This investigation examined the critical intersection between vocabulary instruction timing and communicative task engagement in foreign language acquisition. The research systematically analyzed how strategic vocabulary support at various intervention points influences not only lexical retention but also learner engagement patterns and affective responses during interactive language tasks.

Employing a rigorous experimental design, participants were assigned to distinct treatment conditions where vocabulary scaffolding was provided at pre-task, during-task, post-task, or control conditions. The methodology integrated quantitative assessment of vocabulary acquisition with qualitative discourse analysis to capture engagement markers such as negotiation of meaning, clarification requests, and self-correction behaviors. This approach allowed for comprehensive examination of the relationship between instructional support and learning outcomes.

The findings revealed that the strategic timing of vocabulary support significantly impacts both immediate task performance and subsequent vocabulary retention. Detailed discourse analysis demonstrated that certain intervention led to deeper cognitive processing and sustained engagement with target vocabulary. Furthermore, the research identified a systematic relation between specific engagement indicators and vocabulary learning outcomes, suggesting that optimally timed lexical support creates a virtuous cycle of engagement and learning.

These empirical findings make a substantial contribution to task-based language teaching by establishing evidence-based guidelines for vocabulary instruction sequencing. Preliminary results from this research program were presented as an invited talk at an international symposium on second language acquisition.