Do you wince when you hear the sound of nails on a chalkboard? You may now even have the urge to cover your ears just from thinking about the unpleasant screech (sorry about that). Here's an interest tidbit, though: A recent study suggests that universally disliked sounds such as nails on a chalkboard may produce a unique emotion all its own.
Many shrill noises tend to prompt visceral reactions — think chalk on slate, the squeak of styrofoam rubbing together, or utensils scraping a plate (sorry again). What's fascinating, though, is that apparently they can all have the same adverse effect of sending shivers down the listener’s spine. In Spanish, there is even a word for the emotional response that these unpleasant sounds produce: “grima.” While grima is mostly elicited by sounds (for me, its the clink of teeth on a metal spoon), touching certain materials or objects can bring on the unpleasant sensation as well. So if you hate touching sponges, corks, or packing materials, you're not alone in these feelings!
Researchers at the Complutense University of Madrid explored the concept of grima in a study recently published in the journal Frontiers in Psychology. To better define the concept, the scientists polled a number of Spanish-speaking people to see what the word "grima" meant to them. Volunteers described it as more unpleasant than the feeling of disgust; what's more, when looking for terms synonymous with “grima,” scientists found that " people most frequently mentioned an ‘unpleasant sensation’, ‘shivering’, ‘sounds’ and ‘repulsion’," writes Sam Wong at New Scientist. "Stimuli that elicited grima included squeaking noises, scratching with fingernails and scratching on surfaces."
The researchers then turned to non-Spanish speakers to measure their physical response to grima-evoking sounds. While there is no word for this feeling in English or German (though there totally should be), the bodily reaction that these specific sounds produced in people who spoke these languages was clear. When listening to the nails-on-a-chalkboard sound, volunteers' heart rates fell slightly, then increased sharply before leveling out. Sounds merely deemed “unpleasant” or “disgusting" produced a different distinct reaction, with heart rates crashing more sharply than before, but returning to normal more evenly. Hearing both types of sounds also produced an effect on skin conductance (where skin becomes a better conductor of electricity due to emotional arousal), signaling physiological changes at work.
To test whether grima was truly an “emotional experience” as opposed to a simple “reflex reaction,” researchers asked their Spanish-speaking volunteers to try to suppress their reactions to grima-esque noises. “Participants who were instructed to think 'if I hear grima-eliciting sounds, I will ignore it' rated grima sounds as less unpleasant, but their ratings for disgust-inducing sounds did not change,” Wong describes at New Scientist. "Together, the results suggest grima is similar to disgust, but differs in terms of its triggers and the physiological response." So next time you hear that unpleasant scraping, you are experiencing a unique stress response all its own, which is kinda cool!
There are plenty of theories as to why these specific scraping and squeaking sounds are so distasteful to humans. Most tie these noises to our very evolutionary roots, linking their frequency of 2000-5000 Hz to primitive human survival. It's been noted that the frequencies of these grating sounds are the similar to those of a human scream, a baby's cry, or the warning call of of chimpanzees. It also seems that our ear canal is especially tuned to pick sounds at these frequencies up, so unfortunately we are especially sensitive to them, explaining why they seems to drown everything else out.
Unfortunately, there is nothing we can do about it — unless we all switch to projectors and whiteboards in class, that is.