Scientists discover why nails on a chalkboard make us cringe

Just thinking about the annoying sound of nails on a chalkboard is enough to send shivers down your spine.

Scientists have long puzzled why the squeaky sound made by our fingernails sliding across a chalkboard makes us feel frustrated.

Research has found that this sound has the same frequency as a baby's cry and a human's scream, suggesting that it is associated with survival and elicits a similar response.

The scratching noise elicits a physiological response, such as an increased heart rate, causing an emotional experience rather than a reaction.

Most people described nails on a chalkboard as an “unpleasant sensation” and used words such as “shivering” and “disgust.”

A 2006 study led by Nobel Prize winner Dr. Francis Wismer found that sound frequencies in the middle of the vocal range were most disturbing and were similar to the warning cries of chimpanzees.

The researchers who conducted this work suggested that our reactions to unpleasant sounds stem from predator-avoidance instincts from our evolutionary past.

Sounds in this frequency range, 2000-5000 Hz, cause the ear canal to resonate, so sound travels particularly efficiently.

A separate 2012 study found that the amygdala, a roughly almond-shaped mass in the brain involved in experiencing emotions, could be the culprit behind sound-induced pain.

Dr Sukhbinder Kumar, from Newcastle University, said: “There appears to be something very primitive going on.

Scientists at Newcastle University have discovered increased connectivity between the auditory cortex and motor control areas related to the face, mouth and throat in those with misophonia.

“It's a potential distress signal from the amygdala to the auditory cortex.”

“There is a frequency range where our ears are most sensitive.

“Although there is still a lot of debate about why our ears are more sensitive in this range, it does include screaming sounds that we find intrinsically unpleasant.”

However, some people have more extreme reactions to sounds, especially chewing and loud breathing, and may have a “hypersensitive” brain connection.

Scientists at Newcastle University have discovered increased connectivity between the auditory cortex and motor control areas associated with the face, mouth and throat in those with misophonia.

Misophonia, which means “hatred of sound,” is a condition in which people experience intense, involuntary reactions to certain sounds made by others, referred to as “trigger” sounds.

Dr Sukhbinder Kumar, Newcastle University Research Fellow in the Institute of Biological Sciences, said: “Our findings suggest that for people with misophonia, there is abnormal connectivity between auditory and motor brain areas – you could describe it as ‘hypersensitive connectivity’.

“This is the first time such a link has been identified in the brain for this condition.”