Native-language phonetic and phonological constraints on perception of non-native speech contrasts

Abstract

Adults discriminate many non-native speech contrasts poorly, especially from an unfamiliar language that is not (yet) an L2. The Perceptual Assimilation Model (PAM) [Best et al., JEP: HPP 14, 34 560 (1988)] posits that this difficulty stems from knowledge of both the phonological functions and the phonetic details of native speech segments. Thus, discrimination of an unfamiliar contrast depends not only on whether it resembles a native phonological contrast, but also on perceived goodness of fit between the non-native segments and native phonetic category(s). Cross-language comparisons support PAMs prediction that perceptual assimilation of contrasting non-native segments to a single native category yields poorer discrimination than assimilation to two categories (TC contrasts). Discrimination is worst if both phones are equally similar to a single category (SC), substantially better if they differ in category goodness (CG), near ceiling for TC assimilations, and good to excellent for consonants that fail to be assimilated as speech, instead being perceived as nonspeech events (non-assimilable: NA). Recent findings indicate that, as predicted, SC, CG, and TC assimilations are associated with preferential activation of left hemisphere language regions, whereas NA stimuli yields bilateral brain activation. Other findings with fluent bilinguals indicate a persisting L1 effect on non-native consonant discrimination even if their L2 is acquired prior to 5 years. [Work supported by NICHHD and NIDCD.]