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Why we love big, blood-curdling screams

Among the variety of human screams, it is screams of terror that stand out most vividly.

John Springer Collection/CORBIS/Corbis via Getty Images

Of all the sounds humans produce, nothing captures our attention quite like a good scream.


They're a regular feature of horror films, whether it's Marion Crane's infamous shower scream in “Psycho" or Chrissie Watkins' blood-curdling scream at the beginning of “Jaws."

Screams might seem simple, but they can actually convey a complex set of emotions. The arsenal of human screams has been honed over millions of years of evolution, with subtle nuances in volume, timing and inflection that can signal different things.

Ancestral cues

Screaming can be traced to the prehistoric ancestors we share with other primates, who use screams as a key component of their social repertoire.

Screams are especially important in monkey societies.

Emory University psychologist Harold Gouzoules is one of the world's leading screaming experts. He's been able to show how monkey screams convey a wealth of information. Different screams at different pitches and volumes can communicate different levels of urgency, such as whether a fight is simply about to take place or whether a predator is in the area.

The grammar of monkey screams can be surprisingly sophisticated.

African vervet monkeys, for example, have three main predators: leopards, snakes and eagles. Each type of predator requires different escape routes. To elude an eagle, the monkey must abandon wide-open spaces and seek shelter in dense shrubbery. But this would be exactly the wrong response if a snake were lurking in bushes.

vervet monkeys have a unique language of screams

Vervet monkeys have developed a unique language of screams. (Tim Graham/Getty Images)

For this reason, vervets have evolved a pattern of distinct screams that not only act as a warning but also reveal the type of predator in their midst.

Monkeys can even identify other individual monkeys from their screams.

This is highly adaptive, because it enables the listener to assess the importance of the screamer to the listener, facilitating the protection of children and other relatives.

Why screams of terror stand out

Like monkeys, humans have the ability to identify people they know by the sound of their screams.

Humans produce a range of screams as well: There are screams that reflect more positive emotions, such as surprise and happiness. And then there are screams of anguish, screams of pain and, of course, screams of terror.

Screams can be described according to their place along an acoustic dimension known as "roughness."

Roughness is a quality that reflects the rate at which a scream changes or varies in loudness. The more rapidly the loudness fluctuates, the "rougher" the scream. And the rougher a scream is, the more terrifying it's perceived to be.

Psychologist David Poeppel looked at brain images of people listening to recordings of human screams and found that, unlike other human vocalizations, screams get routed directly to the amygdala, which is the part of the brain that processes fear, anger and other intense emotions.

And among the variety of human screams, it is screams of terror that stand out most vividly. Other unpleasant sounds, such as a baby's cry and fingernails on a chalkboard, share some of the same features that make screams unpleasant and terrifying.

The best screamers survived

It makes good evolutionary sense for screams of terror to be the most attention-grabbing; these are the ones that most clearly warn of an imminent danger.

Humans who couldn't readily distinguish among different types of screams may not have responded with appropriate urgency in life-or-death situations. Over time, this would have diminished the frequency of their genes in the population.

So we're probably the descendants of individuals who were good screamers and were also good at reading the screams of their fellow humans. This may help explain the perverse joy we get by intentionally subjecting ourselves to scream-inducing experiences like horror movies and roller coasters.

How better to celebrate the screaming success of our prehistoric ancestors?

Frank T. McAndrew, Cornelia H. Dudley Professor of Psychology, Knox College.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Physicists have understood at least theoretically, that there may be higher dimensions, besides our normal three. The first clue came in 1905 when Einstein developed his theory of special relativity. Of course, by dimensions we’re talking about length, width, and height. Generally speaking, when we talk about a fourth dimension, it’s considered space-time. But here, physicists mean a spatial dimension beyond the normal three, not a parallel universe, as such dimensions are mistaken for in popular sci-fi shows.

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Image source: camillo jimenez/Unsplash
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  • Early treatment is available but there's been no way to tell who needs it.
  • Using clinical data already being collected, machine learning can identify who's at risk.

The psychological scars a traumatic experience can leave behind may have a more profound effect on a person than the original traumatic experience. Long after an acute emergency is resolved, victims of post-traumatic stress disorder (PTSD) continue to suffer its consequences.

In the U.S. some 30 million patients are annually treated in emergency departments (EDs) for a range of traumatic injuries. Add to that urgent admissions to the ED with the onset of COVID-19 symptoms. Health experts predict that some 10 percent to 15 percent of these people will develop long-lasting PTSD within a year of the initial incident. While there are interventions that can help individuals avoid PTSD, there's been no reliable way to identify those most likely to need it.

That may now have changed. A multi-disciplinary team of researchers has developed a method for predicting who is most likely to develop PTSD after a traumatic emergency-room experience. Their study is published in the journal Nature Medicine.

70 data points and machine learning

nurse wrapping patient's arm

Image source: Creators Collective/Unsplash

Study lead author Katharina Schultebraucks of Columbia University's Department Vagelos College of Physicians and Surgeons says:

"For many trauma patients, the ED visit is often their sole contact with the health care system. The time immediately after a traumatic injury is a critical window for identifying people at risk for PTSD and arranging appropriate follow-up treatment. The earlier we can treat those at risk, the better the likely outcomes."

The new PTSD test uses machine learning and 70 clinical data points plus a clinical stress-level assessment to develop a PTSD score for an individual that identifies their risk of acquiring the condition.

Among the 70 data points are stress hormone levels, inflammatory signals, high blood pressure, and an anxiety-level assessment. Says Schultebraucks, "We selected measures that are routinely collected in the ED and logged in the electronic medical record, plus answers to a few short questions about the psychological stress response. The idea was to create a tool that would be universally available and would add little burden to ED personnel."

Researchers used data from adult trauma survivors in Atlanta, Georgia (377 individuals) and New York City (221 individuals) to test their system.

Of this cohort, 90 percent of those predicted to be at high risk developed long-lasting PTSD symptoms within a year of the initial traumatic event — just 5 percent of people who never developed PTSD symptoms had been erroneously identified as being at risk.

On the other side of the coin, 29 percent of individuals were 'false negatives," tagged by the algorithm as not being at risk of PTSD, but then developing symptoms.

Going forward

person leaning their head on another's shoulder

Image source: Külli Kittus/Unsplash

Schultebraucks looks forward to more testing as the researchers continue to refine their algorithm and to instill confidence in the approach among ED clinicians: "Because previous models for predicting PTSD risk have not been validated in independent samples like our model, they haven't been adopted in clinical practice." She expects that, "Testing and validation of our model in larger samples will be necessary for the algorithm to be ready-to-use in the general population."

"Currently only 7% of level-1 trauma centers routinely screen for PTSD," notes Schultebraucks. "We hope that the algorithm will provide ED clinicians with a rapid, automatic readout that they could use for discharge planning and the prevention of PTSD." She envisions the algorithm being implemented in the future as a feature of electronic medical records.

The researchers also plan to test their algorithm at predicting PTSD in people whose traumatic experiences come in the form of health events such as heart attacks and strokes, as opposed to visits to the emergency department.

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