Why does the scream make us shudder, fear?

Each scream has at least one separate point making them unique. It could be a high-pitched bass or hissing noise and it might sound like it's out of control.

So why does the scream become unmistakable?"If you ask a person on the street, they will say that the scream is loud and jarring," said David Poeppel, neurologist at New York University and Max Planck Institute, Frankfurt. "But that's not the case."

Poeppel knows the answer. In 2015, he and his colleagues discriminated against cries of fear for other noises. They began writing a data about the screams."We spent hours and hours searching the internet, looking for monstrous sounds from YouTube and movies , " Poeppel said, "but then we started bringing people into the lab and asking them to scream".

Then the analysis of the samples. At first, Poeppel also thought that volume and pitch were what made screams a . scream. But then he and the researchers analyzed the auditory properties of the sounds in the database and realized that what they had was an acoustic property, called roughness - speed measurement. Sound fluctuates according to volume.

The bigger the sound, the greater the activity it creates.

The normal human voice changes the noise level four to five times per second, but with the scream, the figure can range from 30 to 150 times per second. This means they occupy a unique position in the sound of human voices and may be the reason they attract attention.

With that information, Poeppel checked the subjects that ranked a list of sounds based on the level of attention, which sounded more and more rough, the more people saw it jarring. They found it similar to the warning whistle of cars, houses, and ambulances - things that have the same roughness index as screams."There is something in common between these sounds that struck your brain and said: Hey, there's something ," Poeppel said.

To find out how this move works, researchers track brain activity when hearing "rough" and neutral sounds inside a magnetic resonance scanner. Not surprisingly, the sounds made blood flow into the auditory cortex. But the raw sound also causes blood to flow into the amygdala, two almond-shaped small gray blocks that combine the processing of emotional response like fear. Poeppel added: "The reaction of the amygdala is not on an off-and-off mechanism. It's a classification response . " In other words: The louder the sound, the greater the activity it creates. Almond nuts act as a measure of screaming sensors.

The next step is to analyze the types of screams - from angry screams to ecstatic cries - and how they affect brain perception and activity."I compare three positive factors and three negative factors," said Natalie Holz, a researcher at the Planck Institute, who also led the study. "On the negative side, they continue to increase their fear, at the same time as the cry of anger and pain. On the positive side, we will see screams when we get positive, surprising things. interesting and sexual pleasure ".