For decades, scientists have puzzled over why most people instinctively associate the word “bouba” with rounded shapes and “kiki” with spiky ones. This phenomenon, known as the “bouba-kiki effect,” has been proposed as a potential clue to how humans first linked sounds to meaning in the development of language. However, a new study reveals that even baby chicks exhibit this same preference, suggesting the connection is far more primal—and less uniquely human—than previously believed.
The Universal Sound-Shape Link
The bouba-kiki effect isn’t just a quirk of human cognition. Research across cultures confirms that people universally agree on these associations, regardless of language or writing system. Some theories suggest this might stem from how our mouths move when making the sounds (rounding for “bouba,” sharp movements for “kiki”). But the new study throws that idea into question.
Chickens Enter the Equation
Researchers at the University of Padua in Italy tested newly hatched chicks before they could learn from their environment. The birds were presented with rounded and spiky shapes while hearing either “bouba” or “kiki.” The results were striking: 80% of chicks consistently preferred the rounded shape when hearing “bouba” and the spiky shape when hearing “kiki.” This innate preference rules out learned behavior, implying a deeply rooted perceptual bias.
“We parted with birds on the evolutionary line 300 million years ago,” notes linguist Aleksandra Ćwiek. “It’s just mind-blowing.”
What Does This Mean for Language Evolution?
The discovery complicates the long-held idea that the bouba-kiki effect explains the very beginnings of language. If chickens share this instinct, the link to human speech origins becomes less direct. Instead, the effect may represent a fundamental cognitive ability: connecting sensory experiences (sight and sound) in a way that helps newborns quickly interpret their surroundings.
Previous studies found that great apes failed the bouba-kiki test, reinforcing the idea that it was uniquely human. But researchers now suggest that apes may have overthought the task due to training, instead of relying on gut instinct.
Beyond Language: A Deeper Cognitive Connection
The implications go beyond just language. The bouba-kiki effect may be evidence of how animals, including humans, evolved to make sense of the physical world. Round objects tend to produce softer, lower-frequency sounds when they move, while spiky ones create sharper, higher-frequency noises. This could explain why our brains instinctively associate certain sounds with certain shapes—a survival mechanism for finding food or avoiding danger.
The study suggests that bouba-kiki isn’t a key to unlocking the origins of language, but rather a window into the fundamental cognitive connections that shape how all animals perceive their environment. The mystery of why “bouba” feels round and “kiki” feels spiky may lie not in language itself, but in the deep-rooted physics of the world around us.
