If I didn't know the dog, it would spook me, but not make me think I should fear for my life. If it was a 120-pound rott snarling and charging full speed, I'd turn around and get out. But a little 42-pound puppy yapping? It's never happened so I have no idea how she would react. Pit bulls typically make terrible guard dogs as they are naturally very friendly with humans. I dunno...guess I'll never know unless it actually happens. In any case, she would hear someone before I would, and if she barks anywhere in the apartment, you can hear her. If someone had broken in and was deterred by a dog, he'd be out the door before either of us left my room. A dog's bark is an instant signal that someone in the house probably knows you're there. So whether or not he left would probably be based on his attitude toward whether or not he wanted a confrontation. As far as I know, very few people break and enter uninvited without some sort of weapon, so I would assume any intruder would be armed.