On the relationship between identification and discrimination of non-native nasal consonants.

To examine the relationship between the identification and discrimination of non-native sounds, nasal consonants varying in place of articulation from Malayalam, Marathi, and Oriya were presented in two experiments to seven listener groups varying in their native nasal consonant inventory: Malayalam, Marathi, Punjabi, Tamil, Oriya, Bengali, and American English. The experiments consisted of a categorial AXB discrimination test and a forced-choice identification test with category goodness ratings. The identification test results were used to classify the non-native contrasts as one of five "assimilation types" of the Perceptual Assimilation Model (PAM) that are predicted to vary in their relative discriminability: two-category (TC), uncategorizable-categorizable (UC), both uncategorizable (UU), category-goodness (CG), and single-category (SC). The results showed that the mean percent correct discrimination scores of the assimilation types, but not the range of scores, were accurately predicted. Furthermore, differences in category goodness ratings in the CG and SC assimilations that were predicted to correlate with discrimination showed a weak, but significant correlation (r= 0.3 1, p<0.05). The implications of the results for models of cross-language speech perception were discussed, and an alternative model of cross-language speech perception was outlined, in which the discriminability of non-native contrasts is a function of the similarity of non-native sounds to each other in a multidimensional, phonologized perceptual space.

Perceptual "vowel spaces" of cochlear implant users: implications for the study of auditory adaptation to spectral shift.

Cochlear implant (CI) users differ in their ability to perceive and recognize speech sounds. Two possible reasons for such individual differences may lie in their ability to discriminate formant frequencies or to adapt to the spectrally shifted information presented by cochlear implants, a basalward shift related to the implant's depth of insertion in the cochlea. In the present study, we examined these two alternatives using a method-of-adjustment (MOA) procedure with 330 synthetic vowel stimuli varying in F1 and F2 that were arranged in a two-dimensional grid. Subjects were asked to label the synthetic stimuli that matched ten monophthongal vowels in visually presented words. Subjects then provided goodness ratings for the stimuli they had chosen. The subjects' responses to all ten vowels were used to construct individual perceptual "vowel spaces." If CI users fail to adapt completely to the basalward spectral shift, then the formant frequencies of their vowel categories should be shifted lower in both F1 and F2. However, with one exception, no systematic shifts were observed in the vowel spaces of CI users. Instead, the vowel spaces differed from one another in the relative size of their vowel categories. The results suggest that differences in formant frequency discrimination may account for the individual differences in vowel perception observed in cochlear implant users.

A cross-language study of the identification of non-native nasal consonants varying in place of articulation.

Seven listener groups, varying in terms of the nasal consonant inventory of their native language, orthographically labeled and rated a set of naturally produced non-native nasal consonants varying in place of articulation. The seven listener groups included speakers of Malayalam, Marathi, Punjabi, Tamil, Oriya, Bengali, and American English. The stimulus set included bilabial, dental, alveolar, and retroflex nasals from Malayalam, Marathi, and Oriya. The stimulus set and nasal consonant inventories of the seven listener groups were described by both phonemic and allophonic representations. The study was designed to determine the extent to which phonemic and allophonic representations of perceptual categories can be used to predict a listener group's identification of non-native sounds. The results of the experiment showed that allophonic representations were more successful in predicting the native category that listeners used to label a non-native sound in a majority of trials. However, both representations frequently failed to accurately predict the goodness of fit between a non-native sound and a perceptual category. The results demonstrate that the labeling and rating of non-native stimuli were conditioned by a degree of language-specific phonetic detail that corresponds to perceptually relevant cues to native language contrasts.