Screaming is instinctual — it's primal and guttural. It's a sound humans make across all age ranges and cultures. Whether due to horror, pain or a baby's cry, a shrill, hair-raising scream is executed instantaneously and demands a response just as quickly. But why do we scream, and why do humans react the way we do when we hear one?
"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," David Poeppel, Ph.D., who heads a speech and language processing lab at New York University, told the American Association for the Advancement of Science. "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."
Poeppel and his NYU colleagues published research in the journal Current Biology that suggested hearing a scream may activate the brain's fear circuitry, sort of triggering an alarm in your head. They collected an assortment of screams from YouTube, movies and even volunteer screamers, who screamed in a lab sound booth and were recorded.
"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, who also directs the Frankfurt Max-Planck-Institute Department of Neuroscience. "In a series of experiments, we saw 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."
The sound barrier
What sets screams apart from other loud sounds is a property called "roughness," which refers to how fast a sound changes in loudness. When people talk to each other, those speech patterns have only slight differences in loudness, but screams change very fast. The more roughness in the voice, the bigger the fear response in the human amygdala, which gauges whether a threat is real and regulates our response. The bigger the response, the more terrifying the scream sounds.
"Roughness is well known, but it has never been considered to be important for communication," researcher Luc Arnal, a neuroscientist at the University of Geneva, told PBS. "Our work is the first to show that roughness is useful to convey information, specifically about danger in the environment."
In subsequent research published in Nature Communications, Arnal and his team took a deeper dive, showing that this type of rough sound triggers activity in brain areas related to aversion and pain — another way our bodies force us to pay attention.
Sounds are perceived as especially harsh when they're between 40 and 80 Hz, and that's because that range commands new areas of the brain to focus.
"These sounds solicit the amygdala, hippocampus and insula in particular, all areas related to salience, aversion and pain," Arnal tells EurekAlert. "This explains why participants experienced them as being unbearable."
This might help explain the range of shrieks that emanate from children. After a short time, parents can discern a baby's hungry cry from its panicked one. Similarly with school-age kids, parents can tell the difference between a loud shriek during a game of tag from a serious one that indicates an injury or problem. (Some things, you just can't fake.)
The health benefits
The idea of screaming in a sound booth for science sounds like great stress relief — and it is. Think of the satisfaction you feel after screaming into a pillow, for example. The stress-reducing power of screaming has led colleges to encourage students to gather together and scream to reduce exam jitters. And some styles of yoga combine poses with yelling and cursing, too.
In the late 1960s, Dr. Arthur Janov put screaming on the map with the invention of Primal Therapy, which claims to allow people who have endured abuse or a traumatic event to face repressed emotions and let them go. At the end of a therapy session with Janov, patients would scream themselves into a fit complete with convulsions and heavy breathing. But when it was over, patient after patient "felt lighter, revived and relieved of the stress holding them down in life," Lifehack reports in this story, which also offers methods to practice screaming and tips on scream-singing.
Editor's note: This story has been updated since it was published in January 2017.