There's really not enough research into stuttering to say anything conclusively. Imo, if it was simply a neurological condition that effects the way speech is processed, then the stutter should be consistent and happen all the time regardless of environment. If I can speak fluently to myself to day long but stutter around certain people, I can't see how it can just be about synapses. In my experience, I stutter more when I'm thinking about other things or being hyper-vigilant. So I'll be observing body language, thinking about what the other person thinks, and trying to speak at the same time. The less I am in the moment, the more I stutter. Then the more I stutter, I more I think about stuttering and it turns into a vicious cycle. More evidence of this is that my stutter is often triggered by key words which have great significance on the conversation. I know using this word will trigger an subconscious response in the conversation partner, and so the word becomes loaded with emotional relevance. Again, I'm thinking about what they will think and how they will react to the word, so I end up stuttering on it. While the experience is unique to each person, given my experience I wouldn't say "it's because you think faster than your mouth", I'd say that I'm thinking about too many things when I really should be focusing on what I'm talking about.