Your brain is a computer with a wide neural network. Actions such as walking, swimming, or throwing a ball are controlled by certain neural pathways. For us stutterers, the pathway that controls speech only knows stuttering, so when you try to speak you go down the same path you have always gone, you predict a stutter, and it happens. The solution to stuttering (i am currently trying this theory out) would be to rewire the brain with fluent repetition to the point where neurogenesis occurs (the brain creates a new neural pathway) and you develop a fluent speech pattern.