M is around 16 months and chats like an old lady. I'm sure it's down to several reasons but her dad used sign language a lot before she became verbal and now constantly commentates to her.
It was pretty inspiring for me. I often zone out and daydream while Aidan plays. He'll be climbing up on the sofa and I'll be thinking about him reaching the summit of Everest.
With sign language you repeat words constantly while emphasizing the sign. The words must be sinking in, even if the sign isn't. Aidan doesn't look at me most of the time and it becomes a histrionic struggle. Even if it isn't helping Aidan's development, it stops me dreaming about scoring winning FA Cup Final goals.