Animals

Apes Can Follow Video Plots

The ability to track the thoughts and actions of others evolved in our primate past -- possibly as a wily way to score more sex.

<p>Photo: Chimpanzee "Lome" who participated in the study. Credit: MPI-EVA</p>

It turns out if you dress an actor in a gorilla suit and put him in a video, real-life apes take notice. Not only that, they follow the plot closely enough to anticipate the thoughts and actions of the video's characters.

Before, it was thought that only humans were capable of such guesswork. We can think about others' thoughts and emotions, such as their goals, perceptions and beliefs. According to new research, published in Science, some other primates do this too, even while watching videos starring actors dressed in shaggy King Kong suits.

This means that the ability to read others' perceptions likely evolved in our primate past -- possibly as a wily way to score more sexual partners.

Photo: Orangutan "Dokana" who participated in the study. Credit: MPI-EVA

Apes "seem to understand the story of videos," Fumihiro Kano of Kyoto University said, comparing the furry primates' ability with that of children. Kano jointly led the study with Christopher Krupenye of Duke University.

"Apes have never confused the videos with real events," Kano said. "They all seem to know that the video events are fake. They were never scared with the events in the monitor."

Photo: Chimpanzee "Kara" who participated in the study. Credit: MPI-EVA

The new research was inspired, in part, by prior studies on kids. Researchers were curious to know when children could pass what's known as the "false belief test." The traditional version of the test involved showing the kid a named character. (Let's say she's called "Sally.") Sally would be seen hiding an item and then leaving a room. Another character would appear and would quickly re-hide the item in a different place.

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The children would then be asked a question like: "Where will Sally look for the item when she returns?" Very young kids tend to pick the spot where they themselves know the item is, but children starting at about age four understand that Sally does not know what they know. They anticipate that she will look in the wrong spot based on her "false belief" of where the item is.

We take such perceptiveness for granted, but it takes sophisticated brain power.

For the new study, Kano, Krupenye and their team created videotaped dramas with variations on the "Sally" plot for chimpanzees, bonobos and orangutans. The actor in the King Kong outfit played a sneaky character who came in and moved an object while the "human" in the drama was either present or absent.

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Eye-tracking revealed that 17 out of 22 apes correctly anticipated that the human would go to the incorrect location to search for the object when this person did not see "King Kong" hide it in a new spot. They essentially read the human actor's mind.

This skill, known as "theory of mind," refers to the fact that we can theorize about what others are thinking and what they might do next. The false belief detection skill takes this ability to a whole new level.

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Krupenye explained, "There will always be some changes in the environment that we do not witness, for example, leading us to have a false belief. Most animals probably have true and false beliefs themselves; however, the ability to understand others' false beliefs is much more restricted. Until now, there was no evidence that this skill might be shared with any nonhuman animals."

Scientists who conducted the more traditional "Sally" test on kids in the past thought that language was key to the ability, since the study involved verbally asking the children questions. More recent studies on children using eye-tracking, as for the apes, find that some 1.5–2-year-olds can pass the test.

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This all means that the ability to understand the thoughts of others, even when those thoughts include false beliefs, evolved way back in our primate past.

Krupenye said the skills might have developed "in response to the demands of living in complex social groups." He explained since males competed with others in their group for access to females, evolution likely favored the males who could outwit their competitors. In this way, the genes for social intelligence were passed on to the next generation.

"Theory of mind," he added, "allows individuals to interpret, predict, and even manipulate others' behavior."

Photo: Bonobo "Jasongo" who participated in the new study on apes. Credit: MPI-EVA

The realization that language isn't required to test the important skill, as presented in the new paper, represents a breakthrough.

Frans de Waal, a professor and director of the Living Links Center at Emory University, is one of the world's leading primatologists. He said the new research "moves us away from language dependency, which hampers research on ASD (Autism Spectrum Disorder) children as well as on apes and other animals. As a result, we don't know if theory of mind deficits are due to the story line or the questions or actual body reading capacities."

The study also suggests that other animals may have the ability to grasp what others know, even when it differs from their own knowledge. Krupenye said it is possible that birds in the crow and jay family, elephants, dolphins, porpoises and whales could all have the skill, since they are known for their complex social groups and sophisticated thinking.

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