I too would associate "Bouba" with the rounded and "Kiki" with the sharper figure, but to me this is just a relatively universal sense of continuity vs discontinuities:
the local curvature is continuous for "Bouba", every point on the curve has a single tangent, which evolves continuously as you walk along this presented curve.
For Kiki: the local curvature is discontinuous: at the inward or outward points, there are 2 tangents, so the tangent abruptly switches value when passing through this point when walking along the curve.
similarly the "B"s in "Bouba" are voiced plosives, while the "K"s in "Kiki" are unvoiced plosives.
I think people would similarily classify "Titi, Pipi, Touta, Poupa, Kouka" like "Kiki" but "Didi, Douda, Bibi, Gigi, Gouga" like "Bouba".
The vowels are obviously voiced by the vocal chord carrier wave "voice".
So when we pass through the unvoiced (T/P/K) plosives, we notice discontinuity like the discontinuously evolving tangents along the boundary curve of the figure.
Obviously mammals like dogs have a concept of continuity, topology, distance, they might get spooked by "open" stairs, because they can see between the planks, etc.
And when we hear voiced (D,B,G) plosives, the voice while muted still evolves continuously.
Maybe because when you pronounce a B, it's very hard to make it sound sharp. The lips rolling off one another naturally have a gentle ramp-up. It's really hard to have a sudden transient. You can record this in a free DAW and see it in front of you.
By contrast, it's very hard to make a K- sound without a sharp transient.
With B you are adding pressure to two soft tissues in contact.
With K you are adding pressure when one tissue is hard, and saliva is present (causing a relatively sudden production of the sound).
Try making B sound sharp, hard to do while saying Bouba.
Try making K sound soft, basically impossible, especially while saying Kiki.
Either similar underlying processing machinery (due to auditory and visual processing evolving from simpler and more interconnected processing circuits) or because when thinking of frequencies of waveforms in light/sound, visual sharpness and auditory sharpness really are the same thing (so even if they didn't co-evolve, it can be more efficient or useful to have some single underlying representation waveform representation that represents these things similarly).
Part of the fun of the experiment is questioning the nominative determinism here. Did cultures pick a name like Baobab for that tree because of something this effect is showing or is just coincidence? We don't really know. Linguists have often wondered if there is a "universal grammar" underlying even our oldest languages that we don't know the full rules of, but coincidences and convergent evolution in our languages seem to tease could exist. Kiki and bouba are one of the more interesting experiments in this space to ever get repeatable results.
Given the 100 years of studies across cultures (and now species), it probably made you think of curves shapes before you'd ever seen a boabob tree, let alone knew its name.
you get "assaulted" "all the time"!? surely this is hyperbole. If not, perhaps consider moving somewhere far away from where you live now, immediately!
> The second experiment, which involved 19 other dogs, was identical in design except that the owners wore headphones playing rock music to stop them from hearing the 'Bouba' and 'Kiki' sounds. The idea here was to remove any owner cues the dogs might have been following.
So they at least attempted to account for it.
Also, why do owners feel the need to unleash their dogs at you in self defense? This is very strange.
My dog barks at runners and he's scared of cyclists. But he loves delivery workers because when he was a puppy he was very excited to meet everyone, and whenever I had something delivered, we would use it as an opportunity work on his door manners: I'd open the door, ask the delivery driver if it was okay for my puppy to meet him, and then if they said yes, I'd give him permission to go out.
I also enlisted delivery drivers as confederates in working on his fear of large motor vehicles! I'd explain that he was scared of trucks and ask if they were willing to feed him some treats from the vehicle. If they agreed, then I'd hand them some treats, go inside to get the dog, and then my dog and I would "discover" that the truck had a nice person inside who wanted to give my dog good things.
My dog loves cats, and it's not an accident. Even though I've never had a cat, I made sure to introduce my dog to cats when he was a puppy. I even made sure to introduce him to cats who were unaccustomed to living with dogs, and unfriendly or indifferent cats who didn't feel particularly inclined to tolerate him in their personal space, because I wanted him to learn to recognize and respect the signs of a cat's discomfort. (Some of that was ultimately undermined by time he spent in the company of my dog sitter's excessively tolerant cats, lol. He has arrived at the mistaken belief that monotonously barking at a cat is a good way to entice it to chase him, which can make him insufferable around cats who aren't interested in him.)
My dog is very small. He's never bitten anyone. But when someone at the park tells me they're afraid of dogs, I still make sure we keep our distance.
I'm sorry for the bad interactions you've had with dogs and the careless owners you've met who have subjected you to frightening or even dangerous encounters with their dogs. That's legit terrible.
But anyway I made an effort, sometimes more successful and sometimes less successful, to try to make my dog well-behaved towards every group you mention. Where I've failed to do so I manage him to keep him away from those critters and people who would rather avoid him. And I think even when people don't do all that, it's more lazy selfishness than it is hate.
There is a degree to which people who have pets assume that everyone should react to animals the way that they do. If someone's dog jumps on its owner, they often react positively, rather than negatively. (In my case, the reaction would instead be "I have serious allergies and do not wish to have an unpleasant allergic reaction for the rest of the day".)
Some dog owners (to be clear, some, not by any means all, but it only takes some to affect other people's general perceptions) seem to think they are objectively correct and the people who do not want that are wrong. So it is not hard for me to imagine someone who finds themselves regularly having unpleasant interactions with dogs feeling like "dog owners should stop that from happening", rather than (as is sometimes the case) acting like there's something wrong with people who think it's a problem. Conversely, it is understandable how people who are close to and friendly with an animal all day will sometimes fail to have sufficient perspective-taking to realize that not everyone feels as they do.
I've personally never had the extremely unpleasant experience of having a large dog try to jump at me. I have on rare occasions had the experience of having a small dog run at my legs, and the owner not immediately treat that as a failure on their part, which was unpleasant. Fortunately, most of those have then had the "I'm so sorry" reaction, rather than reacting with indignance, but I've definitely encountered pet owners who projected indignance that you don't think their animal is a precious sweetums who can do no wrong.
Most pet owners are extremely reasonable people, and it's unfortunate that encounters with the exceptions to that can give people a poor impression.
I think there are several kinds of empathy failures in play in situations like the ones you describe. One is the defensiveness/protectiveness/favoritism thing you highlight. Another is a kind of mind blindness in a dog owner's assumption that because it's obvious to them that their dog's body language is benign, it must also seem benign or tolerable to everyone. Another is an idea that fear or discomfort is only worth accommodating if it's reasonable or rational, or something like "my irrational fears should be honored and soothed, but the apparently irrational fears of others are ridiculous and should be dismissed or mocked". Another still is a kind of lack of empathic imagination, failure to consider cases like yours where an allergy means that close contact will fuck up someone's day no matter how benevolent or gentle the dog is; just a general failure to imagine the upset stranger might have a good reason that doesn't strike us as obvious.
If dog owner is scared, dog will try to protect its owner. I understand that part, but I do not get why they would release dog in such situation.
I understand people get scared, and do not control their emotion. But dog owner should still control their dog! Releasing dog after owner triggers it, is just pure hate!
It is like inviting delivery driver to your house, and latter claiming it was trespass!
I have never seen a dog owner release their dog in a situation where they are scared. Usually if a dog owner is scared they try to keep their dog closer, to protect the dog from the scary thing.
Are you sure the dogs are not already off leash in your area when you are running by. There are many owners who simply have their untrained dogs off leash when they probably shouldn't.
I was taught it was "BOW-ba" or "BOH-ba", but AI actually linked a number of studies that seems to confirm it is supposed to be and usually is "BOO-ba" (i.e. bulging eyes Pepe) in experiments. I don't personally think either pronunciation would change the results though.
The strange spelling is partly intentional to make sure that people read it as a very fake word with no known definition. In English bow, boba, boob are all real words.
They've shifted their em-dash usage to the british standard (any dash+spacing on either side for no discernable reason—probablt a typesetting detail that hasn't made sense forever) and it looks like shit. I know, like other british standards—it's still sad to see.
As a human I agree with dogs that 'Bouba' is round and 'Kiki' is spiky.
In all seriousness, and I am surprised the article does not mention this, as dumb as it sounds Kiki has "sharp" sounds when pronouncing it and "Bouba" has a softer feel to it when pronouncing it.
As the article says it does not matter what language you speak, a word that quickly changes the sound back and forth to the same thing sounds sharp because that is how sharp things look and feel. The serration on a knife has the same angle on either side leading to a point. This is what makes sense to me as to why we correspond Kiki to something sharp.
> In all seriousness, and I am surprised the article does not mention this, as dumb as it sounds Kiki has "sharp" sounds when pronouncing it and "Bouba" has a softer feel to it when pronouncing it.
This is just the same thing though?
It's not actually trivially obvious that different minds would agree on how "sharp" and "soft" apply to sounds and to shapes.
Sure it is. Fourier transform - Bouba and Kiki are far from the same there. And as someone else mentioned, time domain content - attack and decay. There are physical differences in the sounds which are pretty fundamental and can be definitionally linked to sharpness and softness across domains, especially as sharp objects are defined in nearly exactly the same way (except spatially).
It would be more interesting if we had two sounds which didn’t have such apparent objective differences giving rise to specific and universal subjective differences, or if something that was not so cross domain elicited a different response, e.g. linking volume with sharpness as opposed to something like size.
It isn't trivially obvious, no, but the "k" sound is a fricative (EDIT: oops, nope, plosive - see response to this comment), i.e. the tongue rapidly moves close to the palate and then away, creating turbulence, and sounds with a sharp peak and amplitude. I.e. the waveform of a "k" or "kiki" sound looks more spiky. The opposite is the case for the "bouba" sound.
It is a bit mysterious why animals would all map e.g. sharp auditory waveforms to sharper / spiky lines (kiki figure), and then smoother sounds to smoother lineforms (bouba figure), but, reasonably, these senses evolved together and used far more shared underlying processing machinery than they do presently. After all, both light and sound reach us in waves and both carry energy.
Some primitive mush-blob perhaps just started processing all incoming energy waves together, differentiating e.g. smoother vs. more staccatto waves before making the distinction between e.g. sound vs. light. Or I dunno, but IMO it makes more sense when you consider evolution, and don't just look at processing now in isolation from the likely development of these senses.
> The 'b' sound is a plosive too, by the way. It's voiced, vs the voiceless 'k'.
Yeah this I know, by "bouba" being opposite I meant the waveform.
Really the phonetic terms here are not actually relevant and have betrayed me. It's more that the 'k' sound is "more [ex]plosive" in that it seems to build up more pressure and turbulence (probably as you say, because the consonant is in the rear, so pressure builds and bounces around in the mouth more, whereas the "b" just mostly blasts out the front more quickly). And the "k" surely has a more peaky / spikey waveform in the audible range.
k is a plosive, not fricative: there's a discontinuity in the flow of air, not a friction-sounding continuous airflow. that fits your point though, regardless.
Oops, you are right! Thank you for correcting. I checked before posting that some "k" sounds are indeed fricatives, but they definitely aren't in "kiki".
When I want to avoid startling my cat I make sure that the sound of my presence is gradual and not sudden. The syllables of a bouba word all introduce themselves smoothly and not suddenly.
I’ll rush to posit something for others to poke holes in: the definition of a Kiki word is a word where the syllables have a sudden “attack” then decay. And that’s a function of sound, not language.
How about high frequency sounds? Kiki must be higher frequency on a spectrograph. Spikes make high frequency sounds when they hit against things. Soft round objects make low frequency noises. Sort of. (There's holes in this theory, because fur is soft but makes high frequency sounds when brushed.)
Interestingly, even the sound of the word ‘round’ feels gentle, while the word ‘spiky’ has high-frequency peaks (at p and k)! I wonder if dogs (or for that matter, humans) can accurately zero-shot classify words that represent round vs spiky for different languages.
It appears to me that onomatopoeia, at varying degrees, played a role in the spontaneous convergence of verbal communication, and thus the development of a language.
When I studied psychology 20 years ago we had a class which covered this, and at least then there were studies indeed showing these associations are exactly due to these phonetic identifiers.
That such a phenomenon is easily visible in waveform make this pretty expected. Animals likely evolved to discretize audio long before mammals showed up
Which is spikier qktqb or rrqtyun? For me personally, rrqtyun is spikier although certain models seem to disagree. GPT (Astra) believes qktqb is spikier.
This one is also a curiosity
> isn't klop right at the edge between spiky and round
> Yes. “Klop” is borderline, but leans slightly spiky.
Dog's have very good hearing, and their hearing must help them to model the world around them, to understand what different objects in the world are.
So I think it's less about linguistics and more about our audiovisual mapping of the physical world.
Then again, that must be where the origin of language evolved from in the first place.
There's probably an overlap that makes the distinction fuzzy.
Evidence of the bouba-kiki effect in naïve baby chicks - https://news.ycombinator.com/item?id=47105198 - Feb 2026 (107 comments)
Which is "Bouba", and which is "Kiki"? [video] - https://news.ycombinator.com/item?id=46572742 - Jan 2026 (23 comments)
Bouba / Kiki Effect - https://news.ycombinator.com/item?id=45320327 - Sept 2025 (2 comments)
Bouba/kiki effect - https://news.ycombinator.com/item?id=40699583 - June 2024 (170 comments)
Bouba/Kiki Effect - https://news.ycombinator.com/item?id=27885703 - July 2021 (94 comments)
Bouba/kiki effect - https://news.ycombinator.com/item?id=8372550 - Sept 2014 (1 comment)
Why ‘Mom’ and ‘Dad’ Sound So Similar in So Many Languages - https://news.ycombinator.com/item?id=30605239 - March 2022 (1 comment)
Words known better by males than females, and vice versa - https://news.ycombinator.com/item?id=30275159 - Feb 2022 (650 comments)
Why spiky shapes seem angry and round sounds are calming - https://news.ycombinator.com/item?id=20830940 - Aug 2019 (21 comments)
Ability to identify genuine laughter transcends culture - https://news.ycombinator.com/item?id=17634212 - July 2018 (2 comments)
Molyneux's problem - https://news.ycombinator.com/item?id=16778983 - April 2018 (68 comments)
Distant languages have similar sounds for common words - https://news.ycombinator.com/item?id=12510720 - Sept 2016 (60 comments)
Are We All Synesthetes? - https://news.ycombinator.com/item?id=634989 - May 2009 (9 comments)
Oohs And Aahs: Vowel Sounds Affect Our Perceptions Of Products - https://news.ycombinator.com/item?id=54318 - Sept 2007 (4 comments)
https://www.science.org/doi/10.1126/science.adq7188
the local curvature is continuous for "Bouba", every point on the curve has a single tangent, which evolves continuously as you walk along this presented curve.
For Kiki: the local curvature is discontinuous: at the inward or outward points, there are 2 tangents, so the tangent abruptly switches value when passing through this point when walking along the curve.
similarly the "B"s in "Bouba" are voiced plosives, while the "K"s in "Kiki" are unvoiced plosives.
I think people would similarily classify "Titi, Pipi, Touta, Poupa, Kouka" like "Kiki" but "Didi, Douda, Bibi, Gigi, Gouga" like "Bouba".
The vowels are obviously voiced by the vocal chord carrier wave "voice".
So when we pass through the unvoiced (T/P/K) plosives, we notice discontinuity like the discontinuously evolving tangents along the boundary curve of the figure.
Obviously mammals like dogs have a concept of continuity, topology, distance, they might get spooked by "open" stairs, because they can see between the planks, etc.
And when we hear voiced (D,B,G) plosives, the voice while muted still evolves continuously.
By contrast, it's very hard to make a K- sound without a sharp transient.
With B you are adding pressure to two soft tissues in contact.
With K you are adding pressure when one tissue is hard, and saliva is present (causing a relatively sudden production of the sound).
Try making B sound sharp, hard to do while saying Bouba.
Try making K sound soft, basically impossible, especially while saying Kiki.
I do not think this is realible experiment. Dogs are very sensitive to non verbal cues from their owner.
For example if owner is scared, it will defend the owner. I get assaulted all the time, by dog owners who unleash their dogs on me, in self defense.
Edit: just to clarify
I get assaulted about once a week, while running at park at morning. I was at hospital a few times, mostly it is unwanted physical contact.
It is leash only park full of runners, I have no idea why any sane person would allow dogs to run freely there!
I can not afford to move out. I started wearing body cam, and air horn.
???
If you had actually read the article, they explicitly tested for and controlled this...
> The second experiment, which involved 19 other dogs, was identical in design except that the owners wore headphones playing rock music to stop them from hearing the 'Bouba' and 'Kiki' sounds. The idea here was to remove any owner cues the dogs might have been following.
So they at least attempted to account for it.
Also, why do owners feel the need to unleash their dogs at you in self defense? This is very strange.
Perhaps it is just hate. It is well established dog owners hate runners, cyclists, delivery workers, cats, ducks, small kids...
I also enlisted delivery drivers as confederates in working on his fear of large motor vehicles! I'd explain that he was scared of trucks and ask if they were willing to feed him some treats from the vehicle. If they agreed, then I'd hand them some treats, go inside to get the dog, and then my dog and I would "discover" that the truck had a nice person inside who wanted to give my dog good things.
My dog loves cats, and it's not an accident. Even though I've never had a cat, I made sure to introduce my dog to cats when he was a puppy. I even made sure to introduce him to cats who were unaccustomed to living with dogs, and unfriendly or indifferent cats who didn't feel particularly inclined to tolerate him in their personal space, because I wanted him to learn to recognize and respect the signs of a cat's discomfort. (Some of that was ultimately undermined by time he spent in the company of my dog sitter's excessively tolerant cats, lol. He has arrived at the mistaken belief that monotonously barking at a cat is a good way to entice it to chase him, which can make him insufferable around cats who aren't interested in him.)
My dog is very small. He's never bitten anyone. But when someone at the park tells me they're afraid of dogs, I still make sure we keep our distance.
I'm sorry for the bad interactions you've had with dogs and the careless owners you've met who have subjected you to frightening or even dangerous encounters with their dogs. That's legit terrible.
But anyway I made an effort, sometimes more successful and sometimes less successful, to try to make my dog well-behaved towards every group you mention. Where I've failed to do so I manage him to keep him away from those critters and people who would rather avoid him. And I think even when people don't do all that, it's more lazy selfishness than it is hate.
bro wtf are you talking about
Some dog owners (to be clear, some, not by any means all, but it only takes some to affect other people's general perceptions) seem to think they are objectively correct and the people who do not want that are wrong. So it is not hard for me to imagine someone who finds themselves regularly having unpleasant interactions with dogs feeling like "dog owners should stop that from happening", rather than (as is sometimes the case) acting like there's something wrong with people who think it's a problem. Conversely, it is understandable how people who are close to and friendly with an animal all day will sometimes fail to have sufficient perspective-taking to realize that not everyone feels as they do.
I've personally never had the extremely unpleasant experience of having a large dog try to jump at me. I have on rare occasions had the experience of having a small dog run at my legs, and the owner not immediately treat that as a failure on their part, which was unpleasant. Fortunately, most of those have then had the "I'm so sorry" reaction, rather than reacting with indignance, but I've definitely encountered pet owners who projected indignance that you don't think their animal is a precious sweetums who can do no wrong.
Most pet owners are extremely reasonable people, and it's unfortunate that encounters with the exceptions to that can give people a poor impression.
I understand people get scared, and do not control their emotion. But dog owner should still control their dog! Releasing dog after owner triggers it, is just pure hate!
It is like inviting delivery driver to your house, and latter claiming it was trespass!
Are you sure the dogs are not already off leash in your area when you are running by. There are many owners who simply have their untrained dogs off leash when they probably shouldn't.
In all seriousness, and I am surprised the article does not mention this, as dumb as it sounds Kiki has "sharp" sounds when pronouncing it and "Bouba" has a softer feel to it when pronouncing it.
As the article says it does not matter what language you speak, a word that quickly changes the sound back and forth to the same thing sounds sharp because that is how sharp things look and feel. The serration on a knife has the same angle on either side leading to a point. This is what makes sense to me as to why we correspond Kiki to something sharp.
This is just the same thing though?
It's not actually trivially obvious that different minds would agree on how "sharp" and "soft" apply to sounds and to shapes.
It would be more interesting if we had two sounds which didn’t have such apparent objective differences giving rise to specific and universal subjective differences, or if something that was not so cross domain elicited a different response, e.g. linking volume with sharpness as opposed to something like size.
It is a bit mysterious why animals would all map e.g. sharp auditory waveforms to sharper / spiky lines (kiki figure), and then smoother sounds to smoother lineforms (bouba figure), but, reasonably, these senses evolved together and used far more shared underlying processing machinery than they do presently. After all, both light and sound reach us in waves and both carry energy.
Some primitive mush-blob perhaps just started processing all incoming energy waves together, differentiating e.g. smoother vs. more staccatto waves before making the distinction between e.g. sound vs. light. Or I dunno, but IMO it makes more sense when you consider evolution, and don't just look at processing now in isolation from the likely development of these senses.
But the place of articulation kinda flips, from rear consonant/front vowel (kiki), to front consonant/rear vowel (bouba).
If you flipped the voicing, it'd be 'gigi' vs 'poupa', which to my ears at least, is a lot less clear cut.
Yeah this I know, by "bouba" being opposite I meant the waveform.
Really the phonetic terms here are not actually relevant and have betrayed me. It's more that the 'k' sound is "more [ex]plosive" in that it seems to build up more pressure and turbulence (probably as you say, because the consonant is in the rear, so pressure builds and bounces around in the mouth more, whereas the "b" just mostly blasts out the front more quickly). And the "k" surely has a more peaky / spikey waveform in the audible range.
If I stick to the more familiar territory of bad speech synthesis on 8-bit computers using envelopes, /k/ probably starts with a burst of white noise.
Lol, true.
I’ll rush to posit something for others to poke holes in: the definition of a Kiki word is a word where the syllables have a sudden “attack” then decay. And that’s a function of sound, not language.
Same genetics produce the same outcome (mostly).
It appears to me that onomatopoeia, at varying degrees, played a role in the spontaneous convergence of verbal communication, and thus the development of a language.
I must respectfully disagree; kiki is brown, not red, but it’s an easy mistake to make
This one is also a curiosity
> isn't klop right at the edge between spiky and round
> Yes. “Klop” is borderline, but leans slightly spiky.