It's one thing to demonstrate that a bird can react to another bird's actions. If one raven sees another watching its cache of food, it's probably going to try to hide the treasures. But what happens if the raven knows another bird is in the area, but doesn't see it gazing toward the secret stash? Will the hoarding raven still act the same way?
In the weeks leading up to the experiment, the birds were allowed to use peepholes to spy on each other, so they learned that the tiny holes provided enough of a view to spot food stashes. When the experiment began, researchers played auditory cues to signal the presence of a bird in the next cage, even though the subject was actually alone. When the peephole was open, the ravens guarded their food as if they had a clear view of another bird watching them. But when they heard the same sounds from a competitor when the peephole was shut, they carried on with business as usual.
According to lead author Thomas Bugnyar, of the University of Vienna, the results could mean that the birds were relying on their own experiences as peeping thieves to imagine the possible actions of others. They knew whether or not the false raven had the ability to spy on their food, because they'd used the peepholes themselves.
“This strongly suggests that ravens make generalizations based on their experience and do not merely interpret and respond to behavioral cues from other birds,” Bugnyar told the Guardian.
The question of how non-human animal consciousness works is as much about philosophy as it is about animal behavior. If a raven is able to guess how its companion might behave based on its own experiences, is it just a really smart bird? Or is there some deeper kind of cognition happening — one that pushes the boundaries of what we expect in non-primates?
"It could change our perception of human uniqueness, that we share some of that ability not just with chimpanzees and closely related species but also with a very different species," co-author Cameron Buckner, assistant professor of philosophy at the University of Houston, said in a statement. "Finding that Theory of Mind is present in birds would require us to give up a popular story as to what makes humans special, but completing this evolutionary and developmental picture will bring us much closer to figuring out what's really unique about the human mind," he said.
There's more to these findings than just lofty philosophical quandaries, though: If ravens really do possess a level of social cognition comparable to humans and other large primates, the birds might serve as better animal models to study this kind of behavior in the lab – which could help scientists understand why some humans are better at this kind of inference than others, and why some individuals can't manage it at all.