Knock, Knock! Who's There?

Alvin has his natural tail.  I have previously only had cocker spaniels who had had their tails amputated as puppies.  Although there is something very cute about the wiggly little nubs of the remaining tail, Alvin's natural tail is so pretty and I wish people would quit cutting off the tails of cocker spaniels.  I have found that there is one downside to having a natural tail and that is that often when Alvin thumps it against the floor or other objects, he mistakes the sound for a knock at the door and runs to greet his public.  Of course, he continues to run to the wrong door and after the disappointment of no one showing up, he lays back down only to hear that pesky little knock again.  I am trying to teach him the difference in the sound by having no reaction when he thumps his tail and heads for the door, as opposed to my now exaggerated response when someone is at the door.  So far this has been largely unsuccessful and his tail seems to serve as a beacon of hope that a visitor is just right outside our door, if only I would open it before they leave once again.  I wonder how often Alvin internally rolls his eyes at me and wonders why I am so dumb.  The truth is that half the time I am rolling my eyes at myself and wondering the same thing so at least we're often on the same page.