I appreciate the discussion about NDT and would like to make some clarifications and distinctions. My operating principle is that what motivates dogs and animals, isn't necessarily positive outcomes but rather the feeling of encountering and overcoming resistance. This is the basis of social and cooperative teamwork because members of a group have to align and synchronize with each other in order to satisfy an appetite that can't be sated by individual action alone. And so even if something that would normally be considered "bad" happens, and yet the dog overcomes resistance, then the so-called negative becomes integrated into a positive perception of the experience. The dog feels good. Therefore if an owner/handler is the most intense form of resistance that a dog can align, sync and work with towards a common goal, then they become the most positive element of that dog's universe. Hence the pushing exercise. The owner offers resistance that the dog can overcome and this inspires the dog to want to align and sync up even when there are other things that are normally disturbing/exciting/distracting to the dog. At any rate, the concept of overcoming resistance leads to many subtle but I believe important distinctions between the existing theories of a dominance hierarchy and learning by reinforcement.