Autonomous single language interest predicts vocabulary achievement: the latent growth curve model approach

Abstract Recently, a new construct referred to as autonomous single language interest (ASLI) has been introduced in the educational psychology field. ASLI postulates that second language (L2) students who have one autonomously oriented goal for studying the L2 during their learning setting (e.g., during university study) are likely to make greater L2 achievements than those with low ASLI. However, it remains unclear how ASLI predicts later L2 vocabulary achievement and whether its stability or fluctuation that predicts the achievement. A total of 161 Saudi undergraduate students of English as an L2 enrolled in the Department of English were followed up three times over 17 weeks. We used the latent growth curve model (LGCM) to assess the stability and fluctuation of ASLI, and to see which one stability or fluctuation predicts later L2 vocabulary knowledge. The results of the LGCM suggest that initial high levels of the ASLI (i.e. its stability), but not its fluctuation, predicted a significant increase in L2 vocabulary achievement. In other words, students who started their L2 course with an autonomous single language interest and who maintained this sole interest/goal appeared to have higher L2 vocabulary achievement over time. Methodological and pedagogical implications are discussed.