"PWS (Person Who Stutters) are consciously aware when someone enters a room (or a phone call), which in turns triggers stuttering. Remove a person or any social interaction from the room, the stutter disappears." That's not completely true, actually. Many/most PWS stutter when talking in front of other people but they can *sing* completely fluently regardless of how many people are watching. This seems to fit with the "stuttering is neurological" theory, since different parts of the brain are activated when speaking or singing but both activities can be equally anxiogenic (singing even moreso, for many people). Recent studies have also found a difference in (IIRC) blood flow in the brain of stutterers and non-stutterers.