Effects of Fluency on the Consistency and Contrast of English Vowel Production in Korean Elementary School Students

The present study examines how fluency relates to (i) within-category consistency and (ii) between-category contrast in English vowel production by Korean elementary school learners. We analysed both reading and spontaneous utterances produced by 45 male and 49 female students across four fluency levels. Vowel consistency was assessed using compactness scores (ellipse area in the F1–F2 space), and vowel contrast was assessed using Pillai scores derived from MANOVA for six vowel contrasts. The results indicate that vowel compactness is strongly structured by vowel category and shows no reliable effect of fluency for either gender, whereas vowelcontrast distinctness increases with fluency at the highest level (F05). These findings suggest that fluency-related improvement in vowel production is expressed primarily through enhanced contrastive organisation rather than through reduced withincategory dispersion. Accordingly, pronunciation instruction may be more effective when it emphasises contrastive learning rather than general articulatory ‘accuracy’.