Corvids, the family of birds that includes crows and ravens, give a whole new meaning to the term "bird brain."
They show the same level of self-regulation when faced with potential rewards as chimps do, according to a study published last week in the journal Royal Society Open Science -- suggesting that these birds may be just as clever as chimps, despite having smaller brains.
Scientists have long known that brain size alone is not a measure of intelligence, and the international team of researchers behind this new study argues that intelligence may be related to the brain's structure and how many neurons it has.
"Absolute brain size is not the whole story," Can Kabadayi, a doctoral student in cognitive science at Lund University in Sweden and lead author of the study, says in a video (above) that the university released on Tuesday.
The researchers conducted the common "cylinder test" -- which has been used previously to test the intelligence of various primate species -- with five common ravens, 10 Eurasian jackdaws and 10 New Caledonian crows.
The experiment involved placing food in a clear tube and measuring birds' intelligence by looking at whether they gave in to the impulse to retrieve it as soon as they saw it or reached around the side of the tube to access the treat.
The researchers first trained the birds to obtain a treat from an opaque tube, then repeated the test with a transparent tube.
All of the ravens in the study took the food from the ends of the tube in every try. New Caledonian crows did so 97 percent of the time and jackdaws did so in 92 percent of the tests.
"Our study documented that the corvid species performed similarly to the great apes in the cylinder task," Kabadayi told The Huffington Post.
"This research is important to understand the fundamental mechanisms underlying complex cognition," he added. "Such comparative data can give us insights about the building blocks of higher cognition as well as the relationship between various brain measures and the cognitive performance. One fascinating question is how similar cognition can be achieved in such vastly different species such as ravens and chimpanzees."
Corvids share similar fundamental cognitive mechanisms with great apes, the researchers concluded.
These highly intelligent birds are also known for such evolved behaviors as using tools, forming social groups and recognizing faces. Some corvids have been known to hide food in up to 200 locations and remember them all.
However, other scientists not involved in the new study warn against oversimplifying these latest findings.
"I think this research is a significant finding in our ongoing understanding of bird cognition and the differences in brain structure and function between birds and mammals. But, I wouldn’t take it too far," said Dr. Kevin McGowan from the Cornell Lab of Ornithology, who has been studying corvids for nearly 40 years.
"To me the most important finding is that Corvus are able to do ape-level cognitive tasks, despite having smaller brains -- and no hands! -- even as we make the ape-tasks more and more precise," he said. "That, however, is not surprising to non-primate researchers."
Kabadayi said in a statement that more research is needed to better understand the relationship between cognitive abilities and the structure of a bird’s brain, and McGowan agrees.
"Corvid intelligence is an interesting field of study because we are finding exciting results that help us see the world as it is, not what we thought it was, or how we expected it to be," McGowan said.