My female co-worker (who was fired 6 months ago for harassment) used to talk to herself throughout the day. All the time. Since we worked together on many projects and day to day work, she would yell over the cubicle walls when she needed something from me.
Often, when I had someone in my office working with me, we could hear her talking to herself. And during her monologue, she would ask me a question - and I would answer. Those sitting next to me were baffled at how I knew when she was talking to herself vs. talking to me. Like computer network traffic, I learned when I could drop packets and when I needed to cache them!
But (thankfully) she's gone now...
-Z.