Why Do the Sounds of a Scraping Knife on a Plate & Fingernails on a Chalkboard Make Humans Cringe?

Why Do the Sounds of a Scraping Knife on a Plate & Fingernails on a Chalkboard Make Humans Cringe?


Few sounds cause humans to cringe more than
nails across a chalkboard, a fork scraped on a plate, or a heavy metal chair dragged
across a tiled floor. But what exactly is it about this sort of
scraping noise that is so offensive to our brains that many even describe it as painful? Enter researchers D Halpern, James Hillenbrand,
and Randolph Blake. In 1986 the trio of scientists conducted a
study trying to figure out what exactly in these sounds humans the world over hate so
viscerally. In the study, published in the journal Perception
& Psychophysics, the researchers were hypothesizing that it was the high pitched sounds that were
causing the issue, and thus isolated the sounds between low, middle, and high frequencies. After playing these recordings to subjects,
remarkably, they found they were wrong. As Dr. Blake noted, “To our surprise, the
removal of the high frequencies didn’t reduce the aversive qualities of the sound, but removing
the middle frequencies of the sound did.” From there, when looking at these middle frequencies,
they hypothesized that this must resemble either that of a sound produced by a predator
or a warning cry of another primate. They ultimately found, indeed, as stated by
Blake, “It turns out the sound waves associated with primate warning cries, particularly chimpanzee
warning cries, are remarkably similar in appearance to the aversive, middle frequency sound waves
produced by fingernails on a chalkboard…” Potentially worth noting is that a chimpanzees-human
primate was the last common ancestor between humans and our hairier brethren, thought to
have split around 13 million years ago or so, though hypothesized by some to still be
interbreeding up to around 4 million years ago. In any event, Blake then sums up, “Our speculation
was that the reason the sound of fingernails on a chalkboard have an almost universal aversive
quality is that it triggers in us an unconscious, automatic reflex that we’re hearing a warning
cry.” That said, it is widely reported that this
hypothesis has been debunked by a study, Are Consonant Intervals Music to Their Ears? Spontaneous Acoustic Preferences in a Nonhuman
Primate, looking at how tamarin monkeys responded to certain sounds, including nails on a chalkboard-like
screeching and white noise. However, if you actually go read the study,
it didn’t definitively debunk anything with regards to the former study, nor was that
the point of the new study at all. Most pertinent to the topic at hand, all it
showed was that tamarin monkeys didn’t seem to show any more or less aversion to the screeching
noise than white noise, unlike humans who are averse to the screeching sound. As to the debunking angle, this appears to
be yet another case of something a lot of sources say because some source somewhere
said it once, both clearly not bothering to read the study and acting like a single study
was a lot more definitive than it actually was- a favorite practice of media outlets
the world over pretty much as long as there have been scientific studies and media outlets
reporting on their work. From there, nobody else seems to have been
bothered to go actually read the study either, despite it being their job when talking about
this stuff. On this one, it turns out humans and monkeys
are not exactly the same (shocker, we know) and have slightly different evolutionary paths
and in some cases range of vocals. As an example of how this can come into effect
with sounds and tamarin monkeys, we have a 2010 study by Professor Charles Snowdon of
the University of Wisconsin-Madison looking at frequencies of sound that tamarin monkeys
do respond to. Important to note here is that the tamarin
monkeys’ resting heart rate is about twice that of humans and their typical vocalizations
are about three octaves higher. In the study, they found these monkeys responded
most strongly to music centered around their vocal frequencies and tempo of their heart
rate, both in the sounds’ ability to agitate the monkeys and to calm them. Further, the tamarin monkeys had no such responses
to human music played for them. This is a common theme several studies show
is true across various animals with different resting heart rates and vocal ranges than
humans. For more on this, see our video, Do Dogs and
Cats Like It if You Leave the Radio or TV on When You Leave the House? In any event, unsatisfied with this incomplete
and fairly speculative answer of the 1986 study, researchers Michael Oehler and Christoph
Reuter decided to conduct a study ultimately titled Psychoacoustics of chalkboard squeaking,
published in the Journal of the Acoustical Society of America in 2011. This more or less repeated the previous 1986
experiment, but using modern technologies and collecting a lot more data, particularly
looking at heart rate, blood pressure, and skin electrical resistance of the subjects
as they listened to the sounds of nails on a chalkboard, squeaky Styrofoam, forks scraping
on a dinner plate, and chalk making a high pitched squeaking sound against slate. What they found is that if they filtered out
the sounds from 2000-4000 Hz, subjects actually sometimes even described the sounds as pleasant. In contrast, when the offending isolated range
of sound was played for people, they hated it, confirming it is somewhere in the ballpark
of these frequencies that are the offending bits. Noteworthy here for reasons we’ll get into
shortly, typical human speech tends to average around 300-3000 Hz, though for reference humans
can hear up to somewhere in the vicinity of 16 kHz- 20 kHz. Going back to the study, while the researchers
further found if they, for example, told the participants the sounds they were hearing
were from a musical arrangement, people found them much less offensive than if they told
them what they actually were, regardless, there was an observed change in heart rate,
blood pressure and most noticeably skin conductivity when the unpleasant range of frequencies were
being played. While fundamentally this research didn’t really
add too much new to the original study, the researchers here hypothesized that the reason
we react so viscerally to the sounds in this range is because they are already really loud
in many cases and the human ear canal actually amplifies sounds in that range. This is obviously helpful for perceiving human
speech, but if too loud a source can become unpleasant and even perceived as painful. As acoustic engineer Trevor Cox of the University
of Salford sums up, “It hits a range of frequency where your ear is particularly sensitive,
and therefore you would expect a stronger response.” Adding another significant piece to the puzzle,
Sukhbinder Kumar et al in 2012 published the results of their study Features versus Feelings:
Dissociable Representations of the Acoustic Features and Valence of Aversive Sounds. In it, they took fMRI’s of a group of people
listening to these types of sounds, among other more pleasant sounds like babbling water-
in total 74 different types of sounds were looked at. The results? They found that when these sorts of nails
on a chalkboard sounds were perceived, not only did people rate these sounds as unpleasant,
but the level at which they rated a given sound unpleasant was directly proportional
to the activity of the amygdala and the auditory cortext. They also found that the activation of the
amygdala in turn heightened the activation of the auditory processing centers of the
brain, further making your brain pay even more attention to these sounds and, in this
case, not in a pleasant way because of the activation of the amygdala. For those unfamiliar, the amygdala is, among
many other interesting things we’ll get into in the Bonus Fact later, involved with emotional
responses, including things like fear and, in turn, anxiety. On the note of fear, patients who have certain
types of damage to the amygdala tend to fail to exhibit fear where others would, and animals
who have the amygdala completely removed are drastically less likely to exhibit signs of
fear and in turn anxiety. The amygdala also is thought to be a part
of the brain that triggers the fight or flight response. Going back to sounds, the worst rated sounds,
and the ones that likewise showed the most activity between the amygdala and the auditory
cortex were a knife scraped on a bottle, a fork on a glass plate, and the screeching
version of chalk on a chalkboard. And if you’re wondering, one of the most pleasantly
rated sounds was that of a laughing baby. In the study, they further concurred that
the troublesome parts of the sounds appear to be between around 2,000 Hz and 5,000 Hz. Dr. Kumar notes of this, “This is the frequency
range where our ears are most sensitive. Although there’s still much debate as to
why our ears are most sensitive in this range, it does include sounds of screams which we
find intrinsically unpleasant.” Speaking of screams, there is a certain dissonance
to the sound of this sort of nails on a chalkboard scraping, which is also similar to the type
of vibrations created when a baby is crying loudly or a non-parasite human screams. This, perhaps, all lends credence back to
the original hypotheses in the 1986 study that there is something from our long past
that has taught us to fear these sounds to the extent that our brains are apparently
literally wired to induce anxiety and partially trigger the fight or flight response when
they are perceived. As summed up by Dr. Kumar, “It appears there
is something very primitive kicking in… It’s a possible distress signal from the
amygdala to the auditory cortex.” Thus, to sum up the answer to the question
of why people hate the sound of nails on a chalkboard, for whatever reason this triggers
the amygdala to activate and interact with the auditory cortext of the brain, increasing
its activation and creating an overall unpleasant sensation between the two. As to why, the working hypothesis to date
is either because the sounds are being amplified in the ear canal to unpleasant levels, that
the specific sounds in the offending range mimic that of a human screaming or a mini-human
crying loudly, or possibly all of this combined. And speaking of mini-humans, while a baby
crying is likewise one of the most unpleasant sounds, apparently in part from this amygdala
activation, a baby laughing, as noted in the aforementioned 2012 study, is rated as one
of the most pleasant to our brains- perhaps all giving at least one evolutionary benefit
to why this is so encoded into our brains on both ends. Speaking of awesome science and your little
parasites laughing, you’ll get all of this when you do educational activities with them
using KiwiCo!!!… Bonus Fact:
While you might think all of this research on why humans hate the sound of nails on a
chalkboard is kind of trivial and a waste of research dollars and the time of some of
the world’s finest minds, Dr. Kumar takes the opposite line of thinking- that it has
interesting implications to other research. For example, this may help shed some light
into why, for example, autistic individuals are so much more sensitive to many sounds
others don’t find offensive, with some such sounds causing extreme panic responses at
times. This is even more noteworthy when connected
to the fact that autistic people also often exhibit a certain level of facial blindness
and lack of ability to read emotional states of others by their facial expressions and
the like. Why is this connection potentially important? It turns out, not just inducing certain anxiety
responses from sounds, the amygdala also is integral in your ability to recognize faces
of people and their emotional state from this. Interestingly, the amygdala also plays a strong
role in social interactions. For example, it’s been found that the larger
your amygdala, the more likely you are to have a larger and more diverse social sphere,
with many more connections than those with smaller amygdalas. The amygdala also plays a critical role in
storing memories that occurred during emotional times, which is why you can remember them
better. On a similar note, the amygdala also seems
to play a role in learned aversion of certain things. So, for example, should you burn your hand
in a fire, it becomes drilled into your brain to fear fire. For autistic people, this sort of learned
anxiety seems to be turned on overdrive at times, with a minor incident sometimes producing
long term anxiety about the situation in future, even sometimes long after the original incident
is forgotten. From all of this, there seems to be an awful
lot of traits of autistic people that are potentially connected to the amygdala in some
way. As one 2009 study from the University of Washington,
Heightened Level of Amygdala Activity May Cause Social Deficits in Autism notes, “An
increased pattern of brain activity in the amygdalas of adults with autism… may be
linked to the social deficits that typically are associated with the disorder. Previous research has shown that abnormal
growth patterns in the amygdala are commonly found among young children diagnosed with
autism.” The researchers further note of the amygdala
of autistic people, “What we are seeing is hyperexcitability or overarousal of the amygdala,
which suggests that neurons in the amygdala are firing more than expected… If you consider that habituation reflects
learning in as simple a task as looking at a face, slowness to habituate in people with
autism may contribute even more markedly to difficulty with more complex social interactions
and social cognition. If the brain is not reacting typically to
a static face with a neutral expression, you can imagine how difficult it may be for someone
with autism to pick up more subtle social cues.” They also found those autistic individuals
with the highest over-arousal of amygdala also exhibited the greatest social impairment. Going back to sounds, in the end, the results
of this seemingly silly research on why humans are averse to the sound of nails on a chalkboard
is just another research log to throw on the fire of the growing body of evidence that
there is something weird going on with autistic people’s amygdalas and may well be a key contributor
to many aspects of the condition. Most pertinent to the topic at hand, this
potentially may point to why the nails on a chalkboard aversion extends to many other
types of sounds, or even just too much sound from a variety of sources, in autistic people. Something similar might also be occurring
with visual stimulus. For example, vocal autistic people often describe
looking people directly in the eyes when you talk to them as giving the same sensation
as listening to the sound of nails on a chalkboard. And by the way, for those unfamiliar, it turns
out the Spanish language has a word for this rather unique feeling- grima, which is often
defined as “disgust” in English, but for whatever it’s worth, one study done at the Complutense
University of Madrid looking into the matter actually showed people’s skin conductivity
was noticeably different when feeling disgust at certain sounds vs. the sensation when listening
to nails on a chalkboard-like sounds, more or less concluding that this is an inaccurate
translation and grima is a distinct unpleasant sensation from disgust. That poor Grima Wormtongue in Lord of the
Rings never had a chance with that first name… Though apparently on this one it is widely
reported that the first name was actually from the Old English for “mask,” though we
couldn’t find a primary source for this and the Spanish word would make some sense here
as well, unless anyone knows of Tolkein explaining the name origin or some other significant
evidence either way?

100 thoughts to “Why Do the Sounds of a Scraping Knife on a Plate & Fingernails on a Chalkboard Make Humans Cringe?”

  1. Help support our research and writer monkeys and their incessent need for bananas and get your first KiwiCo box free by clicking here! https://www.kiwico.com/brainfood

  2. SIMON: You guys wanna know what makes ME CRINGE? You guys stole LIST25's OPENING-THEME MUSIC🎶 and use it with YOUR Intro???

  3. What makes me cringe the most is when people are buffing their foot skin off. The sound of it and even the feel of anyone doing it to me just makes me feel soooo grossed out.

  4. To help out your sponsor, my son was getting kiwi Co and he adored it. He would do them with his friends or with me. They are very informative, you learn a lot and they come with a fun comic book in the kids edition

  5. Funny how human speech and unpleasant noises have a common range. I reckon that's why it's annoying when women talk too much. Seriously.

  6. i really hate anything coming from tiny parasitic humans. laugh, cry doesnt matter it makes me annoyed if around it long enough

  7. I think the hypothesis is rubbish. I do not have a "fight or flight" response to the offending noise. Far from it. It is just a most unpleasant sound.

  8. The only one that gets me is nails on a chalkboard it cuts though me it's so that I kept skipping this video just cause he might preform the sound but the video is not over but so far so good

  9. As the 'happy news' arrived at the ears of the teacher, his shocked look drew attention of the class. The news causing a stunned look of horror in which he equated to the potential sounds from one more newly born child that would soon arrive to that of the squeaking of the chalk he found himself inadvertently doing while he was being told.

  10. Is there an editing error at 2:21? You seem to be cut off mid sentence and then you're in the middle of a completely different sentence.

  11. I love all your channels. Thanks for putting out great content! I just wanted you to know that instead of saying "autistic people" it's preferred to use person first language. Saying "a person with autism" would be a better way to put it. They are a person first, and they happen to have autism. It does not define who they are as a person. It's a common mistake. I didn't know to use this subtle difference in word choice until I took the class Disabilities: Diagnosis and Intervention while in college.

  12. On a similar note, why when watching someone on tv jumping from a height, do you sometimes anticipate and feel the pain of the landing in your own legs? It is the same thing?

  13. Does anybody else get a cringe feeling when imagining rubbing your teeth on certain fabrics like wool, or any like it?

  14. i was expecting mirror neurons to play some part; speaking personally, the noise itself doesn't bother me anywhere near as much as imagining the feeling of running my nails on that chalkboard – seriously, writing this comment is making me imagine the vibration through my fingernails. it gives me conniptions…

  15. My 12 grade English teacher did this to get the class to be quiet so he could talk lol.

    It sounded more like a grinding sound than a screeching sound though.

  16. Funny those sounds don't bother me nearly as much as the sound of someone chewing or swishing liquid around in there mouth.

  17. Hmmmmm Chalk board? It's a black board named so because it is black so that the chalk shows up. It was a BLACK board I suspect for over a hundred years before some PC knobhead decided to censer our language and I find the new name somewhat offensive.

  18. I always felt like I hated the sound of nails on a chalkboard because it reminds me of the feeling. My hands and arms cringe at the sound of nails on a chalkboard.

  19. Lol as soon as I heard Grima I thought of Wormtongue and then when you started talking about the character my nerd hype went on overdrive

  20. If the unpleasant sounds corresponds to the noise of a scream, obviously people would have an intrinsic feeling of distress. Stuff like that keeps people alive.

  21. As someone with two anxiety disorder diagnoses, who also has many traits in common with autism, this was damn fascinating. Thank you!

  22. i can hear the sound of the pest control device that make a high pitch noise it hurts my head and i have to get away from it i also hear white noise coming from the tv even when its on stand by

  23. As with much from my youth, it appears primarily a young thing. I just listened to some blackboard-scraping, and the effect appeared abated.

  24. Isn’t the easiest way to debunk this to actually play those middle tone chimpanzee warning cries and see if people have an aversion to it?

  25. All these scientists and researchers got it all wrong. It was never the sound, it was the sound bringing up memories of either you scratching your nails or even chalk hard on a chalk board that give your fingers and hands an awful feeling. I want you to hear the sound then think of actually scratching a chalkboard, then you'll shake your hand like it was it pain I'll bet.

  26. Could it be that people with large and diverse social circle are constantly experiencing stress and fear due to said social circle?

    There by stimulating the Amygdala to become larger since it is being worked harder?

    This hypothesis would coincide with studies that show people with large and diverse social groups are less happy than those who don't.

    Perhaps large groups of social diversity is not a strength after all.

  27. Hearing the sound of fingernails scraping on a chalkboard does not make us become alert and look for predators. On the contrary, it probably makes us less alert to other things in our surroundings, because we just want to get away from the sound. That's not how primates react to an alert call, so the alert call theory simply doesn't make sense.

  28. 4 kHz is the response frequency of the eardrum. This is why, the human ear is most sensitive in the range around 4kHz

  29. all these studies and no one knows the truth of why we hate that: it's just the feeling of having your nails on the chalkboard what makes people cringe,not the sound

  30. this makes no sense to me. What does make me cringe is tactile in nature. Running my fingers over certain materials makes me cringe. There's some plastic glasses, (cups), that have a grainy texture that can make me cringe just thinking about it. https://www.google.com/search?q=grainy+textured+plastic&client=firefox-b-1-d&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiCmpy__b_nAhUMZKwKHd_AAvkQ_AUoAXoECAwQAw&biw=1360&bih=632

  31. Wasn't expecting to learn even more about autism (I'm "suspected autistic", but given I show the majority of traits, it's pretty much a case of I AM autistic!!), and the association with the amygdala, fascinating stuff, definitely a TIFO moment… 😀

  32. Also on the list would be the sound of dental drill. Couldn't it be some resonant frequencies of human skull? Or maybe other bones?

  33. Why would you get a cringing feeling if you hear a warning? Wouldn't the logical reaction be to skip a beat instead?

    Or did we in the past actually get afraid of the warning itself instead of the danger? That wouldn't make sense since what about the one making the warning sound, would it be cringing to itself?

    Or did our feeling shift from fight or flight to cringe?

  34. As someone with near perfect hearing who can hear some extreme, by human standards, high frequencies I was literally cringing every time Simon said nails on a chalkboard or the other similar sounds. Physical cringe response and chills down the spine in some cases. Fun times. Great video

  35. The reason the screech is amplified so much in the eat canal is likely because it’s the same resonance frequency; which would make the entire ear vibrate vibrates as opposed to just the eardrum, much like when someone has their subwoofer up too high and it hits the frequency in the song or movie that vibrates your whole body so much so that it makes you cough. It’s unpleasant because the sound isn’t just detected, but it vibrates the area around the detection which is anything but pleasant or comfortable

  36. To my knowledge I’m not autistic (at least not a lot), but I definitely have that nails on chalkboard reaction to looking someone directly in the eyes…

  37. I'm in the "don't mind" to "can tolerate" range of the nails and forks and stuff. The thing that will really REALLY get me though are shrieks of kids. The noise that they unleash on their second wind of crying. The one that they just belt out and is so loud and the pitch just pierces the sobs they've been chugging out and they decide to do so right. into. your. ear………It feels like my ear drums are trying to physically close themselves from that sound when I'm near it and hear it. It just reverberates too much.

    But this research is also as harmful as it is useful. The LRAD (Long-Range Acoustic Device) I'm sure has its frequency within this debilitating range. Also security alarms like fire alarms. I get they're within a certain range and volume to warn EVERYONE in the vicinity, but walking by one blaring results in the same thing as above. I'll also throw in there that I suffer from vestibular migraines, so even more fun when my ears are assaulted.

  38. My sister goes absolutely insane whenever she hears Styrofoam squeeking or being rubbed together. It was one of my main sources of amusement as a child.

  39. my best thorey is not cus of children crying

    our ears are senstive yes.
    but the this particular sound. that triggers our skin crawl. yet we can endure it if intentional
    reason being is due to our fingernails. yep thats right its to protect our fingernails from ripping off.
    chewing our nails prevents the nail from ripping off

    a bone for a fingernail would take to long to heal. while skin would cut and bleed often while swiming climbing and other stuff.
    so we need somthing hard to protect the tips of our fingers yet able to heal fast and be prtective.
    thus why they grow alot none stop. and reason for chewing is so we dont grow them past our finger allowing it to catch and ripp off

    finally the nails that scraping make a ratched sound on rocks on stuff. thus we chew them so the sound dose not appear.

    i say this is a logical reason why we dont like scraping sound especailly nails.

    thats my reasoning of deduction for that particualer sound

  40. Did someone else heard a high pitched sound at the beginning of the video and then it stopped in the middle untill the end of the video?

    Edit: nope, was my head

  41. A seemingly simple question leads to a fascinating whirlwind trip around acoustics, primatology, neurobiology, psychology, lingustics and even fantasy literature. Bravo and well done on checking primary sources – that's some proper journalism or should I say scholarship ?

  42. I wonder if he removed his glasses would his beard help him still retain his Britishness.. Or would the accent trail off and all fall apart

  43. I'm on the spectrum, and all that autism stuff is very accurate. It's interesting to get this kind of insight as to what's going on in my head.

  44. Being on the spectrum, young children definately are parasites when they scream, especially in resteraunts. Also, Daven Hiskey is responsible for the script, not Simon.

  45. For me, it's metal, like stainless steel scratching together.
    Like a fork in a metal pot, etc.
    It like hurts emotionally. I think it might be misophonia.

  46. I think all the researchers still missed it. To me, starting at a very early age, the sound to me equates to a Dillion my hands and body suggested a feeling (even to this day) of losing my grip and and a complete body anticipation of an eminent pending fall. It immediately gives me an involuntary reaction of wanting to re-establish my grip. It was a reaction I was born with, and have to this day. I’m thinking it stems genetically from a time where our environment depended on both hands, feet and nails to keep up from a serious injurious fall, the nail scraping being the first warning of a lost grip.

  47. I always thought as far as I feel the nails on board was more of a “ nails about to be ripped off and that makes me cringe not the sound”

  48. Speaking of annoying sounds, the background music sounds like an out of tune calliope being played by a maniacal circus clown as he slow tortures his poor victims to death…

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