 7.21, p < .001; and compound-complex sentences, t(98) = 6.47, p < .001. These findings suggest that explicit CT instruction fosters not only higher-order thinking but also measurable syntactic development, highlighting a strong link between cognitive and linguistic complexity in EFL writing.<p> </p><p><strong> Article visualizations:</strong></p><p><img src="/-counters-/soc/0423/a.php" alt="Hit counter" /></p>