Delayed Exposure to Second Language Acquisition: The Robustness of Critical Period Hypothesis and the Limitations of the Plasticity Theory

Abstract

Studies of language acquisition have shown that language learning ability declines with age. It has been documented that the overwhelming majority of learners who begin the process of second language (L2) learning after passing the critical period — after a certain age – cannot attain native-like competence (underlying knowledge of language) at the end state. There is a universal folk belief, shared by almost all psycholinguists, that at an early age, the brain is plastic; it can modify its own structure, organization and function as a direct consequence of experiences and learning. According to this belief, the plasticity of the brain fades with age and with the increasing specialisation of the different hemispheres and areas of the brain. However, recently neuroscientists, equipped with the complementary aid of brain neuroimaging, have discovered that mature brain is far from being fixed as previously thought; it has the ability to continuously adapt its structure and function based on internal and external environmental changes and/or input such as experience, ageing, illness, injury and learning, meaning that the brain remains plastic throughout life. The purpose of this article, therefore, is to illustrate that the theory about the loss of brain plasticity during natural maturation is not valid in explaining the question why L2 learning is affected by delayed exposure to a language? It should be mentioned here that until now, the overwhelming majority of L2 researchers tend to think of plasticity as a phenomenon confined to early development; and therefore, evidence supporting plasticity is generally ignored.