Some people say I have a very expressive face. My moods are plain to see and if for a half second I feel disgust, confusion, curiosity, or any other emotion it will flash across my face. That may be true, but I seem to find myself in situations where I'm clearly bored and not paying any attention whatsoever to what a person is saying, and they don't notice. They just keep talking.
It seems to happen most frequently in bars. Maybe it's the darkness. Or maybe some people just like to talk and don't care if the other person listens or not.