Children pick up more than the language itself. They also apply the appropriate body language and head motions to each language.

Our first child was born in the States, but came with us to Israel when he was five months old. He was much too young at that time to socialize with the local children, and as new immigrants, we did not have any local, Hebrew-speaking children as guests in our home until much later.

Nonetheless, shortly after arriving in Israel, he tilted his head to signify no. That's what Israeli children do! Something in the air made him pick up that local behavior.