Substantial research has found that learner–learner collaborative dialogue, accruing from collaborative work, contributes to second language (L2) learning by providing learners with the opportunities for using cognitive resources to co-construct knowledge (Kim, 2008; Leeser, 2004; Swain, 2000; Tocalli-Beller & Swain, 2005). However, there is still little discussion on how learners of English as a foreign language (EFL) may incidentally acquire unfamiliar vocabulary through lexical-related episodes (LREs), a particular type of collaborative dialogue constructing linguistic knowledge.

Kaivanpanah and Miri’s (2017) study offers a way to gauge L2 learners’ acquisition of new vocabulary through LREs. Their study examined how different task types (i.e., composition task and cloze task) affect intermediate-level Iranian EFL learners’ (n = 24) degree of engagement in the negotiation of unknown vocabulary, operationalized as LREs, and subsequent vocabulary acquisition. The participants worked in pairs and completed a composition task on an assigned topic by using 10 target words. Two weeks later, the same pairs of participants completed a cloze task by using another set of words (n = 10). A glossary with first language (L1) translation, L2 meaning, and example sentences was provided to the students during each task. Learners’ collaborative dialogues occurred during the tasks were recorded, with LREs analyzed as a measure of engagement in the negotiation. Participants’ vocabulary gains from each task were assessed by an unannounced immediate vocabulary posttest (i.e., Vocabulary Knowledge Scale). An unannounced delayed vocabulary posttest was administered same as the posttest to assess the participants’ vocabulary knowledge retention.

Based on Tocalli-Beller and Swain’s (2005) and Storch’s (2008) classification of LREs, the participants’ quality of engagement in lexical-related episodes were further categorized as cognitive-conflict episodes (CCEs) and non-CCEs. CCEs indicate a high engagement in which a learner resolves disagreements in dealing with linguistic problems encountered in a task. Non-CCEs imply a limited engagement in which a learner simply repeats and accepts the other learner’s contributions. Examining the LREs produced by the two tasks and scores on the vocabulary tests, Kaivanpanah and Miri (2017) found the composition task was more effective than the cloze task in encouraging students to produce more LREs and correctly resolve CCEs, which, in turn, yielded greater short-term and long-term vocabulary gains.