Perception of identical vowel sequences in Japanese conversational speech

Sequences of more than two identical vowels across word boundaries can occasionally be found in Japanese speech. Our previous study (Kakehi and Hirose, 1998) investigated how hearers perceive such vowel sequences. We used isolated sentences as test materials, provided that the duration of such vowel sequences increases in proportion to the number of morae. We found that hearers can detect the number of morae in the vowel sequence by using cues such as the pitch pattern, speech rhythm, and duration. The present study attempts to examine cases in which the vowel sequence occurs as part of natural conversation (part of planned dialogs). The materials were designed so that the target vowel sequences do not have any distinctive pitch movement. In the recorded sets of conversation that we examined, the relationship between the duration and the number of morae in the vowel sequence was roughly proportional. A series of perception tests investigated whether hearers can correctly detect the number of morae in such utterances, while the pitch movement in the target was kept stable. The results indicated that the duration of vowel sequences does not serve as a sufficient cue to detect the number of morae.