The cognitive revolution was driven in part by the linguist Noam Chomsky, whose articulation of the logical problem of language acquisition and proposed solution via Universal Grammar opened up new avenues for language research, as well as general cognitive inquiry. Chomsky's theory of an innate language-learning mechanism or internal grammar were taken up by second language researchers such as Selinker, who developed the notions of interlanguage and fossilisation.
Attention thus turned from the role of the teacher to that of the learner, and focused on each learner's construction of an individual grammar of the language, highlighting the importance of linguistic input, the nature of evidence, and the existence of developmental sequences which all learners follow in learning a second language.
More recent second language research has shed new light on issues of transfer and age constraints (Long), and led to more dynamic models of second language acquisition, such as emergentist frameworks (Ellis), as an alternative to Chomskyan generativist approaches.