All of the chapters in this section are concerned with the acquisition of the syntactic component of a grammar and all assume the Government-Binding Theory of language outlined in Chomsky (1981, 1986), van Riemsdijk and Williams (1986), and elsewhere. Furthermore, they all, to some extent, focus on the logical problem of foreign language learning (Bley-Vroman), that is, how the adult second language learner who attains reasonable proficiency in the target language does so on the basis of impoverished input – thus necessitating another knowledge source and/or set of learning procedures to be posited, which will, together with the input, suffice to explain the attained proficiency.

The claim that the input to the learner is impoverished needs to be amplified somewhat since it is crucial to the argumentation underlying the work of those espousing a Universal Grammar approach to language acquisition. Let us consider two different kinds of input problems. In the first case, the learner will doubtless hear two phrases: thanks a lot and thanks anyway. The learner's task is to figure out on which occasions each is appropriate and whether or not they are interchangeable. Although the distinction between these two phrases is not necessarily an easy one, the learner will have information from the input indicating that each phrase does occur and that guides in the appropriate use of each phrase. The second case, however, is more complicated. Suppose the learner has figured out how to make wh-questions from simple sentences and is working on making them from more complex sentences.