Dec. 10 (UPI) -- The cognitive capabilities of four-month-old ravens are on par with those of full-grown apes, according to a new study published Thursday in the journal Scientific Reports.
Researchers subjected different-aged ravens to a series of experimental tasks to test the birds' spatial memory, communication abilities and learning capacity.
They also tested the ravens' ability to understand relative numbers and addition, as well as their ability to grasp object permanence -- the understanding that an object still exists when it is out of sight.
"For instance, to investigate whether ravens know where food is located, we hid treats under a cup, and moved it quickly back and forth among other cups that were empty, just as one does in the 'shell game,'" study co-author Miriam Sima said in a news release.
"A raven selected a cup by pecking or pointing at it with its beak, while a chimpanzee would have done this with their fingers," said Sima, researcher with the Max Planck Institute for Ornithology in Germany.
Testing revealed all eight hand-raised ravens, ages 4, 8, 12 and 16 months, to be of similar intelligence, suggesting the species' cognitive capabilities develop at a rather rapid pace.
It makes sense that ravens reach cognitive maturity by four months. Around the same time, the birds tend to first exert their independence and begin exploring their surroundings.
The ravens showed individual differences in their cognitive capabilities, but overall, the eight birds were best at addition and understanding relative numbers, and less adept at spatial memory.
When the authors of the new study compared the performance of the ravens with those of 106 chimpanzees and 32 orangutans, they found the birds -- with the exception of spatial memory -- were just as cognitively capable as the apes.
Authors of the new study suggest the tests show the intelligence of ravens isn't specific to their domain. Their cognitive skills, scientists contend, are exemplary of an impressive general intelligence.
"Our results suggest that ravens are not only social intellects but have also developed sophisticated cognitive skills for dealing with the physical world," researchers wrote.
In followup studies, researchers hope to design tests that reveal the more species-specific cognitive skills.