Dogs are really good at noticing position. In fact, Pamela Dennison in her book The Complete Idiot’s Guide To Positive Dog Training identified 48 dog to dog signals, and more than 20 of these are about position, sitting, lying down, arcing the body, bowing, tail up, tail down, and so on. Given how important position is to communication between dogs, it is only natural that a dog would be very aware of his human’s position too. Since most humans are not nearly as aware of position as dogs, it’s easy for our dogs to learn a signal that we had no idea we were even using!