Cunning ravens can plan ahead, study shows
The ability to consciously plan for the future — from organizing a dinner party to saving for retirement — has long been thought to be uniquely human. (Whether or not we actually succeed at it is another story).
Now, new research from Sweden has found ravens can also think ahead. It's the first study to find an animal other than a human or an ape can plan for an event beyond the current moment. Aside from highlighting a cool critter trait, the discovery may help us understand how different animals can evolve to have the same brand of intelligence.
"One of [our] most interesting results is that intelligence is not restricted to human lineage," said Can Kabadayi, an evolutionary psychologist at Lund University who co-led the study published Thursday in Science. "Maybe we should be more humble in looking at ourselves and we should appreciate that there are other ways toward higher cognition."
Recent studies have found foresight in apes, and Kabadayi said many leading scientists believe the trait evolved across hominid lineages. So, he and cognitive zoologist Mathias Osvath set out to explore if corvids, the family of birds that includes ravens, had this planning ability, because they've been shown to be smart birds.
"They're the largest song birds and the largest brained corvids," Kabadayi said.
Kabadayi and Osvath modeled their research after a 2006 study that focused on monkeys and apes. To see if ravens could learn new skills and use them to solve future problems, like the apes did, the birds faced a series of experiments. Each one dipped into two skills that ravens don't typically perform in the wild: the use of tools and bartering with people.
The team turned to food as motivator, but the setup was tricky because many animals, including ravens, have adaptative behaviors like storing food. Squirrels, for example, hoard food for the winter, but this habit isn't forethought. It's a pre-programmed behavior that can start even before a squirrel experiences its first snowy season.
So, Kabadayi and Osvath not only taught the ravens to use tools to retrieve food — they also challenged the birds to think ahead. The ravens faced a simple task: drop something down a long tube and get a treat on a platform at the bottom. But the birds had to pick which tool to use from four options: three objects that couldn't complete the task and a small rock that could.
Choosing a task outside one ravens would typically face is a strength of the study, said Auguste von Bayern, who wasn't involved in the experiments but studies comparative cognition in corvids at Max-Planck-Institute for Ornithology. This eliminates the possibility that the bird's behavior is due to an instinct or pre-programmed adaptation, she told NewsHour via email.
Each test was slightly different. In the first, a bird picked a tool, but then was made to wait 15 minutes before it could access the tube. A second similar trial made the birds wait 17 hours rather than 15 minutes. These extended times tested how far the ravens could plan ahead. The ravens proved competent in both cases, successfully completing the tasks 73 percent of the time or more.
"I'm just baffled that a 15 gram brain is able to have a concept of time and the future, and able to solve such stuff," Kabadayi said.
The team also tested the ravens self-control by offering an immediate, less appealing reward — a small treat — versus the the opportunity to feast on a bigger meal later on. The bold ravens strutted past the immediate reward to select their rock or bottle cap and store it away for the delayed treat.
A third exercise trained the ravens to barter food for a bottle cap, which the birds had to chose among three other options — again using conditions that challenged their ability to wait or exhibit self-control. They scored just as high on these tests.
Von Bayern said this study "proves in a convincing manner that the birds were sensitive to the time and chose the [rock or bottle cap] for its future value."
Ethologist Valerie Dufour said this study shows the amazing anticipatory skills of corvids. But she questioned some of the experimental design. She wished that Kabadayi and Osvath had tested the longest duration (17 hours) before the smallest one (15 minutes), she said. Doing so could more precisely distinguish between whether the birds were planning long-term or merely becoming too familiar with the task.
It's surprising ravens can plan ahead on par with apes, Kabadayi said, given their common ancestors diverged 320 million years ago. This isn't the first example where drastically different animals evolved similar traits, however: The common ancestor of birds and insects is flightless, yet both can fly.
Looking ahead, Kabadayi wants to probe the underlying biology that enables this foresight, such as the bird's brain structure, to see what else they might share with apes.