Many theorists (e.g., Hyams 1987; Pinker 1984) working in the framework of generative grammar have assumed the “Continuity Hypothesis”. Under this view language acquisition is made up of a series of continuous stages. The child moves from one stage to another, and at each stage the grammar posited by the child is determined by Universal Grammar (UG). The motivation for the movement from one stage to another comes from a trigger in the language environment which causes the child to restructure her grammar, and so move on to the next stage. The Continuity Hypothesis has provided an explanation for the acquisition of many linguistic structures; however, in many instances it has been difficult to explain exactly which data in the language environment act as a trigger, and why they have an effect on the child’s grammar.