Prominence-boundary interactions in speech perception: Evidence from Japanese vowel length

This study examines prominence-boundary interactions as they relate to the perception of durational cues in Tokyo Japanese. We tested if the lexical pitch accent (lexical prominence) status of a word mediates the effects of a prosodic boundary in the perception of contrastive vowel length. We implemented a two-alternative forced choice perception task in which listeners categorized a vowel duration continuum as a phonemically short or long vowel, while we manipulated pitch accentuation and phrasing as contextual cues. We first replicated a recent finding (Steffman & Katsuda [1]) that listeners require longer phrase-final vowel durations (as compared to phrase-medial) to perceive vowel as phonemically long: a compensatory perceptual adjustment for final lengthening. We further find that this boundary effect is mediated by pitch accent, consistent with recent speech production results (Seo et al. [2]) which show that a pitch accent reduces the magnitude of final lengthening in a word (i.e., unaccented words undergo greater final lengthening). Our perception results indicate that listeners accordingly require even longer vowel duration for a long vowel percept when a target word is both phrase-final and unaccented. Overall, our results show that listeners take both prominence and prosodic boundaries into consideration when they compute vowel length: a perceptual analog to intricate prominence-boundary effects in speech production.