Chimpanzees and other great apes seem to understand the beliefs of others, suggesting that this ability is not unique to humans.

Researchers have long debated whether humans are the only primates to have a 'theory of mind' — the ability to attribute mental states such as desires and beliefs to others. To test this, Christopher Krupenye at Duke University in Durham, North Carolina, Fumihiro Kano at Kyoto University in Japan and their colleagues monitored the gaze of chimpanzees, bonobos and orang-utans as they watched short videos. Two videos showed a person watching an object being hidden, and then searching for it. A third video tested the apes' understanding of false beliefs by showing the object being moved while the person was not watching. As the person then prepared to search for the object, most apes looked in anticipation to the location where the person falsely believed the object was hidden.

The authors suggest an implicit theory of mind predates human evolution.

Science 354, 110–114 (2016)