The Role of Individual Differences in Task Complexity and Language Performance: A Systematic Literature Review Protocol

Task complexity has become a central focus in task-based language teaching, grounded in theoretical frameworks such as the Cognition Hypothesis and the Trade-off Hypothesis. Empirical studies have examined how increasing task complexity impacts learners’ language performance; however, findings remain mixed due to differences in task operationalization, measurement, and contextual factors. Synthesizing existing evidence is therefore necessary to identify broader patterns in how task complexity influences language learning and production, specifically regarding the individual difference (ID) variables. Consequently, this study will explore IDs and their roles as investigated within task complexity and language pedagogy scholarship. The study will be both SMART and PRISMA compliant. Scopus, Web of Science, and ProQuest will be accessed to obtain data on primary research published between 2004 and 2026. The predefined eligibility criteria and codebook will guide the screening and data extraction process, respectively. The Theory, Context, Characteristics, Methodology (TCCM) framework will be employed to systematically document and interpret the eligible empirical evidence. This study will inform researchers, task designers, curriculum designers, and task-based language teaching practitioners.