Bonzi said: However, child psychologists often maintain that it is best to let child grasp a very concept of speach with one language first, and than (say, at the age of two)
I do not think this is the case anymore. Having been involved in a study that measured this sort of thing, the best thing for children of bilingual parents is to have both languages spoken right away. Otherwise there may be more confusion. Of course, this assumes children without any mental disabilities, etc.

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