What do the best horror movies all have in common?
They all have memorable soundtracks that bring about an instant sense of terror. In fact, if you watch the films without any sound, they become a great deal less frightening.
But what is it about the music that makes 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 terms of evolutionary biology, there’s an evident survival advantage to the instantaneous detection of a dangerous situation.
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.
Since it takes additional time to process and think about visual information, the animal brain is wired to respond to faster sound-processing mechanisms—a trait that offers survival advantage and has been selected for in the wild.
And that’s exactly what we find in nature: many vertebrates—humans included—generate and react to harsh, nonlinear sounds and vocalizations when frightened. This generates a nearly instantaneous sensation of fear or anxiety.
But what is it about nonlinear sound that makes it scary?
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 distinguish the features of nonlinear sound as abnormal and suggestive of dangerous situations.
The intriguing thing is, we can artificially replicate a wide array 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 manufacture 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 view the scene on mute, it loses most of its affect. It’s only once you add back in the high-pitched screeching and bone-chilling staccato music that the fear response becomes thoroughly engaged.
To reveal our natural aversion to this nonlinear sound, UCLA evolutionary biologist Daniel Blumstein carried out a study investigating the emotional reactions to two types of music.
Participants in the study listened to a collection of emotionally neutral music scores and scores that incorporated nonlinear elements.
As predicted, the music with nonlinear elements aroused the most powerful emotional responses and negative feelings. This response is simply an element of our anatomy and physiology.
Regardless of whether Hollywood understands this physiology or not, it appreciates instinctively that the use of nonlinear disharmonious sound is still the best way to get a rise out of the viewers.
Want to observe the fear response in action?
Listen to these 10 Essential Horror Movie Scores.