I can personally attest to how fast a child will learn a new language when he is given the same kind of language courses an adult is. When I was 6 years old I

I can personally attest to how fast a child will learn a new language when he is given the same kind of language courses an adult is. When I was 6 years old I decided to take Chinese/Mandarin lessons for a few months. If I compare my progress then to my colleague in his 20s who is learning Chinese in the same way - one hour a day, 2 times a week with an instructor - he certainly is learning much faster than I did. After 6 months he has already surpassed my level and is have basic reading/writing skills, which I never achieved. I also had German courses from age 8-10 with a similar schedule. After that 2 year period I still could not have anything but the most elementary conversation in German, despite getting very high grades in that class. On the other hand, I decided to become fully fluent in English in my late teens, and after intense self-directed practice and a few years in an English-speaking environment, no one is able to tell that I am not a native speaker.