Me. I can speak with perfect fluency when alone but can start having issues when alone but speaking infront of a mirror. Not “full-on” as with actual people, but ~ 30% of my normal disfluency. This is why I have found it so helpful to practice speeches, presentations, etc infront of a mirror. I can get a pretty good understanding of what phrases and words are going to give me trouble, and then what techniques I used to get around those. It is It doesn’t make a whole lot of sense, though. When I was a kid, I could be practicing speech is perfect by myself but would have issues with my mom or dad even walked by my room. It just goes to show that a lot of stuttering is mental/psychological in addition to physical.