Many studies have examined the effect of different approaches to teaching grammar including explicit and implicit instruction. However, research in this area is limited in a number of respects. One such limitation pertains to the issue of construct validity of the measures, i.e. the knowledge developed through implicit instruction has been measured through instruments which favor the recipients of explicit instruction. The present study expands on the previous studies by exploring the effectiveness of explicit and implicit instructions through administering a timed GJT and an untimed GJT. Data were collected from three different groups: (a) the explicit group was presented with rules of verb complementation, (b) the implicit group received visually enhanced texts, and (c) the control group received no instruction of the target feature. The results of the mixed between-within subjects ANOVA test revealed that the learners in explicit group outperformed the learners in implicit and control groups in post-tests and delayed post-tests even in the case of the implicit measure. Furthermore, the results indicated the more durable effects of explicit instruction compared with implicit instruction. Taken together, the study provided evidence for the efficiency of explicit teaching compared to implicit teaching in the context of L2 development.
