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Humans Screams Activate Fear Circuitry in the Brain

First Posted: Jul 16, 2015 04:17 PM EDT

Why do human screams resonate so broadly? An airplane can be flying by as a house part rages downstairs, and a wailing baby will still win our attention. Now, scientists have discovered that human screams possess a unique acoustic property that activates not only the auditory brain, but also the brain's fear circuitry.

"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 David Poeppel, one of the researchers, in a news release. "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."

Humans make a variety of meaningful sounds through language and otherwise. In fact, part of what makes us human is how our ears can distinguish speech patterns made from vowels and consonants. In this case, though, the researchers focused on human screams.

The scientists led a series of studies to analyze the properties of screams. They used recordings taken from YouTube videos, popular films and volunteer screamers. Then, the researchers plotted the sound waves in a manner that reflected the firing of auditory neurons and noticed that screams activated a range of acoustic information that they hadn't considered to be important for communications.

"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. 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 findings reveal that acoustical engineers have been tapping into the property of roughness by trial and error. For example, alarms and movie shrieks get our attention in the same way that human screams do.

Currently, scientists plan to continue their investigations of human screams to see if they can be used to help improve alarms.

The findings are published in the journal Current Biology.

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