This study examined the role of EFL elemetary learners' heterogeneity in terms of age in their adoption of Communication Strategies (CSs). A secondary purpose was to probe the probable impact of such an educational context on the students' overall vocabulary achievement. To this end, 60 elementary EFL male learners at an Iranian institute were assigned to two class conditions: the students of one class were at the age of 15 & 16 (the same-age group), and those of the other class were of different ages, ranging from 15 to 36 (the multiage group). The instructional procedures, the materials, and the teacher were consistent in both classes. The course took two and a half months for both groups and both classes received the same amount of instructional content. The results suggest that the kinds and frequency of CSs employed by the students were affected by the interlocutors' age factor. However, no significant difference was observed in the students' overall EFL vocabulary achievement.
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