Assimilation of non-native vowel contrasts to the American English vowel system.

The perceptual assimilation model (PAM) Best et al., JEP:HPP 14, 345–360 (1988) predicts that two non-native sounds that are assimilated to the same nature category will be harder for listeners to discriminate between than sounds that are assimilated to two different native categories (TC contrasts); how difficult will depend on whether they are equally good (or bad) exemplars of the single native category (SC contrasts) or not (CG contrasts). PAM was based on studies of consonant perception, as were subsequent tests of the model. This study extends the model to non-native vowels. American listeners performed keyword identification W. Strange and T. L. Gottfried, J. Acoust. Soc. Am. 68, 1622–1625 (1979) and categorical AXB discrimination tasks using six non-native vowel contrasts, Norwegian /i–y/, /i–■/, French /o–õ/, /œ–y/, /œ–■/, and Thai /■–■/. Assimilation patterns for a particular vowel contrast, inferred from keyword results, were more variable than in consonant studies but nonetheless strongly related to discrimination performance: TC contrasts were better discriminated than CG contrasts, which in turn were better discriminated than SC contrasts. Moreover, listeners who assimilated a particular contrast in TC fashion were better able to discriminate it than listeners who assimilated it in CG or SC fashion. Work supported by NIH.