<blockquote>
  <p>Furthermore the feelings caused by the "nails on a chalkboard" sound do not at all trigger a fight-or-flight response or put me on edge as a loud noise or something that startles me does. If anything it is almost <strong>paralyzing, which seems counter to the evolutionary theory.</strong></p>
</blockquote>

<p>Yes, I agree, it seems to, however what about the <a href="http://en.wikipedia.org/wiki/Fainting_goat">fainting goats</a>? We could have traits which aren't advantageous, yet we were able to survive in spite of them. Like the goats.</p>

<p>Even though it seems perfectly possible (though not logical) to be paralyzed by fear in response to a warning signal, I don't agree with the theory that the sound is indeed a warning signal.</p>

<p>In my experience with hearing fingernails on the chalkboard, its almost as if my teeth hurt.  This leads me to believe it is not predators I'm fearing, but injury.  It could be a fear by association produced from when I was very young and putting many different objects in my mouth.  Some objects may have produced a similar sound and the sound was associated with pain.  If you wish to survive in nature, its very important to have teeth, and injuring our teeth may be an especially important thing to avoid... not only if you expect to eat, but also <a href="http://crowncouncil.com/what-do-singles-want-nice-teeth">attract a mate.</a> A good smile <a href="http://www.businesswire.com/news/home/20120119006098/en/Bad-Teeth-Ranked-1-Turnoff-CosmaLite%E2%80%99s-Dating">is important</a>.</p>

<p>In my search for references to back up my theory, I found <a href="http://amasci.com/amateur/screet.html">this presentation</a>, the author of which seems to agree with my assessment.</p>

<p>I also found at least one other person who claims to feel something in his teeth:</p>

<blockquote>
  <p>I feel the discomfort in my teeth and have always assumed the screeching is at the right frequency to build up uncomfortable vibrations in the teeth.</p>
</blockquote>

<p>That is actually a random comment (pages 11-20 in the comments section at the bottom) to <a href="http://www.scientificamerican.com/article.cfm?id=why-is-the-sound-of-fingernails-on-blackboard">this article</a>.</p>

<p>I don't agree that the sounds would have enough acoutical power to vibrate the teeth.  I think the pain is merely imagined.  Of course, that's my opinion, for what its worth.  Since the prevailing theory is predator-based and not tooth-injury-based, I wouldn't expect to find any studies on the matter.</p>

<p>In addition to the evidence presented so far, I have another reason to doubt the predator theory.  If the sound mimics the cry of danger and the response is instinctual, then why don't we all have the response?  Out of 3 people contributing to this question, 1 has admitted "this sound has no effect on me at all." This argues in favor of my "fear by association" theory.</p>

CC BY-SA 3.0
2013-08-22T19:40:26.853Z
Fainting goats were I believe actually bred deliberately as decoy animals: put one in your herd and if a predator ambushed the herd, the fainting goat would fall over and get eaten, distracting the predator from the rest of the herd.  So no, fainting when startled isn't a survival trait **without humans around to value and breed selectively for it!** With humans around, though, it is in fact a survival trait.
Krysta
CC BY-SA 3.0
2013-08-22T21:01:13.330Z
@Krysta That's an interesting bit of thinking, kinda like my cats who learned not to hunt in favor of begging at the door. But, how does one breed goats to fall over when scared instead of running? And how can I train my cats to do that? Running is usually what gets them killed in this modern world of automobiles. They see a car and immediately dash across the road.
Randy
CC BY-SA 3.0
2013-08-22T21:06:53.180Z
Apparently the fainting trait (also called myotonia) is genetically quite simple.  It shows up like any mutation, and some sharp goatherd realized its use and bred for the trait selectively.   I think you have to be a catherd to do this in felines, though, and we all know how hard that is! ;-)
Krysta
CC BY-SA 3.0
2013-08-22T21:14:53.967Z
@Krysta Opossums also have this trait of playing dead. So, who was herding the opossums? ;)
Randy
CC BY-SA 3.0
2013-08-22T21:22:51.090Z
@Randy I'd guess it has to do with different predator populations: in Spain, where the myotonic goats come from, the apex predators of concern did scavenge, whereas in North America, they didn't.  Either that, or the Borrowers are real and they've been breeding fainting possums for a LONG time!!
Krysta
CC BY-SA 3.0
2013-08-22T23:15:48.763Z
@Krysta Well, cars take out lots of 'possums too, so maybe playing dead while drooling and pooping on yourself is not much of a survival technique :P
Randy
CC BY-SA 3.0
2013-08-19T09:18:11.240Z
2013-08-19T09:18:11.240Z
Randy
<p>Mine is the <a href="http://amasci.com/amateur/screet.html" rel="nofollow">evolutionarily ancient tooth-damage avoidance-response</a> 2003 speculation article, but if I have it right, then toothed animals in general should experience it, not just primates.  Maybe it goes all the way down the entire chain to octopi, snails, clams, any organism which needs to avoid radular-destruction when carefully trying to eat algae from silicate surfaces.</p>

<p><a href="http://www.jneurosci.org/content/32/41/14184.short%20rel=" rel="nofollow">2012 research</a> showed human fMRI to <a href="http://www.dailymail.co.uk/sciencetech/article-2215270/Scientists-identify-sound-nails-scraping-blackboard-unpleasant.html" rel="nofollow">horrid glass-scraping noises</a>, response located in amygdala and mediated by auditory cortex.   With fMRI we need not rely on subjective reports.</p>

<p>Heh, be first to test non-humans, we can crack the mystery and share the igNobel!</p>

CC BY-SA 3.0
2015-06-29T11:10:57.597Z
Welcome to Cognitive Sciences! Sorry for being skeptical - but - While the first part targets the question it is based on a link to a chatty blog with questionable credibility. The second part is nidely referenced, but does not address the question.
AliceD
CC BY-SA 3.0
2015-07-01T02:31:59.723Z
It's *my* pure speculation, and labeled as such.  Wbeaty author, owner amasci.com.   Also, sorry I was unclear, but there aren't two sections above.   I reference fMRI articles to suggest eventual testing of non-humans for aversion response to chalkboard(etc.) sounds.   If it ever turns out that other animals have similar avoidance, then the current theory has problems (current theory is, spectral peak of such noises are basically too loud, since that peak is matched to peak sensitivity of human ears.)
wbeaty
CC BY-SA 3.0
2015-07-01T02:48:21.757Z
CogSci reserves answers for scientifically sound answers. Speculations should be placed as a comment. You have enough rep to do so.
AliceD
CC BY-SA 3.0
2015-06-28T21:58:38.563Z
2015-07-01T02:43:59.980Z
2015-07-01T02:43:59.980Z
wbeaty
<p>I don't understand why there's a bias to assuming that something that doesn't actually touch us can't cause pain. I assure you: the sound that Styrofoam makes is <em>enormously</em> painful to me. (And I grew up in the egg business, where I would have to plug my ears on a daily basis when my father or someone else had to do something with Styrofoam cartons. Ugh.)</p>

<p>We all have different tolerance levels for pain in other ways. The guys who go for Navy SEAL (or equivalent) training, or who play NFL football, clearly have a different tolerance for pain than I do. Why would anyone assume that this is different in terms of one's hearing?</p>

<p>The simplest answer is the best: some of us are caused <em>actual pain</em> when certain sounds are made, most likely because there are frequencies in the sound that we can perceive more or more clearly than others can. I'm an audiophile, and have lots of anecdotal evidence that I can hear higher-pitched sounds than my friends... my guess is that for those of us who have massively painful reactions to these sounds, our ears are genetically wired to be able to hear those frequencies far more clearly than those who aren't susceptible.</p>

CC BY-SA 3.0
2015-06-28T21:41:06.467Z
Was it the pain of intensely loud sound (like a firetruck suddenly coming out from behind a building.  Slap your hands on your ears!)   Or was it the "horrible zing" of watching someone slide their finger along a knife blade.  The sound seems to stab out along all your bones, must clench fists and jaw?   Bad, but different than the ears-ouch-pain of extremely loud sounds?  Or exactly the same as loud-hurt guns and firecrackers?
wbeaty
CC BY-SA 3.0
2015-07-03T00:51:27.907Z
Hmm... it's sudden like the fire truck you refer to, but much more painful. It's not merely a matter of volume... even the slightest squeak of it is painful, and certainly louder is more painful. It doesn't go through my whole body, really... I mean, I react, but the pain is localized to my hearing. That's the best way to describe it. Like most people with nails on a chalkboard.
Scott
CC BY-SA 3.0
2013-08-20T19:57:00.013Z
2013-08-20T19:57:00.013Z
Scott
<p>I am curious as to what current research shows regarding why scraping noises such as fingernails on a chalkboard, a knife/fork scraping against a plate, metal grinding against metal or stone etc are so intolerable to humans. In doing some initial research for this I read <a href="http://en.wikipedia.org/wiki/Sound_of_fingernails_scraping_chalkboard">the wikipedia article on Sound of fingernails scraping chalkboard</a> (there's a wikipedia article on everything!) but I am looking for more references or updated research.</p>

<p>From the reading I have done, there seems to be two competing theories:</p>

<ul>
<li>The sound is reminiscent of the warning calls of primates and triggers an evolutionary response left over from an earlier age designed to protect us from predators</li>
<li>The sound hits a resonante frequency of the inner ear which causes it to be particularly intolerable</li>
</ul>

<p>To me personally the first theory makes very little sense. Hearing the warning calls of primates does not personally trigger anywhere near the same feelings of extreme frustration and irritability that I feel when I accidentally scrape my knife on my plate. Furthermore the feelings caused by the "nails on a chalkboard" sound do not at all trigger a fight-or-flight response or put me on edge as a loud noise or something that startles me does. If anything it is almost paralyzing, which seems counter to the evolutionary theory.</p>

<p>How accurate is the wikipedia article? Is there any newer / more widely accepted research available on what causes the sound of "fingernails on a chalkboard" to be so intensely awful to human beings?</p>

CC BY-SA 3.0
2015-10-03T05:29:51.040Z
Okay, let's say it has an evolutionary cause as suggested by the theory. What the makes me curious is, If we were to find people on earth who do not react adversely to it and further select people who are "normal" (with no hearing problems, psychological problems or any other irrelevant to our  experiment), it would probably be a very small percentage. So, in that percentage, can we say, they have evolved to the "next generation" humans compared to us. Or, is it that, the average percentage for any such characteristics has, is and will remain the same forever.(The balance of probability) ?
Manish Kumar Sharma
CC BY-SA 3.0
2016-12-07T14:14:17.870Z
The torment of fingernails on a blackboard, especially broken fingernails, is more than the sound. I can't even stand to have chalky hands, for chalky hands feels like a chalky blackboard. If I have to do chalky work I grease my hands. The feeling of chalkiness is worse than the sound.
Miguel Lahunken
<evolution><sensation><psychoacoustics>
Why is the sound of fingernails on a chalkboard so intolerable?
Josh
# Why is the sound of fingernails on a chalkboard so intolerable?

(Asked by: username_0 on 2013-08-15)

I am curious as to what current research shows regarding why scraping noises such as fingernails on a chalkboard, a knife/fork scraping against a plate, metal grinding against metal or stone etc are so intolerable to humans. In doing some initial research for this I read [the wikipedia article on Sound of fingernails scraping chalkboard](http://en.wikipedia.org/wiki/Sound_of_fingernails_scraping_chalkboard) (there's a wikipedia article on everything!) but I am looking for more references or updated research.

From the reading I have done, there seems to be two competing theories:

* The sound is reminiscent of the warning calls of primates and triggers an evolutionary response left over from an earlier age designed to protect us from predators
* The sound hits a resonante frequency of the inner ear which causes it to be particularly intolerable

To me personally the first theory makes very little sense. Hearing the warning calls of primates does not personally trigger anywhere near the same feelings of extreme frustration and irritability that I feel when I accidentally scrape my knife on my plate. Furthermore the feelings caused by the "nails on a chalkboard" sound do not at all trigger a fight-or-flight response or put me on edge as a loud noise or something that startles me does. If anything it is almost paralyzing, which seems counter to the evolutionary theory.

How accurate is the wikipedia article? Is there any newer / more widely accepted research available on what causes the sound of "fingernails on a chalkboard" to be so intensely awful to human beings?

**Tags:** evolution, sensation, psychoacoustics

> **Comments:**
> **username_1**: Okay, let's say it has an evolutionary cause as suggested by the theory. What the makes me curious is, If we were to find people on earth who do not react adversely to it and further select people who are "normal" (with no hearing problems, psychological problems or any other irrelevant to our  experiment), it would probably be a very small percentage. So, in that percentage, can we say, they have evolved to the "next generation" humans compared to us. Or, is it that, the average percentage for any such characteristics has, is and will remain the same forever.(The balance of probability) ?  
> **username_2**: The torment of fingernails on a blackboard, especially broken fingernails, is more than the sound. I can't even stand to have chalky hands, for chalky hands feels like a chalky blackboard. If I have to do chalky work I grease my hands. The feeling of chalkiness is worse than the sound.  

---

## 3 answers

### Answer by username_3 on 2013-08-19. Score: 6

> Furthermore the feelings caused by the "nails on a chalkboard" sound do not at all trigger a fight-or-flight response or put me on edge as a loud noise or something that startles me does. If anything it is almost **paralyzing, which seems counter to the evolutionary theory.**

Yes, I agree, it seems to, however what about the [fainting goats](http://en.wikipedia.org/wiki/Fainting_goat)? We could have traits which aren't advantageous, yet we were able to survive in spite of them. Like the goats.

Even though it seems perfectly possible (though not logical) to be paralyzed by fear in response to a warning signal, I don't agree with the theory that the sound is indeed a warning signal.

In my experience with hearing fingernails on the chalkboard, its almost as if my teeth hurt. This leads me to believe it is not predators I'm fearing, but injury. It could be a fear by association produced from when I was very young and putting many different objects in my mouth. Some objects may have produced a similar sound and the sound was associated with pain. If you wish to survive in nature, its very important to have teeth, and injuring our teeth may be an especially important thing to avoid... not only if you expect to eat, but also [attract a mate.](http://crowncouncil.com/what-do-singles-want-nice-teeth) A good smile [is important](http://www.businesswire.com/news/home/20120119006098/en/Bad-Teeth-Ranked-1-Turnoff-CosmaLite%E2%80%99s-Dating).

In my search for references to back up my theory, I found [this presentation](http://amasci.com/amateur/screet.html), the author of which seems to agree with my assessment.

I also found at least one other person who claims to feel something in his teeth:

> I feel the discomfort in my teeth and have always assumed the screeching is at the right frequency to build up uncomfortable vibrations in the teeth.

That is actually a random comment (pages 11-20 in the comments section at the bottom) to [this article](http://www.scientificamerican.com/article.cfm?id=why-is-the-sound-of-fingernails-on-blackboard).

I don't agree that the sounds would have enough acoutical power to vibrate the teeth. I think the pain is merely imagined. Of course, that's my opinion, for what its worth. Since the prevailing theory is predator-based and not tooth-injury-based, I wouldn't expect to find any studies on the matter.

In addition to the evidence presented so far, I have another reason to doubt the predator theory. If the sound mimics the cry of danger and the response is instinctual, then why don't we all have the response? Out of 3 people contributing to this question, 1 has admitted "this sound has no effect on me at all." This argues in favor of my "fear by association" theory.

> **Comments:**
> **username_4**: Fainting goats were I believe actually bred deliberately as decoy animals: put one in your herd and if a predator ambushed the herd, the fainting goat would fall over and get eaten, distracting the predator from the rest of the herd.  So no, fainting when startled isn't a survival trait **without humans around to value and breed selectively for it!** With humans around, though, it is in fact a survival trait.  
> **username_3**: @username_4 That's an interesting bit of thinking, kinda like my cats who learned not to hunt in favor of begging at the door. But, how does one breed goats to fall over when scared instead of running? And how can I train my cats to do that? Running is usually what gets them killed in this modern world of automobiles. They see a car and immediately dash across the road.  
> **username_4**: Apparently the fainting trait (also called myotonia) is genetically quite simple.  It shows up like any mutation, and some sharp goatherd realized its use and bred for the trait selectively.   I think you have to be a catherd to do this in felines, though, and we all know how hard that is! ;-)  
> **username_3**: @username_4 Opossums also have this trait of playing dead. So, who was herding the opossums? ;)  
> **username_4**: @username_3 I'd guess it has to do with different predator populations: in Spain, where the myotonic goats come from, the apex predators of concern did scavenge, whereas in North America, they didn't.  Either that, or the Borrowers are real and they've been breeding fainting possums for a LONG time!!  
> **username_3**: @username_4 Well, cars take out lots of 'possums too, so maybe playing dead while drooling and pooping on yourself is not much of a survival technique :P  

---

### Answer by username_5 on 2015-06-28. Score: 0

Mine is the [evolutionarily ancient tooth-damage avoidance-response](http://amasci.com/amateur/screet.html) 2003 speculation article, but if I have it right, then toothed animals in general should experience it, not just primates. Maybe it goes all the way down the entire chain to octopi, snails, clams, any organism which needs to avoid radular-destruction when carefully trying to eat algae from silicate surfaces.

[2012 research](http://www.jneurosci.org/content/32/41/14184.short%20rel=) showed human fMRI to [horrid glass-scraping noises](http://www.dailymail.co.uk/sciencetech/article-2215270/Scientists-identify-sound-nails-scraping-blackboard-unpleasant.html), response located in amygdala and mediated by auditory cortex. With fMRI we need not rely on subjective reports.

Heh, be first to test non-humans, we can crack the mystery and share the igNobel!

> **Comments:**
> **username_6**: Welcome to Cognitive Sciences! Sorry for being skeptical - but - While the first part targets the question it is based on a link to a chatty blog with questionable credibility. The second part is nidely referenced, but does not address the question.  
> **username_5**: It's *my* pure speculation, and labeled as such.  Wbeaty author, owner amasci.com.   Also, sorry I was unclear, but there aren't two sections above.   I reference fMRI articles to suggest eventual testing of non-humans for aversion response to chalkboard(etc.) sounds.   If it ever turns out that other animals have similar avoidance, then the current theory has problems (current theory is, spectral peak of such noises are basically too loud, since that peak is matched to peak sensitivity of human ears.)  
> **username_6**: CogSci reserves answers for scientifically sound answers. Speculations should be placed as a comment. You have enough rep to do so.  

---

### Answer by username_7 on 2013-08-20. Score: -1

I don't understand why there's a bias to assuming that something that doesn't actually touch us can't cause pain. I assure you: the sound that Styrofoam makes is *enormously* painful to me. (And I grew up in the egg business, where I would have to plug my ears on a daily basis when my father or someone else had to do something with Styrofoam cartons. Ugh.)

We all have different tolerance levels for pain in other ways. The guys who go for Navy SEAL (or equivalent) training, or who play NFL football, clearly have a different tolerance for pain than I do. Why would anyone assume that this is different in terms of one's hearing?

The simplest answer is the best: some of us are caused *actual pain* when certain sounds are made, most likely because there are frequencies in the sound that we can perceive more or more clearly than others can. I'm an audiophile, and have lots of anecdotal evidence that I can hear higher-pitched sounds than my friends... my guess is that for those of us who have massively painful reactions to these sounds, our ears are genetically wired to be able to hear those frequencies far more clearly than those who aren't susceptible.

> **Comments:**
> **username_5**: Was it the pain of intensely loud sound (like a firetruck suddenly coming out from behind a building.  Slap your hands on your ears!)   Or was it the "horrible zing" of watching someone slide their finger along a knife blade.  The sound seems to stab out along all your bones, must clench fists and jaw?   Bad, but different than the ears-ouch-pain of extremely loud sounds?  Or exactly the same as loud-hurt guns and firecrackers?  
> **username_7**: Hmm... it's sudden like the fire truck you refer to, but much more painful. It's not merely a matter of volume... even the slightest squeak of it is painful, and certainly louder is more painful. It doesn't go through my whole body, really... I mean, I react, but the pain is localized to my hearing. That's the best way to describe it. Like most people with nails on a chalkboard.  

---

