حسین کرمی - Assistant Professor, Department of English Language and Literature, Faculty of Foreign Languages and Literatures, University of Tehran, Tehran, Iran.
مهناز اسرافیلی - MA graduate, Department of English Language and Literature, Faculty of Foreign Languages and Literatures, University of Tehran, Tehran, Iran

Vocabulary knowledge has a significant role in communication. Therefore, a plethora of research has investigated the effect of various factors on the acquisition of L۲ vocabulary. This empirical study aimed to examine the predictions of Laufer and Hulstijn’s (۲۰۰۱) involvement load hypothesis (ILH) by considering the impact of task type and involvement index on Iranian EFL learners’ incidental vocabulary learning. The ILH predicts that tasks with the same involvement load should lead to equal vocabulary gains. To this end, forty-five upper-intermediate learners were given one of four different tasks with the same involvement index (i.e., reading comprehension plus dictionary use, cloze-exercise plus dictionary use, inferencing, and sentence writing plus meanings of target words in L۱ + L۲). Participants’ receptive and productive knowledge of target words were tested immediately after fulfilling the tasks and three weeks later. Mixed-plot ANOVAs were run to compare the performance of the participants on the tasks. The results revealed that, contrary to the theory’s predictions, the performance of the learners on the four tasks was significantly different although the tasks had the same involvement indices. The results suggest that depth of processing and involvement are important factors in vocabulary learning. However, it also seems that the relative importance of the components of involvement might require reconsideration.

incidental vocabulary learning, involvement load hypothesis, depth of processing, Task, second language acquisition