My son grows up as a bilingual. At home we speak Arabic or German with him while he usually speaks German at the playschool.
Until his third birthday, I sometimes remarked that he couldn't really switch between languages or more exactly address his conversation partner in the right language: For example, he insisted to talk to my in-laws (Arabic) in German. I'm not quite sure whether he did/does so because he don't know or in defiance of them, because he loves them very much, but they could rarely come to visit us!
On the other hand, he addressed my father, who speaks both Arabic and German, in Arabic.
While he at first used to talk to us in German, now he seems to adapt the language on the actual "on" language!
Therefore, I often wondered if children could easily address their conversation partner in the right language or could realize whether they could understand them or not?
And if so, at what age this would happen?