Another phenomenon that I think is related - if you think you're alone, you can't prepare yourself to not be surprised if someone comes around a corner. You can

Another phenomenon that I think is related - if you think you're alone, you can't prepare yourself to not be surprised if someone comes around a corner. You can tell yourself to pretend there is someone there, and logically it makes perfect sense that if someone really is there, it won't be a surprise. But you will always be startled if they are there. And to take it further - mirrors and shadows. If, out of the corner of your eye, you see yourself moving in a reflection or shadow, you can scare the shit out of yourself. Full-on primal fight or flight. But you can never do it deliberately. And I doubt you can do it more than once every few hours.