It's interesting, I have a severe stutter but when I'm alone I can spend hours talking out loud and not a single blockage, but the moment I perceive or think that someone may be listening to me, a "click" occurs in my brain and I start to stutter, and the more people listen to me, the more I stutter. Sometimes I am alone talking on the phone or sending an audio, suddenly someone enters the room or approaches me and when I realize it, my stuttering automatically increases.