When shapes have sounds : The Bouba-Kiki effect

Bouba or Kiki?

Before you read on, have a look at the image of the two cacti above.

Now take the two names 'Bouba' and 'Kiki' and assign one name to each of the cacti.

OK? Now read on.... 

Most people, regardless of their native language or cultural background, will confidently match "Bouba” with the rounded cactus on the left and "Kiki” with the spiky cactus on the right. This remarkable consistency reveals a fascinating phenomenon known as the 'Bouba-Kiki' effect.

The Bouba-Kiki effect

First documented by German-American psychologist Wolfgang Köhler in 1929, this phenomenon demonstrates how our brains automatically connect sounds with visual forms. The effect suggests that certain phonetic qualities inherently "feel” compatible with specific shapes. The soft, rounded sounds in "Bouba”—produced with lips coming together—seem naturally paired with smooth, curved forms. Meanwhile, "Kiki” contains sharp consonants, mirroring the angular nature of pointed shapes.

The letterforms themselves probably contribute to this effect, too. 'B' has soft, rounded edges, while 'K' is made up of sharp, angular lines.

The original experiment didn't use cactus images at all, but rather the image shown below:

Understanding the Bouba-Kiki effect has revolutionised logo and brand identity design. As a brand identity designer, I strategically use these sound-shape associations to communicate brand personality at a subconscious level.

For example, tech companies like Google and Apple incorporate rounded elements in their logos to convey approachability and user-friendliness.

 Bouba brand logos

However, brands such as HSBC favour angular shapes to project precision and accuracy. While brands such as Nike employ sharp, jagged shapes to convey intensity and competitiveness. 

 Kiki brand logos

By aligning visual elements with phonetic qualities, designers create logos that feel intuitively "right” to consumers, enhancing brand recognition and emotional connection.

The Bouba-Kiki effect offers compelling evidence that our senses are more interconnected than we typically realise, revealing the subtle ways our minds create meaning through unexpected sensory bridges. It's critical to successful brand identity and logo design and why some brands feel more coherent and memorable than others.