Jack-o-lantern in window

What do the best horror movies all have in common?

They all have memorable soundtracks that elicit an instantaneous sensation of fear. In truth, if you watch the films without any sound, they become a great deal less scary.

But what is it regarding the music that renders it frightening? More specifically, if sounds are merely oscillations in the air, what is it about our biology that causes us to respond with fear?

The Fear Response

In regard to evolutionary biology, there’s an evident survival advantage to the instantaneous detection of a life-threatening circumstance.

Thinking takes time, particularly when you’re staring a ravenous lion in the face. When every second counts, you don’t have the time to stop and process the information deliberately.

Considering it takes longer to process and contemplate visual information, the animal brain is wired to react to swifter sound-processing mechanisms—a characteristic that offers survival advantage and has been selected for in the wild.

And that’s precisely what we see in nature: a large number of vertebrates—humans included—produce and respond to harsh, nonlinear sounds and vocalizations when frightened. This results in a virtually instant feeling of fear or anxiety.

But what is it about nonlinear sound that makes it frightening?

When an animal screams, it generates a scratchy, irregular sound that stretches the capacity of the vocal cords past their normal range.

Our brains have evolved to detect the features of nonlinear sound as abnormal and suggestive of hazardous situations.

The fascinating thing is, we can artificially replicate a variety of these nonlinear sounds to get the same instant fear response in humans.

And so, what was once a successful biological adaptation in the wild has now been co-opted by the movie industry to produce scarier movies.

Music and Fear

We all are familiar with the shower scene from the classic movie Psycho, and it’s probably one of the most frightening scenes in the history of cinema.

But if you view the scene on mute, it loses the majority of its affect. It’s only once you add back in the high-pitched screaming and bone-chilling staccato music that the fear response becomes fully engaged.

To demonstrate our instinctive aversion to this nonlinear sound, UCLA evolutionary biologist Daniel Blumstein carried out a study examining the emotional reactions to two types of music.

Participants in the study listened to a selection of emotionally neutral music scores and scores that contained nonlinear elements.

As expected, the music with nonlinear elements elicited the most potent emotional reactions and negative feelings. This response is simply an element of our anatomy and physiology.

Whether Hollywood understands this physiology or not, it knows instinctively that the use of nonlinear discordant sound is still the best way to get a rise out of the viewers.

Want to see the fear response in action?

Check out these 10 Essential Horror Movie Scores.