As a child I remember my neighbours having a German Shepherd guard dog; they'd been burgled so acquired this dog for security. It wasn't a pet, much to my disappointment but just used to circle their house repeatedly and pause and stare at their front door.
I felt so sorry for this beautiful dog as it was like a robot and I used to wonder if it ever slept. My parents explained to me years later the purpose of the dog but I can never remember the official job description!