Segmental Duration as a Cue for Assimilation Compensation in Japanese Perception of English

The current study investigates the threshold of segmental duration necessary to trigger the facilitation effect in Japanese listeners when they process English assimilated sounds. Previous research(1)(2) suggested that Japanese listeners fail to utilize phonological cues in English assimilation unless the assimilated segments are lengthened, presumably to match Japanese moraic timing. To determine the minimum required duration for facilitation, an experiment was conducted with English sentences containing assimilated nasal-final segments, which were digitally lengthened in six incremental steps. Results revealed no significant difference in reaction times across duration levels, suggesting that Japanese listeners require segmental durations close to native Japanese moraic length to perceive facilitation. This supports the hypothesis that duration sensitivity in speech processing is shaped by language-specific phonological structure.