Why are some sounds so unpleasant?

Researchers led by Sukhbinder Kumar of Newcastle University have been studying this burning question: why do some sounds make us flinch? We’re not talking about sounds that are so loud that they hurt our ears, but rather sounds we can’t stand even at what would otherwise be comfortable volumes. It turns out that these sounds create a feedback loop between the auditory cortex, which processes sounds, and the amygdala, which is involved in emotion and memory.

Thirteen healthy volunteers were asked to listen to 74 distinct sounds, many of which had been previously judged to be highly disagreeable, while undergoing MRI scans. The subjects rated each sound from 1 (least unpleasant) to 5 (most grating). Activity in both the auditory complex and the amygdala were linked with the unpleasant sounds. The authors believe that the stimulus travels from the auditory complex to the amygdala, where it is given an emotional tag, and then back to the auditory complex. This cycle can be repeated many times, increasing the degree of aversion to the sound.

Since I’m sure you’re dying to know, here are the ten most reviled sounds:

1. Knife on a bottle
2. Fork on a glass
3. Chalk on a blackboard
4. Ruler on a bottle
5. Nails on a blackboard
6. Female scream
7. Angle grinder
8. Squealing brakes
9. Baby crying
10. Electric drill

I don’t know about you, but just typing that list set my teeth on edge. 

Sukhbinder Kumar, Katharina von Kriegstein, Karl Friston, & Timothy D. Griffiths (2012). Features versus Feelings: Dissociable Representations of the Acoustic Features and Valence of Aversive Sounds Journal of Neuroscience DOI: 10.1523/JNEUROSCI.1759-12.2012