Unequal Impairment of Native and Non-native Tone Perception in Cantonese-speaking Congenital Amusics

Congenital amusia is a neurogenetic deficit that impacts pitch processing in music. Studies have shown that the deficit in amusia not only affects pitch processing in music, but also transfers to the language domain, influencing pitch processing in speech, such as lexical tone and intonation perception. Previous studies have shown that amusics are impaired in lexical tone perception in both native and non-native language speakers. However, it is still unclear whether individuals with amusia are more impaired in the perception of native tones, which have long-term phonological representations, or non-native tones, which depends more on auditory/phonetic pitch processing. To fill this gap, this study examined the discrimination of pairs of native Cantonese tones and non-native Thai tones by 14 Cantonese speakers with amusia and 14 normal controls. Results showed that Cantonese-speaking amusics were more impaired in the discrimination of non-native Thai tones than native Cantonese tones, suggesting a profound impairment in auditory/phonetic pitch processing in amusia. This finding also suggested that early exposure to a tonal language might not compensate for the impairment of lexical tone processing in a non-native language.