In the mid-sixties, the field [acquisition study], which had previously been atheoretical and somewhat underdeveloped, came to be dominated by a type of innatist theory. This theory, derived largely from generative grammar, and in particular from works such as Chomsky [Chomsky, N. 1962. “Explanatory models in Linguistics”, in Nagel, E. et alii Logic, Methodology and the Philosophy of Science, Stanford, Stanford University Press] held that the child acquired language through simple exposure to linguistic data, much of which was “degenerate”- i.e., consisted of sentence fragments, mid-sentence reformulations, and many types of performance error which would render natural speech a very unreliable mirror to mature native-speaker competence. Somehow the child had to sift the wheat from the chaff, and he could only do this, it was claimed, if he had some kind of inbuilt Language Acquisition Device (LAD).
- Bickerton (1981), a pag.136

A LAD would contain a set of linguistic universals, presumed to be innate and genetically transmitted. These universals would not, however, precisely specify a particular potential language […] rather they would define somewhat narrowly the limits on the forms which human language might take, thereby drastically reducing the number of hypotheses that the child could make about the structures of his future native tongue and rendering it correspondingly easy for him to select the correct hypothesis.
- Bickerton (1981), a pag.136-137