Faster and Smoother: Fluency in Chinese Child-directed Speech

Child-directed speech (CDS) is often believed to have a slower speaking rate than adult-directed speech (ADS). This study examined the fluency between CDS and ADS as well as the individual differences in mothers’ speaking rates. We annotated 2917 utterances in a corpus of Chinese ADS and CDS, where 19 mothers told the same story to their 24-month-old children and an adult. We coded and compared the fluency measures between ADS and CDS: speech rate (SR, including utterance-internal pauses), articulation rate (AR, excluding utterance-internal pauses), frequencies of silent pauses, filled pauses, repairs, and repetitions. We have three main findings: (1) CDS was generally more fluent than ADS, with fewer silent and filled pauses. (2) Contrary to common belief, only 7 out of the 19 participants showed a decreased SR and AR in CDS. (3) There were no significant differences in SR or AR between CDS and ADS when the utterance length was shorter than 4 syllables, whereas CDS was significantly faster than ADS when utterances were longer than 5 syllables. This suggests that Chinese CDS is not slower but instead faster than ADS. These findings highlight language-specific and individual variations in the temporal aspects of CDS.