I have always talked to myself. For as long as I remember, I have conversations with myself, but as I think back, they seem to mostly take place when I'm peeing. I know ... WTF?
When I was in grade school, I used to go to the library every day after school ended and wait for my parents to pick me after work. I'd do my homework, I'd read books, if I had money I'd go over to Jack in the Box and buy a taco and some onion rings, maybe even a shake. One day (I guess I was in 4th or 5th grade) I was in the library with a friend and I had to go to the bathroom. I got the bathroom key from the librarian and went to go pee. I guess my friend needed to go, too, because she was outside the door waiting when I was done. She said "Do you talk to yourself? I heard you talking when you were in there."
From that day on, I stopped talking to myself with sound. Now I just move my lips when I have internal conversations while peeing, but it's all silent. Lesson learned: someone can always be listening to you.