Human Brain's reaction to Scary Stuff

[Adny]

Fear is one of the driving forces that led to our very existence today. It is a primal urge that tells us to run or confront ("fight or flight" reaction). It gives us an adrenaline rush necessary to do one of the aforementioned actions, and when we know we are safe from it (i.e. while playing scary games or watching scary movies) that chemical burst becomes a sort of "high".

True fear is the same from person to person, it is only irrational fears that vary. A huge irrational fear of mine is spiders - I know I could easily curve stomp that mofo into oblivion then walk away like nothing happened, but for some reason I just go into the fetal position and whimper.

You brought up the dark - such a fear (or paranoia as you described) is a learned behavior. In scary movies/games, nothing legitimately scary ever happens during the day, but only during the night. We humans with our ever wandering imaginations make the connection between the fictional events and reality, leading to yet another irrational fear.