Perception of allophonic contrast of Japanese high vowel /u/ by Japanese Tokyo
dialect speaking listeners
Kanako Tomaru
Graduate School of Sophia University
Overview: It is commonly observed that non-native sounds are difficult to distinguish (e.g.
Japanese listeners have a hard time discriminating English /l/ and /r/. (Yamada and Tohkura, 1992;
among others) In addition, it was recently suggested that native sounds with weak phonologicalrelation are also imperceptible. For example, sounds in allophonic relations are indistinguishable bynative speakers (Boomershie et al., 2008), and perceptibility of two phones that neutralize in acertain environment is shown to merge when perceived by native listeners (Hume and Johnson,2003). Hume and Johnson, following the evidence from perceptual merge of Mandarin tones,
suggests that perceptual contrast of speech sounds decreases as phonological contrast weakens. The
phonological contrast can be shown with four levels (Hume and Jonson, 2003): 1) fully contrastive(e.g. English /l/ and /r/), 2) partially contrastive (e.g. Mandarin tone 214 and 35), 3) allophoniccontrast (e.g. English ///), 4) non-occurring (e.g. Japanese /l/ and /r/). This paper provides
evidence that 1) native listeners can distinguish allophonic contrast, but not as accurately asphonemic contrast, and 2) allophones in complementary distribution are more perceptible than thosein free variation, through an investigation of Tokyo dialect speakers’ perception of vowel
allophones.
Background: Japanese high vowels must devoice in devoicing context in Tokyo dialect: [+obs][-voice] _ [+obs] [-voice] (e.g. /asuka/ ‘southern region of Nara prefecture’  []). Therefore,
full high vowels and devoiced high vowels show allophonic contrast of complementary distribution
in-between voiceless obstruents in this dialect. High vowels in non-devoicing context, on the otherhand, are optionally devoiced; so they show allophonic contrasts of free variation (e.g. /azusa/ [] or [] ‘a person’s name’. Following the phonological contrast scale of Hume andJohnson’s, the study predicts that allophonic contrast between devoiced vowel and full high vowel
is less perceptible than phonetic contrast between one-mora vowel (e.g. /u/) and two-mora vowels(e.g. /uu/). If allophonic contrast is equally imperceptible, perceptibility of the high vowel is thesame regardless of the devoicing condition; however, if distributional information is important,allophones in complementary distribution, i.e. those in devoicing context, should be more
perceptible. My experiment shows that Japanese listeners are more accurate in discriminatingphonemically contrastive sounds, and also that allophones in complementary distribution are more
perceptible than those in free variation.
Experiment: The experiment tested whether Japanese listeners are able to discriminate allophonesof the Japanese high vowel /u/. The stimuli were pairs of Japanese non-words that contained a pairof sounds that differ in voicing of the vowel ([]-[]). Pairs of words which contained sounds that1differ in length were also prepared ascontrol ([]-[]). The experimental
task was AX discrimination with a filler
word in between the paired words (e.g.
A-filler-X). Japanese Tokyo dialect
speaking listeners judged if the first andthe last words were the same.
The figure shows the results based on 5participants. Statistical analysis was notconducted because of the small
population. As the figure indicates, allophonic contrast in general was heard less accurately thanphonemic contrast. It is also shown that allophones in complementary distribution are more
perceptible than those in free variation.
Conclusion: This report shows that Japanese listeners are less accurate in discriminating allophoniccontrasting pairs than in discriminating phonemic contrasting pairs. In addition, allophones incomplementary distribution are shown to be more perceptible than those in free variation. The
results support the hypothesis that perceptual contrast reflects phonological contrast.

References:Boomershine, A., Hall, K. C., Hume, E., & Johnson, K. (2008). The impact of allophony versus
contrast on speech perception. In Avery, P., Dresher, E., & Rice, K. (Eds.), Contrast inPhonology (pp. 143-172). Berlin: Mouton de Gruyter.
Hume, E., & Johnson, K. (2003). The impact of partial phonological contrast on speech perception.
Proceedings of the 15th international congress of phonetic sciences.
Yamada, R. A., & Tohkura, Y. (1992). The effect of experimental variables on the perception ofAmerican English /r/ and /l/ by Japanese listeners. Perception & Psychophysics, 52, 376-392.

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