Abstract
The present study describes how the two groups of Japanese EFL learners, Proficient Japanese (PJ) and Non-proficient Japanese (NJ), differs in producing duration of inter-stress intervals (ISIs) comparing with a native speaker of American English (NS). Firstly, the duration of ISIs produced by PJ, NJ and NS is measured and analyzed. Secondly, the duration of both stressed and unstressed vowels in ISIs is measured to find the characteristic features of production by PJ, NJ, and NS. Thirdly, the compressed rate for each stressed vowel and unstressed vowel is calculated to confirm the results. Lastly, the classical notion of isochronism of English is argued after finding the evidence for 'foot level shortening' and acquisition order of compressing vowels. Further discussion is taken into account for improving production ability of Japanese learners of English.
