Researchers Discover This Tiny Fish Has An Odd Behavior In Front of a Mirror


A small fish called cleaner wrasse just got boosted to the ranks of mammals and birds that have passed a test to prove its self-awareness.

The tropical fish is as small as a finger, but an international team of researchers realized that it’s size doesn’t count. Some part of their brain is aware of its existence, concluded the researchers as they put a group of fish in front of a mirror.

The MSR – Mirror Self-Recognition Test

The first time this test was used was back in the 1970s by psychologist Gordon Gallup. He used it on young chimps, who first thought they would look at another chimp. After a while, their behavior changed and became aware that it was their image in the mirror. They used the reflection to groom themselves and study their body. Scientists concluded that this test was a way to see if that animal has a kind of self-awareness – they can distinguish their body in the mirror from friends, foes, and environment.

Over the years, other animals like the introspective chimps from the 1970s were added: dolphins, elephants, corvids, and pigeons. Then, ants passed the test and manta rays had an odd behavior in front of mirrors.

For this study on cleaner wrasse, scientists from Japan, Germany, and Switzerland wanted to see if other animals that are not as intelligent as the furry or feathered animals can show self-awareness.

They chose the cleaner wrasse (Labroides dimidiatus) because it can easily spots differences on surfaces (like parasites on other fish, which they pick and eat) and because it has good vision.

Researchers had to follow a golden standard in an unusual reaction in front of a mirror: it’s based on adding a spot on the animal somewhere to see it in the mirror. When it wants to remove it from their body, it will show that they understand the image is theirs.

They put ten fish, each in a tank with a mirror. In the beginning, each fish attacked their reflection, but they soon changed their behavior. They looked friendlier, and after a few days, the fish started to dance, which was weird, considering they are solitary species.

Then the next stage was to dag a spot of colored gel on the head of eight of the fish, somewhere that could be seen in the mirror.

All fish except for one spent more time in the mirror to look at the spot, and some even scraped against the environment to remove their spot.

This test didn’t work on dogs and cats!

Animals we consider very intelligent and social like dogs, cats or octopuses failed the mirror tests, and even some humans cannot pass the trial until the age of six or older.


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