Ravens 'can imagine how others are thinking'
Ravens display a human ability to imagine how others are thinking, a study has shown.
Scientists conducted an experiment proving out of sight does not have to mean out of mind for the birds, members of the crow family and a symbol of wisdom in many cultures.
The discovery shows that what psychologists call the "Theory of Mind" - understanding that mental states may differ between individuals - is not confined to humans and apes.
In the study, ravens were taught to be aware that they could be spied on through a peep hole as they hid a cache of food.
When the peep hole was open and the recorded sound another raven played over a loudspeaker, the birds took extra care to ensure their food was placed out of sight.
They did not have to see the rival peering through the peep hole, thereby providing a visual cue. The birds seemed to be able to imagine that a potential thief could be spying on them, and planted their food away from the hole.
When the peep hole was closed they did not react the same way, despite hearing the raven sounds.
Writing in the journal Nature Communications, the scientists led by Dr Thomas Bugnyar, from the University of Vienna in Austria, said: "We show that ravens .. can generalise from their own experience using the peep hole as a pilferer and predict that audible competitors could potentially see their caches (through the peep hole).
"Consequently, we argue that they represent 'seeing' in a way that cannot be reduced to the tracking of gaze cues."
Previous studies have left open the possibility that animals only understand what others see by observing the direction of their gaze.
US co-author Dr Cameron Buckner, from the University of Houston, said the experiment shed new light on the concept of Theory of Mind.
He added: "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 ..
"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."
Ravens are similar to humans in the way their social life goes through a series of phases, said the researchers.
As adolescents their social world was "fluid" but as adults they often defended territories in stable breeding pairs.
"There is a time when who is in the pack, who's a friend, who's an enemy can change very rapidly," said Dr Buckner. "There are not many other species that demonstrate as much flexibility."