Something To Know: Only Nine Species (Besides Humans) Can recognize Themselves In A Mirror Test

How to differentiate human animals from other animals has been a scientific and ethical issue for centuries. Once upon a time the answer seemed obvious. But that has changed over time. When I was much younger humans were thought to be the only animals to use tools. No so. Now we use a “mirror test.”

close up photo of gorilla
Not surprisingly, gorillas often pass the mirror test. But not always. Photo by Pixabay on

Over the last few decades, scientists have developed a “mirror test” to determine which animals can recognize their reflection in a mirror.

This kind of self-awareness is critical to consciousness of self and is an important distinction between humans and other animals.

The mirror test is simple. The subject is provided with a mirror. When it is used to the mirror a mark is placed on the animal. The mark is in a location that can only be viewed with the mirror. If the animal shows curiosity about the mark and realizes the mark is not part of the body it passes. Moving to get a better view of the mark is an example of recognition behavior.

The subject is not without controversy. The strictest observers feel only humans and great apes pass.

But others believe at least eight creatures have “passed” the mirror test. Of course the largest number consists of close relatives but suprisingly, sea mammals and birds are also on the list.

Killer whale
Killer whales act in a manner consistent with self-recognition when shown a mirror. Killer whale by National Park Service is licensed under CC-CC0 1.0

Here are the animals:

Asian elephants (Elephas maximus). Some but not all pass and these elephants display a wide range of behaviors when marked. Researchers speculate that since elephants are more used to putting things on their body (such as mud) they may not notice or care about stickers or marks. Some clearly do.

The Great Apes, in general, bonobos (Pan paniscus) chimpanzees (Pan troglodytes) orangutans (Pongo pygmaeus) and gorillas (Gorilla gorilla and G. berengei) all can pass the test. But not all do. Sometimes it appears age related – young and old failed more often. Gorillas avoid eye contact with the mirror and may not look at it long enough.

Bottlenose dolphins (Delphinus truncatus). These dolphins show great interest in their reflection – even sticking their tongues out. They also inspect markings.

Orca whales (Orcinus orca) show behaviors similar to the dolphins.

Eurasian magpies (Pica pica). When marked with contrasting stickers they try to remove them. If the stickers are invisible they don’t. A big surprise that shook up understanding of where self-awareness arises in the brain.

Ants of different species. This is a bit of a question mark. Some ants with blue dots put on their faces appeared to groom themselves and otherwise exhibit “recognition” behavior. There are skeptics. It is thought that brain size is key to the ability to recognize self. Some ants have a brain about 15 percent of their mass. Researchers think it is “plausible” they can recognize themselves.

Fire ant worker, Solenopsis invicta
Fire ant worker, Solenopsis invicta by Insects Unlocked Project is licensed under CC-CC0 1.0 Some of the 12,000 or so ant species may be capable of self-recognition. They have large brains in proportion to their bodies .Some tests show promising results. Ants marked with blue dots shown a mirror will groom themselves and examine the dot.

But there is much work to be done: As Animal Cognition says:

“If an animal can pass the mirror test, it’s certainly strong evidence of self-recognition, and indicates the possibility of self-awareness (i.e. a “sense of self”). However, it’s not definitive proof. And if an animal isn’t able to pass, that doesn’t necessarily mean that they do not possess these abilities.

For example, animals that rely on other senses more heavily than their vision may not take much interest in the sight of their reflections. Dogs, who recognize others mainly by their sense of smell, might quickly conclude that their mirror image is not of themselves or any other animal, because it lacks a corresponding scent. Furthermore, some animals may be able to recognize themselves in the mirror and see that they have been marked, but do not find the mark important enough to warrant touching or inspection.”

Here are some links to posts we have done about human -like behavior in our relatives:

Chimps practicing medicine. How orangutans may have influenced our use of language. And chimpanzee gesture dialects.

Published by ursusrising

long time writer and editor living in Los Angeles

Leave a Reply