Vocabulary Acquisition in English: Explicit vs. Task-based Instruction

Being aware of the positive effect of teaching vocabulary to enrich lexical knowledge, the present study aims at investigating the impact of explicit teaching (and its two modes: verbal and visual) and task-based instruction on the vocabulary achievement of Iranian EFL learners. On the basis of Cambridge Placement Test, the participants of the study were randomly selected from among 94 intermediate EFL learners, from which 75 were randomly assigned into three verbal, visual and tasked-based groups. All groups were required to use the same textbook and ancillary materials. The groups were taught a set of vocabulary selected from Harrington Elster’s Verbal Advantage (2000) employing verbal techniques of synonymy and exemplification to the verbal group; visual aids of pictures, flashcards, and PowerPoint presentation to the visual group; and some teacher-made tasks to the task-based group. A post-test was administered at the end of the course to measure the difference between the achievements of the three groups with respect to the type of vocabulary teaching techniques employed for each group. Results of One-way ANOVA and Scheffe test revealed effective superiority of task group performance over the other groups and visual group over verbal group. It might be concluded that to enhance EFL learners’ lexical knowledge, task-based instruction is more effective than visual or verbal explicit instruction. The findings of this study may have significant implications for curriculum designers and EFL teachers.