April 16, 2021

The fish that manages to recognize itself in the mirror | Science

The fish that manages to recognize itself in the mirror | Science

Five years ago, in a fish tank in Osaka, a small fish named number 1 He looked in the mirror. He did not look at him, he looked at himself. Likewise. He saw the reflection of the body that returned the polished glass and knew he was looking at himself. "It was so surprising that I fell off the chair to the ground," Masanori Kohda, the scientist who studied the behavior of the fish, acknowledges by email. Why number 1 he saw that he had a brown spot on his belly, at a point that he can only see through the mirror, and thinking that it was a parasite, he ran to the bottom of the tank to rub himself to remove it.

This gesture, so simple for us, is an authentic mental feat for 99% of animals, since it implies being able to think outside, having self-knowledge as an individual, knowing oneself different from others. Only some of those considered smartest -The great apes, elephants, dolphins and magpies- have managed to overcome this test of the mirror, which is what scientists call it. When an animal touches a spot on your face or body, one that you could only see in the mirror, it is considered to have self-awareness. The puppies humans do not usually achieve it until the second year and before, when they see themselves reflected, they simply see a nice colleague.

Darwin already guessed it in 1838, when he handed over a mirror to Jenny, an orangutan that they wore as a woman in the London zoo. The English naturalist said that the orangutans were "extraordinarily amazed" to see themselves reflected, gesticulating and experimenting, investigating this piece of magic glass. In the decade of 1970, the psychologist Gordon Gallup wanted to repeat the experience with chimpanzees and his reaction went through three very defined phases. First, I distrust that unknown subject in the mirror; later, they perform atypical gestures to verify that it is their reflection and finally they go to scrutinize themselves more in detail. Then Gallup devised the test of the brand. They slept the chimpanzees, painted them on their eyebrows without being noticed, and when they woke up, they were left alone in front of the mirror. As a human would, they would take their hand to the spot to see what it was.

"It was so surprising that I fell off the chair to the ground," acknowledges the scientist who was studying the little fish

To the surprise of the researchers, several of these minnows went through the same phases as the chimpanzees. They also started swimming upside down and in strange positions, as in the mythical scene of the Marx Brothers, supposedly to verify that they are that fish that they see reflected. Something that experts consider unprecedented in these animals. And so it turned out that the blue cleaner wrasse, which is what this fish of 10 centimeters and a brain of 0.1 grams is called, had a reaction characteristic of very developed minds. So to overcome the challenge to try to clean the brand.

The researchers chose these little fish precisely because they thought they could pass the test given their social intelligence and their special interest in finding spots. "This is the most intelligent fish, capable of deception strategies against other individuals, and it is also the cleanest because it pays attention to a point of color in the body of another fish and tries to eliminate it," he explains. Kohda. The cleaners, as the name suggests, are dedicated to the hygiene of marine animals much larger than them, eliminating their parasites. But sometimes it is tempting to nibble on their scales, skin or mucus. Therefore, 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 special care that gives them back their trust.

So, if the cleaners have passed the mirror test, are they self-conscious? Do these minnows have an awareness of the life of shiner What are they wearing? "I do not believe that these fish are aware of themselves, they pass the test, but I do not consider this to be evidence of self-awareness or self-knowledge," he says. Alex Jordan, evolutionary biologist at the Max Planck Institute and co-author of the finding with Kohda, from the University of Osaka. They believe that the test is not the cotton test of the consciousness of the animal "I" that has been thought for decades. And the high capacities of the cleaners are a good argument: they are programmed evolutionarily to recognize subjects and spots. In the great apes, passing the mirror test demonstrates the cognitive powers they treasure; in other animals, it can be just a demonstration that they are specially prepared for such a challenge.

Only some of the most intelligent animals – the great apes, the elephants, the dolphins and the magpies – have managed to overcome this test of the mirror

However, their social skills are a point in favor of self-knowledge: more social animals, more needy or accustomed to recognize other individuals of their species are the most prepared to distinguish themselves. For example, chimpanzees raised in isolation are unable to pass the mirror test: the other is needed to think of the self. "A hypothesis used for babies, which could be explored beneficially in cleaning fish, is that some aspects of social cooperation foster self-awareness," he says. Kim Bard, former president of the Primatological Society of the United Kingdom, who has studied the differences between children and chimpanzees when passing the test and considers this study "quite convincing".

However, the pioneers of the mirror test, like Gallup himself, question the results of Jordan and Kohda: they claim that their study does not show that the cleaners have passed it. These reluctance forced them to increase the controls of their study for three years, until they publish it this week in a scientific journal (PLOS Biology). Kohda says that 11 fish have passed the test since he achieved it number 1. "Although they showed interesting behavior towards the mirror, they are not indicative of self-recognition, they do not seem to me a direct proof of self-directed behavior," says specialist Diana Reiss, consulted by EL PAÍS. She is responsible that both elephants and dolphins have passed that test, but admits that it can not 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 behavior self-directed towards the mirror ".

The 'Happy' elephant with her brand.
The 'Happy' elephant with her brand.

But it is that initially it was thought that the elephants were not capable. Researchers placed human-sized mirrors in front of their cages where they could only see legs between bars. When the Bronx zoo allowed Reiss to place a 2.5-meter mirror in an open enclosure, the elephant Happy he demonstrated what he was capable of: he was very interested in his reflection (full body) and the day he drew a white cross on his face, he did not stop touching it. On the other hand, the mirror is probably not the best test for less visual animals, like dogs. It has been proposed that these are perfectly capable of passing a Self-knowledge test based on smellWhat is your thing? Nor will it be final for animals that do not give any importance to a spot, for example, so the test should adapt to their way of perceiving the world and himself.

Monkeys have the key: they do not pass the test naturally, but it has been observed They feel much less anxiety in the presence of their reflection than in 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), they managed to get the macaques to pass the mirror test. They were taught to see the mark on their face and now they recognize themselves in the mirror without problems, without needing help. If they put one in their cabin, they take advantage spontaneously to look at their genitals or teeth, as chimpanzees do, although months before they were unable to see their reflection. Does this mean that those macaques were not aware of themselves and now they are? Have the Chinese scientists enlightened these chosen ones and the rest of their congeners live in a lower mental state?

Darwin already told that the orangutans were "extraordinarily amazed" to see themselves reflected in the mirror

The renowned ethologist Frans de Waal believes that the capacity for self-knowledge is something gradual and not by jumps that imply that some animals have everything and others nothing. "There are many aspects of daily behavior that require individuals to know themselves," Bard explains, "as their own weight in relation to the weight that the branches will hold when jumping on them or their own fighting skills in relation to the of potential competitors. " That is why De Waal believes that he has come up with the perfect metaphor: "And if the self-consciousness develops like an onion, building layer upon layer, instead of appearing at once?"

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