Learning non-native vowel categories

Two hypotheses have recently been put forward to account for listeners´ ability to distinguish and learn contrasts between speech sounds in foreign languages. Best´s (1994) perceptual assimilation hypothesis predicts that the ease with which a listener can tell one non-native phoneme from another varies directly with the extent to which these sounds assimilate to different native phonemes. Pisoni et al. (1994) have argued that training listeners to identify non-native phonemes teaches them sets of exemplars rather than leading to the abstraction of more general prototypes. We report the results of four experiments examining how American English listeners learn to perceive the contrasts among the front rounded vowels of German. The results suggest that listeners´ responses are a function of the phonetic dissimilarity of the vowels themselves rather than their assimilability to American English vowels, a result incompatible with the strong phonological interpretation of Best´s hypothesis, but compatible with the weaker category recognition interpretation. These results also show strong speaker effects, and are thus compatible with Pisoni et al.´s exemplars-not-prototypes interpretation of non-native category learning