What do the top horror movies all have in common?

They all have memorable soundtracks that elicit an instantaneous feeling of terror. As a matter of fact, if you watch the films without any sound, they become a great deal less frightening.

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 makes us react with fear?

The Fear Response

In regard to evolutionary biology, there’s an evident survival advantage to the immediate recognition of a dangerous situation.

Thinking takes time, especially 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 consciously.

Considering it takes longer to process and think about visual information, the animal brain is wired to respond to quicker sound-processing mechanisms—a trait that offers survival advantage and has been selected for in the wild.

And that’s precisely what we see in nature: numerous vertebrates—humans included—produce and respond to harsh, nonlinear sounds and vocalizations when alarmed. This results in a virtually instantaneous sensation of fear or anxiety.

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

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

Our brains have evolved to identify the characteristics of nonlinear sound as abnormal and indicative of hazardous situations.

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

So, what was once an effective biological adaptation in the wild has now been co-opted by the movie industry to produce scarier movies.

Music and Fear

We all know the shower scene from the classic film 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 when you add back in the high-pitched screaming and bone-chilling staccato music that the fear response becomes thoroughly engaged.

To confirm our natural aversion to this nonlinear sound, UCLA evolutionary biologist Daniel Blumstein conducted a study examining the emotional reactions to two types of music.

Study participants listened to a collection of emotionally neutral scores and scores that incorporated nonlinear properties.

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

Regardless of whether Hollywood comprehends this physiology or not, it appreciates instinctively that the use of nonlinear discordant sound is still the most effective way to get a rise out of the audience.

Want to witness the fear response in action?

Check out these 10 Essential Horror Movie Scores.