While the actual mechanisms will very from person to person, most of the current literature seems to agree that stuttering has a neurological basis, whether through differences of physical brain structure as seen in adults who exhibit a persistent stutter since child, neurogenic causes as in adults who experience acquired stuttering after childhood, or psychogenic causes resulting from severe emotional trauma. The amount of variation between any two individuals' stutter is part of what makes pinning down an actual physiological cause so difficult, so, as with most things, if you think you understand the cause behind one person's stutter, you understand the cause behind *one person's* stutter.