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Objects that have sharp edges generate higher frequency harmonics when agitated, because lower-size features resonate on higher frequencies (like shorter strings ring on higher pitch). Objects that are round resonate on low frequencies only. The "kiki" sound has more high frequency content than the "bouba" sound, and it's no mystery why the brain associates one with the other.

That's one theory. Another one I can think of is that sharp edges are scary, and most distress calls are high pitched.

Also, the thing about high frequencies and sharp edges lead to a contradiction: babies are more round than adults and produce higher pitched sounds, this is almost universal across all species.

There are other tentative explanations, such as how the vocal tract acts when producing these sounds, with "bouba" sounds being the result of smoother movement more reminiscent of a round shape.

"kiki" is not just higher pitched, it is also "shaped" differently if you look at the sound envelope, with, as expected, sharper transitions.

So to me, the mystery is still there. Is is the kind of thing that sounds obvious, in the same way that kiki sounds obviously sharper than bouba, but is not.

> Also, the thing about high frequencies and sharp edges lead to a contradiction: babies are more round than adults and produce higher pitched sounds, this is almost universal across all species.

It's more in terms of harmonic content than the pitch fundamental. There are more harmonics from a thing with sharp transitions than there are in a thing with rounded transitions regardless of the fundamental pitch. Compare harmonic content of a pure sine wave (it's just the fundamental) with that of a square wave, which has an infinite series of higher harmonics.

Babies are also smaller, which means higher fundamental pitch.

> "kiki" is not just higher pitched, it is also "shaped" differently if you look at the sound envelope, with, as expected, sharper transitions.

Exactly!

EDIT I think this is interesting: it also applies to images as well, not just sound. You can "low pass filter" a photograph and it'll reduce some of the detail, smoothing out transitions (typically used for noise reduction). Detail is high frequency information (or high frequency noise depending on whether you want it or not.)

So you know the "bock bock" sound?

Hens make it occasionally when laying eggs, but it's also the rooster alarm sound. The "cock-a-doodle-doo"/crowing sound is more the all-clear/I'm-a-rooster-here-I-am/flock-assemble cry.

When there's a threat, the rooster switches to a loud, BAWK BAWK BAWK alarm.

In nature there's few things laying around that resonate particularly well.

Hollow things are common, and of interest to many animals. If I thump a log and it makes a noise like it has a hollow space (low tones), then it may contain an animal nest or a beehive & honey, or it may be something I could use as a box or basket or shelter.

Scratch a thin pointy branch across e rock -> sharp high noise.

Thump a round club/log against a rock -> dull bump noise

Thump two round rocks together -> sharp noise

Thump pointy branch against a tree -> dull noise

And chickens aren't using tools.

They're scratching for gizzard stones and food though, with their built-in beak, fwiw

I challenge you to find two objects of a similar size and cut them into shapes that would produce a sharper sound for the rounder object.

In your example it's obviously the round tree trunk that produces the dull sound.

I thought the same but they used chicks that just hatched with zero world experience.

World experience can be encoded through evolution.

E.g. a spider does not learn if/how to weave a web from its parents.

So then the mystery would be why other primates do not appear to show the bouba-kiki effect ...

> The "kiki" sound has more high frequency content than the "bouba" sound

And where did you get that from? In non-tonal languages the pitch conveys almost no information and people speak at very different ones (and for instance a male saying "kiki" will say it at lower frequencies than a woman saying "bouba" most of the time) so I find your affirmation very dubious.

> and it's no mystery why the brain associates one with the other.

Specialists of the field find that mysterious but some smartass on HN disagrees.

That's what I was thinking. But then I was wondering: if it was that obvoius, would there be such research about it?

Some of the research, including this paper, is trying to get at the question of whether a species' sensitivity to the bouba-kiki effect might be at the root of language or not. Since it seems accepted that chickens do not have language in any meaningful sense of that term, finding that they still show this effect decouples it from "the origins of language".

You do need to research "obvious" things every once in a while. They have this annoying tendency of being proven wrong occasionally.

It's a hypothesis. How would you prove or disprove that it's because of that? (and I would say, a priori, it's not utterly obvious that the brain would relate spacial and temporal frequencies like this)

For each chick they do 24 trials divided into 4 blocks with retraining on the ambiguous shape and actual rewards after each block. During the actual tests they didn't give rewards. In figure 1 they show the data bucketed by trial index. It's a bit surprising it doesn't show any apparent effect vs trial number, e.g. the first trial after retraining being slightly different.

I have to admit I'm super skeptical there's not some stupid mistake here. Definitely thought provoking. But I wish they'd kept iteratively removing elements until the correlation stopped happening, so they could nail down causation more precisely.

I do agree my skepticism level rises extremely high in any experimental psychology experiment. There’s just so many ways to bias results, in addition to “do enough experiments and one of them will get a statistically unlikely result” problem.

This group does a lot like this https://www.dpg.unipd.it/en/compcog/publications … so that’s tempting to think they keep trying things until something odd happens (kind of like physicists who look for 5th forces… eventually they find something odd but often it’s just an experimental issue they need to understand further).

This is just one micro-instance of a much larger thing. Brain encodes structural similarity across modalities. Corollary: language is far from arbitrary labels for things.

No, language is still pretty close to arbitrary labels. The handful of tenuous common threads like the bouba-kiki effect don't change the overall picture that much. The simple fact that language varies as much as it does is sufficient to prove that it's only loosely bound to anything universal.

https://en.wikipedia.org/wiki/True_name

>language is far from arbitrary labels for things

I think this is a misunderstanding of the arbitrariness of the sign. Arbitrary doesn't mean "random" or "uniformly sampled." The fact there are systematic tendencies among languages in how things are called doesn't negate the arbitrariness of the sign, they could have been called other things. We can also decide to refer to things by another name and we can use any arbitrary name we like! There is no limits on what names we can use (besides silly physiological constraints like having a word with 50 000 consonants). But, of course, there's much more to language than just labels!

For me, the interesting thing in this paper vis-à-vis language is that it shows how much innate structure in cognition must shape our language.

Arbitrariness of the sign is a principle that requires so many epicycles to present as "true" that it's more of a warning against overgeneralization than an insight with any significant predictive power in its own right.

Let's call the arbitrariness of the sign, blinga. Why do you think blinga requires "epicycles"? Blinga makes pretty modest claims: there is no requirement that the form of a sign matches that which it signifies in any way.

I'm not entirely sold by this discovery. For example when you learn to train dogs, you learn about the 3 voices. Encouraging voice, atta boy, negative voice, more stern, and the big "NO!".

To some degree these words type sounding language are doing the same thing. Some sounds will irk, some will soothe, and it would affect this 'evidence' found.

I think the researchers agree with your premise. The “evidence” is not that chicks have more language understanding than previously understood, but rather that the source of the universality of bouba/kiki is due to something more primitive than built in human language hardware.

Preprint: https://www.biorxiv.org/content/10.1101/2024.05.17.594640v1....

Is this not reducible to whether a speech sound contains fricatives and stops or not? They produce spiky sounds

But I guess it's about why so we associate those with spiky shapes, though surely it's because they represent sharp immediate changes in frequency?

I'd be interested on results of shapes imagined when you take the source as musical or other non speech sounds.

> But I guess it's about why so we associate those with spiky shapes, though surely it's because they represent sharp immediate changes in frequency?

Sure, but it's a very abstract connection between objects being sharp in vision and frequencies changing sharply in hearing. There's no guarantee any given organism would make the connection.

In the book „the design of everyday things“ it is mentioned that „natural mappings“ exist. Moving the knob of a vertical slider to the upper end universally means „brighter“ or „louder“, not „less bright“ or „more silent“.

maybe the chicks and norman get it, but i'm currently renting an apartment in france that has a bunch of these light switches installed all upside down, with "-" at the top:

https://www.legrand.com.gh/en/catalog/products/arteor-push-b...

> Moving the knob of a vertical slider to the upper end universally means „brighter“ or „louder“, not „less bright“ or „more silent“.

Except for the organ drawbars?

Which way would a vertical weight slider go?

I don't think it's abstract at all. Rub something sharp (anything from a stick to a phonograph needle) on an object and you'll directly transcribe its spatial frequency spectrum into an audio frequency spectrum.

Do you think it's obvious that a chick would understand that connection?

"Spatial frequency spectrum" typically refers to visual elements of an object, and has nothing particularly to do with its structure. Entirely smooth surfaces banded in different colors have a "spatial frequency". Extremely irregularly surfaces have no effective spatial frequency. Objects on the same scale as, say, a human head, would have to be "rubbed" at ridiculous high rates (and repeatedly) to even get into a "frequency" range that might include pressure variations that would be considered as a "wave".

I think you're imagining an entirely too limited set of objects.

>But I guess it's about why so we associate those with spiky shapes

I think the why just got a lot tricker than we imagined. Because we failed to replicate this experiment on other primates, we couldn't avoid a semantic suspicion about those associations. Now we probably have to set semantics aside or let it get a lot weirder, because we can replicate across ~300My.

>surely it's because they represent sharp immediate changes in frequency?

Maybe, and I think "multi-sensory signal processing" is the best framing, but the representation could also carry harder to think about things like "harm".

It's also super cool because the bouba-kiki effect framing was chosen due to methodological convenience for linguists and cultural anthropologists and their experimental bounds, not neuroscientists or signal processing folks. We could potentially find other experiments quickly, since chicks are a model organism and the mechanism is clear.

Things could move fast here.

I think it’s natural to think of this in terms of frequencies so the kiki shape has a higher visual frequency. As does the word have a higher audio frequencies within in than bouba so that is naturally associated with the lower frequency undulating line of that shape.

https://news.ycombinator.com/item?id=44280619 it's a good analogy.

I'm very intrigued by this, but I'll be much more interested when this is replicated on non-domesticated animals...!

It must take some strange things to survive co-evolution with humans for several thousands years

I wonder if this is a result of a Fourier transform type operation that turns the serial time domain into something that can be processed in parallel?

As someone with a passing familiarity with both baby chicks and experimental setups, I have strong doubts about this research.

Very likely this experiment suffered from a lack of thorough double blind control. Researcher bias may have generated subtle subconscious queues to the chicks on which shape to pick unrelated to the sounds.

What's the N value of this study

I don’t know, but it really should be in units of N dozen.

From the preprint linked above:

> We tested a total of 42 subjects, 17 of which were females.

The published one repeated the experiment w/ day old chicks and IIRC the same number w/ the same results, so it's got a little more N than the preprint.

baba is keke

baba is you

All the universal translators in fiction make more sense now lol.

Believe it or not: This is pure and unadulterated advancement of civilization.

Please elaborate.

This is irony. The study is stupid, society has reached a stupid stage of development. Kiki and bouba explain nothing and serve nothing. Culture is in shambles.

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An interesting explanation that happens to be completely hallucinated. That line doesn't appear anywhere in either the play or the movie.

ha, ha, and they say AI does not hallucinate anymore!

Okay Gemini

If you don't recognize a quote, it's obviously AI? Might want to rethink your logic, or outsource it to AI. Might help you