Decoding How Articulation and Pauses Influence Pronunciation Proficiency in Korean Learners of English

This study investigates how temporal fluency cues shape human ratings of L2 English pronunciation in Korean learners, using a large read-speech corpus annotated with five-point pronunciation scores. We focus on two timing-derived measures-articulation rate (AR) and mean silence duration (SilMean)-and examine whether these cues predict (i) articulation-accuracy ratings and (ii) prosody/fluency ratings. To account for dependencies in corpus data and to control for key learner- and task-level covariates, we fitted cumulative link mixed models with random intercepts for speakers and scripts, including proficiency band (ability), age, gender, and test type as fixed effects. Across models, faster articulation and shorter silent intervals were associated with higher articulation ratings, and a combined model including both AR and SilMean provided the best fit (lowest AIC). Temporal cues were even more strongly associated with prosody ratings, supporting construct alignment between timing measures and the prosody dimension of the rubric. Marginal predicted probabilities illustrate how the likelihood of receiving high ratings (score ≥ 4) increases with AR across proficiency and linguistic-complexity strata (with SilMean held constant), and how long silent intervals reduce these probabilities when AR is held constant. These findings indicate that temporal organization provides robust information about perceived pronunciation quality in read L2 speech and underscore the importance of construct-aware modeling when developing AI-based scoring and feedback systems trained on human-labeled data.