Prevalent linguistic analyses divide spoken language into three subsystems: (a) phonology-the system for producing sounds and rules for combining speech sounds to form words; (b) syntax-the system of rules for ordering words to make sentences; and (c) semantics-the system of meanings or conceptualizations. Semantics can be further subdivided into the meaning of individual words (lexical semantics) and the meaning of sentences (sentential semantics).
This section will begin with a discussion of the child's acquisition of the phonological system. Next we will consider the semantics of individual words and how the child acquires word meanings. Children's use of single words will be discussed both as holophrases (attempts to represent complete conceptualizations in single words) and as lexical units (individual units of meaning such as words) to be used in combination with other words to represent conceptualizations as sentences. Finally, we will consider the processes believed to be involved in the acquisition of syntax.
In the first step toward the development of language, the child begins to reproduce the sounds (phonemes) of the language he will eventually learn. Newborns do produce sounds with their vocal apparatus, but these sounds are simply cries. Some time around the sixth or eighth week babies begin to produce a class of sounds unrelated to crying-those of cooing and mewing. By the time the infant is six months old, cooing sounds become well differentiated and he can produce many different varieties of sounds. Vowels and consonants emerge as distinct from each other.
It is now possible to describe the child's vocalizations in the same way as adult speech sounds-in terms of distinctive phonological features. In the babbling of infants at this stage linguists can detect the distinct phonemes of the adult language (Deese, 1970). It is not until this stage that the sounds produced by infants in different linguistic environments can be told apart. In the early stages it is even impossible to distinguish a deaf from a hearing child by the sounds they produce. In the babbling stage, often the child acquires the stress and intonation patterns of meaningful speech, but not the words. The result is that the child sounds like he is saying sentences in a strange language.