Native and non-native perception of phonemic length contrasts in Japanese: A categorization study

Abstract

Segment length is distinctive in Japanese, for example, /kaze/ (‘‘wind’’) versus /kaze:/ (‘‘taxation’’). Such length contrasts are not necessarily categorical for non-native speakers. To study this property precisely, a series of perception experiments were conducted. Stimuli were based on a pair of nonsense Japanese words, /erete/ and /ere:te/. A continuum gradually varying between these words was synthesized using STRAIGHT, a high-fidelity speech analysis, synthesis, and manipulation system [Kawahara et al., Speech Commun. 27, 187–207 (1999)]. Three subject groups were tested: (1) English speakers with no Japanese experience; (2) English speakers who had spent 1–6 months in Japan; and (3) native Japanese speakers. All subjects participated in a single-stimulus two-alternative forced-choice identification task. Subjects in the second group were tested a second time after five days of perceptual training on phonemic length contrasts during which they were exposed to 1800 pairs of real Japanese words that minimally differed with respect to vowel length. Results suggest that identification boundaries of English speakers are less sharp than those of native speakers, and that identification boundaries sharpen with both exposure to Japanese and with perceptual training. Implications of these findings for second-language learning will be discussed. [Work supported by TAO, Japan.]