Screaming is instinctual — it's primal and guttural. It's a sound humans make across all age ranges and cultures. Whether due to pain, horror 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 does the sound of one make humans react the way we do?
"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."
In July 2015, 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.”
This might help explain the range of shrieks that emanate from children. After a short time, parents of infants 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 bellowed 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.