You know that weird, shivery, uncomfortable feeling you get when you hear the screech of nails on a chalkboard? Maybe you get it from other things, too: On one Reddit thread, users described experiencing the same sensation after licking a wooden Popsicle stick, or in response to the sound of two pieces of Styrofoam rubbing together; for me, it’s the feeling of flour on my hands; psychologist Inge Schweiger Gallo, a researcher at the Complutense University of Madrid, recently told New Scientist that it happens to her when she touches foam rubber.
Researchers have been trying for a while to figure out what it is that makes the feeling so unpleasant — one study, for instance, found that the sound created by nails on a chalkboard falls within the range of frequencies that the human ear is most sensitive to — but the challenge is that it’s easier to talk about what causes it than what it actually is. In a study published earlier this month in the journal Frontiers in Psychology, Gallo and her colleagues attempted to shed a little more light on the subject, working to create a more specific definition of what the Spanish call grima:
[The researchers] began by asking Spanish speakers what grima means to them. The people most frequently mentioned an “unpleasant sensation”, “shivering”, “sounds” and “repulsion”. Stimuli that elicited grima included squeaking noises, scratching with fingernails and scratching on surfaces. The volunteers rated grima as being less pleasant than disgust …
The team then asked Spanish volunteers to try to suppress their responses to grima. 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.
To make sure the reaction wasn’t unique to Spanish speakers, the study authors also ran an experiment on people whose native language — either German or English — had no word for the sensation that grima described. When they played the same grima-inducing noises, the participants’ hearts fluctuated in different patterns than they did for other unpleasant sounds. Taken together, New Scientist wrote, the two parts of the study imply that “grima is not a reflex reaction, but an emotional experience that can be influenced by thought, and is distinct from disgust.” We may not have our own separate term for it, other than the unwieldy “nails-on-a-chalkboard feeling,” but it’s possible our brains have their own separate response.