High variability phonetic training (HVPT) enhances L2 learners’ ability to perceive difficult contrasts, but learning outcomes vary depending on individual and training-related factors. This study examined whether individual differences in working memory and vocabulary size influence HVPT outcomes across different training structures. Seventy-nine Korean learners of English completed a pretest, five training sessions, an immediate posttest, and a delayed posttest 2 weeks later. Participants were randomly assigned to one of three conditions: 1-talker (n = 29), 6-talker blocked (n = 25), or 6-talker mixed (n = 25). Training involved word identification with feedback, targeting the English vowel contrasts /i/-/ɪ/ and /ɛ/-/æ/. Tests measured identification accuracy for trained and untrained items produced by a novel talker. Working memory was measured by digit span tasks; vocabulary size was assessed with a vocabulary size test. Mixed-effects modeling revealed a main effect of training (pre–post), with greater gains in the 6-talker conditions. Vocabulary size predicted accuracy overall, while working memory interacted with training structure: in the 1-talker condition, higher working memory was associated with larger gains. The mixed condition yielded more sustained improvement than the blocked condition, particularly among learners with higher vocabulary. These results suggest that cognitive and linguistic factors shape HVPT effectiveness depending on the structure of variability.
Kim et al. (2025) studied this question.