What is so disturbing about screams? Aside from the obvious–that they represent a fellow human’s pain or fear of mortal peril?
While it may seem clear on an emotional level why a scream is an upsetting sound to hear, scientifically, it appears that screams and other rapid changes in volume trigger the fear centres within our brains.
A study led by New York University neuroscientist David Poeppel uncovered that shrieks and wails grab our attention in such a powerful manner because an average scream has so many rapid changes in volume per second. While regular speech fluctuates in volume at an approximate rate of 4-5 times per second, screams can fluctuate from 30-150 times per second! This results in “roughness”, a vocal affect mimicked by sirens, and one that our brains associate with fear.
Additionally, Dr. Poeppel’s researchers conducted fMRI scans while participants listened to various screaming volunteers, and found that the amygdala–the brain region associated with the fight-or-flight response–was activated.