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Another common misconception is that bilinguals have equal knowledge of their languages. In fact, bilinguals know their languages to the level that they need them and many are dominant in one of them.

There are also the myths that real bilinguals do not have an accent in their different languages and that they are excellent all-around translators. This is far from being true. Having an accent or not does not make one more or less bilingual, and bilinguals often have difficulties translating specialized language. Then there is the misconception that all bilinguals are bicultural (they are not) and that they have double personalities (as a bilingual myself, and with a sigh of relief, I can tell you that this is not the case).

про детей, а не вообще, там тоже есть

И даже такое:

If parents want their children to grow up bilingual, they should use the one person - one language approach. WRONG. There are many ways of making sure a child grows up bilingual: caretaker 1 speaks one language and caretaker 2 speaks the other; one language is used in the home and the other outside the home; the child acquires his/her second language at school, etc. The critical factor is NEED. The child must come to realize, most of the time unconsciously, that he/she needs two or more languages in everyday life. This is where the one person - one language approach often breaks down as the bilingual child quickly realizes that the weaker (often minority) language is not really needed (the caretakers or other family members often speak the other, stronger language, to one another, so why keep up the weaker language?). A better approach is that all family members use the weaker language at home, if at all possible, so as to increase the child's exposure to it and mark the language's "main" territory.

Актуальное мне. Валя тут папе заявил, что с мамой он может И по-итальянски разговаривать, потому что мама понимает итальянский. Мое недоуменное кручение-вращение головой аки сова его не убедило:

Children raised bilingual will always mix their languages. WRONG. If bilingual children interact in both bilingual and monolingual situations, then they learn to mix languages at certain times only. When they are with monolinguals (e.g. Grandma who doesn't speak any English), they quickly learn to speak just the one language (communication breaks down otherwise). It is important though that the situation be truly monolingual (and not a "pretend situation" in which a bilingual parent pretends not to know the other language); children will make an effort to speak only one language if they feel it is vital for communication. Thus, caretakers will want to create natural monolingual environments where children will need, and hence use, just one language.

http://www.francoisgrosjean.ch/myths_en.html

http://www.francoisgrosjean.ch/bilingualism_is_not_en.html