ABSTRACT
This chapter presents some of the arguments which are taken to be the most compelling for the parameter-setting approach come from two types of cases: the existence of a universal grammatical principle for which there seems to be no evidence available to children in the input, and the production of forms during language development which have no direct model in the adult speech to which children are exposed but which are a possibility sanctioned by universal grammar (UG) and which occur in other languages. WH-questions and their acquisition provide important examples of both types and have been cited in the literature as strong evidence in favor of the parameter-setting model. The first type of argument involves the principle of subjacency, which is proposed as a universal constraint on the formation of WH-questions and related constructions. The second type of argument involves the production by children learning English of long-distance WH-questions containing a medial WH-expression, as reported in Thornton.
