Meet Bouba and Kiki. Who’s who? Well, that’s precisely the question — and you likely already know the answer. Without direction or explanation, over 95%  of people instinctively assign “Kiki” to the jagged, spiky shape and “Bouba” to the soft, round one. But, why?

This curious phenomenon – known today as the Bouba-Kiki effect – was first documented in 1929 by German psychologist Wolfgang Köhler. Using the words "takete" and "maluma," Köhler found that people consistently paired “takete" with angular shapes and “maluma” with rounded ones. Nearly a century later, the words have changed, but the effect persists – across languages, cultures, and even among pre-linguistic children, opening a doorway into the distinctive* architecture of human language and attention.

Our brains don’t compartmentalize our senses. Instead, they seek harmony and congruence, intuiting patterns that often make spontaneous sense – mapping sound to shape, movement to emotion, sensation to meaning. The sharp, staccato syllables of “Kiki” feel like they belong to something pointed; “Bouba” rolls gently off the tongue, echoing the curve its meant to describe*.

Researchers have turned to this effect to explore the origins and evolution of language itself, challenging the notion that words are random, disconnected from the concepts they aim to convey. Instead, Bouba and Kiki seem to further bond attention and language in their co-creative powers – each shaping and shaped by the other – in service of a deeper drive for coherence: a quiet, intuitive knowing that some things just fit.