When children are very young they actually are able to distinguish between different language sounds very well. Once their own language sounds are �set � they lose this ability to quite a degree.
eg: The difference between L and R in languages that don �t have those English sounds.
Making �th �, or an English speaker trying to correctly pronounce sounds not in English.
The other problem is the fine motor muscles of the tongue and face. It is much easier for children to learn the correct pronunciation while they still have the ability to train these muscles automatically.
Children at an early age gain new vocabulary easily in great volumes. Their brains are wired that way. The older one is the more difficult it becomes to retain new words without a lot of practice.
I always found it interesting that Charles Berlitz, linguist and author (Berlitz Travel Guides) learned 4 different languages as a child, all spoken by different members of his family. He was unaware they were world languages. He just thought people had different ways of speaking.
These are the reasons I think �the earlier the better � for learning new languages.
