cooing and babbling
The earliest use of speech-like sounds has been described as cooing. During the first few month 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) ans (g) , 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 vowel (i) and (a) and discriminate between syllables like (ba) and ga)