The University of Tennessee's Walters Life Sciences Building is a model animal facility, spotlessly clean and careful in obtaining prior approval for experiments from an animal care committee. Of the 15 000 mice housed there in a typical year, most give their lives for humanity. These are good mice and as such won the protection of the animal care committee. At any given time, however, some mice might escape and run free. These mice are pests. They can disrupt experiments with the bacteria organisms they carry. They are bad mice and must be captured and destroyed. Usually, this is accomplished by means of sticky traps, a kind of fly paper on which they become increasingly stuck. But the real point of the cautionary tale, says Dr. Leister, an animal behaviorist with the facility at the university, is that the labels we put on things can affect our moral responses to them. Using sticky traps or the more deadly snap traps would be deemed unacceptable for good mice. Yet the killing of bad mice requires no prior approval. Once the research animal hits the floor and becomes an escapee, says Herza, its moral standard is instantly diminished. In Leister's own home, there was a more ironic example when his young son's pet mouse Willy has died recently it was given a tearful ceremonial burial in the garden. Yet even as they mourned Willy, says Leister, he and his wife were setting snap traps to kill the pest mice in their kitchen with the bare change in labels from pet to pest, the kitchen mice obtained totally different moral standards and treatments.