There is some speculation that dogs use their sense of smell to determine the passage of time. The theory is that when an owner's scent diminishes to a certain

There is some speculation that dogs use their sense of smell to determine the passage of time. The theory is that when an owner's scent diminishes to a certain point they know that the owner will soon be back. Dogs that normally wait at the door or at a window can be tricked by the reintroduction of the owner's smell and will fail to get ready for the event.