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Do you hate the sounds of chewing? Now scientists know why

Misophonia chewing sounds
Some people who have misophonia hate the sound of chewing. Photo: Getty
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If the everyday sounds of other people chewing, slurping and breathing drive you mad with frustration, finally there’s an explanation.

The disorder is called misophonia, and it’s when certain sounds trigger emotional or even violent responses that most people see as unreasonable given the circumstances.

For many people who have misophonia, the sounds of someone slurping a thick shake or breathing loudly over their shoulder is so irritating it’s enough to make them flinch, run away or scream out loud.

 

beaver chewing probably loudly

Now, scientists think they know why.

Brain scans performed by researchers at England’s Newcastle University show people with misophonia have stronger connectivity between the part of the brain that processes sounds, and the part of the premotor cortex responsible for mouth and throat muscle movements.

When people with misophonia were played a “trigger sound”, the scans showed the brain region involved in mouth and throat movement was over-activated compared with a control group of volunteers who did not have the condition.

Dr Sukhbinder Kumar, a neuroscientist at Newcastle University, said the research suggested “that in misophonia, the trigger sound activates the motor area even though the person is only listening to the sound”.

“It makes them feel like the sounds are intruding into them,” he said.

During the experiment, the various trigger sounds activated what is called the brain’s mirror neuron system.

Mirror neurons typically light up in our brains when we perform an action, and also when we see another person make a particular movement, like a dance move.

They help us learn by imitation, and allow us to reflect body language, facial expressions and emotions.

Activating the mirror neuron system with trigger sounds didn’t make people with misophonia involuntarily chew or swallow, but the researchers believed it could produce an urge to do what they call “hyper-mirroring”.

That may lead some people with misophonia to copy the sound that sets them off because it brings them a sense of control over the sensations they feel, Dr Kumar said.

Irritating sounds

The sounds of breathing and chewing are just a few examples of potential triggers, said Craig Anderson, the director of the neurological and mental health division at Sydney’s The George Institute for Global Health.

“Tapping a spoon on a bowl drives me crazy,” Professor Anderson told The New Daily. 

“Licking and smacking lips is one. Some people also make little snorting sounds when they’re speaking.”

Professor Anderson said misophonia was probably linked to personality and brain development.

“It overlaps a bit with obsessive compulsive tendencies, and it may overlap with autism and spectrum disorders,” he said.

“We all have things we don’t like and for some people it’s particular sounds or actions that evoke a more dramatic emotional reaction.”