Phonological and phonetic contributions to perception of non-native lexical tones by tone language listeners: Effects of memory load and stimulus variability

The present study examined native language phonological and phonetic factors in non-native lexical tone perception by tone language listeners, manipulating memory load and stimulus variability to bias listeners towards a more phonological or more phonetic mode of perception. Mandarin and Vietnamese listeners categorised the five Thai lexical tones to their native tones, and discriminated five selected Thai tone contrasts that were predicted by the Perceptual Assimilation Model (PAM, Best, 1995) to be discriminated differently. Categorisation responses showed more phonologically-based patterns under high than low memory load but were unaffected by talker and vowel variability, whereas discrimination accuracy was reduced by talker and vowel variability but not by memory load. Phonological factors indicated by type of categorisation and category overlap generally predicted the discrimination of non-native tone contrasts in line with PAM principles. Phonetic factors reflected in category overlap scores and fit index difference scores predicted variations in discriminating contrasts of the same contrast categorisation type. These findings uphold the extension of PAM principles to non-native tone perception by native listeners of other tone languages. Native phonological and phonetic contributions to non-native speech perception differ between categorisation and discrimination tasks, as reflected in differential modulation by memory load and stimulus variability.