The effects of task type and word processing on incidental vocabulary learning: an eye-tracking extension of Hill and Laufer (2003)

While research suggests that vocabulary learning through task completion is more effective than direct instruction, the underlying cause of this advantage—whether task involvement load (IL) or time spent on tasks—remains unclear. Extending the work of Hill and Laufer (2003, International Review of Applied Linguistics in Language Teaching , 41 , 87–106), this study examines the effects of IL and employs eye-tracking to investigate how time spent on tasks, target words, and context, as well as regressions to targets, influence incidental vocabulary acquisition. Seventy-three second-language (L2) English learners were randomly assigned to a control ( n = 24) or one of three conditions: reading-only task ( n = 16; low IL), meaning-oriented task ( n = 16; low IL), and form-oriented task ( n = 17; mid IL). Participants completed a pretest, an immediate posttest and a 2-week delayed posttest assessing receptive form knowledge (recognition) and receptive form–meaning relation knowledge (recall and recognition). Eye movement data were collected to measure time on task and processing of target words. Results generally align with the predictions of the IL hypothesis that higher IL led to better learning, and indicate vocabulary acquisition was not solely attributed to time on task. Notably, time spent processing the context was negatively associated with recall of receptive form–meaning relation knowledge (retention), and regressions to the targets negatively affected receptive form knowledge (learning). Methodologically, this study demonstrates the potential of integrating online and offline measures for a deeper understanding of L2 vocabulary acquisition. The findings support the pedagogical value of form-oriented vocabulary tasks, such as fill-in-the-blanks, in enhancing incidental vocabulary learning when tailored to learners’ needs.