Individuals with congenital amusia show degraded performance in a nonword repetition task with lexical tones

Congenital amusia is a disorder characterized by abnormal pitch processing, including pitch encoding and pitch memory. Individuals with amusia were impaired in speech perception, but they showed comparable speech production as those without (mainly investigated in tonal languages). Nonetheless, most previous studies collected amusics' recordings based on real words, and little is known about how amusics produce nonwords that incorporate phonological components of syllables and lexical tones. In this study, two participant groups of amusics and typical, musically intact controls (18 participants per group) attended a nonword repetition task. All nonwords were syllable-tone combinations created following the Chinese word structure. The length of the nonwords gradually increased from one to seven syllables. Repetition accuracy and error patterns were analyzed using linear mixed-effects models. Results showed that amusics had fewer correct responses to syllables and tones within a nonword, especially for longer nonwords. Besides, amusics' error rates for the double-type error, meaning the simultaneous mistakes on both syllables and tones, were also larger than controls in the longer lengths. It was revealed that amusics repeated the nonwords less accurately than controls, and they were struggling with concurrent processing of different phonological components within a nonword. This study provides novel evidence that amusics exhibit degraded nonword repetition involving both syllables and tones, which supports the perception-production link and sheds light on designing intervention programs to soften the disorder of amusia.