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?
tbf for me the Bouba evokes curvature because it makes me think of a Baobab tree. Not so sure about the dogs :)
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.
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.
Or a bubble.
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).
This would mean that understanding "bouba" and "kiki" evolved as a concept before dogs split from us as a species.
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.
While this explains why the sounds are sharp/soft, IMO the interesting part is: why is there seemingly such a fundamental connection between "sharpness" in spoken language, and "sharpness" in our (visual) understanding of the world?
These two concepts are not fully equal, so why don't we have two different words and see them as separate concepts?
I believe you're looking at this like a classic programmer and that's why you're thinking "bouba.jpg" and "bouba.wav" are two different concepts. I used to think of the bouba kiki issue from that POV too. A good (and imo better) modern analog to the human brain thought process is a LLM that can definitely match different inputs to a single concept. Also the vocal cords have very specific shapes in the vowel continuum and that alone would help explain why for humans it's simply intuitive.
There's also another comment mentioning how it works for consonants, which I believe helps explain how it might work for dogs.
> I believe you're looking at this like a classic programmer and that's why you're thinking "bouba.jpg" and "bouba.wav" are two different concepts. I used to think of the bouba kiki issue from that POV too. A good (and imo better) modern analog to the human brain thought process is a LLM that can definitely match different inputs to a single concept.
Actually, I always intuitively "knew" that our brains process different sensory inputs in the same latent space. Since I was a child, words and numbers always felt like they had "shapes" and "colors" in my head, and at some point I noticed that these associations actually help with solving real-world tasks, because words that have similar mental shapes often had actual connections.
When I tried talking to others about this, nobody ever knew what I meant, so it's satisfying to see this being accepted more broadly :)
But that still doesn't answer the interesting question: why do our brains match these concepts together? Why is bouba not sharp, and kiki not round? The baby chick experiment suggests that animals need basically no life experience to make this association, so it seems to be more fundamental than "we learned it".
> Also the vocal cords have very specific shapes in the vowel continuum and that alone would help explain why for humans it's simply intuitive.
I don't think that I can feel the shape of my vocal cords when I'm speaking, and I don't have any intuitive understanding of a "vowel continuum", so I don't think this explanation really works.
> There's also another comment mentioning how it works for consonants, which I believe helps explain how it might work for dogs.
Could you link the comment you're referring to? Thanks!
I do love your point because I felt like synesthesia might fit in my first comment but was not sure how to phrase it.
By vowel continuum I really only meant all vowels between A and U; basically all the vowels a human is capable of making. Even though you might not feel the shapes, your brain certainly does. There are videos that show the folds as someone speaks and you can see those shapes are deterministic.
I've realized those shapes while learning polyphonic singing. By doing the usual exercise of going from one vowel to another you begin to understand there are specific shapes for vowel sounds: O (in portuguese) is very "bouba" (round) while I is very sharp like a spear; kiki.
As for the comment on consonants, it was not made by me but I do like it: https://news.ycombinator.com/item?id=50094626
Ah, gotcha!
I guess our sensation of speaking could be a component, but that doesn't explain dogs apparently agreeing with us. And if you argue that dogs built a comparable association due to observing humans, then we still have to find another explanation for baby chicks.
IMO it's much more likely that this phenomenon is an artifact of our neural hardware. After all, there's no reason to assume we start as completely neutral blank slates.
Because sounds are made by shapes. The shapes of our mouths and the shapes of objects colliding. And sounds have shapes, shapes over time.
Yes, our mouths. What's interesting about this is that dogs make sounds very differently than humans.
Frequency and amplitude changes in the sound which change direction rapidly and significantly would generate a waveform that looks like the Kiki shape.
Dogs don't know about the frequencies or amplitudes yet they can make the connection. Why does a sound match visual stimuli with such high correlation?
Speaking of the topological intuition of mammals I guess “Boubas” are the big soft round ones and “Titis” are the firm pointy ones.
Irish cíocha, and Japanese chichi (BC diet?)
"Sisi" for regular sized, or gently addressed, and "sis'ki" for rather large, or rudely addressed in Russian.
I think "i" and "ou" also meaningfully differ for round / sharp. To make the "I" sound, you have to restrict your vocal chords more, and for "ou" you already make a rounded shape with your lips.
Many human languages lack voiced plosives entirely, the most notorious one being one of the biggest languages in the world, Mandarin Chinese.
I don't think there is such a universal sense of continuity considering that tonal languages sound very discontinuous...