Why can't you fool babies?

Why can't you fool a baby? We have given Rosie a real mobile phone (with no battery or chip in it obviously) because she is so keen on pressing the buttons. But no matter how much you give it to her she will throw it down, and I mean throw it down if she sees the real thing nearby. In this picture she has just reached up to pull the home telephone off its cradle to press all the buttons. That is why she is looking at the camera in that "what have I done?" look. It's the same with remote controls. We have given her any number of remote controls to play with - but she only really wants the Sky+ and DVD controllers. These are the only ones that do anything ... so I suppose babies are't stupid!