According to Georgia State University communications professor Greg M. Smith, the secret to the perfect scary movie can be summed up thusly: set an eerie mood, spread out the bad stuff, and let the audience's imagination do the work.

"It's a very intricate balance between letting the audience imagine the fear and feeding them with a horror ingredient," said Smith. His book "Film Structure and the Emotion System" was published this month, analyzing the elements of fear and the horror movie.

He cites movies like "Alien" and "Jaws", which contain a few gruesome scenes spread out among longer periods of dreadful waiting.

Pacing is the key, he says. Too much gore numbs the audience, while too much buildup bores them. Smith reminds us that horror movies appeal to viewers just like romance or drama: through emotion.

"Movies are full of cues, cues to feel one way or another," Smith said. "Emotions work through associations. You've got five or 10 minutes at the beginning of a movie to establish those associations, to say, 'Here's the world, here's how it works, here's how you need to feel about it.' It's a pretty basic idea. But it's a very rare film that hits it exactly on the head."

Source: CNN [1]