If you’ve ever been seated next to a stranger or even a friend noisily chomping away at their food and been overwhelmed by intense feelings of anger and frustration, you’ll be interested to know there’s more at play there than just a question of manners.

Your seemingly irrational and uncontrollable reaction could be the result of misophonia, a term that translates literally to “the hatred of sound.” There’s no diagnostic test, and you won’t find it in the DSM-IV, but it’s a condition that’s been extensively studied to understand why certain “trigger sounds” just rub us the wrong way.

A team at the University of Newcastle recruited 42 subjects, 20 exhibiting signs of misophonia and 22 who did not. They were monitored in an MRI machine while played an assortment of sounds, some neutral, some simply regarded as “unpleasant,” and some thought to be trigger sounds. The published report, found here in Current Biology, saw that those suffering from misophonia demonstrated a spike in brain activity, most often anger, when played the trigger sounds.

Witness an extreme case of misophonia in this video from ABC News:

Another study found that 80% of trigger sounds emanated from the mouth and 60% of them were repetitive, which would explain why habits like gum-snapping, lip-smacking, or even heavy breathing can cause such ire in others.

So while you don’t need a scientific reason to be upset at someone for eating loudly, you might have one. Which could be handy if you ever find yourself on trial for strangling that guy on the airplane next to you.