Each type of horror appeals to different parts of the human psyche and requires unique methods of creation. Apocalypse Now is Francis Ford Coppula's adaptation of Joseph Conrad's novel, Heart of Darkness. It is the story of a Green Beret named Williard who journeys through Vietnam by river to confront an officer who had left the army in the pursuit of his own, private war. Because Williard's trip down the river is a metaphorical journey into the human mind it presents a perfect example of how each type horror is created and their effect on the human mind. The skilled cinematography used in this moves makes the effect of each type of horror on the movie's characters, and the desired effect on the audience obvious to the observed.
Psychological horror is fear of a believable, reasonable force.
Psychological horror walks the fine line between the rational and irrational mind. The human ability to ration in contrast with the tendency to exaggerate. What is possible versus what is likely. It is a case where the danger is know, but the likelihood is in question. Each action has a tangible, but unknown probability of danger attacked to it.