Phonetic Distinction between Simple Past and Present Perfect Verbs: A Perception Experiment

Stress is a linguistic property of a word that specifies which syllable in the word is stronger than any of the others. Early studies such as Fry (1955, 1958), Lieberman (1960), Beckman (1986), Harrington, Beckman, and Palethorpe (1998) (see also Laver, 1994 for an overview) have shown that there are clear acoustic differences between stressed and unstressed syllables: stressed syllables are realized with higher pitch, higher intensity, longer duration, and more peripheral vowel quality than unstressed syllables. Studies in many stress-accent languages show that the stressed realization of a syllable differs from the unstressed realization of the same syllable by having higher pitch. Also, results have showed that speakers consistently use duration to distinguish between open and central vowels that contrasted in stress at the word level. In contrast with F0 and duration, the relation of intensity variation in the speech signal to word stress is still controversial.In this paper, we investigated the role of acoustic factors involved in perceptually differentiating simple past from present perfect verbs in Persian, through manipulation of fundamental frequency (F0) and duration. Thus, tokens were resynthesized from the phonetic forms of Persian simple past and present perfect verbs in which F0 and duration were manipulated in several steps. The target tokens were presented to some native Persian participants to identify as simple past or present perfect. Results suggested that Persian listeners’ judgements of the tense of the target tokens depend, to a great extent, on the local F0 values of the verbs’ syllables as any amount of increase in the local F0 points of the respective syllables can categorically change the listeners’ judgements about the temporal reading of the verbs involved. On the other hand, results for duration showed that values of this parameter fail to produce a significant effect on listeners’ judgements.