Perceptual boundary and discrimination sensitivity of Japanese singleton and geminate stops in Japanese and Taiwanese Mandarin speakers

To clarify non-native speakers?perception of Japanese singleton and geminate stops, the perceptual boundary and discrimination sensitivity of these stops were investigated with native speakers of Japanese and Taiwanese Mandarin. The perceptual boundary of Japanese speakers varied with speaking rate, but Taiwanese Mandarin speakers had an almost constant perceptual boundary regardless of speaking rates. Taiwanese Mandarin speakers also had a much lower discrimination sensitivity, only about 15% that of native Japanese speakers. These results indicate that Taiwanese Mandarin speakers?perception of Japanese singleton and geminate stops is ambiguous due to their inadequate perceptual boundary and low discrimination sensitivity. Meanwhile, vowel devoicing preceding or following the stops decreased the discrimination sensitivity in both Japanese and Taiwanese Mandarin speakers, suggesting an effect of language-independent hearing processing on discrimination sensitivity instead of an effect of language-dependent speech processing. Our results suggest that multiple factors play a role in non-native speakers?perception of Japanese singleton and geminate stops.