A 4-year-old spayed female cat has stopped using the litter box, urinating on the owner's bed. Purely Medical View: Urinalysis and culture. Treat for UTI. Purely Behavioral View: Stress, territorial insecurity, or dislike of litter substrate. Integrated Veterinary Behavior View: The vet performs a urinalysis (medical) and an environmental history. They discover the owner recently switched to a scented, crystal litter. Even after the UTI is cleared, the cat still avoids the box. The science of sensory aversion (olfactory behavior) explains that cats have 200 million olfactory receptors; the perfumed scent is aversive to the point of pain. Solution: Change litter back to unscented clumping clay. The behavior resolves.