Jack-o-lantern in window

What do the top rated horror movies all have in common?

They all have unforgettable soundtracks that arouse an instant sense of terror. 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 makes 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

With respect to evolutionary biology, there’s an evident survival advantage to the immediate identification of a detrimental scenario.

Thinking is time consuming, especially 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 a bit longer to process and contemplate visual information, the animal brain is wired to react to quicker sound-processing mechanisms—a characteristic that provides survival advantage and has been selected for in the wild.

And that’s precisely what we discover in nature: numerous vertebrates—humans included—generate and react to harsh, nonlinear sounds and vocalizations when alarmed. This yields a nearly 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 extends the capacity of the vocal cords beyond their normal range.

Our brains have evolved to recognize the properties of nonlinear sound as unpleasant and suggestive of life-threatening circumstances.

The intriguing thing is, we can artificially imitate a variety of these nonlinear sounds to bring about the same immediate fear response in humans.

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

Music and Fear

We all know the shower scene from the classic film Psycho, and it’s probably one of the most terrifying scenes in the history of cinema.

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

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

Participants in the study listened to a selection of emotionally neutral scores and scores that included nonlinear properties.

As expected, the music with nonlinear elements elicited the most powerful emotional responses and negative feelings. This response is simply an integral part of our anatomy and physiology.

Regardless of whether Hollywood understands this physiology or not, it knows intuitively that the use of nonlinear disharmonious sound is still the most effective way to get a rise out of the audience.

Want to observe the fear response in action?

Listen to these 10 Essential Horror Movie Scores.