Why Is the Sound of Nails on a Chalkboard So Unpleasant? The act
of scraping nails down a chalkboard creates a sound so awful
that most people have an instantaneous reaction: A shiver runs
up the spine, and they slap their hands over their ears.
Anything to block out that noise! But why do unpleasant sounds
affect us like this? Newcastle University scientists think
they’ve pinpointed why. For a new study , the researchers placed
13 subjects inside functional Magnetic Resonance Imaging (fMRI)
machines, which measure brain activity by detecting changes in
blood flow. As they played a range of 74 sounds, the scientists
watched what happened in the brain. They found we recoil from
unpleasant sounds because of the interaction between two areas
of the brain: The auditory cortex, which processes sound, and
the amygdala, which is active when we process negative emotions.
So when someone screams, or a baby cries, the amygdala takes
over, heightening the activity in the auditory complex and
creating a negative reaction