When Pitch Falls Short: Reinforcing Prosodic Boundaries to Signal Focus in Japanese

This production study examines how Japanese speakers mark information structure through an Edge-Reinforcing Strategy—a prosodic system that signals focus via boundary-based cues, independently of lexical pitch accent or phrasing constraints. While many Japanese dialects mark focus with F0 expansion and post-focal compression, such strategies are limited in utterances containing unaccented words and in systems without lexical accent or multiword Accentual Phrases. We hypothesize that when pitch cues are constrained, speakers rely on temporal and spectral cues aligned with prosodic edges, such as silence insertion, jaw opening, and duration asymmetry. Nine educated speakers of Japanese standard produced 48 genitive noun-phrases (e.g., umáno hizume ‘horse’s hoof’) under Broad and Narrow Focus. Acoustic measures included word duration, and F1-based estimates of jaw opening and silence insertions. Results showed that silence and duration were the strongest predictors of Narrow Focus, functioning additively and independently of pitch accent. F1-based measurements of jaw opening played a secondary, compensatory role, particularly in unaccented contexts. Cue-profile analysis revealed a functional hierarchy: silence and duration together were most effective, while jaw alone was less informative. These findings broaden current models of focus realization, showing that prosodic restructuring can emerge from gradient, edge-based cue integration.