The effect of syllable variation on the perception of lexical tones in Cantonese-speaking amusics

Congenital amusia is a neurogenetic disorder of fine-grained pitch processing. Though there is some evidence that this disorder extends to the language domain and negatively influences lexical tone perception, its deficiency mechanism remains unclear. This study designed a series of perception tasks to probe different levels of lexical tone perception, and expected to shed light on the mechanism underlying tone perception in amusia. Sixteen Cantonese-speaking amusics and 16 matched controls were tested on the effects of syllable variations on the perception of Cantonese tones with low variations, i.e., tones were always associated with the same syllable, versus high variations, i.e., tones were always associated with different syllables. Results of the identification task showed a trend of more pronounced group differences in the low variation condition compared to the high variation condition. In the discrimination task, the group difference was larger in the low variation condition, where more acoustic constancy was provided. These findings suggested that the amusics’ tone perception abilities, in terms of both domain-general pitch processing and high-level phonological processing are impaired. Furthermore, Cantonese-speaking amusics seemed to be more impaired in the low acoustic variation context, implying a possible ‘anchoring deficit’ in congenital amusia.