Priming is an interesting psychological phenomenon where parts of our memory are awakened and make us feel a certain way or jump to certain conclusions. Stimuli in any given situation may subconsciously bring our minds back to previous experiences, and make us feel emotions which we did not expect.
In horror movies, this technique is used literally non stop. Though the actual events in a horror movie may not be that scary, the audience is primed to feel fear. Often there is no music, which sets the audience on edge. Spooky images are thrown in simply to get the audience in the right mind set, such as fog, shadows, skulls, crows etc. Camera movement is also essential in an effective horror film, and the audience’s eyes often move with the camera, priming them to feel confined and easy to sneak up on.
The example below, from The Others, shows all of these elements very well. Though walking into a room full of unused furniture is not actually scary, the movie primes the audience to be terrified. No music is playing, the camera follows behind the actress, and the imagery of white sheets reminds us of ghosts. Using these techniques, a simple action can be turned into a white-knuckling experience, as the audience is primed for suspense.