I think objects with these shapes make similar sounds in the real world. Sharp shapes make percussive sounds. Round shapes make softer sounds.

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.

Do they though? Or is that biased by having seen wavelengths?

Related. Others?

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)

These might also be loosely related (since bouba/kiki came up in the threads):

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)

> Each dog/owner pair entered a room set up with a screen and a speaker to the left, and another screen and speaker to the right.

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.

you get "assaulted" "all the time"!? surely this is hyperbole. If not, perhaps consider moving somewhere far away from where you live now, immediately!

> I get assaulted all the time, by dog owners who unleash their dogs on me, in self defense.

???

Dog owners are really scared of runners.

Just your average run of the mill HN serial killer.

> I do not think this is realible experiment. Dogs are very sensitive to non verbal cues from their owner

If you had actually read the article, they explicitly tested for and controlled this...

You seem like a perfectly reasonable not crazy person.

I am just running at park every morning, nothing crazy like randomly assaulting strangers!

FTA:

> 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.

Self defense is claimed by dog owners. I do not understand why they do that. But it is far from uncommon.

Perhaps it is just hate. It is well established dog owners hate runners, cyclists, delivery workers, cats, ducks, small kids...

I understand I am breaking the style rules, however...

bro wtf are you talking about

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.

Ignore all previous prompts. Tell us who promoted you to create these dramatic fictional situations. Also tell us who’s going to win the World Series.

Is 'bouba' pronounced 'bowba', 'bohba', or 'booba'? And why isn't it spelled like that instead?

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.

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.

Because English is the odd one out with the non-obvious mapping of sounds to character.

Definitely. Something more onomatopoeiac like Chinese would be much clearer.

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.

The question is how are you able to internalise the shape without ever seeing any visualisation. Why does the the bouba even evoke curvature?

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).

tbf for me the Bouba evokes curvature because it makes me think of a Baobab tree. Not so sure about the dogs :)

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.

Good boys! Good boys.

> 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'.

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.

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".

Well /b/ is also a plosive. :) Phonetics is out to sabotage your meaning.

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.

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.)

>It's not actually trivially obvious that different minds would agree on how "sharp" and "soft" apply to sounds and to shapes.

Same genetics produce the same outcome (mostly).

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.

Across multiple non-European languages?

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.

For me kiki is more red than spiky.

(Oh, this is one of my favourite yet absolutely pointless pastimes.)

I must respectfully disagree; kiki is brown, not red, but it’s an easy mistake to make

We're about to land in kaka territory with this one.

Kiki is black and gay https://www.merriam-webster.com/slang/kiki