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Gorillas may have greater self-awareness than scientists previously thought. A new study finds that gorillas perform just as well as chimpanzees in tests that require awareness of their own bodies. A research team, led by Utrecht ľ�ϸ���Ӱ�� biologist Jorg Massen, performed the study. The researchers now encourage their peers to use different types of tests to better understand self-awareness in animals.

Do animals know they exist? Chimpanzees have long been known for their high self-awareness, but now there is solid evidence for gorillas too.

A team of biologists draws this conclusion after studying chimpanzees and gorillas at Burgers’ Zoo in Arnhem. The research team included scientists from Utrecht ľ�ϸ���Ӱ��, the ľ�ϸ���Ӱ�� of Vienna, and the ľ�ϸ���Ӱ�� of Amsterdam. The findings are now published in the American Journal of Primatology.

Mirror test

To test self-awareness, scientists often use the so-called mirror test. In this test, animals get a mark on their body that they can only see when looking in a mirror. If the animal tries to touch or remove the mark on their own body, it shows they recognize themselves, which suggests self-awareness.

Not suitable for all animals

“The mirror test works well, but it’s not suitable for all animals,” says Massen. “Some animals don’t rely much on vision and may dislike looking at faces. These species might fail the mirror test even if they are self-aware.”

Massen believes gorillas may be in this category. Gorillas usually score poorly on the mirror test, perhaps because they generally avoid eye contact. They may find looking in a mirror uncomfortable, making it harder for them to recognize themselves.

Body-awareness test

To explore this further, Massen’s team tried a different experiment. In this test, chimpanzees and gorillas had to open a box lid to get food. Sometimes, the researchers placed the box on a pole, forcing the animal to sit on the lid itself. In this situation, the animals had to realize that their own body was blocking the lid.

To succeed, the animals had to understand that their own body was the obstacle. “This is a basic form of body awareness. In humans, this develops at around 1.5 years old,” says Massen.

Don’t just sit there

Surprisingly, both chimpanzees and gorillas performed equally well. “What stood out was that both species quickly realized they needed to move off the box to open it,” says Massen. “This shows they were aware of their own bodies as an obstacle. So the fact that gorillas usually perform poorly in mirror tests doesn’t mean they lack self-awareness.”

The inner world of gorillas may be richer than we previously thought

Massen and his team believe that scientists should go beyond the mirror test when studying animal self-awareness. “Thanks to this body awareness test, we now know more about the inner life of gorillas, which may be richer than we previously thought, or at least had scientific evidence for,” says Massen.

The evolution of self-awareness

Using various tests could also reveal more about how self-awareness evolved in humans and animals. Some biologists believe self-awareness developed early in the common ancestors of humans and great apes. Others suggest it may have evolved separately in different ape families. For example, scientists are still exploring whether chimpanzees and orangutans share the same kind of self-awareness.

By combining different tests, we can better understand differences in self-awareness

Massen: “It’s possible that apes have a similar type of self-awareness, but it could also be quite different. By combining different tests, we can better understand these differences.”

What is consciousness?

These findings raise questions about how we define self-awareness, says Massen. He believes the research shows that self-awareness can take different forms. “Animals we often consider ‘less intelligent’ may actually have more complex thoughts than we imagine.”