It is also part of a puppy's instinct to not soil areas where they eat or sleep, which explains why crates work great for house training. (puppy-training-solutions.com)
Puppies understand the two distinct areas because they have an instinct to not soil the areas where they eat / drink / sleep. (pethelpful.com)
Recognizing its own scent on the carpet, floor, or furniture, a cat may be reluctant to soil the area again. (drelseys.com)