Vocalization and babbling

The primary expression of deep instinctual feelings is vocal: cries, wails, moans, chuckles, sobs and yells, etc. For the first three months, the preverbal infant uses the voice to express instinctual feelings such as yearning for nourishment and distress. Its melody rises and falls like a siren. Trevarthen (1979, 1987) indicates that vocalizations of newborns have remarkable features that could be related to the basic foundation of speech. Within weeks, the mother is able to distinguish her child’s cry from that of many others without face-to-face contact due to her innate ability to detect the idiosyncratic baby’s voice with its special rhythm and melody. In addition to these tonal cries, the baby also makes what are called vegetative sounds, or reflexive vocalizations such as coughs, hiccups, lip smacking, burps, and wheezes, which result from physiological processes (Dromi, 2001; Loewy, 1995; Newham, 1994). At around three months old, a new quality of cry emerges- the first so-called pleasure cry. The mother then learns to differentiate between different cries. She has the capacity to perceive in the infant’s melodic arrangement of pitch a language, which is as sophisticated as the baby’s needs (Newham, 1994). According to Hsu and Fogel (2001), studies that rest on a stimulus-response model of communication claim that within a dyadic communication system, adult responsiveness (e.g., looking, smiling, touching, and verbalizing) is thought to be the main factor in eliciting infant’s vocal responses. However, the authors prefer an alternative model that is a

dynamic process characterized by continuously coordinated and mutually regulated actions by both partners (see p. 89 for reviews).

Towards the end of the first year, the hearing baby’s vocalizations change considerably from the involuntary, reflexive sounds produced shortly after birth to non-reflexive vocalizations (e.g., cooing, playful productions and yelling). The baby then engages in more vocal play until about 30 weeks of age (Dromi, 2001; Stoel-Gammon, 1998). Then, the hearing infants start to repeat a single syllable over and over again. They can do this replicated babbling (such as ‘dadadada’or ‘mamama’) any time between seven and ten months of age. Babbling is defined as “reduplicated sequences of consonants (C) and vowels (V) (Schauwers, Govaerts, & Gillis, 2002, pp. 25-26). Some authors define it as ‘babble’ if it consists of a consonant and a vowel. The repetition of CV sequences give rise to the labels ‘repetitive babbling’, or

‘canonical babbling’” (Schauwers et al., 2002, pp. 25-26). Dromi (2001) indicates that during the extremely important canonical babbling stage, two types of production emerge:

1. Reduplicated babbling: Identical repetitive sequences of CV syllables (e.g.,

‘ma/ma, da/da);

2. Variegated babbling: Sequences of different consonants and vowels (e.g., CV, V, VC, VCV= /ga/e/im/ada).

Stoel-Gammon (1998) claim that although canonical syllables represent a key stage in vocal development, they do not represent the most frequently occurring type of vocalization.

Parents imitate their babies by babbling back to them or reshaping babble sequences into words. This serves as a motivator for the baby to continue, as well as allowing the baby to match his/her own sounds with those produced by the parent. As a result, the baby modifies and increasingly refines subsequent sound production (Herman, 2004b).

Regardless of the language spoken at home, studies of parents have shown that adults are particularly responsive to babies and make similar changes to their speech patterns when addressing the babies. These include using a higher overall pitch, more varied intonation, a slower tempo and a singsong rhythm (Muir & Slater, 2000).

These changes, referred to as 'baby talk', 'motherese' or 'infant directed speech' make speech sound more interesting to the baby and serve as a signal to the child to attend.

In addition, the early ‘conversations’ between parents and babies have highly repetitive nature. This repetition is extremely helpful to the baby who will soon be trying to make sense of what is said (Herman, 2004b). Papoušek, Paoušek, and Bornstein (1985) add that besides many repetitions, motherese is characterized by shorter utterances, and longer pauses between each utterance. Trevarthen (1979) and Stern (2000) indicate that musical features such as melodic contour, tonal intensity, dynamics and rhythmic patterns serve as crucial early models of emotional and social communication.

Until the age of ten months, babies will vocalize many different sounds; then, they will start focusing in playing around with the speech sounds of their mother language (Bates, Thal, Finlay, & Clancey, 2002).

A stage called ‘jargon babble’ (or intonated babble’), starts at around 12 months of age. This stage occurs with both the canonical babbling stage and the use of early words and is characterized by strings of sounds and syllables uttered with a variety of stress and intonational patterns (Stoel-Gammon, 1998).

The vocalization and babbling produced by most children likely serves an important function of helping children tune their phonological system (Bricker, 1992). Stoel-Gammon (Stoel-Gammon, 1992) summarized longitudinal studies which showed that babbling serves as a foundation for subsequent acquisition of speech and language. A late onset of canonical babbling is a predictor of risk for future speech and language pathology. The onset of this stage can be monitored effectively through parents’ interview (Oller, Eilers, Neal, & Schwartz, 1999).

Compared to babies with NH, babies who are deaf cannot be soothed by the parent’s voice and do not learn implications of tone and voice but they do vocalize from an early age. Their vocalizations are reflexive rather than intentional (Herman, 2004a). In addition, the more a baby practices babbling, the greater the opportunity to establish the auditory and kinesthetic feedback loops necessary for producing and monitoring his/her own speech (Stoel-Gammon, 1998). However, since babies who are deaf have little or almost no auditory feedback, and since feedback cannot occur in the absence of practice, their repertoire of vocalization tends to show differences from infants with NH from about six to nine months of age at which time their vocalizations dramatically diminish if they do not receive auditory feedback by means of amplification or a cochlear implant (Kent, Osberger, Netsell, & Goldschmidt-Hustedde, 1987; Koopmans-van, Florien, Clement, & van den Dikkenberg-Pot,

2001). Oller and Eilers (1988) found that infants who are deaf, even though they have been intensively stimulated and provided with auditory amplification, show substantial delay in the emergence of canonical babbling and also a decreased variety of consonants from eight months onward. The authors note that if one might ask why the children who are deaf ever produced canonical babbling, the most plausible response seems to be that however hearing impaired the children were, they did have a means of perceiving speech sounds - visually and through residual (amplified) hearing.

Some studies indicated that babies who are deaf and are exposed to sign language develop a form of hand babbling during the second half of the first year (e.g., Petitto, Holowka, Sergio, & Ostry, 2001; Petitto & Marentette, 1991; Schauwers et al., 2002).

Schauwers et al. (2002) indicate that children who are deaf and received cochlear implants need up to four months of exposure to sound in order to start babbling while hearing infants need six to ten months. The authors raise the question whether this is due to the more advanced maturation of the children with CI compared to the infants with NH who are much younger. They also cautiously conclude that one surely needs a certain amount of auditory stimulation for babbling to appear.