The Combined Effect of Task Complexity and Task Condition through Collaborative Activities on EFL Learners’ Vocabulary Learning: A Focus on L2 Proficiency

The present study probed into the combined effect of task complexity and task condition through collaborative activities on EFL learners’ vocabulary learning with a focus on the role of L2 proficiency. To this end, 121 female Iranian EFL learners from Safir Institute in Babol were initially given Oxford Placement Tests (OPTs) to select homogeneous participants in terms of language proficiency. Then, 80 female pre-intermediate and intermediate Iranian EFL learners were selected and randomly divided into four groups: two experimental groups and two control groups. Each group consisted of 20 learners. There were a vocabulary pretest and a posttest. The experimental groups benefited from two complexity tasks, namely a ''fill-in task'' and a ''sentence writing'' task with different derivatives of the words. The two experimental groups were required to perform the tasks collaboratively. However, the control groups were not exposed to any complexity tasks and followed their conventional vocabulary learning individually. Results revealed that task complexity and task condition had a statistically significant impact on the learners’ vocabulary learning in both experimental groups (i.e., pre-intermediate and intermediate) compared with their control group counterparts. Practical implications and directions for future research are also discussed.