Apes understand that some things are all in your head

October 6, 2016
Image: Wikipedia.

We all know that the way someone sees the world, and the way it really is, aren't always the same. This ability to recognize that someone's beliefs may differ from reality has long been seen as unique to humans.

But new research on chimpanzees, bonobos and orangutans suggests our primate relatives may also be able to tell when something is just in your head.

The study, led by researchers at Duke University, Kyoto University and the Max Planck Institute for Evolutionary Anthropology, is scheduled to appear Oct. 7 in the journal Science.

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 young child's ability to fully comprehend the thoughts and emotions of others—what psychologists call theory of mind.

Such skills are essential for getting along with other people and predicting what they might do. They also underlie our ability to trick people into believing something that isn't true. 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 Christopher Krupenye of Duke, who led the study along with comparative psychologist Fumihiro Kano of Kyoto University.

To some extent 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 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.

Understanding that beliefs may be false requires grasping, on some level, that not all things inside our heads are real, 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 one, 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.

"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.

"This is the first time that any nonhuman animals have passed a version of the false belief test," Krupenye said.

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.

"If future experiments confirm these findings, they could lead scientists to rethink how deeply apes understand each other," Krupenye said.

Explore further: Apes know a good thriller when they see one

More information: "Great Apes Anticipate That Other Individuals Will Act According to False Beliefs," Christopher Krupenye, Fumihiro Kano, Satoshi Hirata, Josep Call and Michael Tomasello. Science, Oct. 7, 2016. science.sciencemag.org/cgi/doi … 1126/science.aaf8110

Related Stories

Apes know a good thriller when they see one

September 17, 2015

Remember the scene in the classic movie Alien, when that creepiest of creatures bursts out of John Hurt's belly as he writhes in pain? Well, according to a study reported in the Cell Press journal Current Biology on September ...

Great apes communicate cooperatively

May 24, 2016

Human language is a fundamentally cooperative enterprise, embodying fast-paced interactions. It has been suggested that it evolved as part of a larger adaptation of humans' unique forms of cooperation. In a cross-species ...

Scientists complete Bonobo genome

June 13, 2012

In a project led by the Max Planck Institute for Evolutionary Anthropology in Leipzig, an international team of scientists has completed the sequencing and analysis of the genome of the last great ape, the bonobo. Bonobos, ...

Great apes know they could be wrong

March 24, 2010

orangutans, chimpanzees, bonobos and gorillas - realize that they can be wrong when making choices, according to Dr. Josep Call from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Dr. Call's study ...

Recommended for you

Tasmanian tiger doomed long before humans came along

December 12, 2017

The Tasmanian tiger was doomed long before humans began hunting the enigmatic marsupial, scientists said Tuesday, with DNA sequencing showing it was in poor genetic health for thousands of years before its extinction.

Typhoid fever toxin has a sweet tooth

December 11, 2017

Although the insidious bacterium Salmonella typhi has been around for centuries, very little is actually known about its molecular mechanisms. A new study from researchers at the College of Veterinary Medicine addresses this ...

4 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

ddaye
5 / 5 (1) Oct 06, 2016
These kinds of stories drive me crazy.
"This cognitive ability is at the heart of so many human social skills."
No doubt. But how is this not also true for all social animals? Just think of the tasks a social animal must do. How could any social animal pack, at least those that hunt cooperatively, possibly function without individuals' knowing and seeking to know the minds of others in the group? The simplest explanation seems to me to be that social animals are necessarily interested in and aware of others' minds. I'd think the burden would be on devising explanations for group behavior based on members' ignorance of each other.
xponen
not rated yet Oct 07, 2016
@ddaye
your point make sense and most likely correct, but you miss the larger picture of these seemingly "oh, of course primate is smart" experiment(s). When you compare the mental capabilities of several primates, eg: bonobo & chimpanzee (as in this experiment), you can use our understanding of primate evolution to deduce the timeframe for the beginning of such human mental trait. Based on this experiment, we can conclude that the "theory of mind" begin at least 18million years ago.

In general, experiment like these provide insight into our intelligence, and it is useful for testing hypothesis.

What still a mystery is the evolution of our mind. How can we deduce from cave painting and psychology of our closest relative; the primates, how our mind evolve?
optical
Oct 09, 2016
This comment has been removed by a moderator.
optical
Oct 09, 2016
This comment has been removed by a moderator.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.