Yes, sometimes I stutter when I am alone. As far as I know he causes aren't psychological but rather physiological. And there's a lot of evidence that points to it being genetic. There is no "mental block". Again, what is your source? Edit: Here's mine: https://www.sciencedaily.com/releases/2015/02/150223154854.htm Sorry if it doesn't fit your narrative. Edit: More sources! http://www.stutteringhelp.org/genetic-and-neurological-factors-stuttering http://www.casafuturatech.com/neurology-of-stuttering/