Effects of task complexity and task condition on Chinese EFL learners’ word engagement and incidental vocabulary learning

Abstract Despite numerous studies on the effect of task complexity on language learning, little attention has been paid to incidental vocabulary learning (IVL). This study examined the combined effects of task complexity (i.e., simple vs. complex) and task condition (i.e., individual vs. collaborative) on Chinese EFL learners’ word engagement and IVL. Participants ( n = 84) were assigned to individual or collaborative groups to complete two decision-making tasks of varying complexity and then underwent immediate and delayed vocabulary post-tests. The collected data were analyzed and revealed the following results: 1) The complex task triggered learners’ word engagement and facilitated their immediate meaning recognition; 2) While types and frequency of word engagement varied between groups during task performance, collaboration consistently promoted IVL; and 3) notably, a significant interaction showed that collaboration improved learners’ immediate meaning recall in the complex task, with both groups performing similarly in the simple task. These findings provided new insights into IVL and suggested pedagogical implications.