Baby Chickens Exhibit the ‘Bouba-Kiki’ Effect, Linking Sounds to Shapes

Humans across cultures consistently associate the nonsense word “bouba” with rounded shapes and “kiki” with spiky ones. Now, research reveals that even baby chickens demonstrate this same intriguing connection, suggesting a deeply rooted evolutionary basis for how we perceive and categorize the world.

The Bouba-Kiki Effect: A Universal Phenomenon

The “bouba-kiki effect” has been observed across diverse cultures, with individuals overwhelmingly pairing “bouba” with rounded forms and “kiki” with jagged, pointed shapes. Researchers have even found this association in human infants as young as four months old, leading to speculation that these innate connections may have played a role in the development of language. The idea is that these shared associations could have provided a foundation for building more complex spoken symbols.

Chicks Join the Club

A recent study published in the journal Science explored whether this effect extended to the animal kingdom. Researchers at the University of Padova in Italy tested chicks, choosing them for their early stage of development. “With chicks, we had the chance to test animals at the incredibly, very first stage of life,” explains researcher Maria Loconsole. This allowed the team to determine if any observed associations were innate, rather than learned through experience.

How the Experiment Worked

The researchers first trained three-day-old chicks to seek food behind panels displaying both spiky and blobby shapes. Once the chicks learned this task, they were presented with two panels – one rounded and one spiky – while the sounds “bouba” or “kiki” were played repeatedly. The chicks consistently showed a preference for the rounded panel when hearing “bouba” and the spiky panel when hearing “kiki.”

A second experiment with one-day-old chicks involved displaying moving objects on video screens. The researchers found that the chicks moved towards spiky shapes when they heard “kiki” and towards rounded shapes when they heard “bouba.”

Implications for Language Evolution

“I was surprised by it,” says Marcus Perlman, a linguistics and communication researcher at the University of Birmingham in the United Kingdom, who was not involved in the study. Loconsole suggests that the findings indicate a basic linkage between perception in chicks, similar to humans, that “in our species was then co-opted and exploited for language.”

Perlman believes this points to a deeply rooted evolutionary connection, potentially tracing back to a common ancestor of birds and mammals. “So that’s interesting,” he says. “It shows that the vertebrate’s sensory systems are primed to expect certain regularities in the world.”

Beyond Bouba-Kiki: Broader Sound-Shape Associations

The bouba-kiki effect is part of a larger pattern of sound-shape associations. For example, high-pitched sounds are often linked to smaller, lighter objects, while lower-pitched sounds are associated with larger, darker ones. Another recent study found that people tend to associate a trilled “r” sound with rough surfaces rather than smooth ones.

However, Perlman emphasizes that humans possess a unique capacity for generating novel symbols and communicating meaning through various means, including gestures and drawings. “We’re really good at it, and effectively, no other animal does anything like charades,” he says. “That’s a creative capacity, that maybe in some cases leverages certain hard-wired associations.”