TL;DR (always put a TL;DR when posting a multi-page article) - thinking to yourself ("inner speech") sends the same signals to muscles as speech but also sends a "stop" command. stuttering is caused by a mixup where your brain believes you want to use inner speech even though you are trying to talk. As I was reading I was thinking it was BS, but the end kind of convinced me. The article talks about how we are using both "inner" and "outer" speech when talking to other people and having some speech be "inner" and other be "outer" makes the mixups more common (explaining why we can speak much more fluent when not talking to someone else), It also explains why in emergency situations, when we are around people we are comfortable with, and when highly emotional stuttering tends to lesson: we only have 1 train of thought to keep track of and it it all comes spilling out so no mixing inner and outer speech and less stop signals.