Animal Intelligence
New research has demonstrated that multiple species of apes appear to understand that individuals have different perceptions about the world. This work overturns the human-only paradigm of the theory of mind, and once again shows that perhaps we are not the only intelligent animals on this planet.
New research on chimpanzees, bonobos and orangutans suggests our primate relatives may also be able to tell when that someone’s beliefs may differ from reality. They also have been found to use this knowledge in their choice of actions.
The 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.
The study, led by researchers at Duke University, Kyoto University, the University of St. Andrews and the Max Planck Institute for Evolutionary Anthropology, has been published in the journal Science.
As humans, we tend to believe that our cognitive skills are unique, not only in degree, but also in kind. Research like this shows that the more closely we look at other species, the clearer it becomes that the difference is one of degree. The researchers examined three different species of apes, finding they were able to anticipate that others may have mistaken beliefs about a situation.
The capacity to tell when others hold mistaken beliefs is seen as a key milestone in human cognitive development. We develop this awareness in early childhood, usually by the age of five. This step marks the beginning of a young child’s ability to fully comprehend the thoughts and emotions of others—what psychologists call theory of mind.
These skills are essential for getting along with other people and predicting what they might do. They also are the foundation our ability to trick people into believing something that isn’t true. Moreover, the 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."
“This cognitive ability is at the heart of so many human social skills,” said Christopher Krupenye of Duke, who led the study along with comparative psychologist Fumihiro Kano of Kyoto University. Related articles
To some extent apes can read minds too. Over the years, studies have shown that apes are remarkably skilled at understanding what others want, what others might know based on what they can see, 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. Understanding that beliefs may be false requires grasping, on some level, that not all things inside our heads correspond to reality, explained study co-author Michael Tomasello, professor of psychology and neuroscience at Duke and director at the Max Planck Institute for Evolutionary Anthropology. “It means understanding that there exists a mental world distinct from the physical world,” Tomasello said.
In the study, the apes watched two short videos. In the first, 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 since 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.
“We offer them a little day at the movies,” said Krupenye, now a postdoctoral researcher at the Max Planck Institute for Evolutionary Anthropology in Germany. “They really seem to enjoy it.”
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, and suggest apes have taken a key first step toward fully understanding the thoughts of others.
“This is the first time that any nonhuman animals have passed a version of the false belief test,” Krupenye said. “If future experiments confirm these findings, they could lead scientists to rethink how deeply apes understand each other.”
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