ABSTRACT
Within the Principles and Parameters theory of grammar (see e.g. Chomsky & Lasnik, 1993), first language acquisition is viewed as the change from an initial state to the steady state that is the mature grammatical competence of the individual. This competence includes the blueprint not only of what is possible but of what is impossible in the language. It is a basic tenet of this theoretical framework that the initial state is equivalent to universal grammar (UG), which restricts the possible kinds of grammar available for acquisition. UG is genetically determined and uniform for all members of the human species. The child's exposure to natural language (primary linguistic data) triggers the setting of the appropriate parameters for the language being acquired.
