Loud Shirts and Sweet Words

One of these things is called "kiki" and one is called "bouba." Which would you guess is which?

Most people label the spiky object on the right as "kiki." When asked why, they'll say things like:

• the sounds of "kiki" seem sharper and more angular.
• the letters of the word "kiki" have sharp angles and lines, where as the letters in "bouba" have more curves.
• when we say "bouba," our mouths move in more rounded and fluid ways, but "kiki" has sharp stops.

All of these explanations are shape-based. So let's try taking shape out of the equation.

Here are two, equally rounded objects. Imaging the taste of each. Which taste seems "kiki" and which seems "bouba"?

Most people say the sourness of the lemon feels more "kiki" and the sweet, chocolately warmth of the cocoa seems more "bouba."

Now listen to these two pieces of music: which is more "kiki" and which is "bouba"?

Most people say the piccolo is more "kiki" and the bass is more "bouba!"

People generally agree on their answers to these questions: there is relatively strong consistency across age groups and languages (though people with autism may show the effects less strongly).

The kiki-bouba effect (referred to as "sound symbolism") is one type of crossmodal association: using words from one sense to describe the experience of another sense.

For example:

He's wearing a loud shirt
She has a sweet disposition
There was a heavy silence

Shirts don't actually have a volume, personalities don't have a taste, and silences don't have weight. But all these associations clearly convey information we understand!

Why do we have associations between stimuli from different senses?

One reason for these crossmodal associations is that we form connections in our minds between things that lead to similar emotional responses. Things that are soft, warm, sweet and gradual tend to be more physically pleasant and less dangerous than things that are sharp, cold, bitter, or sudden. As a result, we can use use things like soft and warm as stand-ins for pleasant and safe.

If you overheard someone say "He sent me a pretty spiky text," chances are you'd assume the text was mean, even though you've likely never heard that expression before. We all know what spiky things feel like—we have to handle them carefully, they can hurt us, they can be dangerous. So we carry those connotations of literal spiky objects with us into our interpretation of something that cannot actually have spikes.

Another possible explanation for crossmodal associations has to do with how the brain processes sensory stimuli.

In order for us to have a sensory experience (i.e., smell a rose, hear a sound, see a bird), our sensory organs (nose, ears, eyes) must convert the input (chemicals, sound waves, light) into signals the brain can understand: a series of electrochemical changes. Brains are just a collection of cells—a three pound meatloaf in our skulls. Brains themselves can't actually smell, hear, and see. All they can do is interpret the signals they receive.

The electrochemical signals that come from our eyes, ears, and other sensory organs share some commonalities. In many cases, stimuli that are more intense (ie., louder, brighter, heavier) tend to lead to a larger pattern of electrochemical changes. Therefore, there is a common way of signaling "THERE IS A LOT OF THIS SUBSTANCE PRESENT," regardless of whether that substance is light, heat, sound, or something else.

Therefore, when we say "loud shirt" we are conveying the commonalities between the subjective experience of an intense sound and an intense sight.

We are constantly being bombarded by a huge amount of sensory information, and describing it to others can be a challenging task! Borrowing words from other senses can help us convey the experience we are having to other people.

Note: Crossmodal associations are different from Synesthesia—a condition in which input from one sensory system leads to automatic, involuntary experiences in another sense. Most people experience crossmodal associations, but synesthesia is a relatively rare condition.