Very very very good speculation, this is something I've been thinking about intently since my stutter has gotten bad. ​ I have a problem with moving my tongue/mouth during a block. As for primary symptoms for blocks, the main process for a block to occur is me (1) thinking about a word that I have trouble with, then (2) my mind puts up a wall/barrier, which causes me to not be able to move my tongue/mouth, making it feel like this stutter is infinitely lasting. To elaborate on the primary symptoms, I'm pretty sure every single instance of a block originates from fear; fear of a certain word, fear of messing up, fear of stuttering always looming, etc. ​ The most important part which you asked, 'why do I do this stutter symptom', I still have not been able to deduce an answer for. Of course, the root of this lies in issues of anxiety/confidence I'd say, but as for the specific cause of **why** I do this stutter symptom, I don't know. I think that it's a mixture of internalizing that I can't say said word & **subconsciously having my heart rate speed up to overdrive when I think that I'm going to stutter**. Because I don't (really) stutter when I'm talking to myself, sure I may have internalized that I can't say a word, but I don't have the added anxiety that I'm obliged to speak normally to the person I'm speaking with. When I'm talking to somebody, my heart rate speeds up, and with all the pressures of stuttering causing a negative feedback loop in my mind, I end up feeling like my block is infinitely lasting. I explained myself very poorly in this paragraph, like I said, it's something I'm trying to think about currently.