Crows Have a Human-Like Grammar Skill, Scientists Find

Yet another study spotlights how intelligent crows are.

A crow on a rock

Susan Walker / Getty Images

Crows are undeniably intelligent. From making tools to holding grudges, crows have been surprising the scientific community with their skillset. In fact, a study published in the journal Current Biology found "the crow brain is the same relative size as the chimpanzee brain."

Now, a study published in Science Advances finds crows understand a complex cognitive principle known as recursion. Prior to this study, recursion was believed to be unique to humans.

"We were interested in the ability to represent recursive structures—defined here as having elements be embedded within other similar elements," Diana Liao, the study's first author and a postdoctoral researcher at the University of Tübingen in Germany, tells Treehugger.

Liao says it was surprising to discover crows "were able to extract the underlying recursive structure of the sequences" upon first exposure. This makes the birds similar to humans, who are able to extra patterns with little experience. "Recursion is thought to be a key feature of human symbolic systems such as language or mathematics—and since these are thought to be unique to humans—there’s been intrigue in whether non-human animals can grasp and generate recursive structures," says Liao.

What exactly is recursion? Liao explains: "A classic example sentence with a center-embedded recursive structure is ‘the mouse the cat chased ran’ where the clause “the cat chased” is embedded within the clause “the mouse [who] ran”. These complex structures are found in human languages but not in animal communication systems which suggest that recursion might be what separates them."

What's the Difference Between Ravens and Crows?

If you see an all-black bird soaring overhead, it's likely a crow or a raven. Which of the two classes of corvid it belongs to, however, can feel like anyone's guess to a beginner birder. Here's a rundown of the two conspicuous, lookalike birds and how to identify one when you hear its raucous calls in your neighborhood. Read more.

The findings of this study are significant since they show recursive ability in animals that are not closely related to primates. "This suggests that this ability is either very evolutionarily ancient or that is a product of convergent evolution," says Liao. "Also, it would propose that certain brain structures—such as the layered neocortex in primates—is not necessary to support this cognitive ability since birds have a dramatically different neural architecture."

Liao says scientists know crows are smart but the extent of their intelligence is surprising. "Everyone has the impression that crows are super smart but it’s still surprising to me just how intelligent they are. They have a large brain-to-body ratio and their brains have a lot more neurons in them."

This article was written by the Treehugger editorial team and the interview with Diana Liao was conducted by Mary Jo DiLonardo.

Why This Matters to Treehugger

Wild animals large and small are often the spark that nudges someone to want to take better care of the planet. At Treehugger, we believe that sharing the fascinating curiosities of wildlife, like crows, can go a long way in inspiring people to want to live a more sustainable life.