These Weird Videos Could Prove That Apes Have "Theory Of Mind"

Two common chimpanzees

Apes have much more complex cognative skills than many give them credit for. apple2499/Shutterstock

The ability to know what someone else is thinking, and understand that those beliefs might be wrong, requires great cognitive skills. It has generally been thought that only humans actually had this ability, but now new research shows for the first time that apes are also capable of this, backing up what many suspected to be true in the first place.

It has previously been shown that apes can understand what others are thinking based on what they’ve seen and heard, but never has it been shown before that they know what another is thinking even if those thoughts are wrong. This, it is claimed, requires the ape to understand to a certain degree that not everything inside our heads is real.


“It means understanding that there exists a mental world distinct from the physical world,” explains Michael Tomasello, co-author of the study published in Science.

To test this, the researchers showed two videos to three species of apes: chimpanzees, bonobos, and orangutans. These videos were specifically created to not only test whether or not the apes were able to anticipate whether the humans featured in the videos held false beliefs, but also to hold the primates' attention.

In the first, a man in a gorilla suit attacks a human who is holding a stick. The gorilla-man then hides in one of two haystacks in full view of the human, before the human disappears through a door. At this point, in some of the videos the gorilla switches haystacks, or runs off completely before the human returns and then hits the haystack where he believes the gorilla is hidden.

To judge where the apes thought the human thinks the gorilla is hidden, the researchers used eye tracking technology. They found that the primates would look first and longest at the haystack the human thought the gorilla was hiding in, even though the apes themselves would know that it wasn’t actually there.


These results mirror those when two-year-old children do the experiment. “This is the first time that any nonhuman animals have passed a version of the false belief test,” says Christopher Krupenye.

The second video was based on a similar concept, but this time the gorilla was instead hiding a stone under one of two boxes in front of the human, before either switching them or removing it entirely when the person was out of view.

Again, the results showed the apes staring first and longest at the box that they thought the human believed the rock to be under. According to the researchers, though, one of the most difficult aspects of the experiment was not figuring out how to know what the apes were thinking, but in making a video that they actually wanted to watch.

Many have thought that apes must be capable of this anyway, but they had never passed the test until now. This reinforces once again that humans are perhaps not as unique as we often like to think.


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