Experts unlock the science of screams
16 Jul 2015
A team of researchers has identified a property that gives human screams their fear-inducing quality.
The property, known as roughness, refers to the speed at which a sound changes in loudness.
Screams, which stand out above virtually all other loud noises, possess a unique roughness found to activate not just the auditory brain but also the brain’s fear circuitry, the researchers at New York University (NYU) and the University of Geneva suggest.
“The only exception - and what was peculiar and cool - is that alarm signals also activate the range set aside for screams
Lead researcher David Poeppel
“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 NYU.
“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.”
As there is no real repository of human screams, the researchers used recordings taken from YouTube videos, films and volunteers to conduct their research.
The researchers plotted the sound waves in a manner that reflects the firing of auditory neurons, and they noticed that screams activate a range of acoustic information that scientists hadn’t considered to be important for 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,” said Poeppel.
“In a series of experiments, we saw [that] this observation remained true when we compared screaming to singing and speaking, even across different languages,” he said.
“The only exception - and what was peculiar and cool - is that alarm signals also activate the range set aside for screams.”
Looking ahead, the researchers plan to continue investigating human screams in the lab, especially those of infants, to see if their screams are particularly rough.
What’s more, the researchers also want to apply their analyses to animal screams to learn how much this trait is conserved across species.
A full account of the research has been published in the journal Current Biology.
