Something I've always been curious about: does the physiological stress or the psychological stress come first? Do you think "I'm stuttering" first, or does that tension you experience precede it?
Good question. For me it's just a mixed bundle and self fulfilling. I can map out the stuttering words and sounds and I jam up when I realize I can't replace the word elegantly. My stutters are now so far between that people are thrown back when it appears suddenly.
There is an anticipation you experience, it feeds back from previous instances of stuttering on a sound and can ingrain itself pretty strongly in your psyche. There’s a word for this, “anticipation” or something.
Thinking about it, they both feed each other, if you start with on you will get the other.