by Jean Sumner

Created on: April 22, 2007   Last Updated: May 02, 2007

Even though they can't yet speak, infants are quite responsive to language from the day they are born. In fact, in the first few days and weeks of life, babies already have the ability to differentiate a variety of speech-like sounds. Because humans seem to be "prewired" at birth to organize and make sense of speech, children who are in an environment without language may risk missing the "critical period" for language learning.

What's so critical about the critical period of language acquisition? The idea of a critical period suggests that language learning is not only easier earlier in life, but may even occur differently earlier in life: it seems that the brain and cognitive system of a young child is especially suited for learning language. Linguists such as Noam Chomsky believe humans are biologically programmed to acquire language. He proposed in the 60s that an inborn language processor, activated by verbal input, facilitates babies' knowledge of the rules that are common to all languages. Erik Lenneberg's (1.) "sensitive period hypothesis" supports this idea. He proposed that languages are most easily acquired between birth and puberty.

So what is happening in the brain during this critical period of language acquisition that makes it easier for us to learn languages between birth and puberty? Apparently the left hemisphere of the brain is specialized to some aspects of language from birth. Modern technological marvels allow us to use brain scanning devices to peer into the brain's inner workings. The very day that a baby emerges from the womb, listening to her mother speak will elicit more electrical activity from the left side of her brain than the right (2.). Interestingly, when bilinguals that acquired both languages early in childhood speak either of their two languages, the *same* area of the brain is activated with brain scanning techniques. However, when bilinguals who learned a second language after puberty, two *different* areas of the brain are activated on a brain scan (3.).

We've probably all noticed from personal experience that learning a second language as an adult is a seriously difficult endeavor! If language really is most easily learned during a critical period, children who were deprived of a language rich environment will find it difficult to acquire language later in life. In fact, several case studies support the sensitive-period hypothesis. One is the case of Genie, a girl who was locked away in a back room as an infant. No one

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