A study on word duration in English sentences uttered by native speakers of Japanese is conducted, in which the difference in focus between the English and Japanese languages is taken into account. The durations of Japanese speakers are compared with those of English speakers in regard to a percentage distribution of an individual word relative to all words in a sentence. The results of statistical analysis reveal that defects of focus, which are shorter for English speakers, occur on nouns and on words at the ends of sentences in Japanese speakers. The former result suggests that English speakers put focus on nouns, whereas Japanese speakers tend not to have the same rhythm as English speakers. The latter result suggests that phrase-final lengthening is insufficient in Japanese speakers. Also, these results can be explained by the difference in focus between English and Japanese. Additionally, a correlation is recognized between the defects in focus and the English proficiency of Japanese speakers.

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In this study, brain activation when listening to spoken Japanese with incorrect pitch accents was investigated. In the event-related fMRI experiment, four kinds of stimuli were prepared. (1) NORMAL: Real words with a correct pitch accent. (2) INCORRECT: Real words with incorrect pitch accent. (3) PSEUDO: Pseudo-words, and (4) BASE: amplitude-modulated pseudo-speech noise. Fifteen normal right-handed participants were scanned by functional MRI while listening to these stimuli. Region of interest (ROI) analyses were performed. The contrast between INCORRECT and NORMAL revealed significant activation in the bilateral inferior frontal, the bilateral precentral, and the left supplementary motor area, and the right superior temporal gyrus. The result supports the view that speech perception is a sensory-motor process, and suggests that when the pitch accent of the stimulus does not match the template, silent rehearsal might be repeated to enable a lexical decision to be made.

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