1. There will probably be very complicated answer to this question. But I am convinced it cannot be something magical. It must be related to how the speech production works in a brain (similarly, geometric visual halucinations from psychedelics can be explained by the knowledge of how visual cortex process visual data and how it is built). Obviously it is a very complicated system that self-corrects by various kinds of feedbacks, especially audiotory feedback. You know, fluent people will have difficulty speaking when they listen to their delayed voice (also known as speech jammer, for stutterers this is actually the speecheasy device which helps some people for a short period of time). It is known that if you talk in a rythm or sing, stutter usually disappears and it is related to a simple fact that you have provided a system the external timing trigger. I guess that for stutterers the internal timing and synchronization is somehow broken. If I am not mistaken this is part of some theories that tries to explain and model stuttering. So by syncing the system externally by some rythm, it starts to work flawlessly. 2. 3. Yes ! I was then complimenting them that they talk so beautifuly fluently and they were of course surprised by it, nobody ever complimented their fluency, no wonder xD.