Influence of second dialect use on the production of first dialect lexical tones

This study focuses on suprasegmental features and investigates how the use of a second tonal dialect influences the production of tones in the first dialect among bidialectal speakers of Chengdu Mandarin (CM) and Standard Mandarin (SM). Using a word-naming task, this study analyzed the acoustic differences between tones in SM and CM that share similar pitch contours and assessed the impact of SM use on CM tone production. How bidialectal listeners perceptually map SM tones onto CM categories was further evaluated using a dissimilarity rating task. The finding of the acoustic analysis revealed that greater SM use led to dissimilatory drift in CM tones that SM tones were perceptually mapped to; however, there was also an attenuation of within-dialect phonological contrast for CM tones that were not perceptually linked to SM tones. These results demonstrate that bidialectal speakers form a shared phonetic space for both dialects. These results also suggest that maintaining both within- and cross-dialect contrasts at the suprasegmental level may pose greater challenges for speakers.