Novelty of any sort evokes stress in most if not all animal teloi. Researchers know that animals can be trained by reward to willingly accept some physically painful experimental procedures. In one instance, a friend of mine was drawing blood from dogs daily for a vaccine study. She would enter the facility, play with each dog, draw the blood, and then give the dog a treat. On one occasion, one of the dogs set up such a howl as she was leaving that she raced back to see if his paw was caught in the cage door. It turned out she had forgotten to draw blood from that dog, and he had missed his play and his treat, which bothered him more than the blood draw. Such examples illustrate three major points: