According to a new study published in the journal Science, three different species of great apes — chimpanzee, bonobo, and orangutan — are able to anticipate that others may have mistaken beliefs about a situation.
Humans aren’t the only ones who can tell when someone’s beliefs don’t match reality. Image credit: Jochemy.
The capacity to tell when others hold mistaken beliefs is seen as a key milestone in human cognitive development.
Humans develop this awareness in early childhood, usually before the age of five. It marks the beginning of a child’s ability to fully comprehend the thoughts and emotions of others – a phenomenon called ‘theory of mind.’
An inability to infer what others are thinking or feeling is considered an early sign of autism.
“This cognitive ability is at the heart of so many human social skills,” said study lead co-author Dr. Christopher Krupenye of Duke University.
To some extent apes can read minds too. Over the years, studies have shown that they are remarkably skilled at understanding what others want, what others might know based on what they can see and hear, and other mental states. But when it comes to understanding what someone else is thinking even when those thoughts are false, apes have consistently failed the test.
“Although great apes share with humans many social-cognitive skills, they have repeatedly failed experimental tests of such false-belief understanding,” Dr. Krupenye and co-authors explained.
“We use an anticipatory looking test — originally developed for human infants — to show that three species of great apes reliably look in anticipation of an agent acting on a location where he falsely believes an object to be, even though the apes themselves know that the object is no longer there.”
The researchers studied chimpanzees, bonobos, and orangutans as they watched short videos on a monitor, tracking their gazes noninvasively using an infrared eye-tracker.
The apes observed as a human witnessed the hiding of an object in one location. Next, the object was moved by an actor in a King Kong suit to a second location while the person was either present or absent.
In both conditions, the object was then completely removed before the person returned to search for it.
In the scenario where the human did not observe the relocation of the object, eye-tracking data reveals that 17 out of 22 apes correctly anticipated that the human would go to the incorrect location to search for the object.
The apes’ correct anticipation of where the human expected the object to be suggests that they understand that person’s perspective.
“This is the first time that any nonhuman animals have passed a version of the false belief test,” Dr. Krupenye said.
The team’s findings suggest the ability is not unique to humans, but has existed in the primate family tree for at least 13 to 18 million years, since the last common ancestors of chimpanzees, bonobos, orangutans and humans.
Dr. Krupenye said: “if future experiments confirm these findings, they could lead scientists to rethink how deeply apes understand each other.”
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Christopher Krupenye et al. 2016. Great apes anticipate that other individuals will act according to false beliefs. Science 354 (6308): 110-114; doi: 10.1126/science.aaf8110
