The Relationship between Language-Specific Prosodic Timing and Intersegmental Transition Speed : Japanese and English Vowel Sequences

Following a review of previous studies on diphthongs and coarticulation, evidence is presented showing radical differences between Japanese and English in the temporal properties of vowel sequences which are not adequately accounted for by conventional views of vowel-to-vowel coarticulation. It is hypothesized that these differences are related to language-specific differences in timing which may be partly prosodic in nature. Why and how such differences come about are issues which are discussed, but firm conclusions must await more exhaustive empirical findings and more detailed studies of the respective vocalic and prosodic systems. Two studies are reported. These attempt to clarify the issues using(l)spectrography to measure actual Japanese and English diphthongs, and (2) speech synthesis to test perception. One interesting result was that Japanese listeners tolerated faster VV transitions than English listeners. There are implications for our understanding of coarticulation and prosody, especially concerning mora and non-mora timing, and also for the teaching of English in Japan. Proposals are made for more thorough investigations, including articulographic studies, which are essential to validate the present results