No, I think you're wrong about the dog's tail thing. In my experience, dog's wagging their tail means they're uncertain about a situation. Many times I've given a dog credit for a monster cause of the famous tailwagging tell, only to be shown a strong drawing hand. So I think they usually do have to have something to exhibit this, but it implies some uncertainty in their holdings. I don't think this applies to many of the smaller dogs, though. I'll write another post some other time about this Chihuahua I played with in Mexico City, but that'll have to wait.