The Bouba Kiki Effect Explained: Why Shapes Have Personalities

The Bouba Kiki Effect is a psychology experiment that explains design decisions like why modern smartphones have smoothly rounded corners, why hospital waiting rooms and toys avoid hard edges, and why a Lamborghini looks terrifying while a Volkswagen Beetle seems friendly.

The experiment itself is simple, but it shows that our brains don’t treat shapes as decoration. They read them as signals.

Look around. Your phone. A bottle of water. Running shoes by the door. A spoon resting next to your coffee mug. Google’s pill-shaped search bar. None of these objects ended up looking this way by accident.

Every curve, corner and point in a product communicates something before you even touch it.

The Bouba Kiki Effect doesn’t tell us that curved is always “good” and pointy is always “bad.” It shows that rounded and angular forms carry different feelings, and people pick up on them almost instantly.

So today at Emoris, let’s understand the Bouba Kiki Effect through 9 real-world examples.

What Exactly Is the Bouba Kiki Effect?

Imagine someone shows you two strange shapes. One is smooth and balloon-like, just like a cloud. The other is jagged and star-like, every edge biting out sharply.

Now give those shapes two made-up names: Bouba and Kiki.

Without thinking too much, you almost certainly match Bouba to the round shape and Kiki to the spiky one.

In fact, when neuroscientists Ramachandran and Hubbard (2001, Page 17) ran this test, over 95% of people called the blob “Bouba” and the star “Kiki”. That wasn’t an accident.

Decades earlier (in 1929) psychologist Wolfgang Köhler in his book Gestalt Psychology had noticed the same tendency (using the names “Maluma” and “Takete”).

Across cultures and languages even among toddlers people consistently pair rounded shapes with soft sounds and jagged shapes with sharp sounds.

No dictionary teaches this connection. It’s built into our brains. Saying “bouba” uses a soft, round mouth shape and flowing vowels; the sound itself feels smooth.

Saying “kiki” comes out with hard consonants and short vowels; the sound feels sharp(and tangy). Our senses naturally tie these impressions together.

The Bouba Kiki experiment reveals a surprising cross-sensory habit: shapes and sounds connect in our mind.

Designers and marketers know people read those shapes without words. That’s how they guide the products utilising Bouba and Kiki to design the choices we touch and see every day.

1. Your Phone Is Bouba – Its Notifications Are Kiki

Pick up a modern smartphone: iPhone, Pixel, Galaxy… or the one in your hand. Notice anything in common?

No one made these phones with perfect right angles. The screen curves into rounded corners. The glass and metal edges blend into each other. The phone feels like it belongs in your palm, designed to stay as close to your body as possible.

Apple’s designers even won a design patent for the iPhone’s rounded-rectangle shape.

Rounded hardware corners aren’t just pretty; they make the device inviting.

Samsung’s S24 Ultra had sharp corners and Samsung rounded it in their S26 Ultra as it felt too pointed and a bit uncomfortable.

Rounded edges disappear into your grip. Every iPhone back to 2007, every modern Samsung Galaxy, every Google Pixel shares that principle.

Now look at a notification. Your phone buzzes or pings: “Ding!”

A short, piercing chime appears throughout your day. That sound is pure Kiki: bright, attention-grabbing, even a bit alarming.

The phone and its sound are speaking two visual-sound languages. The device’s form says “hold me comfortably”. The notification sound says “interrupt and listen”.

Product designers wanted the phone to be pleasant to hold (Bouba), but they want notifications to break the calm (Kiki) and attract your attention.

This article we wrote shares 9 similar product design examples that we overlook in daily life.

2. Hospitals use Bouba to Reduce Stress

Hospitals already make most people nervous, and for obvious reasons. Tests, syringes, surgeries, long waiting, sterile hallways, it’s all anxiety-inducing. Designers of medical spaces try to soften that on a subconscious level.

Imagine two waiting rooms. In one, every corner of the desk and every chair is sharp. In the other, desks curve toward you, seating has gentle armrests, and hallways have arched doorways.

Which feels more calming?

Modern hospitals go with the latter.

Look at this Hospital sleeper chair – They use flowing, rounded forms and even an organic rug inspired cover to look “non-medical” and welcoming.

Corridors sometimes bend instead of leading to blank walls. Reception desks end in soft angles. Even kids’ hospitals use playful, curved imagery rather than sterile straight lines.

Curved shapes feel safer and remove safety hazards: no one gets accidentally cuts or bruises on a tabletop with no sharp corners.

Before anyone speaks a word, the waiting area signals “you’re not in a factory.” The interior is designed to balance the kiki environment of the hospital with curved boubas so patients can focus on care instead of subconsciously panicking at every turn.

3. Why Baby Toys and Snack Brands Avoid Sharpness?

Go to a toy store’s kid section and you’ll find that nothing is covered in spikes.

A baby panda plushie has bulbous hands, legs to grasp. A baby rattle is rounded or cylindrical ensuring the baby doesn’t hurt himself and is big enough to not choke on it.

Brands utilises Bouba language to comfort people: Snack wrappers, cereal logos, ice cream tubs: curves rule them all.

“Oreo” is drawn in a soft, rounded font. Kinder eggs have plump letters and smiling cartoons.

Both baby toys and snack foods want similar feelings: reassurance and happiness. Toys shouldn’t look dangerous to little hands; snacks shouldn’t feel like diet penalties.

By using Bouba shapes, they deliver a subconscious message: these things are safe and fun.

The toy says “I’m okay to mouth and squeeze,” and the chocolate says “I’m a treat, not a threat.”

In each case, designers cleverly use bouba(round shapes) to say “go ahead, enjoy,” long before a child can speak.

4. Why Some Cars Smile While Others Look Ready to Attack?

Imagine pulling into a parking lot and seeing a classic VW Beetle and a bright Lamborghini Revuelto. From far off, they look completely opposite in personality.

The Beetle has round headlights that resemble big friendly eyes and a dome-shaped hood like a grin. It looks almost like a cheerful bug that just came out from a comic strip.

The Lamborghini, on the other hand, looks like an animal about to pounce. Its headlights slant down to a glare. Every body panel ends in a sharp crease. Vents and intakes stab outward. Even the silhouette leans forward, as if on tiptoes.

Neither design is “wrong.” They’re just speaking opposite visual languages.

The Beetle’s curves (introduced in 1938 and refreshed in 2012) say “cute and friendly”. No wonder cartoonists love drawing it(you might have seen it in a lot of cartoons), the car is already a smiling face.

Lamborghini’s angular aggressiveness says “power and speed”. It literally shouts the point: that car isn’t here to be gentle with traffic. Shapes defining personality!

The Beetle is Bouba: it invites trust and even affection (people often name their Beetles).

The Lamborghini is pure Kiki: it asks for attention and respect first.

Car designers chose each form to match an identity.

5. Digital Interfaces Subtly Became Rounder

Open Google on a desktop in 2010. The search box is a simple, sharp, grey rectangle. It was a kiki designed to say “we are the future to your queries at 3 a.m and we are here to stay”

Slide your finger on an iPhone home screen in 2015. The app icons introduced had gentle rounded corners (Apple even applied a 10/57 ratio of corner radius to icon size so every icon shares the same softness).

Today, almost all apps use border radius in their interface.

By 2018, Google Search had switched to a pill-shaped search bar with fully rounded ends. It’s bouba today.

Android 12 and iOS 14 both drew attention to rounding elements: notifications, widgets and buttons all have consistent curves. Each update, each redesign, shifted shapes toward round.

Why? Because curves feel easier on the eyes and finger.

A credit card in your hand, a text field to tap: rounded corners feel like natural extensions of modern hardware.

Yet Kiki hasn’t vanished from the digital world. Popup alerts and error dialogs often use sharp corners or exclamation icons to warn you. A notification badge might pop onto your screen with a jarring sound and a pointed triangle icon.

Designers know you want buttons to look friendly (Bouba) but critical alerts to demand focus (Kiki).

6. Water Bottles: Cylinders for Your Hand

Fill your grocery cart with water bottles and you’ll notice one thing: Nearly all single-serving bottles are simple cylinders with rounded shoulders and caps.

Take Milton’s 1000ml water bottle – it’s literally a smooth tube. The metal curves all the way around so there are no edges against your palm.

But it could have been a rectangle too, no? Imagine the discomfort, it would feel rigid, the edges putting pressure from 3 sides on your palm when you are holding 1 kg of weight and it would also slip more easily.

Naturally, our hands grip best around curved surfaces. A cylinder puts even pressure on the whole palm. Brands understand this. Through geometry, they favor bulges over bevels.

A question for you: Is warm water Bouba or Kiki? Is ice-cream brain freeze a Bouba sensation or Kiki?

7. Running Shoes Are Bouba. High Heels Are Kiki.

Check your closet. Most athletic shoes have bulbous soles and rounded toe boxes. They mirror the soft curves of human feet.

Look at how the front of the shoe arcs to protect toes, or how cushioned the heel is. It’s all soft lines. That design feels natural and reassuring because it follows our body’s curves.

It literally is Bouba: a shoe that says “keep going, this fits you.”

Now contrast that with a pair of heels or pointed pumps. A classic Manolo Blahnik heel, for example, narrows dramatically and tapers into a needle.

The color might be sleek black or red, and the toe is often sharply pointed.

That’s intentional Kiki. High-fashion heels use sharpness to communicate assertiveness and elegance, not comfort.

The two designs send opposite messages. Sneakers are built for motion and support: Bouba that invites activity.

Heels are built to signal sophistication and power: Kiki that draws the eye.

No one wears spiky heels for comfort. Conversely, no one makes joggers with discomfort.

Each shoe type matches the emotion its wearer wants to convey (just like we saw earlier with car designs): trust and freedom in round sneakers(or Beetle), or boldness and drama in pointed heels(Lambo).

8. Your Body: Curves and Angles All Around

We aren’t just comparing products, our own bodies speak both languages.

Stand in front of a mirror. Notice your face: cheeks are soft and round, eyebrows arch like gentle hills, lips curve into smooth lines. Those areas are Bouba.

But look at your jaw and wrists: there are angles there too, collarbones, knuckles, nails and even your teeth have points. Those parts are Kiki.

Think of a smile: it’s a curved crescent that makes you look kinder. Frown lines and furrowed brows have sharper angles and convey tension.

Children’s bodies are mostly Bouba: soft round cheeks and bellies. As we age, we develop more Kiki-like structure: angular shoulders, pronounced cheekbones. It’s no wonder we associate baby faces with innocence and adult expressions with seriousness.

Even our movements use both. A slow hug is all curves; a sharp gesture (like punching or pointing) is all angles. Nature mixes them for function.

Biologically, we seem wired to find Bouba in human curves and Kiki in certain body parts. That affects design too: action figures or robots usually blend organic curves for appeal with just enough angles to look dynamic.

9. Spoon vs. Fork: Different Tools, Different Messages

Finally, something you pick up at every meal. A spoon and a fork are two tools with opposite roles and opposite shapes.

A spoon is practically a small bowl. Its edges sweep in a continuous curve, forming a smooth surface to collect soup or rice. Holding it, you feel a comforting wrap around your fingers. It feels nurturing and safe. A bouba!

A fork, on the other hand, has prongs that jut out sharply. Those spikes lift salad or meat by puncturing them. A fork’s silhouette says “precision and action.” It is a Kiki tool, not designed for warmth, but for task.

You feel gentle confidence with a spoon, alert caution with a fork.

Conclusion

Tomorrow you’ll pick up your phone and sip from that water bottle without a second thought. Nothing’s changed in those objects. But you are.

You will see their shapes as choices, not coincidences. A designer thought “friendly” or “important” before a single decision was taken.

The next time your phone trings (sharp and loud) while its body rests, or when you pass a candy bag full of smiling curves, you’ll catch yourself noticing Boubas and Kikis.

Note: The writer of this article kept thinking in Boubas and Kikis straight for 7 days. It’s addictive.