Ravens are able to infer what a competitor might be able to see, even when they are unable to see the other raven themselves, finds a study in Nature Communications. This provides support to the notion that members of the crow family possess a so-called ‘Theory of Mind’ - the ability to predict the mental state of other individuals - which was once thought to be confined only to humans and non-human primates.
Previous studies testing whether birds might possess a basic Theory of Mind found that scrub-jays are able to infer that they are being watched by competitor birds who might steal their stores of hidden food. However, these studies have been unable to discount the possibility that focal individuals might be following gaze cues from competitor birds, for example by following their line of sight to the food.
Thomas Bugnyar and colleagues discount this possibility by observing individual ravens' food-hiding behaviour when they are unable to see a competitor. By placing an individual raven in a study area that is completely enclosed except for a small peephole, they simulate the possibility that the individual is being observed by playing the recorded sound of another raven on the other side of the peephole.
When the sound is played, the individual raven hides its food in a way that is consistent with the possibility of it being observed by a competitor through the peephole, and it does the same when provided with full visual access to a live bird. This strongly suggests that ravens make generalizations based on their experience, and do not merely interpret and respond to behavioural cues from other birds.