2 Ears?

S and E are always finding themselves competing for listening time. I am trying to teach them to listen to each other as they are talking and not to interrupt. Many afternoons when S gets home from school, they both try and talk to me at the same time. Today S was sitting at the kitchen table telling me about her school day when E can up to tell me something. As they were both talking at the same time, I stopped them and reminded them that I could not hear either one of them when they were both talking. E looked at me, and matter-of-fact pointed out that "mom, there are 2 of us and you have 2 ears, so you should be able to hear us both" I understand your reasoning, but it doesn't quite work that way!