They provide more evidence that fish recognize themselves in a mirror

They provide more evidence that fish recognize themselves in a mirror

Scientists at Osaka City University have provided further evidence suggesting that the fish have the ability to MSRthat is, they recognize themselves when they see themselves in a mirror.

The MSR is considered a test of self-awareness and pass the mark test, in which animals touch or scratch a mark placed on their body in a location that can only be seen indirectly in a mirror, used to determine the MSR capability of a animal.

Aside from chimpanzees, the evidence that other animals have passed the mark test has been criticized and is therefore inconclusive. By addressing criticism of their previous work on the cleaner fish Labroides dimidiatus, the oska City team has obtained more evidence to support their thesis. This new experiment was recently published in PLOS Biology.

Professor Kohda says it's a statement: "Previously, using a brown tag in the throat area of ​​L. dimidiatus, we had shown that three out of four cleaner fish scraped their throats multiple times after swimming in front of a mirror, a number on par with similar studies done in other animals such as elephants, dolphins and magpies."

However, one of the criticisms of this result was the size of the sample and the need for repeated studies showing positive results. Teaming up with researchers from the Max Planck Institute for Animal Behavior in Germany and the University of Neuchatel in Switzerland, this study increased the sample size to 18 cleaner fish, with a positive result of 94% of 17 of them that showed the same behavior of the previous study.

But why a brown mark? "After looking at similar studies done on monkeys, pigs, dogs, cats, etc., which were clearly negative, we wondered if the reason these animals didn't pay attention to the brand was because It didn't represent something they would be concerned about in their natural environment," says Professor Kohda. "In our previous study, we used a brown mark as it may look like a small parasite that is a main food source for L. dimidiatus."

One criticism in response to this was the possibility that the physical sensation of the mark, coupled with seeing the brown mark in the mirror, may trigger behavior that is not conclusively suggestive of MSR. To address this, the team tested how the fish would respond to a physical stimulus at the throat. injecting the brown mark 3 mm deep (instead of 1 mm).

At such a depth, the mark was barely visible, but they found that fish with the deepest injection scraped their throats at a similar rate, regardless of whether a mirror was present or absent. To further solidify the importance of using brands that are ecologically relevant to animals in MSR studies, the team found that no fish injected with green or blue tags demonstrated the scraping behavior.

Lastly, some critics wondered if L. dimidiatus recognized the mirror image as itself and not as another fish. A mirror-trained animal is one that is presented with a mirror image of itself and goes through three steps. First, it expresses some kind of aggressive behavior, since it probably perceives the image in the mirror as another animal; then it shows an unnatural movement, but not aggressive, as it confirms that the image in the mirror is not another animal; and lastly, he repeatedly looks at his own body without aggression. At this point, MSR is possible as it can now see the mark and try to scratch it.

Professor Kohda says: "Our previous study demonstrated MSR in L. dimidiatus, however studies with other animals have shown that simply moving a mirror rekindles aggressive behaviour, suggesting that the animal has only learned a spatial contingency, not MSR". To address this, the team transferred mirror-trained cleaner fish to a tank with a mirror on one side of the tank and then, three days later, to a tank with a mirror on the other side. and they saw that the fish showed no aggression towards their mirror image in both tanks.

Additionally, to ensure that the L. dimidiatus that passed the tagging test actually recognized themselves, they placed mirror-trained fish in adjacent tanks that were separated by clear glass. After two or three days, when the fish had greatly reduced their aggressive behavior towards each other, they were tagged in the standard way the following night. None of the fish scraped their throats during the 120-minute exposure to each other the next morning.

"This result suggests that a visually and ecologically relevant stimulus in another fish is not sufficient to induce throat scraping in tagged subjects," says Professor Kohda. "We still have a lot of work to do, especially quantitatively, to show that fish, like other animals, have the ability to MSR; however, as a result of this study, we reiterate our previous study's conclusion that It is either necessary to review consciousness in animals or the validity of the mirror test."

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