Humans are fearful creatures. We can’t help it, we evolved that way to help us survive. When a pre-technological human was kneeling by a stream to get a drink of water and there was rustling in the nearby trees, the human assumed that the unexpected noise was a potential threat and immediately took up a series of defensive moves. The assumption of threat is called the intentional stance, and is the idea that until proven otherwise, the human assumes that the noise was not the mere rustling of the wind, but rather that the noise was created by some creature or agent, potentially a creature or agent with intent, perhaps with the intent to eat you or cause harm. Even today, we very often assume intelligent or purposeful intent to what are random or statistically meaningless events. The assumption of intelligent intent means that a random or statistically meaningless event is assumed to be done with some deliberate or intelligent purpose, by some kind of agent. The makers of horror movies know this reflex very well and use it over and over to achieve their desired reactions among the audience. They will often substitute ominous sounding music for the rustling of the wind in the climatic build-up to a fear-inducing scene. You just know something awful will happen when you hear that music.