Overview

The onset of canonical babbling (CB) marks an important milestone in preverbal infants' vocal development. Unlike the sounds that infants produce before this stage, CB (e.g. “mama,” “bababa”) consists of well-formed, consonant–vowel syllables which have adult-like spectral and temporal properties (Oller, 1986). Much acoustic evidence shows that there is a significant degree of continuity between the sound system of babbling and that of early speech (Vihman et al., 1985). Thus, an understanding of how infants learn to produce CB is important for an understanding of how they acquire spoken language.

Within infant's typical development, CB first occurs around 6–10 months of age. The onset period of CB has been considered to be consistent for all infants, regardless of their language environments (Oller & Eilers, 1988; Koopmans-van Beinum & van der Stelt, 1986). With regard to the onset of CB in Japanese infants, few studies have investigated the period when infants start to produce CB. Recently, Ejiri (1998a) showed, from her longitudinal study of 28 Japanese infants, that the average age of CB onset is 29.6 weeks (range: 21.4 to 38.6 weeks). This result is also consistent with the data reported from the other language environments.

Several researchers have proposed the idea that babbling is one accomplishment in a series of overall developments of the infant's rhythmic behavior (e.g. Eilers et al., 1993; Locke et al., 1995; Meier et al., 1997; Thelen, 1991).