>The mechanism that causes stuttering (in the physical sense) appears to be somewhere in the voice box / vocal cords. No, there's no scientific consensus about anything like that. >When it isn’t activated, such as in whispering, there’s no disruption. Stutter varies so much that I'm sure we can find stutterers who have experienced stutter while whispering (in fact, I seem to recall just that myself). We can of course also find stutterers who have experienced _not_ stuttering during "activation" (in whatever mode of communication given), so the point is moot.