Discrimination of non-native consonant contrasts varying in perceptual assimilation to the listener's native phonological system

Classic non-native speech perception findings suggested that adults have di fficulty discriminating segmental distinctions that are not employed contra stively in their own language. However, recent reports indicate a gradient of performance across non-native contrasts, ranging from near-chance to nea r-ceiling. Current theoretical models argue that such variations reflect sy stematic effects of experience with phonetic properties of native speech. T he present research addressed predictions from Best's perceptual assimilati on model (PAM), which incorporates both contrastive phonological and noncon trastive phonetic influences from the native language in its predictions ab out discrimination levels for diverse types of non-native contrasts. We eva luated the PAM hypotheses that discrimination of a non-native contrast shou ld be near-ceiling if perceived as phonologically equivalent to a native co ntrast, lower though still quite good if perceived as a phonetic distinctio n between good versus poor exemplars of a single native consonant, and much lower if both non-native segments are phonetically equivalent in goodness of fit to a single native consonant. Two experiments assessed native Englis h speakers' perception of Zulu and Tigrinya contrasts expected to fit those criteria. Findings supported the PAM predictions, and provided evidence fo r some perceptual differentiation of phonological, phonetic, and nonlinguis tic information in perception of non-native speech. Theoretical implication s for non-native speech perception are discussed, and suggestions are made for further research. (C) 2001 Acoustical Society of America.