Science

The fish that manages to recognize itself in the mirror

Five years ago now, in a fish tank in Osaka, a small fish called number 1 looked in the mirror. He didn’t look at it, he looked at himself. Himself. He saw the reflection of the body returning the polished glass and knew he was looking at himself. “It was so surprising that I fell from the chair to the ground,” says Masanori Kohda, the scientist who studied the fish’s behavior, by e-mail. Because number 1 saw that he had a brown spot on his belly, at a point he can only see thanks to the mirror, and thinking it was a parasite ran to the bottom of the fish tank to rub it off.

This gesture, so simple for us, is an authentic mental feat for 99% of the animals, since it implies being able to think of oneself from the outside, to have self-knowledge as an individual, to know oneself differently from others. Only some of those considered more intelligent – the great apes, elephants, dolphins and magpies – have managed to pass this mirror test, which is what scientists call it. When an animal touches a spot on its face or body, located in a place that it could only see in the mirror, it is considered to have self-consciousness. Human puppies don’t usually achieve this until the second year and before that, when they see themselves reflected, they simply see a nice colleague.

Darwin already guessed it in 1838, when he gave a mirror to Jenny, an orangutan who was dressed as a woman at the London Zoo. The English naturalist said that the orangutans were “extraordinarily astonished” to see themselves reflected; they gesticulated and experimented, investigating that magical piece of glass. In the 1970s, psychologist Gordon Gallup wanted to repeat the chimpanzee experience, and the apes’ reaction went through three distinct phases. First, they were suspicious of that unknown subject in the mirror; then, they made atypical gestures to verify that it was their reflection and finally they went on to scrutinize themselves more in detail. Gallup then devised the brand test. They slept the chimpanzees, painted them on their eyebrows without them noticing it, and when they woke up, they were left alone in front of the mirror. As a human would do, they took their hand to the stain to see what it was.

To the surprise of researchers, several of these little fish went through the same phases as chimpanzees. They also began to swim face down and in strange postures, as in the mythical scene of the Marx brothers, supposedly to verify that they are the fish they see reflected. Something that experts consider unpublished in these animals. And so it turned out that the blue cleaning lábrido, which is what this fish of 10 centimeters and a brain of 0.1 grams is called, had a reaction of its own from very developed minds. So to overcome the challenge when trying to clean the mark.

The researchers chose these small fish precisely because they thought they could pass the test given their social intelligence and their special interest in finding spots. “This is the smartest fish, capable of deceiving other individuals, and it is also the cleanest, because it pays attention to a colored spot on another fish’s body and tries to eliminate it,” explains Kohda. The cleaners, as their name suggests, are dedicated to the hygiene of marine animals much larger than themselves, eliminating their parasites. But sometimes it’s tempting to be able to chew on their scales, skin or mucus. That’s why, although they are able to serve 2,000 customers a day, they have a prodigious memory that allows them to compensate the angry customer with a special care that restores their confidence.

So, if the cleaners have passed the mirror test, are they self-conscious? Do these little fishes have the life awareness of the shoeshine boys they carry? “I don’t think these fish are self-conscious. They pass the test, but I don’t think this is evidence of self-consciousness or self-knowledge,” says Alex Jordan, an evolutionary biologist at the Max Planck Institute and co-author of the finding with Kohda of Osaka University. They believe the test is not the animal “I” consciousness cotton test that has been thought of for decades. And the high capabilities of the cleaners are a good argument: they are evolutionarily programmed to recognize subjects and stains. In great apes, passing the mirror test demonstrates the cognitive powers they possess; in other animals, it can be just a demonstration that they are especially prepared for such a challenge.

However, their social endowments are a point in favor of self-knowledge: the animals that are most social, most needy or accustomed to recognizing other individuals of their species are those that are most prepared to distinguish themselves. For example, chimpanzees raised in isolation are unable to pass the mirror test: it takes the other to think about the self: “One hypothesis used for babies, which could be explored beneficially in cleaning fish, is that some aspects of social cooperation foster self-awareness,” says Kim Bard, a former president of the UK Primatological Society, which has studied the differences between children and chimpanzees on passing the test and considers this study “quite convincing.

However, the pioneers of the mirror test, like Gallup himself, question Jordan and Kohda’s results: they say that their study does not show that the cleaners have passed. These reluctances forced them to increase the controls of their study for three years, until it could be published this week in a scientific journal (PLOS Biology). Kohda says that 11 fish have passed the test since she was number 1. “Although they showed interesting behaviors toward the mirror, they are not indicative of self-recognition. They do not seem to me to be emphatic evidence of self-directed behavior,” says specialist Diana Reiss, consulted by EL PAÍS. She is responsible for the fact that both elephants and dolphins have passed this test, but admits that it cannot be a touchstone for the entire animal kingdom: “It is not the test of fire and should only be performed after an individual demonstrates evidence of self-directed behavior toward the mirror.

But initially it was thought that elephants were not capable. Researchers placed human-sized mirrors in front of their cages in which they could only see legs between bars. When the Bronx Zoo allowed Reiss to place a 2.5 metre mirror in an open space, the Happy elephant showed what she was capable of: she was very interested in her (full body) reflection and the day she had a white cross drawn on her face, she did not stop touching it. On the other hand, the mirror is certainly not the best examination for less visual animals, such as dogs. It has been proposed that they are perfectly capable of passing a test of self-knowledge based on smell, which is theirs. Nor will it be definitive for animals that do not give any importance to a stain, for example, so the test should be adapted to their way of perceiving the world and themselves.

Monkeys have the key: they do not pass the test naturally, but it has been observed that they are much less anxious about the presence of their reflection than about that of an unknown congener. As if they were in an intermediate step of recognition. In recent years, Chinese researchers went further and thanks to a laser (2015) and many hours of work (2017), made the macaques pass the test of the mirror. They were taught to see the mark on their face and now recognize themselves in the mirror without problems, without the need for help. If they put one in their cabin, they spontaneously take advantage of it to look at their genitals or teeth, as chimpanzees do, although months before they were unable to recognize their reflection. Does this mean that these macaques were not aware of themselves and now they are? Have the Chinese scientists illuminated these chosen ones and the rest of their fellow human beings live in an inferior state of mind?

The renowned ethologist Frans de Waal believes that the capacity for self-knowledge is something gradual and does not make jumps that imply that some animals have everything and others nothing. “There are many aspects of everyday behavior that require individuals to know themselves,” explains Bard, “such as their own weight in relation to the weight the branches will hold when jumping on them or their own fighting skills in relation to those of potential competitors. That’s why De Waal believes he has come up with the perfect metaphor: “What if self-awareness develops like an onion, building layer upon layer, rather than appearing once and for all?”.

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