22-05-2025
Forget compass, crows can spot geometric flaws without Math tools: Latest study
A crow doesn't need a compass or a protractor to know when something looks off. That's the latest revelation from a study in Science Advances, which shows that carrion crows can spot geometric regularity- symmetry, parallel lines, and right angles. Two birds, no math class, and yet they could tell when a shape wasn't spot on.
We humans have long considered geometric intuition our exclusive domain. The ability to recognise when shapes follow orderly principles and to instinctively grasp concepts like symmetry and perpendicularity has been described as a unique human talent. Geometry is a way of thinking found across cultures, even in people with no formal education. This basic sense of shape regularity underpins centuries of human thought, from Euclid's Elements to modern design.
But that story may need a rewrite, or at least a footnote.
Researchers at the University of Tübingen in Germany trained two crows to play a visual game on a touchscreen. Six shapes would appear, and the task was to peck the one that didn't belong. At first, the differences were obvious --- five identical shapes and one distinctly different one. Then came the real test --- sets of four-sided shapes that looked almost identical. Squares, parallelograms, trapezoids, and versions with just one angle or edge slightly off.
Despite having never encountered this type of geometric challenge before, the crows performed well. They didn't just identify the intruder; they showed a pattern of performance that closely mirrors how humans perceive shapes.
The birds were most accurate when the base shapes were regular. Their accuracy dropped as the regularity declined, suggesting their sensitivity to symmetry and parallelism matches our own. Even their mistakes resembled ours. Like many human subjects, the crows struggled most with the rhombus, a shape that often slips past our intuitive sense of irregularity.
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What makes this finding especially striking is that other species have failed at similar tasks. Baboons, despite being far more closely related to us, couldn't learn to detect these geometric differences, even after extensive training. Yet crows, whose lineage diverged from ours more than 300 million years ago, succeeded spontaneously.
Crows have been surprising people for years. They belong to a remarkably intelligent bird family, the corvids, known for solving problems that stump other animals. Crows craft tools, solve multistep puzzles, remember human faces for years, and even grasp the concept of zero. In one well-known experiment, a New Caledonian crow bent a straight wire into a hook to retrieve food from a narrow tube --- a task that requires abstract reasoning and defeats many young children.
The crows in this study were familiar with visual tasks and interacted with a touchscreen to earn treats. But this experiment tested their understanding of shape regularity, something far more abstract. To rule out chance, the researchers rotated and resized the shapes, randomized their positions, and analysed dozens of trials per bird. The crows still got it right.
Birds navigate complex environments, build nests with structural precision, and use spatial memory to cache thousands of food items. A natural grasp of shape, angle, and spatial relationships would be useful. What we consider abstract mathematics might, for them, be a survival skill.
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The researchers don't claim that crows are unique- only that they're the first non-human animals shown to have this ability. Their findings open the door to testing other intelligent species such as parrots, dolphins, and elephants that might also possess this form of visual reasoning.
If birds and humans both show this ability, despite their vast evolutionary distance, then perhaps geometric intuition isn't a human invention. It may be older, more deeply rooted, and not limited to humans and crows.
Anirban Mahapatra is a scientist and author, most recently of When The Drugs Don't Work: The Hidden Pandemic That Could End Medicine. The views expressed are personal.
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