Incidental vocabulary learning from information-gap tasks

Meaning-focused output tasks are central to communicative language teaching, yet their potential for incidental vocabulary acquisition (IVA) remains underexplored in EFL contexts. This study investigated whether a 15-minute information-gap speaking task could facilitate IVA among lower-intermediate Japanese EFL learners (n = 113), targeting spoken meaning-recall (SMR) and written form-recall (WFR). A control group (n = 31) controlled for test-related learning effects. Surprise testing revealed acquisition of 3.14 words at the SMR level and 7.08 at the WFR level — a finding that challenges established assumptions about L2 vocabulary knowledge development. Retention remained strong one month later, with WFR showing a small but significant decline. L2 reading proficiency, target word frequency rank in a film and television corpus, and meaning negotiation emerged as significant IVA moderators. These findings suggest that brief meaning-focused speaking tasks can yield meaningful and durable lexical gains, raising questions about task modality and vocabulary development in EFL classrooms.