Fish do have self-awareness

Three years ago, a team of Japanese scientists published in the journal PLoS Biology some amazing and unusual results: some small fishes reef (Labroides dimidiatus)specialized in cleaning parasites and dead skin from others, had passed the test of self-recognition in the mirror.

This test, considered evidence of self-awareness, consisted of making a brown mark on a place on their body – usually the throat area – that they could only see indirectly in their reflection. Of the four animals with which the experiment was carried out – a figure similar to that of other studies carried out with other animals – three touched or scratched the signal after swimming towards the mirror, thus confirming the capacity of the fish for self-recognition.

fish with a conscience

The work was a milestone since few animals, most of them with large brains -among which the chimpanzees, the dolphins, the asian elephants and the magpies–, they had shown this ability until then.

Despite the finding, the investigation was criticized Y questioned for several reasons; the main one is that it had been carried out on small fish, the most primitive vertebrates with small brains. The other comments questioned the sample size (n=4), that the subjects might regard the mirror images as known individuals rather than themselves, and that the tag might provide a physical stimulus to the fish.

“Therefore, there could have been errors in the methodology”confesses to SINC Masanori Koda, from the Graduate School of Science at Osaka City University in Japan. Now, the expert provides new evidence in a new study, published in the same journal, where he rejects all criticism and firmly supports the conclusions of his first work.

“Our results reject the critics on the capacity of self-recognition in the mirror of fish, and indicate that fish should be included in the group of animals with this capacity”Kohda points out. Furthermore, the new research suggests that “many other vertebrates could pass the mark test and have self-awareness, something not previously appreciated”keep going.

According to Japanese scientists, in collaboration with researchers from the Max Planck Institute for Animal Behavior, in Germany, and University of Neuchatel, in Switzerland, work is “an advance for studies not only of animal Cognition, but also of psychology, which considers that only humans have self-awareness”they emphasize

Larger sample, more evidence

To corroborate their results, the experts increased the sample size to 18 cleaner fish, with a positive result of 94%, that is to say that 17 of them showed the same behavior as in the previous study.

In the first work, the scientists performed a brown mark in fish because it could look like a small parasite, which is their main food source. They made this decision after observing similar studies carried out in monkeys, pigs, dogs or cats, with negative results, where they realized that perhaps the signal in these animals “it did not represent something in its natural environment that worried them”Kohda comments.

To respond to criticism about the tag, whose physical sensation could trigger the behavior, the team tested the fish’s response to a physical stimulus in their throat by injecting the brown tag 3mm deep (instead of 1mm). There the mark was barely visible, however, they discovered that the fish with the injection The deeper ones scratched their throats at a similar rate, whether there was a mirror or not.

In order to further cement the importance of using tags that are ecologically relevant to the animals in these types of studies, the team found that no fish injected with green or blue tags demonstrated scraping behaviour.

Do they recognize themselves?

But how could the fish know that it is they who appear in the mirror and not others? An animal looking at its reflection goes through three states: first it expresses aggressive behavior –since it probably perceives the image in the mirror as another animal–, then it shows an unnatural, but non-aggressive movement –since it confirms that the image in the mirror is correct. the mirror is not another animal – and finally looks repeatedly at his own body without aggression.

At that last point is when the self recognition it is possible, because the fish can see the mark and try to scrape it. This happened in the first job with L. dimidiatus, but the question was whether moving the mirror could rekindle his aggressiveness. To test this, the team transferred the cleaner fish to a tank with a mirror on one side and, three days later, to a tank with a mirror on the other side. In none of the containers did the fish show aggression towards their own image.

“Fish are self-aware, like chimpanzees, or even humans, suggesting that fish have a ‘mind'”, stresses SINC Kohda. However, there is still a lot of work to be done, especially qualitative, to continue demonstrating that fish, like other animals, have the capacity for self-recognition.

Font: Adeline Marcos / SINC Agency

Reference article: https://www.agenciasinc.es/Noticias/Nuevos-experimentos-confirman-que-los-peces-si-tener-conciencia-de-si-mismos