These fish can recognize themselves in pictures, hinting at self-awareness

Some fish can recognize their own faces in pictures and mirrors, a skill usually given to humans and other animals that are particularly brainy, such as chimpanzees, scientists report. The ability to find it in fish suggests that self-awareness is far more widespread among animals than scientists once thought.

“It is widely believed that animals with larger brains are more intelligent than animals with smaller brains,” such as fish, says animal sociologist Masanori Kohda of Osaka Metropolitan University in Japan. Maybe it’s time to rethink that undertaking, Kohda says.

Kohda’s previous research has shown that bluestreak herb cleaners can pass the mirror test, a controversial cognitive assessment that purportedly shows self-awareness, or the ability to be the object of one’s own thinking. The experiment involves exposing the animal to a mirror and then surreptitiously placing a mark on the animal’s face or body to see if they notice it in their thoughts and try to touch it with their body. Previously, only a few large species, including chimpanzees and other great apes, dolphins, elephants and picas, had attempted it.

In a new study, cleaner fish that passed the mirror test were then able to still distinguish their own faces from other cleaner fish in photographs. This suggests that fish recognize themselves in the same way humans are supposed to – by forming a mental image of a face, Kohda and colleagues report on February 6. Journal of the Academy of Sciences.

“I think it’s really amazing that we can do this,” says primatologist Frans de Waal of Emory University in Atlanta, who was not involved in the research. “I think it’s an incredible effort.”

De Waal is quick to point out that the lack of mirror evidence should not be considered evidence of a lack of self-awareness. However, scientists wonder why some species known to have cognitive abilities, such as monkeys and crows, did not cross over. The researchers also asked if the test would be suitable for species like dogs that rely more on smell, or like pigs that don’t care enough about a body mark to try to touch it.

The mixed results in other animals make it all the more remarkable that small fish can pass. In the first mirror experiment of the study, published in 2019 and 2022, Kohda’s team detected wild cleaner fish in each of the eight mirror tanks. The researchers then injected a brown dye under the fish’s throat scales, marking a similar parasite that these fish eat from the skin of larger fish in the wild. When the marked fish saw themselves in the mirror, they began to hit their throats on the rocks or sand at the bottom of the tank, apparently scraping the marks.

In the new study, 10 fish that passed through a mirror shell were then shown a photograph of their own face and a photograph of the face of an unfamiliar, cleaner fish. All the fish acted aggressively towards the unfamiliar photo as if it were a stranger, but they were not aggressive towards the photo of their own face.

When eight other fish that had spent a week with the mirror but had not previously been tagged were shown a photograph of their own face with a brown mark on their throat, six of them began to scratch their throats as the fish passed the mirror shell. . But he didn’t shave when he was shown a photo of another familiar fish.

Animals that recognize their reflection in a mirror most likely first learn to recognize themselves by seeing the animal’s movement in the mirror match their own, researchers think. Because even the cleaner fish could still recognize their own faces in their images, they, and possibly other animals that have passed through the mirror of experience, can recognize themselves by developing a mental image of their own face, so that they can compare it to what they are. in the mirror or images, say the authors.

“I think it’s a big next step,” says comparative cognitive psychologist Jennifer Vonk of Oakland University in Rochester, Mich., who was not involved in the study. But he would like to see more research before concluding what is represented in the mind of a nonverbal being like a fish. “As in most other studies, it still leaves room for further follow-up.”

Kohda’s lab planned to continue more experiments to explore what was going on in the brain of the cleaner fish, and to test a new method of photographic recognition on another popular research fish, the three-striped fish.Gasterosteus spiny).

Jonathan Balcombe, author of the book What does Pisces know?he is now convinced, describing the new study as “robust and quite brilliant”. It shouldn’t be surprising that humans are aware of fish given that they’ve already been shown to have complex behaviors including resource use, planning and collaboration, Balcombe says. “It’s time we stopped thinking of fish as somehow inferior to the vertebrate pantheon.”