There have been quite a few attempts to write comprehensive "grammars" (systems of generative rules), of the type developed by Chomsky, that could characterize a child's speech at various stages, including the more advanced ones (Braine, 1963, 1971; Miller and Ervin, 1964; Bloom, 1970; Bowerman [see Brown, 1973]; Brown, Cazden, and Bellugi, 1969). These researchers have attempted to describe the syntactic structures of children's utterances at a given stage by formulating a set of rules that could generate equivalent structures. The set of rules is considered to reflect the child's knowledge. As the child progresses, some rules are modified, others added, and the grammar gets reorganized so that each stage is characterized by a different set of rules. It is important to note that these grammars have generally been concerned only with syntax and not with meanings. The child's language has generally been viewed as advancing from two-word speech to a stage when the child begins to use combinations of words that can be generated by relatively simple phrase-structural grammars. This phrase-structural grammar becomes more complex and eventually becomes reorganized in certain ways. The child is now viewed as adding transformational rules to his knowledge. He is approaching adult grammatical competence.

The work of Klima and Bellugi (1966) on tracing children's acquisition of the rules for negation in English clearly illustrates some of these steps. (The authors also trace the acquisition of questions in a similar way, but negation provides a sufficient example by itself.) The acquisition of negation is divided into three stages:

In the first stage, negative markers ("no" or "not") are simply attached to either the beginning or the end of the utterance to be negated. There are no negatives within the utterance, nor are there any auxiliary verbs in the child's speech. Examples at this stage include: "Wear mitten no," and "Not a teddy bear."