Apes may very well have the ability to guess what others are thinking – an ability that was limited to humans up until now.
Researchers at Duke University in Durham, US, said that through their findings they have been able to unearth evidence that point to this ability of the apes wherein they can correctly anticipate that humans will look for a hidden item in a specific location, even if the apes know that item is no longer there.
Researchers say their findings, published in journal Science, indicate towards apes’ ability to grasp what others know even when it differs from their own knowledge, demonstrate that nonhuman primates can recognise others’ beliefs, desires, and intentions — a phenomenon called “theory of mind” (ToM). This is the first ever time that nonhumans have been able to pass a version of the false belief test, researchers say.
Researchers made apes watch two short videos in the study. In the first video, a person in a King Kong suit hides himself in one of two large haystacks while a man watches. Then the man disappears through a door, and while no one is looking the King Kong runs away. In the final scene, the man reappears and tries to find King Kong. The second video is similar, except that the man returns to the scene to retrieve a stone he saw King Kong hide in one of two boxes. But King Kong has stolen it behind the man’s back and made a getaway.
The researchers teased out what the apes were thinking while they watched the movies by following their gaze with an infrared eye-tracker installed outside their enclosures. To pass the test, the apes must predict that when the man returns, he will mistakenly look for the object where he last saw it, even though they themselves know it is no longer there. In both cases, the apes stared first and longest at the location where the man last saw the object, suggesting they expected him to believe it was still hidden in that spot.
Their results mirror those from similar experiments with human infants under the age of two. The apes’ correct anticipation of where the human expected the object to be suggests that they understand that person’s perspective.
Humans have the ability to tell when others are holding mistaken beliefs and this is something that has been pegged as a key milestone in our cognitive development. This particular ability has helped humans to get along with other people and have enabled them to fairly predict what other might do. While it was believed that the ability is one of the advanced abilities of cognition and limited to humans only, it is not so and researchers suggest that it has been existing in the primate family tree for at least 13 to 18 million years since the last common ancestors of chimpanzees, bonobos, orangutans and humans.
Researchers intend to carry out future studies wherein they want to concretely establish this abilities and if it does happen, scientists will have to rethink how deeply apes understand each other.