A human's urge to scream seems to be an inherent quality, and researchers are gaining insight into what exactly makes these sounds so terrifying.
New research suggests screams boast a unique acoustic property that can activate fear circuitry in the brain, Cell Press reported.
"If you ask a person on the street what's special about screams, they'll say that they're loud or have a higher pitch," said study senior author David Poeppel, who heads a speech and language processing lab at New York University. "But there's lots of stuff that's loud and there's lots of stuff that's high pitched, so you'd want a scream to be genuinely useful in a communicative context."
To make their findings, a team of researchers looked at recordings of creams taken from YouTube videos, popular films, and volunteer screamers. They plotted the sound waves in a way that reflected the firing of auditory neurons, and found the sounds activated acoustic information regions that researchers had not thought were involved in communication.
"We found that screams occupy a reserved chunk of the auditory spectrum, but we wanted to go through a whole bunch of sounds to verify that this area is unique to screams," says Poeppel, who also directs the Frankfurt Max-Planck-Institute Department of Neuroscience. "In a series of experiments, we saw [that] this observation remained true when we compared screaming to singing and speaking, even across different languages. The only exception--and what was peculiar and cool--is that alarm signals (car alarms, house alarms, etc.) also activate the range set aside for screams."
Screams have a unique quality, called roughness, which refers to how the sound changes in volume. Human speech modulates in loudness in moderation, but screams dramatically fluctuate in volume. In a survey, participants tended to classify screams with more roughness are the most unsettling.
"Screaming really works," Poeppel said. "It is one of the earliest sounds that everyone makes--it's found across cultures and ages--so we thought maybe this is a way to gain some interesting insights as to what brains have in common with respect to vocalization."
The researchers believe these findings could be used to improve the effectiveness of alarm systems. For example, incorporating more roughness into a burglar alarm could make it more attention-grabbing.
"The same way a bad smell is added to natural gas to make it easily detectable; adding roughness to alarm sounds may improve and accelerate their processing," Poeppel said.
The findings were published in a recent edition of the journal Current Biology.
