
A "scary story" or "horror story" comprises of the following
-Normal everyday occurrences to build a scene.
-Something unusual
-Information that will reflect on the story causing you to suddenly realize how scary it was.
You then become scared when your conscious sees a "scary picture" or reads the "scary text" causing a natural reflex in the subconscious to make you aware of your surroundings and very easy to startle. This is from the instinct to avoid being attacked by a predator, and make you ready to flee and be aware when the attacker comes. This emotion is what we call "fear".