Researchers who analyzed how the human brain processes screams said that the high-pitched and loud noise targets a brain structure named the amygdala, which plays a crucial role in fear learning and danger processing.
Luc Arnal, a neuroscientist at the University of Geneva said that they were aware of the frequencies being used by speech and in which brain regions the speech processing is involved: the auditory cortex and other regions like Broca’s area, for example. However, why screams are so unpleasant and special and how they are processed by the human brain was unclear. Scientists said that an acoustic quality named ‘roughness’, which is a quick change in loudness of the sound, sets the screams apart from any other sounds.
Arnal explained the roughness of the screams by saying that normal patterns in speech have only small loudness differences, between 4 to 5 Hertz, but screams could modulate extremely fast, from 30 to 150 Hertz. Hertz are sound wave cycles that happen every second. Scientists used recordings of screams from popular horror movies in their study and YouTube videos and others made by volunteers in a laboratory and requested individuals to judge how distressing those screams were. The screams with the highest level of roughness were the most frightening of them all.
In order to understand how screams were processed, the scientists monitored the activity in the brain by using a neuroimaging method named functional magnetic resonance when the subjects of the study were listening to the screams.
The researchers discovered that screams enhanced the stimulation of the fear response inside the amygdala, a structure shaped like an almond which is deep inside the medial temporal lobe of the brain. Arnal said that the findings might be used in order to perfect how alarm sounds are designed. In the same way an awful smell is added to gas in order to make it more detectable, adding more roughness to the sounds of an alarm could accelerate and improve its processing.
The scientist said that he wants to research even further on the screams from infants in order to see if those screams have more roughness to them. He added that he began being interested by screams when one of his friends said that the screams of his newborn were literally seizing his brain. He said that this made him wonder what it is about screams that work incredibly well as alarms.
The findings were published in the Current Biology journal.
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