What's the purpose of a scream? Some researchers set out to find out.
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Screaming is important and not just to ward off the Boogeyman. Even so, the higher pitch and abruptness evoke immediate surprise and response. Screams sound scary and in many instances evoke fear. In the case of some post-doctoral students at New York University (NYU) who were also new parents, rattled nerves and bleary eyes from being kept up all night by their own babies’ shrieks, prompted them to not only sympathize with each other but to also begin asking questions relating to the effectiveness and importance of screams.
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Students from David Poeppel’s speech and language processing lab decided to look into the science of those questions, reports The Star, July 18. Their research led them into a section of communication that hadn’t really been considered relevant to human communication before.
“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,” explains Poeppel, lead study author and NYU professor of psychology and neural 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.” Further, as related by the co-author of the study, Luc Arnal, this same observation occurs when screaming is compared to singing and speaking, even across multiple languages. Speech and singing patterns vary as do their frequencies.
One of the factors to figure was why screams so effectively evoked fear above and beyond perhaps a vocalist singing a high-pitched note. Researchers surveyed and analyzed myriad examples of screams via online videos, popular horror films, and volunteer screamers in order to understand why screams give those who hear them an immediate sense of urgency or even chills.
It comes down to a trait known as “roughness,” and it’s a trait that researchers found to be unique to screams. Normal speech patterns usually have frequencies that vary only slightly, ranging in numbers between four and five Hertz (Hz or vibrations per second). Singing can range in higher numbers but does not exhibit the same kind of roughness that screams do; that is, screams “fluctuate wildly and rapidly, varying between 30 and 150 Hz.” Further, this range in human communicative sounds also triggers fear. The more roughness (or fluctuations) contained in a scream, the scarier it is, noted a set of people asked to judge myriad examples of screams.
Researchers also looked at brain activity of subjects who listened to scream samples and other sounds. Screams registered in the amygdala, the area of the brain that is responsible for the fight or flight response when humans feel threatened or are in danger. Researchers gleaned other non-threatening sounds for use, as well, increasing their roughness to see what would happen. When roughness was magnified, subjects’ fear responses also rose and the activity in their amygdalas increased.
"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."
Previous studies have pointed to the fact that screaming can do more than signal endangerment or need. Screams can provide a way of venting and releasing pent up tension. The tactic is often used in anger management programs, especially for those who tend to bury their emotions. The cathartic act can empty repressed emotions and can ease the burden of carrying them. Screaming can be good medicine, so long as it is not directed in a way that harms others or damages the vocal chords.
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