Abstract
Normal infants start to produce canonical babbling (CB) at the age of 6 to 10 months. CB consists of reduplicated sequences of consonant-vowel syllables which have adult-like acoustical features. Therefore, onset of CB is considered to be a landmark in the development of spoken language. The previous study indicated that a behavioral synchronization of vocalizations with rhythmic actions occurred in infants before the onset of CB. The present study examined the function of synchronization. Acoustical analyses were conducted on vocalizations of four infants during three-months-period including the month when synchronization occurred most frequently. The results show that both utterance length and formant frequency transition duration of synchronized vocalizations are shorter than those of non-synchronized vocalizations. These acoustical features, which are required to produce CB, persisted even after the synchronization has disappeared. The present study suggests that synchronization of vocalizations with rhythmic actions has the function of prompting infants to produce CB.
