The Identification and Discrimination of Synthetic Vowels

Abstract

A series of thirteen two-formant vowels was synthesized and used as the basis of labelling and discrimination tests with a group of English-speaking listeners. The sounds varied only in F1/F2 plot and the resulting vowel qualities were such that listeners found no difficulty in assigning each sound to one of three phonemic categories, those of the vowels in bid, bed and bad. The results of the tests were compared with those previously obtained in experiments involving the consonant phonemes /b, d, g/. It appears from the data that the phoneme boundaries in the case of the three vowel phonemes are less sharply defined than in the case of the stop consonants. The labelling functions for the vowels show a gradual slope and the discrimination functions do not show any marked increase in sensitivity to change in the region of the phoneme boundaries. It is clear also that the listeners were able to discriminate differences very much smaller than would need to be distinguished simply in order to place vowels in the appropriate category. The results show further that the effect of sequence or acoustic context in the perception of vowels is very considerable. In all the aspects examined in these experiments, the perception of synthetic vowels is found to be different from that of synthetic stop consonants. These differences lend some support to the hypothesis that the degree of articulatory discontinuity between sounds may be correlated with the sharpness of the phonemic boundaries that separate them.

New Insights Into Old Puzzles From Infants' Categorical Discrimination of Soundless Phonetic Units

“…For example, neither affricates or fricatives (Ferrero, Pelamatti, & Vagges, 1982;Rosen & Howell, 1987) nor vowels (Abramson, 1961;Fry, Abramson, Eimas, & Liberman, 1962) are categorically perceived. Might we expect this to be true of signs as well?…”

A unified account of categorical effects in phonetic perception

“…Unlike consonants, vowel discriminability cannot be closely predicted from the identification data, which itself is much more prone to context effects (Eimas, 1963). Relatively continuous perception has been found repeatedly in the /i/-/I/-/E/ continuum (Fry et al, 1962;Stevens et al, 1963;Stevens et al, 1964), as well as in perception of vowel duration (Bastian and Abramson, 1962) and perception of tones in Thai (Abramson, 1961). Further support for more continuous perception of vowels comes from mimicry experiments (Chistovich, 1960;Kozhevnikov & Chistovich, 1965): When participants were asked to mimic stop consonants and vowels, their ability to reproduce vowels accurately was much greater than for consonants, which tended to be reproduced with prototypical members of the category.…”

“…Discrimination is little better than would be expected if listeners used only category labels to distinguish sounds, and between-category differences are extremely pronounced (Liberman et al, 1957;Wood, 1976). At the other end of the spectrum, vowel discrimination is much more continuous, so much so that some early experiments seemed to suggest that vowels displayed no categorical effects at all (Fry et al, 1962). Since these classic studies, it has become evident that stop consonant perception is not purely categorical, while vowel perception can also exhibit categorical effects (Pisoni & Lazarus, 1974;Pisoni, 1975).…”

A limit on behavioral plasticity in speech perception

“…Yet, according to (Repp, 1984p. 260): "In the earliest discrimination study, (Fry et al, 1962) found no discrimination peak at category boundary, but this was probably due to a ceiling effect, coupled with the use of imperfectly controlled stimuli. Most later studies (e.g., Fujisaki and Kawashima, 1969;Fujisaki and Kawashima, 1970;Pisoni, 1971;Stevens et al, 1969) have found clear peaks on vowel continua, so there is good reason to believe that there is a phonetic component in vowel discrimination".…”