Hannah sent us something this week, and it's one of those things where the second you read it you realize you've seen it a hundred times and never once thought about it. She's noticed that when people meet her and Daniel's baby — pretty much anyone who isn't European or American — they all make this same clucking sound at him. A kind of rhythmic tongue-click. And she wants to know what that sound actually is, how it's physically made, why it shows up across so many cultures, and whether babies genuinely respond to it in a way they don't to other sounds.
This is exactly the kind of thing that makes me wish I'd paid more attention in certain moments in the clinic. Because she's right — it's everywhere, and I never once stopped to ask what it was.
So we went digging into the phonetics, the anthropology, and the infant cognition literature. And the answer is weirder and more specific than you'd think.
So first, let's actually pin down what this sound IS. Because it's not just a noise — it's a specific articulatory event. What Hannah's describing is a lateral click or a palatal click. The tongue tip or the blade of the tongue presses up against the alveolar ridge — that's the bony shelf behind your upper teeth — or against the hard palate further back, and it creates a sealed pocket of air. When you release that seal, you get a sharp suction pop.
So it's literally a tiny vacuum chamber in your mouth.
That's exactly what it is. And the key distinction — and this is where most people get it wrong — is that this is not the same thing as the dental click you use for "tsk tsk" when you're annoyed. That disapproving sound uses the tongue tip right behind the teeth. The baby cluck is further back, and it's softer, slower. It's usually produced as a lateral click — the sides of the tongue are what release, so the air rushes out the sides of the mouth rather than the front.
Which is why it sounds rounder.
Right. And it's almost never a single isolated click. The pattern is cluck-cluck-cluck — two or three beats, rhythmic, often with a rising pitch contour. The voice usually comes in on the second or third click, so it's like... click, click, cluck-oo. Almost melodic.
You just did it.
I've been doing it at babies for thirty years. I never thought about the mechanics.
Nobody does. That's the thing Hannah's noticing. It's completely unselfconscious.
And the acoustic signature is fascinating. Clicks are among the loudest and most distinctive consonant sounds in human speech. They have an extremely sharp onset — the sound goes from zero to full amplitude almost instantly. That's called a fast attack time, and it means the sound cuts through ambient noise in a way that sustained vowels simply don't. If you're a baby and there's a room full of adults talking, the click is going to be the thing that reaches your auditory system first.
So we've got a sound that's a small vacuum popping in someone's mouth, produced in a rhythmic two or three beat burst, with a pitch that rises. That's the physical reality. Now the question becomes: why does this exact thing show up everywhere?
And this is where it gets surprising. The cluck appears in West African baby-directed speech, across the Caribbean, throughout South Asia, the Middle East, Latin America. It's not one culture borrowing from another. It's convergent — the same behavior arising independently.
Meanwhile I grew up with "goo goo ga ga."
Yes. And that's the contrast that makes this interesting. There was a major cross-cultural study published in twenty twenty-two — the lead author was Courtney Hilton, and they looked at infant-directed vocalizations across something like twenty-one societies, including small-scale hunter-gatherer groups. What they found was that certain acoustic features keep showing up in how adults talk to babies, regardless of language or geography. Higher pitch, wider pitch range, slower tempo. But also these percussive, rhythmic elements.
So the cluck fits into a broader pattern of what they call affective vocalizations — sounds that aren't quite language but aren't random noise either. Things adults produce to engage an infant's attention or regulate their emotional state.
Right. And what's striking is that these patterns are consistent even in cultures that have no contact with each other. The cluck isn't spreading by cultural diffusion. Something about the human vocal tract and the human infant brain keeps producing this same solution.
Which brings us to the baby's side of the equation. Do they actually respond to this specifically?
They do, and we know something about why. There was a study back in two thousand seven — Gervain and colleagues — that looked at infant auditory preferences. Infants as young as two months show differential neural responses to click-like acoustic features versus sustained vowels. The sharp onset, the percussive quality — it triggers something.
Two months. So we're not talking about learned preference here.
No, that's the key. The human auditory system is tuned from birth to be sensitive to certain acoustic features. Rapidly modulated sounds, sharp onsets, high-frequency energy — these are all things the infant brain is wired to attend to. And the cluck has all of them in one tidy package.
The sharp onset triggers what they call the orienting reflex. It's the same thing that makes you turn your head when someone snaps their fingers.
And then the rhythmic repetition — cluck-cluck-cluck — holds the attention once you've got it. Infants show preferential attention to rhythmic auditory patterns from birth. There's something about periodicity, about predictable timing, that the infant brain finds compelling. It may be that rhythm is one of the first things the developing auditory system latches onto as a way of making sense of sound.
So the cluck grabs them with the sharp pop and then keeps them with the beat.
And then the pitch contour — that rising melody on the second or third click — that's the emotional content. The baby isn't just hearing "attention, attention, attention." They're hearing "attention, and also I'm friendly."
Which is a lot of information in a sound that lasts maybe a second and a half.
It's incredibly efficient. And I think that's part of why it's so widespread. It's a low-cost, high-reward signal. Anyone can produce it, it doesn't require language, and it works.
So the sound itself is perfectly designed to grab an infant's attention. But that raises a bigger question — why do some cultures use it and others don't? If it's so universal and so effective, why did Anglo baby-talk drift away from percussive consonants toward vowel-heavy cooing?
This is the part I find most interesting, and I should say up front — nobody has a definitive answer. But there are some compelling possibilities. One is that English and other European languages have a baby-talk register that's overwhelmingly focused on pitch modulation. "Goo goo ga ga" — it's all vowels. The consonants that do appear are the early-acquired ones, the bilabials — "mama," "papa," "baba." These are sounds babies can produce themselves early on.
Whereas a lateral click is not something a baby is going to produce for quite a while.
Right. English baby-talk is, in a sense, meeting the baby at their own production level. It's modeling sounds the baby can eventually imitate. The cluck isn't about modeling — it's about engaging. It's a different function.
So it's not that Anglo cultures don't click at babies. It's that the whole register of baby-directed speech evolved in a different direction.
And there may be a historical-linguistic reason for that. Click consonants are not phonemic in English or most European languages. That is, they don't appear as meaningful speech sounds that distinguish one word from another. In languages like Xhosa or Zulu, clicks are fully integrated into the phonological system. They're consonants just like "t" or "k." So speakers of those languages have clicks readily available in their vocal repertoire in a way that English speakers don't.
That's a really interesting point. The cluck might feel natural to a Xhosa speaker because their mouth is already trained to make those sounds in everyday speech. For an English speaker, a click is a paralinguistic sound — it exists outside the language system.
And paralinguistic sounds tend to be used for specific functions. The dental click for disapproval. The lateral click for... well, for urging a horse forward, actually. That's one of the few places clicks survive in European vocal behavior.
Wait — so the sound you make to get a horse moving is the same articulatory gesture as the baby cluck?
Very close. It's a lateral click. And that's not a coincidence. It's an attention-getting, movement-urging sound in both cases. The function is similar even when the recipient is different.
That's going to be hard to un-know.
The horse thing is interesting because it suggests these sounds have been around in European vocal behavior — they just got assigned to animals rather than babies. The cluck didn't disappear from Anglo culture. It got specialized.
So let's talk about the evolutionary angle. You mentioned earlier that clicks might be among the oldest consonant types.
This is where linguistics gets ancient. Some researchers argue that click consonants may predate the dispersal of modern humans out of Africa. The reasoning is that clicks are found almost exclusively in African languages — particularly in southern and eastern Africa — and that this distribution suggests they were present in the ancestral human population before the major migrations.
So the cluck could be a kind of fossil behavior. Something our ancestors were doing a hundred thousand years ago.
It's speculative, but it's not crazy. The articulatory gesture for a click is relatively simple — you don't need fine motor control of the larynx, you don't need complex tongue shaping. It's a basic suction release. And it produces a sound that carries well and is acoustically distinctive. For early humans trying to communicate before fully developed language, clicks would have been useful building blocks.
And if that's true, then the baby cluck isn't just a cute thing aunties do. It's a behavior that may literally be older than language itself.
That's the deep version of the argument. The more conservative version is simply that clicks are an efficient acoustic signal for getting infant attention, and human cultures independently discover this because it works. You don't need the evolutionary story to explain the convergence. The physics of the sound and the biology of the infant auditory system are enough.
But the evolutionary angle does explain something the physics alone doesn't. Namely, why it feels instinctive. Nobody teaches you to cluck at a baby. You just... do it.
And that feeling of instinct is probably real. Not in the sense of a dedicated "baby cluck" gene, but in the sense that we have a deep-seated tendency to produce rhythmic, percussive sounds when we want to engage an infant's attention. The specific form it takes — a lateral click — may be shaped by the fact that the human vocal tract has a natural affordance for making that sound. It's easy to produce, it's acoustically effective, and it works.
Let's talk about the feedback loop. Because this is where it stops being just about the sound and becomes about the relationship.
This is crucial. The cluck isn't a one-way signal. The adult clucks, the baby responds — smiles, laughs, turns their head, vocalizes back — and that response reinforces the adult's behavior. It's a dyadic loop. The adult doesn't need to understand why the cluck works. They just know that when they do it, the baby lights up, so they keep doing it.
And the baby, for their part, is getting something valuable too. They're learning that sounds can be directed at them, that vocalizations can be social, that there's a back-and-forth rhythm to interaction.
Some researchers think percussive consonants like clicks may actually help infants segment the speech stream into syllables. The sharp onset marks a boundary. If you're a baby trying to figure out where one sound ends and the next begins, clicks are like highlighter pens on the audio.
So the cluck might not just be entertainment. It might be doing real developmental work.
It's speculative, as I said. But it fits with what we know about how infants learn to parse language. They're sensitive to statistical regularities in the sound stream, and sharp acoustic boundaries make those regularities easier to detect. The cluck is basically a neon sign saying "pay attention to this sound event."
Which makes the Anglo absence even more interesting. If the cluck is developmentally useful, what are English-speaking babies getting instead?
They're getting exaggerated pitch contours and vowel elongation. "Hiiii baaaaby." The information is in the melody rather than the percussion. Different route, possibly similar destination — both are ways of making the sound stream more salient and easier to parse.
It's like two different engineering solutions to the same problem.
And neither culture sat down and designed it. They just... emerged.
Here's something I keep coming back to. Hannah's observation was specifically that non-European and non-American people do this. And she's not wrong — the cluck is noticeably less common in Anglo baby-talk. But it's not completely absent. I've heard Irish relatives do something close to it.
And in the American South, there's a tradition of clicking at babies that some older people still do. It's not as widespread, but it exists. The boundary isn't as sharp as "Europeans don't, everyone else does." It's more of a gradient.
The cluck is present but less prominent. Which actually makes the question more interesting. Why would it fade in some places and not others?
One possibility is that as baby-directed speech became more "verbal" in Western cultures — more focused on language modeling, on talking to the baby in simplified but real sentences — the paralinguistic clicks got edged out. They're pre-verbal sounds. If your cultural model of baby interaction is "talk to them so they learn words," you might unconsciously drop the non-word sounds.
Even though the non-word sounds are doing something words can't do as efficiently.
Right. And this is the tension. The cluck is incredibly good at getting attention. Words are better at teaching language. Different cultures weight those priorities differently.
There's also a class and education dimension here that I think is worth flagging. In some cultures, the cluck is associated with more traditional, less "modern" child-rearing practices. You see educated urban parents moving away from it because they perceive it as old-fashioned.
Which is fascinating because the acoustic science says it's actually perfectly adapted to infant perception. The old-fashioned thing turns out to be exquisitely well-engineered.
Tradition accidentally optimizing for the thing that works.
That's basically the story of human culture. We do things because they work, then we forget why we started doing them, then someone comes along with a microphone and a spectrogram and says "actually, your grandmother was right."
Let's talk about the specific studies, because you mentioned the twenty twenty-two paper and the two thousand seven paper. What did they actually measure?
The Hilton study from twenty twenty-two was a massive cross-cultural survey. They collected recordings of people singing, speaking, and making other vocalizations to infants across twenty-one societies — everything from urban Americans to Hadza hunter-gatherers in Tanzania. And they found that certain acoustic features were consistently different when people directed sounds at infants versus adults. Higher pitch, brighter timbre, slower tempo in singing. But also — and this is the relevant part — these rhythmic, percussive, attention-getting sounds kept appearing.
And the cluck was one of them.
The cluck specifically wasn't the focus of that paper, but it fits perfectly into the category of what they'd call an affective vocalization directed at infants. The paper's main contribution was showing that these patterns aren't culturally specific. They're human universals.
And the two thousand seven study?
Gervain and colleagues. They used near-infrared spectroscopy to look at infant brain responses to different types of sounds. What they found was that newborns and young infants show distinct neural activation patterns for sounds with sharp onsets and rapid modulation — the kind of acoustic profile a click has — compared to sustained, slowly-changing sounds like vowels. The infant brain is literally wired to process these sounds differently.
Near-infrared spectroscopy on newborns. That's a sentence.
It's a cap with sensors that measures blood oxygenation in the brain. Completely non-invasive. The baby just sits there listening to sounds. And the data is striking — you can see the brain lighting up differently for different acoustic features.
So we're not guessing about infant preference. We can see it in the brain.
We can see differential processing. "Preference" is a slightly stronger claim — but when you combine the neural data with behavioral studies that show infants turning their heads more toward click-like sounds, the picture is pretty consistent. These sounds are salient to babies in a way that other sounds aren't.
And that salience is what makes the cluck work across cultures. It's not that Ghanaian grandmothers and Indian aunties all independently invented the same cultural tradition. It's that they all independently discovered the same acoustic fact: this sound gets the baby's attention.
Once you've discovered it, you keep using it because the baby's response is so rewarding. That smile, that head turn — it's immediate positive feedback. You don't need a theory of infant auditory processing. You just need to notice that the cluck works.
We've been talking about this in the abstract — but Hilbert, you've actually worked with this sound professionally, haven't you?
Hilbert: Early two thousands. Sound designer for a children's television show. Educational content for the under-two set.
I didn't know this.
Hilbert: It was a job. We were tasked with creating what the producers called "universal baby-appeal sounds." They wanted audio cues that would work regardless of language, regardless of culture. Something that would grab an infant's attention anywhere in the world.
You landed on the cluck.
Hilbert: We landed on it by accident. One of the sound designers — woman named Marisol, from Trinidad — she was in the recording booth doing some Foley work and her phone buzzed. It was her sister sending a video of her nephew. And without thinking she just started doing the sound. Click-click-click. The producer heard it through the talkback and said "what was that, do it again."
She was just reacting to a baby video.
Hilbert: Instinctively. And the producer had the sense to recognize it was exactly what we'd been trying to manufacture.
So you recorded it.
Hilbert: We built a whole library. Marisol spent an afternoon doing variations — different speeds, different pitches, with voice and without. We labeled the folder "ethnic baby cluck."
I'm sorry. The folder was labeled what.
Hilbert: Ethnic baby cluck. That's what the producer called it. I didn't name it.
Hannah's term — which she thought she was inventing — is literally what a children's TV production team was using twenty years ago.
Hilbert: Apparently.
What did you use it for?
Hilbert: Magic moment cue. Whenever a character appeared or something surprising happened on screen, we'd layer it in. It tested off the charts. Focus groups with infants — we'd bring in twelve, fifteen babies at a time, play different audio mixes, and measure attention. The cluck cue consistently outperformed everything else we tried.
How do you run a focus group with infants?
Hilbert: You put them in front of a screen and you watch where they look. Infants who are engaged look at the screen. Infants who aren't look at the ceiling or their own hands. The cluck brought their eyes back to the screen every time.
You had empirical evidence that this specific sound captures infant attention better than alternatives, and you built it into the show's sound design.
Hilbert: We used it in dozens of episodes. The producers knew it worked. Nobody asked why. They just knew that when the cluck played, babies watched.
Marisol from Trinidad just had this sound in her repertoire because it's what you do with babies where she's from.
Hilbert: She didn't think about it. It was just the noise you make.
Did anyone ever try to explain to the producers what was happening acoustically?
Hilbert: I tried once. Mentioned the sharp onset, the orienting reflex. They nodded and went back to talking about merchandising.
The show used a cross-cultural, possibly ancient human vocalization as an attention-grabbing sound effect, labeled it "ethnic baby cluck," and never thought about it again.
Hilbert: That's television.
Do you still have the sample library?
Hilbert: Somewhere. Hard drive in a box. Probably still works.
That sample library detail is going to haunt us.
The thing that strikes me is that Marisol's instinctive reaction to a baby video — something she did without thinking — turned out to be more effective than anything the sound design team could deliberately create. They spent weeks trying to engineer universal baby appeal, and the answer was already in someone's mouth.
Hilbert: That was the lesson of that job, really. The things people do without thinking are usually more interesting than the things they plan.
The label. "Ethnic baby cluck." It's so reductive and yet so... accurate.
Hilbert: It described the thing. Nobody was trying to be elegant.
Did Marisol ever find out her sound became a recurring cue?
Hilbert: She knew. She thought it was funny. Said her grandmother would be proud.
Of course.
Hilbert: She also said we were overthinking it. "You make the sound, the baby looks. What else is there to know?"
She's not wrong, but I'm very glad we spent forty minutes on the acoustic mechanics anyway.
Hilbert: You two would have.
That feels like a compliment and also not.
Hilbert: I'm going to get coffee.
Here's the open question I'm left with. If the cluck is this universal, this ancient, this effective — why did Anglo baby-talk drift away from it? We touched on the language-modeling hypothesis, but I don't think that fully explains it. Plenty of cultures model language and still cluck.
I wonder if it's partly about the professionalization of child-rearing advice in the West. In the twentieth century, you get this explosion of expert guidance — Dr. Spock, parenting manuals, developmental psychology filtering into popular culture. And a lot of that advice emphasized talking to babies in words. Real sentences, simplified but grammatical. The implicit message was that paralinguistic sounds were somehow less valuable, less educational.
The cluck got classified as something uneducated people do.
Possibly. And once that association forms, it's self-reinforcing. Middle-class parents who want to do the right thing by their babies avoid the cluck because it feels... folksy. Traditional. Not aligned with expert guidance.
Even though the expert guidance, if you dig into the actual developmental science, would probably support using both. Words for language learning, clicks for engagement.
The science and the culture got decoupled. And the cluck lost.
The other thing I keep thinking about is what this says about the things we do without knowing why. Hannah noticed this because she was paying attention. Most people never do. They just cluck at babies and move on with their lives, never once wondering why that specific sound came out of their mouth.
When you do stop to examine it, it turns out to be this incredibly rich phenomenon. Acoustics, anthropology, developmental neuroscience, evolutionary linguistics — they all converge on this one little tongue-pop.
A sound that takes about three-tenths of a second to produce, and it's connected to the deep history of human speech.
That's the thing about instinctive behaviors. They feel simple because they're effortless. But effortless doesn't mean simple. It means the complexity is somewhere you can't feel it.
The next time someone clucks at Ezra, Hannah can tell them they're producing a lateral click with a sharp acoustic onset that triggers the orienting reflex in his developing auditory system.
I'm not sure that's what the aunties want to hear.
Probably not. But she'll know.
She'll know. And that's the real gift of this show — ruining casual social interactions with excessive technical detail.
That should be our tagline.
We already have a tagline.
Do we?
I don't actually know.
Thanks to Hilbert for producing, and for revealing that a hard drive labeled "ethnic baby cluck" exists somewhere in a box.
If you find it, Hilbert, we want that sample.
This has been My Weird Prompts. If you've noticed something weird that people do without thinking — with babies or otherwise — send it to us at show at my weird prompts dot com.
We'll be back soon.
