A cross-language investigation of phonetic and phonological processing of lexical tone

In an investigation of how lexical tone is perceived and processed at the phonetic and phonological levels, listeners from diverse language backgrounds participated in three perceptual studies. In the first, native Mandarin and Thai listeners assimilated non-native tones to their native tone categories. Results indicated that occurrence of a lower-level phonetic and a higher-level phonological assimilation process was related to listeners’ tone experience, as inexperienced listeners recognized only the phonetic distinctions, whereas experienced listeners were sensitive to both the phonetic and phonological distinctions between native and non-native tone categories. In the second study, native Mandarin, Thai and English listeners participated in a forced-choice tone perception test in which they identified the four Mandarin tone categories. Identification accuracy and confusion patterns revealed that previous tone experience predicted tone perception at the phonetic and phonological levels. Better performance was demonstrated for native than non-native, and experienced than inexperienced listeners. Experienced Thai listeners also showed more native-like performance than experienced English listeners. Tone 2 and Tone 3 were the most confusable tone pair for all but the inexperienced English listeners. Lexical information from the carrier words was also found to help Mandarin and English listeners recognize difficult tones. In the third study, participants from the second one completed a dichotic listening test assessing tone lateralization in the brain. The results demonstrated a strong influence of acoustic properties, as tones with dynamic F0 contours were lateralized to the left hemisphere while those with flatter F0 contours were lateralized to the right hemisphere. Meanwhile, native and non-native tone experience was associated with a larger degree of left hemisphere activation for Mandarin and experienced Thai listeners relative to those in the remaining groups. In summary, these three studies indicate tone perception and processing at both the phonetic and phonological levels. In relation to tone experience, inexperienced listeners may attach more importance to phonetic variation while experienced listeners are sensitive to both the phonetic and phonological differences. In terms of theoretical contributions, tone perception results extend the current models of speech perception to the suprasegmental level while tone lateralization results provide evidence supporting the acoustic and functional hypotheses.