Cats hate doors. In the evolutionary history of cats, there has never been a place for doors. Doors often hinder the cat's patrol activities, preventing it from exploring its nest territory (i.e., the animal's activity range - editor's note) as it pleases, and preventing it from freely returning to its safe central base. Cats need to simply patrol their territory, learn about the activities of other cats in the neighborhood, and then return home with all the necessary information. Humans often do not understand this need of cats: cats like to patrol frequently, but do not want to go out for long periods of time. Spend time outdoors unless there are unexpected and special changes in local cat population conditions.

This forms the obvious perverse character of pet cats. It wants to run outside when it is indoors, and wants to come in when it is outdoors. If the owner does not install a pet door on the back door of the home, the cat will regularly attract the owner's attention and ask the owner to assist it in completing regular territory supervision. Part of the reason why it's so important for cats to constantly check out the outside world is because of the scent-marking ten-hour rest system.

Every time a cat rubs or urinates on a landmark in its territory, it leaves behind a personal scent, but the scent quickly begins to lose its potency. The rate at which this smell decays is very stable, allowing the cat to determine how long ago the cat that left the smell rubbed or peed. The reason why cats repeatedly inspect their territory is to seize new and gradually fading scent signals. The job done, it will need comfort and safety again, so once again the anxious cat face appears outside the window.