Audiovisual speech perception in Cantonese-speaking children: Developmental trajectories and the role of noise.

The development of audiovisual speech perception in tone-language-speaking children remains debated, and this study addressed this issue by examining Cantonese-speaking children, extending prior work on Mandarin speakers to a tone language with greater phonological complexity. Using the McGurk paradigm, 82 typically developing Cantonese-speaking children (42 girls, 40 boys; aged 4-11 years) and 21 adults (11 females, 10 males) from Hong Kong completed audiovisual speech perception tasks in quiet, moderate background noise (10 dB speech-to-noise ratio, SNR), and severe background noise (-10 dB SNR). Results showed developmental shifts in sensory dominance among Cantonese-speaking children around age 10: from relying mainly on auditory cues to integrating auditory and visual cues in quiet and 10 dB conditions, and from audiovisual-integrated to visual-dominant processing in the -10 dB condition. This developmental pattern aligns with the predictions of the Statistically Optimal Hypothesis. These findings also indicate that Cantonese-speaking children undergo this shift later than Mandarin-speaking peers, highlighting the adaptive nature of this developmental process.