Jack-o-lantern in window

What do the top horror movies all have in common?

They all have unforgettable soundtracks that elicit an immediate sense of fear. Indeed, if you watch the films without any sound, they become a great deal less scary.

But what is it about the music that renders it frightening? More specifically, if sounds are simply vibrations in the air, what is it about our biology that causes us to react with fear?

The Fear Response

In regard to evolutionary biology, there’s an evident survival advantage to the automatic identification of a life-threatening situation.

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

Considering that it takes more time 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 exactly what we see in nature: many vertebrates—humans included—generate and respond to harsh, nonlinear sounds and vocalizations when frightened. This produces a nearly instantaneous feeling of fear or anxiety.

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

When an animal screams, it produces a scratchy, irregular sound that stretches the capacity of the vocal cords beyond their typical range.

Our brains have evolved to detect the attributes of nonlinear sound as unpleasant and indicative of life-threatening circumstances.

The intriguing thing is, we can artificially replicate a wide array of these nonlinear sounds to get the same immediate fear response in humans.

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

Music and Fear

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

But if you view the scene on mute, it loses most 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 reveal our instinctive aversion to this nonlinear sound, UCLA evolutionary biologist Daniel Blumstein carried out a study evaluating the emotional reactions to two types of music.

Study participants listened to a selection of emotionally neutral music scores and scores that incorporated nonlinear elements.

As anticipated, the music with nonlinear characteristics elicited the most powerful emotional responses and negative feelings. This response is simply a natural part of our anatomy and physiology.

Whether Hollywood understands this physiology or not, it appreciates 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.