Baby chickens pass key language test with 'bouba-kiki' effect

Baby chickens pass a key language test

New research shows that baby chickens, like humans, associate certain sounds with specific shapes. This phenomenon is known as the "bouba-kiki" effect.

In humans, the vast majority of people will identify a soft, rounded shape as "bouba" and a sharp, spiky shape as "kiki." The new study, published in the journal Animal Behaviour, demonstrates this cross-sensory connection exists in animals with no language at all.

What the bouba-kiki effect reveals

The effect is considered a cornerstone of spoken language. It reveals a fundamental, pre-linguistic link between how a word sounds and what it might mean.

This sound-shape mapping is thought to be a building block for how words are created. The fact that it appears in chickens suggests this cognitive tool is ancient and not unique to humans or even primates.

How scientists tested the chicks

Researchers from the University of Padova and Johns Hopkins University tested 40 newborn chicks. The chicks were shown two shapes on a screen—one rounded and one spiky—while hearing a made-up word.

One group heard a "bouba"-like word ("maluma" or "oro"), while another heard a "kiki"-like word ("takete" or "kiki"). The scientists then tracked which visual shape the chicks approached after hearing the audio cue.

• Chicks hearing "bouba" sounds approached the rounded shape.
• Chicks hearing "kiki" sounds approached the spiky shape.

The association was formed immediately, without any training. "This suggests they are born with this predisposition," said lead author Chiara Santolin.

Why this discovery matters

The findings challenge the idea that such sound symbolism is a product of human language or advanced cognition. Instead, it points to a shared biological mechanism across species.

"This is one of the first times we have seen this effect in animals," said co-author Giorgio Vallortigara. The research implies that the roots of language are deeper and more widespread in the animal kingdom than previously understood.

It provides strong evidence that some foundations of language are not learned but are innate biological traits. This pushes the evolutionary timeline for language precursors back significantly.

The bigger picture for language evolution

Scientists have observed the bouba-kiki effect in human infants as young as four months old. It has also been shown in some primates, but the chick study offers the clearest evidence in a non-mammal.

The team's next steps involve testing whether other bird species, or even insects, display the same bias. This could help map how widespread this cognitive trait is.

The discovery opens new doors for understanding the biological underpinnings of communication. It suggests that the path to human speech began with very basic, hardwired connections between senses that we share with many other creatures.