Crows can recognize geometric patterns in shapes

For centuries, humans believed they held a monopoly on geometric intuition. The ability to recognize structure in a shape – its right angles, symmetry, and parallel lines – was seen as a mark of human cognition. But a new study suggests that this mathematical sense may not be ours alone.

Carrion crows, long admired for their cleverness, have now demonstrated the ability to detect geometric regularity in shapes. This discovery, led by researchers at the University of Tübingen, opens a surprising chapter in the story of animal intelligence.

The research does more than showcase the brainpower of birds. It questions whether our deepest ways of understanding space and form might be shared with other species – and perhaps even rooted in evolution itself.

Why geometry matters in the animal mind

Geometry isn’t just about math classes or architectural blueprints. At its core, it reflects the brain’s ability to process structure.

In humans, even those without schooling or exposure to formal mathematics can recognize simple geometric rules. Symmetry stands out. So do parallel lines and equal sides. We notice when something is off.

Until now, this perception seemed absent in other animals. Many can navigate, estimate quantities, or even use tools, but they appeared blind to the subtler rules that define shapes.

Previous research with baboons, our close evolutionary cousins, found they could not consistently recognize regular quadrilaterals. That led some scientists to believe geometric insight might be uniquely human.

But carrion crows, members of the corvid family known for problem-solving, proved otherwise with their surprising shape recognition abilities.

“Claiming that it is specific to us humans, that only humans can detect geometric regularity, is now falsified,” said Andreas Nieder, the study’s lead researcher. “Because we have at least the crow.”

Crows played a shape-spotting game 

Nieder and his team worked with two male carrion crows, both over ten years old, and trained to interact with a touchscreen. These birds had previously shown the ability to count, and now they faced a new kind of challenge.

They were presented with an array of six shapes. Five were similar, one was not. Their task? Pick the odd one out.

Initially, the birds encountered easy trials – five stars and a crescent moon, for example. They quickly learned that pecking the unique shape earned them a tasty reward: mealworms.

After they consistently succeeded with simple patterns, researchers introduced more complex ones. The new shapes were all quadrilaterals – four-sided figures – carefully adjusted to vary in geometric regularity.

Here’s where things got interesting. These quadrilaterals weren’t easy to distinguish. The researchers made only subtle changes: shifting a single corner to distort the shape’s symmetry or right angles.

Crows recognized regular shapes

The birds had never seen these quadrilateral comparisons before, and yet, when tested, they performed far above chance.

On their very first try with the quadrilateral shapes, the crows performed strikingly well. Crow 1 correctly picked the outlier in 50% of the trials, while crow 2 managed 60%. Since there were six options, random guessing would result in a success rate of just 16.7%.

What’s more, their ability didn’t depend on familiarity. The shapes were randomly rotated and scaled. The irregular shape, called the “intruder,” changed position every trial. Yet both crows maintained impressive accuracy. Their detection rate remained well above chance across 60 initial tests.

Statistical analysis confirmed the results. Performance differences also matched the degree of geometric regularity. The birds identified intruders more easily when the base shapes followed stronger geometric rules – parallel sides, right angles, equal lengths.

These effects emerged immediately. The birds showed no need for additional training or repeated exposure. The researchers tested whether results improved over time. They found slight learning effects, but the core skill was present from the beginning.

Human-like cognition, yet bird-brained

To probe deeper, the researchers compared the birds’ success with the types of quadrilaterals shown. These included squares, rhombuses, trapezoids, and more irregular shapes. Both birds performed better on the most regular shapes and struggled more as irregularity increased.

In some cases, their struggles mirrored those seen in humans. The rhombus, despite being highly regular, tripped up both the crows and people in earlier studies. This suggests a shared perceptual bias – a tendency to overlook certain features or prioritize others when judging shape.

“The evidence is actually quite convincing,” said Mathias Sablé-Meyer, a cognitive neuroscientist who worked on the earlier baboon study.

“I have to accept the result and think, you know, that’s pretty cool! And then the question is, where does that even come from?”

The answer may lie in the way animals process embedded features – nested shapes, equal angles, and structured lines. Crows, like humans, seem capable of recognizing these shape relationships, even without formal instruction or language.

Birds excel in shape recognition 

If baboons can’t do it, but crows can, what does this say about intelligence? Not all cognition follows the same evolutionary paths. Birds and primates diverged long ago, yet both have evolved complex cognitive abilities.

The crows’ success in shape recognition may stem from a broader sensitivity to visual detail. Unlike the baboons, which failed to reach consistent accuracy even after training, the crows met high performance standards across multiple sessions.

They also faced more exaggerated shape deviations – one vertex of each intruder was shifted by 75% of the average edge length, a bolder change than in the baboon experiments.

But that alone may not explain their success. Birds such as pigeons and chickens have shown sensitivity to symmetry in patterns and mate selection. Some use regularity in spatial cues for navigation. What this new study reveals is something more abstract: an ability to detect structure in shape for its own sake.

“I hope that my colleagues are looking into other species,” said Nieder. “I’m pretty sure they may find that other intelligent animals can also do this.”

The evolution of shape intuition

This study challenges the idea that geometry emerged solely with human civilization. Instead, it suggests that the roots of this ability run deeper – into the biological foundations of perception.

Carrion crows did not learn geometry in classrooms. They did not measure angles or discuss theorems. Yet they saw order in shape. They recognized what fit and what did not. That’s the very heart of geometric intuition.

By watching these birds peck at a screen, researchers have unearthed something remarkable. The way we understand space may be less of a cultural invention and more of a shared instinct – one that humans, birds, and perhaps many other creatures carry within.

The study is published in the journal Science Advances.

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