If chewing sounds irk you, blame your brain

The sound of someone slurping coffee or crunching an apple can be mildly annoying — but it leaves some people seething. These people aren’t imagining their distress, new research suggests. Anger and anxiety in response to everyday sounds of eating, drinking and breathing come from increased activity in parts of the brain that process and regulate emotions, scientists report February 2 in Current Biology.

People with this condition, called misophonia, are often dismissed as just overly sensitive, says Jennifer Jo Brout, a clinical psychologist not involved with the study. “This really confirms that it’s neurologically based,” says Brout, founder of the Sensory Processing and Emotion Regulation Program at Duke University Medical Center.
Researchers played sounds to 20 people with misophonia and 22 people without. Some sounds were neutral, such as rain falling. Others, like a wailing baby, were annoying to both groups of people but didn’t cause a misophonic response. A third set were sounds known to cause distress in people with misophonia — chewing and breathing noises.

MRI brain scans showed that both groups of people reacted similarly to the neutral and annoying sounds. But misophonics responded far more dramatically to the chewing and breathing. They showed more activity in their anterior insular cortex, a brain structure involved in emotional processing. Scientists found structural differences, too — more connections from the anterior insular cortex to structures like the amygdala and the hippocampus, which also help with processing emotions.
People with misophonia also showed increased heart rate and skin conductivity. That’s the same sort of flight-or-fight response that gets triggered when facing a wild animal or a public speaking engagement.
Sounds most people ignore in their day-to-day listening create a very strong emotional response in misophonics, says study coauthor Sukhbinder Kumar, a cognitive neuroscientist at Newcastle University in Newcastle upon Tyne, England. Their brains are ascribing extra importance to certain sounds. But it’s still unclear why only specific sounds cause a reaction.