The ability to distinguish between reality and what someone else thinks is reality has long been considered a uniquely human trait.
But new research suggests that chimpanzees, bonobos and orangutans may also be able separate beliefs from reality.
A knowledge of other people’s misconceptions is key to social interaction, and is believed to be acquired in humans by the age of five.
Christopher Krupenye of Duke University, who led the study along with comparative psychologist Fumihiro Kano of Kyoto University, said: “This cognitive ability is at the heart of so many human social skills.”
Michael Tomasello, professor of psychology and neuroscience at Duke University said: “It means understanding that there exists a mental world distinct from the physical world.”
The study involved apes watching two videos. In the first, a man dressed as King King hides in a haystack while someone watches. When the man stops looking, the King Kong runs away. The man returns to try to find him in the same place he last saw him.
In the second, the man tries to retrieve a stone which he watches the King Kong place in the box, despite the fact the King Kong removed it while he wasn’t looking.
By following the apes’ gaze with an infrared eye-tracker, the researchers were able to estimate what the primates were thinking.
The apes had to predict the man will look for the object where he last saw it, even though they know it’s no longer there.
When watching both videos, the apes looked first and longest at the location where the man had last seen the object, the scientists said.
“This is the first time that any nonhuman animals have passed a version of the false belief test,” Krupenye said.
He added: “If future experiments confirm these findings, they could lead scientists to rethink how deeply apes understand each other.”
The study was published in the journal Science.
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