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.
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.
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).
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.
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.
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.
> 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.
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.)
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.
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.
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.
> 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.
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 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.
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.
DoctorOetker | 4 days ago
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.
po1nt | 59 minutes ago
notahacker | 51 minutes ago
Wolfenstein98k | 12 minutes ago
D-Machine | 43 minutes ago
Wolfenstein98k | 13 minutes ago
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.
DrProfresher | 19 hours ago
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.
yhjc2692 | 16 hours ago
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.
moi2388 | an hour ago
Angostura | an hour ago
jstanley | an hour ago
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.
card_zero | an hour ago
D-Machine | an hour ago
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.
jjtheblunt | an hour ago
D-Machine | 50 minutes ago
card_zero | 11 minutes ago
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.
Cordiali | 6 minutes ago
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.
Waterluvian | an hour ago
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.
_kulang | an hour ago
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.
gsich | an hour ago
Same genetics produce the same outcome (mostly).
dang | an hour ago
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)
dang | an hour ago
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)
sweetdingoes | 57 minutes ago
dizhn | an hour ago
jurf | an hour ago
I must respectfully disagree; kiki is brown, not red, but it’s an easy mistake to make
n4bz0r | 46 minutes ago
ralusek | 21 minutes ago
throw9394030 | 52 minutes ago
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.
preommr | 46 minutes ago
???
pixl97 | 44 minutes ago
throw9394030 | 28 minutes ago
D-Machine | 46 minutes ago
If you had actually read the article, they explicitly tested for and controlled this...
kQq9oHeAz6wLLS | 45 minutes ago
> 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.
throw9394030 | 36 minutes ago
Perhaps it is just hate. It is well established dog owners hate runners, cyclists, delivery workers, cats, ducks, small kids...
Wolfenstein98k | 24 minutes ago
bro wtf are you talking about
throw9394030 | 13 minutes ago
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!
idiotsecant | 40 minutes ago
throw9394030 | 33 minutes ago
leoc | 50 minutes ago
profsummergig | 43 minutes ago
Permik | 30 minutes ago
Wolfenstein98k | 23 minutes ago
D-Machine | 29 minutes ago
gste | 41 minutes ago
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.
Wolfenstein98k | 25 minutes ago
rfgplk | 25 minutes ago
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.