Some would say that babies are narcissistic, but in staring at themselves in the mirror they're making associations between moving
that muscle and getting, say, their tongue to stick out. Before I thought I needed a little mirror at their eye-level, but then I was inspired to use the one in our room: G and BB can't run off with it, and theoretically it wouldn't fall on Z either. I've kept her occupied for ten and fifteen minutes like this.