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The Mirror Test: The Key to a Sense of Self?

When fish and ants pass the test for “a higher sense of self” — but dogs and even kids in some cultures don’t — we should ask some questions

A recent article in the Proceedings of the National Academy of Sciences provided even more evidence that some fish, in particular the tropical cleaner wrasse (Labroides dimidiatus) can recognize and respond to their own images. The fish is best known for cleaning dead skin and parasites off larger fish, without getting eaten.

But it turns out they are also remarkable for recognizing themselves in mirrors and photographs. Following up on a 2019 open access paper demonstrating that these fish have that ability, the researchers added a new wrinkle:

After the cleaner wrasse passed the mirror test, the researchers showed each fish four photographs: a photo of itself; a photo of an unfamiliar cleaner wrasse; a photo of its own face superimposed on an unfamiliar fish’s body; and a photo of an unfamiliar cleaner wrasse’s face on its body… Though cleaner wrasse typically attack other cleaner fish that stray into their territory, they didn’t attack photos of their own faces. They did, however, attack the photos that showed the faces of unfamiliar cleaner fish.

Avery Hurt, “Can Fish Recognize Themselves? These Cleaner Wrasses Passed the Mirror Test,”Discover Magazine, Aug 18, 2023

A Higher Sense of Self

The researchers are quite confident that they have shown that the fish has a sense of self:

From the Significance Statement: “Our results suggest that cleaner fish with MSR ability can recognize their own mirror image based on a mental image of their own face, rather than by comparing body movements in the mirror. This study demonstrates how animals recognize self-images.”

From the Abstract: “We demonstrate that combining mirror test experiments with photographs has enormous potential to further our understanding of the evolution of cognitive processes and private self-awareness across nonhuman animals.”

And from a media release:

“This study is the first to demonstrate that fish have an internal sense of self. Since the target animal is a fish, this finding suggests that nearly all social vertebrates also have this higher sense of self,” stated Professor Kohda.

Osaka Metropolitan University. “‘It’s me!’ Fish recognizes itself in photographs, say scientists.” ScienceDaily. ScienceDaily, 10 February 2023.

Well, wait a minute. There is also research showing that ants passed the mirror test. But dogs and cats don’t pass the test. Nor do gorillas, or anyway not reliably. Yet they are clearly social vertebrates.

It gets better. Children in some cultures, who clearly have a sense of self, don’t pass either.

Researchers found the widely accepted finding only applied to kids from Western nations, where most of the previous studies had been done. Now, a study published September 9 in The Journal of Cross-Cultural Psychology is reinforcing that idea and taking it further. Not only do non-Western kids fail to pass the mirror self-recognition test by 24 months—in some countries, they still are not succeeding at six years old.

Maggie Koerth-Baker, “Kids (and Animals) Who Fail Classic Mirror Tests May Still Have Sense of Self,” Scientific American, November 29, 2010

A lot may depend on the significance attributed to a mirror in a given culture.

No surprise, the test is controversial

At any rate, we have a test for a “higher sense of self” that ants and fish pass but kids don’t? No surprise, it’s controversial. It may be time, once again, to clarify that passing the mirror test is probably only weakly related to a sense of self.

A bit of history. Back in 1970, evolutionary psychologist George Gallup developed the test, since used on tried on a number of species (here’s a list) from 2015. But Gallup didn’t agree with colleagues that dolphins, elephants and European magpies had passed.

Cats typically don’t pass either:

Reactions of cats to being shown their reflection in a mirror vary; some will ignore the reflection, some will attempt to investigate behind the mirror to find the cat that is presumably back there, some will act wary or aggressive towards what appears to be another cat able to counteract its own gestures perfectly. This is a freaky thing, if you don’t know that it’s you in the mirror.

Dan Nosowitz, “This Cat Did Not Figure Out How Mirrors Work,”Popular Science April 10, 2013

It’s not clear whether Sox “knows” that the image in the mirror that fascinates him is himself. But it is also not clear why his sense of self would depend on that. A useful question to ask may be, how would Sox, left to himself, recognize himself? Or other cats or humans? Wouldn’t it mainly be by smell? One could say the same of a dog, of course. Would the same animal who is confused by his own reflection be as confused by his own scent?

In a world where the leading theory of human consciousness has been assailed by top neuroscientists as “pseudoscience,” it might be wise for animal behavior researchers to steer away from concepts like a “higher sense of self” and focus on behaviors that are easier to gauge and interpret.

You may also wish to read: Mirror, mirror, am I a self? Scientists ponder, how would animals show self-awareness? A controversy in animal psychology centers on whether or not an animal can recognize itself in a mirror. But a number of scientists are beginning to doubt that the mirror test shows animal self-awareness.

Denyse O'Leary

Denyse O'Leary is a freelance journalist based in Victoria, Canada. Specializing in faith and science issues, she is co-author, with neuroscientist Mario Beauregard, of The Spiritual Brain: A Neuroscientist's Case for the Existence of the Soul; and with neurosurgeon Michael Egnor of the forthcoming The Human Soul: What Neuroscience Shows Us about the Brain, the Mind, and the Difference Between the Two (Worthy, 2025). She received her degree in honors English language and literature.

The Mirror Test: The Key to a Sense of Self?