Quote Originally Posted by Dayuhan View Post
I've never seen any scientific studies on the matter and I'm certainly no linguist, but my own observations convince me that people who grow up with multiple languages, or at least have early exposure to multiple languages, find it easier to pick up languages for the rest of their lives.
It's like playing a musical instrument (or learning a martial art or style of skiing or a number of other skills): every time you know one more well,* the next one comes more easily. It is generally thought that children enjoy a full access to Universal Grammar which adults do not, but the evidence is not unequivocal in that regard.

*The caveat is well. Going on to the next one before getting a good grasp on the one you have started tends to lead to confusion.