Quite awhile ago we taught Isabelle how to make this noise with her tounge and lips. She was doing really well and then we couldn't get her to do it for quite awhile. Now she is doing it again. It almost seems like she does it to show off.
One day Mark and Helen babysat Izzy for us and I guess Mark was doing that to her and she was copying him and Mark got all excited that she was copying him, much to his suprise he did not know that she already knew how to do that.