A new study reveals how ravens seem to detect and feel when they are being watched by other birds, which points to the Theory of Mind, which is the ability to connect with mental states of others. 

Scientists from the University of Vienna discovered how ravens can interpret or identify what their competition might be able to see, even when this other bird is not within view.

In this new study, the team observed ravens hiding their food when they could sense another bird, even if they cannot see them. An individual was placed in a study area under controlled conditions, where it is enclosed with nothing more than a small peephole. The team manipulated the situation by playing a recorded sound of another raven, from the other side of the peephole leading for the enclosed raven to think of a competitor nearby.

Upon playing the recording, the raven immediately hid its food in a manner suggesting that it was wary of the possibility that another raven is spying through the peephole. Within full view of another bird, the raven did the same as well however, it did not show the same urgency when the peephole was closed, even when the sound is playing.

Theory of Mind involves the ability to understand about how other humans think, since we have the same minds. Further research into this theory involves other primates such as chimpanzees, those that are similar to humans however, chimps often rely on their ability to see the other animal with "gaze clues".

This suggests that other animals cannot necessarily think abstractly, since they rely on visual cues rather than thinking about understanding what the other animal might see.

During this raven study, the test subjects were relying on the idea that its competitor might look through the peephole, and discover where the food is hidden, even if they cannot see the other raven. 

Researchers say that this way of "seeing" without "gaze clues" can represent how ravens can generalize and learn from their own experience using peepholes and even predict the possibility of stealing their food, when they hear their competitors.

The team says that further research is needed to identify the process and limitations of ravens and other animals, as this new study can provide strong evidence against the hypothesis that social cognition of animals are limited to reading behavior via gaze clues.

This new study is published in the journal Nature.