Crows are able to look at a handful of four-sided shapes and correctly distinguish those that exhibit geometric regularity from those that don't, according to a provocative new study.
It's the first time a species other than humans has been shown to have this kind of geometric intuition, says Andreas Nieder, a cognitive neurobiologist at the University of Tübingen in Germany.
"Claiming that it is specific to us humans, that only humans can detect geometric regularity, is now falsified," says Nieder. "Because we have at least the crow."
Previous research has demonstrated that regardless of age, culture, or education, humans are really good at noticing geometric regularity in shapes.
Other critters might have an inherent sense of geometry, too, says Nieder, but until now, researchers mostly haven't focused on this ability in their tests of animals' mathematical skills.
"I would never dare to say that this is the only species," he says, "it's just now opening this field of investigation."
He and his colleagues tested the abilities of two carrion crows that live in their lab. Previously, Nieder's group has shown that the crows' counting ability rivals that of toddlers.
These crows "are very tame, so they like to work with us," he says.
The birds' work involves basically playing computer games that are designed to tease out how much they know about math.
For this study, the birds would look at a computer screen and see a group of six shapes. To get a treat of tasty mealworms, they'd have to peck on the shape that was different from the others.
"Initially we presented some very obviously different figures," says Nieder. "For instance, five moons and one flower."
When the crows pecked on the flower shape, they got a snack.
After the birds understood this game, the researchers started showing them sets of shapes that included squares, parallelograms, or irregular quadrilaterals.
The crows might see, for example, five perfect squares along with one four-sided figure that was just slightly off.
What the researchers wanted to know is whether or not "with these quadrilaterals, they could still continue to find the outlier, even though the outlier was looking perceptually very similar to the other five regular shapes," explains Nieder.
Yes. It turns out, the crows could.
In the journal Science Advances, the researchers describe a series of tests showing that crows clearly had a sense of right angles, parallel lines, and symmetry.
Before these results, says Nieder, "there was no single animal that demonstrated this capability of detecting geometric regularity."
In fact, a recent study in baboons suggested this non-human primate couldn't do it.
"Baboons are so much closer to us and we trained them so much more," says Mathias Sablé-Meyer, a cognitive neuroscientist now at the University College London who worked on that study. "After failing to train the baboons to do it, I wouldn't have expected crows to do it."
He called this new research on crows "pretty impressive."
"The evidence is actually quite convincing," he says. "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?"
He says since there's been virtually no work on this aspect of mathematics in species other than humans, it's hard to know.
Nieder suspects that the geometric abilities of humans build on precursor capabilities that are more present in the animal kingdom than previously thought.
"I hope that my colleagues are looking into other species," says Nieder. "I'm pretty sure they may find that other intelligent animals can also do this."
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