Linguist Noam Chomsky challenged the behaviorist model of language learning. He proposed a theory called Transformational Generative Grammar, according to which learners do not acquire an endless list of rules but limited set of transformations which can be used over and over again. With a fairly limited number of these transformations, according to Chomsky, language users can form an unlimited number of sentences. Other theorists have also proposed ideas that have influenced language teaching. Stephen Krashen, for example, studied the way that children learn language and applied it to adult language learning.
Learners use the comprehensible input to deduce rules.
Krashen's views on language teaching have given rise to a number of changes in language teaching, including a de-emphasis on the teaching of grammatical rules and a greater emphasis on trying to teach language to adults in the way that children learn language. While Krashen's theories are not universally accepted, they have had an influence. Developments in various directions have taken place since the early 1970s. There has been developments such as a great emphasis on individualized instruction, more humanistic approaches to language learning, a greater focus on the learner, and greater emphasis on development of communicate, as opposed to merely linguistic, competence. In addition, there has been a disillusionment with the whole methods debate, partly due to inconclusiveness of research on methods, and calls for a deeper understanding of the process of language learning itself.