Slide Slam D14
Categorical Perception of Mandarin tones in Children with Developmental Dyslexia
Chanyuan Gu1,2,3, Hong-Yan Bi1,2; 1Institute of Psychology, Chinese Academy of Sciences, 2University of Chinese Academy of Sciences, 3The Hong Kong Polytechnic University
Introduction: Categorical perception is a significant characteristic of speech perception, indicating that people can perceive the continuously changing speech signals as discrete speech categories and classify the countless speech signals into limited speech categories. Studies with segmental information have found that individuals with dyslexia are hyposensitive to between-categorical stimuli and oversensitive to within-categorical stimuli compared with typical readers. Combining the between-categorical and within-categorical perception deficits, researchers proposed that dyslexics formed the abnormal perception signals instead of establishing the effective speech perception signals. Chinese is a tonal language, and tone is a kind of suprasegmental information. The tone has not only the characteristics of categorical perception, but also the unique neural mechanism. Although previous studies have examined tone perception in Chinese children with developmental dyslexia (DD), these studies mainly focused on the between-categorical perception of tone in individuals with dyslexia. According to the studies with segmental information, nonetheless, the perception deficit in individuals with dyslexia is not only related to the between-categorical attribute, but also the within-categorical attribute. By combining the between- and within-categorical performance, we can systematically reveal the categorical perception of tone in individuals with dyslexia. Methods: We adopted the level tone (/yi1/) and rising tone (/yi2/), and created tonal continua as stimuli. Two studies were designed to systematically investigated the categorical perception of Mandarin tones from the behavioral and neural levels in Chinese children with DD. Children with DD and the corresponding chronological-age control group were recruited as participants. All participants are primary school students at 5th or 6th grade in Beijing. Adopting identification and discrimination tasks simultaneously, study 1 examined the categorical perception of Mandarin tones in Chinese children with DD at the behavioral level. Study 2 examined the categorical perception of Mandarin tones in children with DD at the neural level using the passive oddball paradigm, with mismatch negativity (MMN) and late discrimination negativity (LDN) as the neural markers. Results: We have two critical findings: (1) Dyslexic children were hyposensitive to the between-categorical stimuli. Dyslexic children exhibited a smaller absolute value of identification slope and a lower accuracy in discriminating between-categorical stimuli at the behavioral level. At the neural level, compared with chronological-age children, the LDN amplitude was smaller for dyslexic children on the left, middle, and right sides of the brain; (2) Dyslexic children were oversensitive to the within-categorial stimuli. When dyslexic children perceived the within-categorical stimuli, they exhibited larger MMN than chronological-age children on the right side of the brain; (3) The between-categorical perception was positively correlated with reading performance or reading-related skills in two groups. Conclusion: The present study systematically examined the categorical perception of Mandarin tones in children with DD from behavioural and neural levels for the first time. The findings showed both the deficit of hyposensitive perception in between-categorical stimuli and the deficit of oversensitive perception in within-categorical stimuli for Chinese children with DD. This study deepens the understanding of the nature of Chinese dyslexia and inspires future intervention and remediation in Chinese children with DD.