The earliest use of speech-like sounds has been described as cooing. During the first few months of life, the child gradually becomes capable of producing sequences of vowel-like sounds, particularly high vowels similar to [i] and [u]. By four months of age, the developing ability to bring the back of the tongue into regular contact with the back of the palate allows the infant to create sounds similar to the velar consonants [k] and [ɡ], hence the common description as “cooing” or “gooing” for this type of production. Speech perception studies have shown that by the time they are five months old, babies can already hear the difference between the vowels [i] and [a] and discriminate between syllables like [ba] and [ɡa].

Between six and eight months, the child is sitting up and producing a number of different vowels and consonants, as well as combinations such as ba-ba-ba and ga-gaga. This type of sound production is described as babbling In the later babbling stage, around nine to ten months, there are recognizable intonation patterns to the consonant and vowel combinations being produced, as well as variation in the combinations such as ba-ba-da-da. Nasal sounds also become more common and certain syllable sequences such as ma-ma-ma and da-da-da are inevitably interpreted by parents as versions of “mama” and “dada” and repeated back to the child

As children begin to pull themselves into a standing position during the tenth and eleventh months, they become capable of using their vocalizations to express emotions and emphasis. This late babbling stage is characterized by more complex syllable combinations (ma-da-ga-ba), a lot of sound-play and attempted imitations. This “pre language” use of sound provides the child with some experience of the social role of speech because adults tend to react to the babbling, however incoherent, as if it is actually the child’s contribution to social interaction.

One note of caution should be sounded at this point. Child language researchers certainly report very carefully on the age of any child whose language they study. However, they are also very careful to point out that there is substantial variation among children in terms of the age at which particular features of linguistic development occur. So, we should always treat statements concerning development stages such as “by six months” or “by the age of two” as approximate and subject to variation in individual children.