Paper Title
The Development of L2 Vocabulary Size of High School Learners in Relation to their Affective Factors

This study investigate show the L2 vocabulary size (VS) of high school learners develops along with their affective factors of interest, motivation, self-efficacy, attitude, and anxiety. VS tests and a questionnaire on vocabulary learning were administered to a cohort of 76high school English learners in Japan. Cluster analysis was employed and they were assigned as two groups based on their VS at three points from when they started high school aged 15 until they completed their high school studies aged 18. One-way repeated measures analysis of variance (ANOVA) and post hoc Bonferroni tests confirmed that Cluster 1, the upper group, improved the overall scores of VS and significant growth tested at each grade. On the other hand, although Cluster 2, the lower group, made progress during their first and second year, there was no statistically significant increase inscores between the second and third year. Results also prove that motivation and attitude have an influence on the development of VS throughout their time at school and self-efficacy playsa functional role in both the first and the third year. The findings provide empirical evidence of the importance of being aware of the multiple aspects of affective factors in the process of learners’ growth in vocabulary knowledge. Keywords - Vocabulary size, Affective factors, Motivation, Attitude, Self-efficacy