All normal children develop language at roughly the same time, along much the same schedule. Since we could say the same thing for sitting up, crawling, standing, walking, using the hands and many other physical activities, it would seem that the language acquisition schedule has the same basis as the biologically determined development of motor skills. This biological schedule is tied very much to the maturation of the infant’s brain.

We could think of the child as having the biological capacity to cope with distinguishing certain aspects of linguistic input at different stages during the early years of life. Long before children begin to talk, they have been actively processing what they hear. We can identify what very young children are paying attention to by the way they increase or decrease “sucking behavior” in response to speech sounds or turn their heads in the direction of those sounds. At one month, for example, an infant is capable of distinguishing between sounds such as [ba] and [pa]. During the first three months, the child develops a range of crying styles, with different patterns for different needs, produces big smiles in response to a speaking face, and starts to create distinct vocalizations.