Effects of phonotactic predictability on sensitivity to phonetic detail

Japanese speakers systematically devoice or delete high vowels [i, u] between two voiceless consonants. Japanese listeners also report perceiving the same high vowels between consonant clusters even in the absence of a vocalic segment. Although perceptual vowel epenthesis has been described primarily as a phonotactic repair strategy, where a phonetically minimal vowel is epenthesized by default, few studies have investigated how the predictability of a vowel in a given context affects the choice of epenthetic vowel. The present study uses a forced-choice labeling task to test how sensitive Japanese listeners are to coarticulatory cues of high vowels [i, u] and non-high vowel [a] in devoicing and non-devoicing contexts. Devoicing contexts were further divided into high-predictability contexts, where the phonotactic distribution strongly favors one of the high vowels, and low-predictability contexts, where both high vowels are allowed, to specifically test for the effects of predictability. Results reveal a strong tendency towards [u] epenthesis as previous studies have found, but the results also reveal a sensitivity to coarticulatory cues that override the default [u] epenthesis, particularly in low-predictability contexts. Previous studies have shown that predictability affects phonetic implementation during production, and this study provides evidence predictability has similar effects during perception.