Children in general acquire a foreign language almost without any conscious effort. There are children who start by speaking more then one language. It is easy to notice that a young child can pick up a new language rapidly if he/ she moves to a school abroad.
Researchers came to the conclusion that a child is able to quickly acquire new language up to around the age of six. Children are not capable only of learning languages, but also of forgetting them. They replace the forgotten language structures with new language as if they were changing their articles of clothing. But this process of unconscious learning is at its best before the child reaches puberty. After children have reached puberty, it becomes more and more difficult for them to learn a new language very fast.
Learning and Teaching English