Cleaner Wrasse, a Species of Fish Able to Recognize Themselves

New Study Reveals This Species of Fish Can Recognize Themselves in Mirrors, Photos

In the animal kingdom, self-awareness is an exceedingly rare characteristic, long thought to be reserved for humans, primates, elephants, dolphins, and a select few others. A new study, however, revealed that certain species of fish can recognize themselves in photos and mirrors, suggesting that self-awareness might be a trait more common among animals than scientists once thought.

Researchers from Osaka Metropolitan University in Japan and the University of Neuchâtel in Switzerland specifically studied the bluestreak cleaner wrasse, a type of cleaner fish, publishing their findings in Proceedings of the National Academy of Sciences.

Their findings revealed that the tiny cleaner fish can pass the mirror test, demonstrating that they recognize themselves in photographs. In the study, however, the group maintained that self-recognition doesn’t necessarily equate to self-awareness. “Implications for self-awareness remain uncertain and controversial,” they wrote.

How Scientists Discovered Fish Could Recognize Themselves

To carry out the experiment, researchers first placed a mirror in a fish tank, giving the fish enough time to acclimate to their own reflection. They then removed the mirror and moved on to photos, first showing fish pictures of themselves and then those of other fish.

Interestingly, the fish gathered for the study only showed aggression toward the photos of other fish, never toward their own photos.

These findings indicate that fish may identify themselves the same way humans do, through a mental image of their own face. “I think it’s truly remarkable that they can do this,” Frans de Waal, a primatologist not involved in the study, told Science News. “I think it’s an incredible study.”

As De Waal pointed out, however, just as fish recognizing themselves doesn’t automatically mean they’re self-aware, the opposite is also true. Failing the mirror test shouldn’t stand as clear-cut evidence of a lack of self-awareness.

Monkeys and ravens, for example, animals known to have complex cognitive abilities, don’t always pass. Additionally, scientists must take species into account. A dog might not pass the test, not because they don’t recognize themselves but because they rely on scent over sight.

Mirror Test Provides Hope for Greater Understand of Animals

If anything, though, these mixed results only make the little fish that much more impressive. It goes against much of what we assume about the animal kingdom.

“It is believed widely that the animals that have larger brains will be more intelligent than animals of the small brain,” such as fish, animal sociologist Masanori Kohda explained. Until now, only a few large-brained species have passed the mirror test, such as apes, dolphins, and elephants.

Researchers believe that animals learn to recognize their reflection by observing that the animal in the mirror matches their own movements. The cleaner fish, however, recognized themselves in still images, suggesting that they do, in fact, store mental images.

The studies into this phenomenon are far from complete. But scientists hope that the mirror test provides a first step to understanding nonverbal beings like fish.