Second Language

Dr. Susan Curtiss, Professor of Linguistics at UCLA, who studies the way children learn languages, notes that in language development there is a window of opportunity in which the child learns that first language normally. After this period, the brain becomes slowly less plastic and by the time the child reaches adolescence, the brain cannot develop "richly and normally any real cognitive system, including language."

The four- or five-year old learning a second language is a "perfect model for the idea of the critical period." According to Dr. Curtiss:

...the power to learn language is so great in the young child that it doesn't seem to matter how many languages you seem to throw their way...They can learn as many spoken languages as you can allow them to hear systematically and regularly at the same time. Children just have this capacity. Their brain is just ripe to do this...there doesn't seem to be anyjavascript:void(0) detriment to...develop(ing) several languages at the same time.
When children wait until high school to start studying a foreign language, the job is much harder. The task now involves learning the rules of grammar, translating, reading, and trying to develop language learning strategies. The task is a different one than it was for the young child in the sensitive period for language learning. Brain plasticity has been lost, the number of synapses has greatly reduced, and the brain no longer has the same facility to restructure itself that it had when the child was young.