Investigating the effect of codeswitching and L2 exclusive instructional strategies on learning and retention of L2 vocabulary

This study sought to investigate the effect of teacher codeswitching, as compared to monolingual (L2) instruction, on L2 vocabulary learning and retention. Though a sizeable body of research on teacher beliefs and behavior regarding classroom L1 use has diminished the efficacy of monolingual pedagogy, the potential of strategic codeswitching for facilitating L2 learning has only recently come under empirical scrutiny. While past research has shown explicit vocabulary teaching and intentional learning to be advantageous, empirical evidence has been limited to reading comprehension studies giving little attention to the comparative value of providing lexical information in L1 or L2. However, evidence from psycholinguistic research on bilingual lexical development suggests similar advantages for codeswitching. Thus, 10 Japanese adult EFL learners were assigned to either codeswitching (CS) or English-only (NCS) conditions, and assessed regarding the quality and efficiency of learning and retention of 24 target words for which they had received condition-specific instruction and subsequent communicative exposure. Results echo similar studies that codeswitching is superior to L2-exclusive instruction for more accurate short-term learning, but participants' proficiency, among other limitations, potentially influenced this outcome. Results also show codeswitching to be more efficient despite long-term retention suffering more than L2-exclusive instruction. Pedagogical implications are discussed.