Postdoctoral students at the New York University have recently started to wonder why of all noises in the world screams make us so uneasy. They started thinking of this after they became parents and had to deal with baby cries and screams every night.
According to the study published in the journal Current Biology screams do not activate only the part of our brain which takes part in auditory processing, but also the fear circuitry of our brain.
For the study the researchers created a bank of sounds which included various types of human vocalizations such as sentences and screams, sound intervals and artificial sounds such as instrument sounds and alarms. They used horror films from YouTube videos such as the famous movie Psycho.
Even though people believe that screams are more unpleasant than other sounds they cannot explain why it is so. For the study researchers conducted brain scans in order to measure how the screams the auditory neurons. David Poeppel, a professor of psychology and neural science at New York University remarked:
“When you ask someone what a scream is, a person on the street will say they are loud or high-pitched. But there’s lots of stuff that’s loud or high-pitched. … It’s something that’s actually not understood well at all.”
Researchers observed that the key element was roughness, meaning how much a sound fluctuates in volume. Unlike normal speech sounds which fluctuate in small amounts screams fluctuate widely. The fluctuation in normal sounds is between four and five hertz and in the case of screams the fluctuation varies between 30 and 150 hertz.
It was observed that rougher sounds were considered scarier. Brain imaging data indicated that rougher human cries activate the brain’s fear circuitry. This area of the brain is also activated by alarm signals such as car alarms or ambulance sirens. The roughness of a scream activated the amygdala, which is a part of the brain essential to critical response.
This study explains why screams make us so uneasy and the impact they have on our brains. Poeppel believes that this could help develop more effective alarms which are harder to ignore and even create scarier horror movies.
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