I'm unsure how they tell or how it looks, because those are external things. I know that it frightened me and I disliked losing even little bits of time. When I hear them speak in my head there are vocal differences to do with age. There are personality differences, but from the outside that might just appear as mood. The anger one moves and speaks differently than I ever would. I have come back when they used my name or asked a question that belonged to me. It's like swimming up from underwater for me.