Of all the loud and annoying sounds in everyday life, few have the ability to command our attention like a scream—whether it's a crying baby, shrieking preteens or late-night revelers. It turns out there's a reason for that.
It's not just the noise and pitch of screaming that jars us, but something in our hard wiring. When we hear a scream, the sound taps right into the brain's fear center.
Although our ancestors have presumably been screaming since the dawn of time—to warn fellow villagers of rampaging predators or club-wielding invaders—not much research had been devoted to the topic.
But Luc Arnal, a post-doctoral researcher in a speech and language processing lab at New York University, set out to analyze what makes screams so scary. He discovered that compared with other sounds, screams have more of a characteristic known as roughness, which describes how quickly they vary in volume.
When Arnal asked people to pick out the most-frightening screams, they chose the ones with the greatest roughness. The researchers also found a correlation between the roughness of a sound and the degree to which it activated a fear response in the brain's amygdala. Arnal and his team published the results last month in the journal Current Biology.
And they also made another discovery: Hearing an alarm produces the same response as hearing a scream, which could help create better warning devices.