Ravens and crows are as smart as chimpanzees, study finds

Ravens and crows have long been seen as some of the most advanced creatures in the animal kingdom, but it seems we may have underestimated them a little—as a new study has found that these birds are equally as intelligent as chimpanzees.

“Absolute brain size is not the whole story. We found that corvid birds performed as well as great apes, despite having much smaller brains,” said Can Kabadayi, doctoral student, in a statement.

The study was issued in response to a previous one from 2014, in which Duke researchers found that across 36 different species (mostly primates), larger brain size meant greater intelligence—with great apes being the most intelligent. However, the authors noted in the paper that the dominance of primates as study subjects might mean that one might not be able to generalize their findings across all animal groups.

Filling in the gaps

The authors of the new paper quickly noticed that no birds from the genus Corvus—as in, ravens and crows—were included in the study. They believed that including such animals might indeed show that a bigger brain does not mean more cleverness.

“Corvids have one of the largest relative brain sizes among birds, while ravens have the largest absolute brain size among corvids: roughly three times that of the jackdaw and twice that of the New Caledonian crow,” wrote the authors in the paper published in Royal Society Open Science. “Corvids have often been likened to the great apes in terms of complex cognition involved in physical, social and memory skills as well as self-control tasks.”

Intelligence is a tricky trait to test (even in humans), but one good indirect measure of it involves something known as inhibitory control—or, the ability to override certain impulses in lieu of performing a more rational behavior.

How did they test for intelligence?

The 2014 Duke study examined various animals’ inhibitory control using a cylinder test. First, they trained animals to take food out of a hollow, opaque cylinder with openings on both ends. Then, they presented the animals with the same cylinder, now transparent, with food in the middle.

The impulse for most creatures would be to reach directly for the food, ignoring the cylinder and their previous training. Thus, inhibitory control—and therefore, intelligence—would be shown by an animal ignoring this impulse and instead reaching for the food using one of the tube’s ends. And in this case, the Great Apes succeeded, going for the openings instead of directly to the food every time.

The new study applied the same exact test on three types of corvids: ravens, New Caledonian crows, and jackdaws.

And, lo and behold, these birds did nearly or equally as well as great apes. The ravens in particular succeeded with flying colors, entering the tubes from the ends with every trial. The jackdaws and crows did nearly as well, with performances very close to 100 percent—similar to the results of bonobos and gorillas in the Duke study.

“This shows that bird brains are quite efficient, despite having a smaller absolute brain size. As indicated by the study, there might be other factors apart from absolute brain size that are important for intelligence, such as neuronal density,” said Kabadayi.

“There is still so much we need to understand and learn about the relationship between intelligence and brain size, as well as the structure of a bird’s brain, but this study clearly shows that bird brains are not simply birdbrains after all!”

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Image credit: Thinkstock

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