Handbook of Language and Literacy Development - a Roadmap from 0 to 60 Months

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Vocalizing (4 – 6 Months) – Vocal Play Emergesclick to print Print
Research Review / Parent

Written by: Carrie Gotzke and Heather Sample Gosse, University of Alberta

Vocal development in the first three months was driven by reflexive vocalizations, such as crying. In the four- to six-month period, however, infants are developing increasing control over the vocal mechanism (Owens, 2001). This period can be characterized as a time of vocal play. Infants are increasingly responsive to their environment and are more able to react to feedback from the world around them. Continued successful communication development depends both on the ability of the infants to signal messages clearly and the ability of their caregivers to interpret those signals. Vocal skills continue to develop in the context of interaction with others. For information on this critical context, please refer to Interacting 4 – 6 Months.

Oral Control - The Foundation for Vocal Skills

Between four and six months, infants continue to demonstrate back-and-forth jaw movement when swallowing. This suck-swallow pattern persists until swallowing without jaw movement is achieved at about three years of age (Owens, 2001). Two distinct sucking behaviors – nutritive and nonnutritive – continue to be exhibited with nonnutritive sucking gaining increasing prominence. While the objective of nutritive sucking is to acquire nutrition, the objective of nonnutritive sucking may be to explore the environment or to obtain comfort. By four months of age, infants may engage in up to four hours per day of nonnutritive sucking of fingers and objects and of exploring their faces and mouths (Owens, 2001). Both nutritive and nonnutritive sucking behaviors help infants develop control of the muscles used to produce speech.  

Vocalizations – Increasing Sound Control

The range of vocalizations during the first three months was partially limited by the shape of infants’ vocal tract (Menn & Stoel-Gammon, 2005). With continued growth of the neck and head, increased control over the vocal mechanism (e.g., jaw, tongue, lips), and development of discrimination to touch, pressure and movement in the tongue tip and lips, infants become able to produce a greater variety of sounds.

Quasi-Resonantal Nuclei and Cooing

Between four and six months, infants continue to produce quasi-resonantal nuclei and to “coo,” as they continue learning to manipulate their vocal apparatus. Infants of this age are also able to produce fully resonated nuclei vowel-like sounds similar to “aw” (as in “hot”) (Owens, 2001). As jaw control develops, other vowel sounds such as “ih” (as in “hit), “ae”(as in “date”) and “eh” (as in “pet”) may also be produced. From four to six months, vowel sounds predominate (Menn & Stoel-Gammon, 2005). By six months, infants are increasingly able to control the lips resulting in the production of labial or lip sounds (i.e., /m, p, b/) (Owens, 2001).

Vocal Play

Vocalizations from four to six months of age are also characterized by increased variety and vocal play (Apel & Masterson, 2001; Menn & Stoel-Gammon, 2005; Owens, 2001). Vocalizations may vary in loudness (loud to soft), pitch (high to low), rate (fast to slow) and quality (screams to growls). Raspberries (i.e., bilabial trills) may also be produced by vibration of the lips. 


Infants’ vocalizations are predominantly single consonant-vowel or vowel-consonant syllables (Owens, 2001). With time, infants may produce strings of syllables (i.e., babbling) as vocalizations become increasingly complex. Babbling may be described as “random sound play” (Owens, 2001). Reduplicated babbling, in which infants repeat a single consonant-vowel or vowel-consonant syllable production (such as “ma-ma-ma-ma”), becomes more common. Infant vocalizations become increasingly complex, containing longer sequences and prolonged individual sounds.

The sounds produced during babbling may be different from those found in the native language. Three possible explanations for the production of these non-native sounds have been hypothesized (Owens, 2001). Differences in the size and shape of the vocal tract between infants and adults affect the resonance and laryngeal tone, which may result in the production of non-native sounds. As well, infants are still developing motor control of the speech mechanism affecting their ability to produce accurate sound productions. Finally, infants may not have acquired an awareness of which sounds are in their native language and how they are distributed, and as a result, produce non-native sounds.

Vocalizations – Increasingly Expressive

As infants play with their developing vocal mechanism, they become able to express their emotional state. Sustained laughter, consisting of rapid alternation of voiced and voiceless sounds, emerges around four months. To indicate the need for attention, four-month-old infants are able to vary the volume, pitch and rate of their vocalizations. Beginning at five months, infants will express pleasure, displeasure, satisfaction, anger, and eagerness via different vocalizations.  

Effect of the Language Environment

The sounds and sound patterns of the infant’s environment will affect the sounds that infants produce (Menn & Stoel-Gammon, 2005; Sachs, 2005). Infants will stop using sounds not heard and will start producing syllables with the timing and pitch contour of their language environment. For example, French, English, Swedish and Japanese infants will produce the same types of sounds but the frequency with which individual sounds are produced will vary according to the frequency of occurrence in their home language (Menn & Stoel-Gammon, 2005). As well, the intonation contour of the babbled sequence will vary among infants from different language communities. 

Gotzke, C. & Sample Gosse, H. (2007). Research Review: Vocalizing 4 - 6 Months. In L.M. Phillips (Ed.), Handbook of language and literacy development: A Roadmap from 0 - 60 Months. [online], pp. 1 - 8. London, ON: Canadian Language and Literacy Research Network. Available at: Handbook of language and literacy development