Discrimination of English Vowel Contrasts by Persian Speakers Based on Perceptual Assimilation Model

The present study addressed the perception of English vowel contrasts /i-I/ and /u-U/ by Persian speakers in light of the theoretical assumptions underlying the Perceptual Assimilation Model. The lexical pair (feet-fit) and (fool-full) illustrating the contrasts /i-I/ and /u-U/ were extracted from a natural English spoken corpus, and then duration, first and second formant frequencies were resynthesized. Persian native speakers completed a discrimination task on the non-native vowel contrast. Results suggested that responses are sensitive to variation in duration, and this sensitivity holds irrespective of whether the subjects are familiar with the English language or not. In contrast, variation in the first and second formant frequencies (as acoustic manifestation of vowel quality) failed to produce significant changes in the responses. Moreover, discrimination was not any better for the combinatory stimuli (duration + vowel quality) than the single stimuli duration. In sum, discrimination was consistent with the Perceptual Assimilation Model, showing that assimilation of the two vowel contrasts /i-I/ and /u-U/ with the Persian sound system is a two-category assimilation (TC) for which discrimination is highly accurate.