I believe, I have seen you saying something like this in other posts (might be wrong). Not sure why you are saying this but it is literally wrong. Stuttering is a neurological problem, which could be reinforced by psychological (mental) issues as a result of negative experience while communicating with others. Either way, the basis is neurophysiology and genetics, otherwise, everybody would stutter when they get nervous (actually stutter, not just mess up with words, as a result of cluttered thoughts).