Word segmentation in Persian continuous speech using F0 contour

Word segmentation in continuous speech is a complex cognitive process. Previous research on spoken word segmentation has revealed that in fixed-stress languages, listeners use acoustic cues to stress to de-segment speech into words. It has been further assumed that stress in non-final or non-initial position hinders the demarcative function of this prosodic factor. In Persian, stress is retracted to a non-final position in words containing enclitic affixes. The present research explores the question as to whether Persian listeners are able to identify word boundaries given the tonal structure of words in Persian phonology or not. The paper was also intended to investigate to what extent Persian native speakers use H peaks to identify word stress pattern. Two perceptual experiments were conducted in this regard. Given the tonal structure of words in utterance non-final position in Persian, it was hypothesized that listeners are likely to identify the end of a high plateau as a cue to word boundary. In addition, given that peaks in utterance non-final position are delayed, it was further hypothesized that perceived prominent is likely to be attributed to a syllable that precedes another syllable carrying a pitch peak. The basic stimulus for the first experiment was a nonsense sequence of nine “dA” syllables with equal duration ([dA1.dA2.dA3.dA4.dA5.dA6.dA7.dA8.dA9]) across the syllables. The peak was located at the beginning of the consonant in [dA4] in the stimulus. The duration of the H plateau following the H peak was varied continuously to create 6 different stimuli with varying temporal plateau. The stimuli were presented randomly to 10 native speakers of Persian. The participants were asked to chunk the sequence of identical syllables they hear into two parts as if they were two independent words. They were also asked to identify the most prominent syllable in a separate identification test. The results showed that the ending point of a high H plateau acts as a prosodic cue to word boundary detection in Persian. For example, when the end of the H plateau was located on the end of the vowel in dA4, listeners identified the end of dA4 as boundary between two hypothetical words. However, when the end of the plateau was located on the end of the vowel in dA5 or the beginning of the consonants in .dA6 listeners identified the end of dA5 as the word final boundary. The results of this experiment further revealed that listeners are sensitive to the position of H peaks to identify within-word position of prominence in Persian. Listeners consistently identified dA3 as the most prominent syllable as this syllable preceded dA4 on which the peak was located, and the rate of their identification was not affected by the duration of H plateau following the pitch peak. In the second experiment, listeners’ ability to use F0 contour as a cue to word boundary was tested on resynthesized speech in which the spectral properties of the signals were intentionally deformed. The results replicated the findings previously obtained for the first experiment, indicating that the end of a high plateau acts as a robust cue to word boundary detection in Persian.