Ravens have paranoid, abstract thoughts about other minds
Cementing their status as the most terrifying of all the birds, a new study has found that ravens are able to imagine being spied upon -- a level of abstraction that was previously thought to be unique to humans.
The study, published in Nature Communications, found that if a nearby peephole was open, ravens guarded pockets of food against discovery in response to the sound of other birds -- even if they didn't see another bird. This was not replicated when the peephole was closed, despite hearing the same auditory clues.
According to the study's authors, the discovery "shed[s] a new light on Theory of Mind" -- the ability to attribute mental states to others. A number of studies have found that animals are able to understand what others see -- but only when they can see the head or eyes, which provide gaze cues. This suggests that these animals are responding only to surface cues, and are not experiencing the same abstraction as humans.
The ability to hide food is extremely important to ravens, and they behave completely differently when they feel they are being watched -- hiding food more quickly, for example, and are less likely to return to a hiding place for fear of revealing the location to a competitor.
The study replicated this behaviour. Two rooms were connected by windows and peepholes, both of which could be opened and closed.
The ravens were trained to look through the peepholes to observe human experimenters making stashes of food. Finally, both windows were covered while a single peephole remained open -- and, though no bird was present, the ravens still hid the food as if they were being watched.
"We showed that ravens can generalise from their own experience using the peephole as a pilferer, and predict that audible competitors could potentially see their caches through the peephole," the authors wrote. "Consequently, we argue that they represent 'seeing' in a way that cannot be reduced to the tracking of gaze cues."
Although ravens may not seem similar to humans, the two species do have something in common -- their social lives. Like humans, ravens go through distinct social phases, from fluid interaction with other birds as adolescents to stable breeding pairs in adults. "There is a time when who is in the pack, who's a friend, who's an enemy can change very rapidly," said Cameron Buckner, lead author of the research. "There are not many other species that demonstrate as much social flexibility. "Ravens cooperate well. They can compete well. They maintain long-term, monogamous relationships. It makes them a good place to look for social cognition, because similar social pressures might have driven the evolution of similarly advanced cognitive capacities in very different species".
It's not the only thing ravens can do -- they've also been found to mimic human speech, complete complex logic puzzles and show empathy for fellow birds, which Buckner says could "change our perception of human uniqueness". "Finding that Theory of Mind is present in birds would require us to give up a popular story as to what makes humans special," he said. "Completing this evolutionary and developmental picture will bring us much closer to figuring out what's really unique about the human mind".