I was pondering this thread last night as I walked the dog at half past eleven at night. We went down through the village and out down 'the back hill' which is a road that runs through open countryside. No lights. No wind. Just the occasional sheep burp and some rooks out late, partying.
As I turned round to come back, I got the distinct creeps and had to tell myself very sternly that it was exactly the same trees, bushes, shrubs and burping sheep that I run past every single morning, and have yet to savage me to death.
It was simply that I couldn't see. My brain kept trying to tell me that 'something' was hiding in the shadows. My rational mind knew there was nothing there, but my subconscious just kept on trying. We came back rather faster than we went out, yet as soon as I reached the first houses of the village, I was fine again, even though all was in darkness. As though knowing there were people there, albeit asleep, helped.