You bring up a good question ... one which I don't really know the answer to.

I've always thought in terms of sound/words (I've heard other people think in terms of pictures/images) so I have a constantly running internal dialogue of sorts.

I also talk to/converse with myself (not so much after stopping drinking and starting on meds) and laugh at jokes that I come up with in my mind. I guess from the outside perspective that would come across as pretty weird
This usually happens during periods of time where I'm experiencing an extreme lack of sleep or am under high stress and feeling lonely.