The effect of backward noise on lexical tone discrimination in Mandarin-speaking amusics

Congenital amusia is a neurogenetic disorder, affecting music pitch processing. It also transfers to the language domain and negatively influences the perception of linguistic components relying on pitch, such as lexical tones. It has been well established that unfavorable listening conditions impact lexical tone perception in amusics. For instance, both Mandarin- and Cantonese-speaking amusics were impaired in tone processing under simultaneously noisy conditions. Backward noise is one of the adverse listening conditions, but its interference mechanism is distinct from the simultaneous noise. Therefore, it warrants more studies to explore whether and how backward noise affects tone processing in amusics. In the current study, eighteen Mandarin-speaking amusics and 18 controls were tested on discrimination of Mandarin tones under two conditions: a quiet condition involving relatively low-level processing and a backward masking condition involving high-level processing (e.g., tone categorization) where a native multi-talker babble noise was added to target tones. The results revealed that amusics performed similarly to controls in quiet conditions, whereas their performance was found poorer in backward masking conditions. These findings shed light on how adverse listening environments influence amusics' lexical tone processing and provided further empirical evidence that amusics may be impaired in the high-level phonological processing of lexical tone.