Speaking rate normalization across different talkers in the perception of Japanese stop and vowel length contrasts

Perception of duration is critically influenced by the speaking rate of the surrounding context. However, to what extent this speaking rate normalization depends on a specific talker's voice is still understudied. The present study investigated whether listeners' perception of temporally contrastive phonemes is influenced by the speaking rate of the surrounding context, and more importantly, whether the effect of the contextual speaking rate persists across different talkers for different types of contrasts: Japanese singleton-geminate stop contrast (/k/-/kk/) and short-long vowel contrast (/e/-/ee/). The vowel contrast carries more reliable talker information than the stop contrast; hence, listeners' rate-based adjustments may be more talker-specific for vowels than for stops. The current results showed that context speaking rate impacted the perception of the target contrast across different talkers, and this influence was evident for both types of the contrasts tested. These results suggest that listeners generalized their rate-based adjustments to different talkers' speech regardless of whether the target segment carried reliable talker information (i.e., vowel contrast) or not (i.e., stop contrast). The current results bear on the issue of how speaking rate information is processed with respect to talker information.