Newspaper article The Christian Science Monitor

Anatomy of a Scream: What's the Science Behind a Shriek?

Newspaper article The Christian Science Monitor

Anatomy of a Scream: What's the Science Behind a Shriek?

Article excerpt

Of all the sounds humans are capable of producing, a scream tends to get the most attention. A universal signal for extreme distress. But what's the science behind the scream?

According to a new study, screams make use of a sonic quality called "roughness," which activates a neural response relating to fear. Neuroscientists David Poeppel and Luc Arnal also found that screams occupied an acoustic niche, not shared by other human vocalizations. They published their findings Thursday in the journal Current Biology.

On the surface, screams are a simple concept. They are loud, high- pitched, and intended to convey extreme distress or danger. But conventional wisdom aside, the scientific community never settled on a concrete definition, nor did it explain our responses to screaming.

This came as a surprise to Dr. Arnal, a researcher at the University of Geneva, and Dr. Poeppel, a professor of cognitive neuroscience at New York University. They conducted a "slightly unconventional" acoustic study, collecting a host of different human and non-human sounds. Another group listened to the sounds, rating them based on how alarming they were.

As it turns out, a true scream isn't characterized by volume or pitch. The real key is an acoustic feature called roughness. When the frequency of a sound modulates more quickly than our ears can differentiate, it is considered "rough" and we perceive it as unpleasant. Hearing very rough sounds is correlated with activity in the brain's amygdala, a region associated with feelings of fear. Screams, along with dissonant chords and artificial alarm sounds, all fell within the "roughness domain."

"The more such roughness modulation a sound has, the more scary it seems - and the more effectively it activates the amygdala," Poeppel explains.

Poeppel and colleagues also found that screams occupied a "privileged acoustic niche" - completely separate from the frequencies found in speech and gender-associated modulations. …

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