“If you didn’t learn a foreign language as a child, you will never be fully proficient in its grammar”
This is a more general version of the “foreign accent” myth described in the previous article in the series. It has its roots in the Critical Period Hypothesis proposed by Eric Lenneberg in 1967.
Lenneberg suggested that one’s first language must be acquired before puberty (about 12 years of age). After puberty, he claimed, neurological changes in the brain make it impossible to fully learn a language. To support his hypothesis, Lenneberg pointed to examples of children who were kept in isolation from others and had no contact with their first language until after puberty. Such children kept making basic grammar mistakes, no matter how long they tried to learn the language.
The Critical Period Hypothesis has been generalized to refer to second/foreign language acquisition, leading to statements such as: “If you don’t acquire a second/foreign language before puberty, you will always have problems with some parts of grammar” This causes language learners to interpret their flaws as a neurological necessity and discourages them from trying to improve.
Grammar proficiency has more to do with how much input you get than how early you begin learning.
Take my example: I was born in Poland and started attending English classes at 6. Despite my young age (which, in theory, should have allowed me to learn very quickly), I didn’t manage to acquire the language. After 9 years of attending classes my knowledge of grammar was extremely limited and I would always make tons of grammar mistakes. Finally, at 15, I started taking English seriously — reading books, using SuperMemo, using dictionaries, etc.
According to many linguists, I was already past my critical period, but guess what — I started making fantastic progress. I was learning faster than I had ever learned as a child. In 2-3 years, I managed to master native-like grammar, pronunciation, and vocabulary.
Today, my English is nearly as good as a native speaker’s. My writing is natural and basically flawless. After a few days of speaking practice, my accent becomes indistinguishable from that of an American native speaker. When I went to California this spring, I met some people who couldn’t believe I hadn’t been born in America until I showed them my Polish passport.
I occasionally make mistakes (I’m almost always aware of them), but it doesn’t bother me, because I have reasons to believe they would quickly disappear if I spoke English on an everyday basis.
I am 25 years old and I’m sure I could master another European language just like I mastered English. (I’m not sure about Chinese and other non-European languages.) Based on my experience, I certainly don’t think I would be “too old” to absorb any part of French or German grammar.
Directly taken from:http://www.antimoon.com/other/myths-child.htm