Atypical prosodic realization by Mandarin-speaking autistic children: Evidence from tone sandhi and neutral tone

Introduction Atypical prosodic features have been widely reported in autism spectrum disorder (ASD), primarily in non-tonal language speakers. Nevertheless, the prosodic realizations in autistic people who speak tonal languages were relatively understudied. This study aimed to investigate the acoustic and phonetic patterns at the word-level speech in Mandarin-speaking autistic and typically developing (TD) children at different age ranges. Methods Thirty Mandarin-speaking autistic children (15 three- to five-year-olds and 15 six- to eight-year-olds) were recruited into the ASD group. The TD group consisted of 30 age- and gender-matched children. We employed a picture-naming task to elicit the spontaneous speech production of Mandarin disyllabic words in which tone change processes occur, namely Tone 3 (T3) sandhi and neutral tone (T0). Results The phonetic analysis showed that the ASD group generally could produce typical-like T3 sandhi and T0 in terms of pitch height. However, relative to the TD group, they exhibited flatter pitch contours during T3 sandhi production. Moreover, the acoustic pitch mean of citation tones in the ASD group was also significantly higher, accompanied by more rigid pitch curves in contour tones. In addition, the atypical temporal realization in the ASD group was manifested by the longer duration of T0 and the earlier inflection position of T3. Conclusions Mandarin-speaking autistic children under eight had the phonological ability to produce context-dependent tones based on connected tonal information at the word level. Nevertheless, their phonetic prosodic realization of tone change processes was atypical. Our findings provide evidence of atypical prosody in autistic children who speak tone languages. Clinically, these findings may be attributable to underlying neural differences in autistic children.