The Business of Jump Scares
Most horror films rely on jump scares. Something appearing out of nowhere, almost invariably accompanied by a striker chord that further signals you to flinch. There are different kinds of jump-scares, some a lot cheaper than others. Almost all horror films rely on a healthy number of fake-outs. SOMETHING JUMPS OUT FROM OFF-SCREEN -- but "oh, it's just my daughter", or "oh, it's just the cat..." (Always cats, never really dogs. Dogs -- non-ghost dogs -- telegraph their approach too much. Cats are just assholes.)
The stronger jump-scares occur a little further on. SOMETHING JUMPS OUT FROM OFF-SCREEN -- AND IT'S A REAL THREAT!!! You still get the same striker chord but then the volume is sustained to inform the viewer that the danger is real and continuing.
More elevated kinds of scares, IMHO, are ones that involve sustained tension. Voyeur scares: the protagonist hides under a bed (or in a closet, or some other poor hiding place) as the killer enters the room and stomps around. The camera covers the scene from the protagonist's pov and the audience shares in the fear of being discovered, while also surreptitiously getting a glimpse of the killer in his/her element. But even sustained tension sequences are usually punctuated with a jump scare.
Modern horror movies, I think, are over-dependent on the jump scare. There are far fewer horror films that deal in more sustained tension, the way THE SHINING did. A movie like SINISTER does rely on a lot of jump-scares throughout, but the use of the 8mm films creates a different kind of tension. It's a movie about found footage that doesn't restrict itself to the modern parameters of that genre, because the movie you're watching isn't itself supposed to be the found footage.
There's something almost mathematical about how a horror film can be effective. But beyond the equations that make up a traditional horror flick, there is the question about what it's really about.
Why are we scared and what is the significance of this fear...?