ABSTRACT
The notion that there is a critical period for language development is a widely accepted one. The woman-in-the-street is convinced that her children can learn a foreign language more quickly, easily, and well than she or her husband, and if pressed would attribute these age differences to the adult’s lack of “flexibility” in learning new rules, new sounds, and new ways of thinking. Introductory psychology textbooks present a version of the same idea phrased more specifically in terms of neuropsychology, or biological limits on learning,
There is an important and familiar problem we have ignored thus far—language learning is very much easier in children than in adults. This and related facts are often regarded as evidence that there is a critical period for language learning. This period is thought to extend from roughly three months to puberty. According to the hypothesis, some characteristics of the brain change as the critical period draws to its close so that later language learning (both of the first language and of later ones) becomes more difficult. (Gleitman, 1981, p. 403)
Several phenomena suggest that there is a critical period for language learning in humans, just as there is for the development of bird song in certain sparrows. Evidence comes from studies of isolated children, of second-language learning, and of recovery from aphasia. (ibid., p. 411)
