Now, everybody’s got their own personal taste in music.
Your driving tunes might sound to me like a couple of computers got in a fist fight,
and my wind-down playlist might sound to you like you’re stuck on hold with customer
service.
But no matter how different our musical tastes, I bet there are at least some sounds we can
agree on.
Namely, the worst, most skin-crawling, ear-covering, cringe-inducing ones ... like fingernails
on a chalkboard.
Just saying it gives me the willies.
And it turns out that there’s a good scientific reason why certain sounds set most people’s
teeth on edge: human ears are extra sensitive to a particular range of pitches.
… although where that sensitivity comes from is still up for debate.
In 1986, a group of neuroscientists tried to get to the bottom of these intense reactions
by doing what so many researchers do: unpleasant things to volunteers.
Specifically, they asked 24 adults to rank a series of 16 sounds based on how unpleasant
they thought those sounds were.
And although that isn’t a very big sample size, the noises that were consistently rated
the nastiest -- like the sound of a fork scraping a plate or squealing brakes -- all had something
in common:
They share a frequency range between 2,000 and 5,000 hertz, where our ears happen to
be especially sensitive.
The researchers wondered if there might be an evolutionary explanation for this, and
tried comparing those sound waves to the calls of seriously distressed macaque monkeys.
They found that there were some similarities between those warning calls and the nasty
scraping sounds, and suggested that our strong dislike for those noises might be leftover
from an ancient reflex.
And that kind of does make sense -- I mean, it’s helpful to be especially alarmed by
the sounds of your friends screaming.
But…
it’s also kind of hard to prove.
Plus, a 2004 study that subjected cottontop tamarins to those icky sounds and found that
the animals reacted in similar ways to both the bad noises and just plain old white noise.
So maybe our hatred for those sounds isn't a vestigial trait -- or at least, not one
we share with cottontops.
It could be that we’re remembering the image of nails on chalkboard, or imagining the feeling
of our own fingers scraping -- and that’s what triggers the willies.
And it’s working for me...
Then again, that’s just one study, and it’s possible that the results would have been
different in, say, macaques, or other species.
But whether or not our reactions have an evolutionary basis, humans are generally more sensitive
to these kinds of noises.
And there are a few different theories about how our brains turn a seemingly-innocent scrape
into a painful screech.
One 2012 study out of Newcastle University tried to get a better picture of what these
noises do to human brains by just looking directly at those brains.
They subjected 16 people to 74 different sounds -- from running water to the scrape of knives
on glass -- and then asked them to rank the sounds on a scale from pleasant to excruciating.
Once again, the worst of the sounds fell in that bad-Hertz sweet spot, but more interesting
than how the offensive sounds ranked was what they did to the people’s brains.
With the help of an MRI machine, researchers kept tabs on which brain parts lit up in response
to the more irritating sounds.
They found a strong connection between the auditory cortex, which processes sound, and
the amygdala, which is involved in emotions like anger and fear.
So it’s possible that when we hear these cringe-worthy noises, the amygdala influences
the auditory cortex’s response, making it more sensitive and causing a negative emotional
reaction.
Basically, that horrible screechy-scrape of nails-on-a-blackboard makes your amygdala
take charge -- and suddenly, the auditory part of your brain processes that awful sound
much more intensely than it would something more soothing, like flowing water or a soft
applause.
Other researchers think these noises might suck so bad because the anatomy of the human
ear amplifies particular frequencies -- to the point that they trigger real, physical
pain.
So, there are a lot of different possibilities, and we may never have a definitive answer
for why we loathe these noises so much.
But to all the teachers out there still using chalkboards: please, try to be careful.
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