Abstract:
This study investigated the effects of interleaved form-focused instruction (FFI) on Thai lower secondary students’ grammatical knowledge, long-term retention, and their perception towards the instruction. Students took a pre-test, an immediate post-test, and a one-week delayed post-test, and were also interviewed at the end of the implementation. The test scores were to investigate the improvement of grammatical knowledge as well as the long-term retention, and the data from the semi-structured interview were analyzed to figure out the perceptions towards the overall instruction. The results showed significant improvement of grammatical knowledge in all areas of form, meaning, and use and also elicited statistical significance of the long-term retention with the increase of scores in both the immediate and delayed post-test. For students’ perception, the results disclosed that interleaved FFI seemed to be harder and more exhausting at first, but after getting familiar with it, the lessons were more preferable. The study recommended that interleaved FFI tended to be an effective method to improve students’ grammatical knowledge and to enhance long-term retention, and that it should be applied in language classroom with well-designed lessons.