Crows May Grasp Basic Geometry: Study Finds the Brainy Birds Can Tell the Difference Between Shapes Scientists tested crows on their ability to recognize “geometric regularity,” a skill previously assumed to be unique to humans Carrion crows (Corvus corone) can tell the difference between geometric shapes, according to new research. Pexels Crows are arguably among the smartest creatures on the planet, possessing some cognitive abilities that rival those of 5- to 7-year-old human children. Now, a new study adds basic geometry to the list of subjects these brainy birds seem to be able to master. In a paper published in the journal Science Advances last week, researchers report that carrion crows can recognize “geometric regularity,” meaning they may discern traits like length of sides, parallel lines, right angles and symmetry. In the study, they could tell the difference between shapes like stars, crescents and squares, as well as between squares and irregular figures with four sides. Researchers once thought this ability was unique to humans. But the findings suggest that’s not true—and they hint at the possibility that other species may be capable of similar feats, too. “The crows show a sort of intuitive, strictly perceptual recognition of geometric properties,” says Giorgio Vallortigara, a neuroscientist at the University of Trento in Italy who was not involved with the work, to Scientific American’s Gayoung Lee. To test the birds’ mathematical abilities, scientists in Germany placed two male carrion crows (Corvus corone) in front of a digital screen in a laboratory. They displayed six shapes on the screen, then trained the birds to peck at the outlier—the one that looked different from all the others. Whenever the birds chose correctly, researchers rewarded them with a tasty snack, either a mealworm or a bird seed pellet. At first, the researchers made the outliers obvious—such as one flower amid five crescents, reports NPR’s Nell Greenfieldboyce. But as the birds got more comfortable with the task at hand, the team made the experiment increasingly challenging. They showed the crows similar-looking squares, parallelograms and other irregular four-sided figures. Even as the game got more difficult, the crows could still pick out the outlier. They continued correctly pecking at the outlier, even after the scientists stopped giving them treats. Researchers rewarded the birds with a tasty treat—like a mealworm—when they correctly pecked at the outlier shape on a digital screen. Schmidbauer et al. / Science Advances, 2025 Why would crows need to be able to tell shapes apart? Researchers don’t know for sure. But they suspect this ability may help them with navigation and orientation as they fly around, they write in the paper. The birds may also have developed this ability to help them forage for food or identify other individual crows—including mates—based on their facial features. “All these capabilities, at the end of the day, from a biological point of view, have evolved because they provide a survival advantage or a reproductive advantage,” study senior author Andreas Nieder, a neurophysiologist at the University of Tübingen in Germany, tells Scientific American. In the future, researchers hope to investigate which areas of the birds’ brains are helping them excel at geometry. Birds don’t have a cerebral cortex—at least, not in the same way that humans do. But for us, that part of the brain is responsible for thinking and other complex functions. Crows still have these abilities, so the researchers posit there must be something else going on inside their heads. “Obviously, evolution found two different ways of giving rise to behaviorally flexible animals,” Nieder says to Scientific American. The team also hopes future research will probe the “geometric regularity” abilities of other species. In the past, researchers have run similar experiments with baboons. But even after extensive training, the primates didn’t seem to share our mathematical understanding. Still, scientists say it’s unlikely that humans and crows are the only animals with this ability. “It’s just now opening this field of investigation,” Nieder tells NPR. Crows are the whiz kids of the animal kingdom. Past research has found that they can vocally count up to four, distinguish between human voices and faces, and grasp a pattern-forming concept thought to be unique to humans. Some species can build tools for future use, while others are likely aware of their own body size. These and other examples of animals’ intelligence are upending the long-held notion that humans are the only species capable of high-level cognitive functioning. “Humans do not have a monopoly on skills such as numerical thinking, abstraction, tool manufacture and planning ahead,” Heather Williams, a biologist at Williams College, told CNN’s Scottie Andrew last year. “No one should be surprised that crows are ‘smart.’” Get the latest stories in your inbox every weekday.