Oh Ga-hee, science columnist and science content producer ‘OhY LAB.’ representative
Planning/Organization = Reporter Kim Yun-ju
/Graphics=Jaeil Yoo
Humans know that what they see in the mirror is themselves. There is no object in nature that reflects itself as clearly as a mirror. At best, it’s just a reflection in the water. Mirrors are very special objects created by humans. This means that in nature, animals cannot access mirrors that reflect their reflections. Thanks to this, you can see interesting reactions when you show a mirror to an animal. Scientists often study how animals perceive themselves by studying their reactions when they first look at a mirror.
Rats raised in isolation do not respond to mirrors
An interesting study related to mirrors was published in the December 6 issue of ‘Neuron’, an international academic journal in the field of neurology. Takashi Kitamura, a professor in the Department of Neuroscience at the University of Texas Medical Center in Southwestern, and the research team Jun Yokose put ink on the foreheads of experimental rats, showed them a mirror, and observed how the rats reacted. Rats with black fur were dipped in white ink and black ink, respectively. White ink would have been much more visible than black ink, right? The area covered with ink was also varied: 0.2㎠, 0.6㎠, and 2㎠. We also divided the subjects into rooms with and without mirrors and observed their reactions.
The rats’ reactions were clearly different. First, the rats that were dipped in black ink or 0.2 cm2 of white ink did not spend a particularly long time in front of the mirror. I behaved as usual, with or without a mirror. On the other hand, some rats that had 0.6 cm2 or 2 cm2 of white ink spent a long time in front of the mirror, trying to erase the ink.
So which of the mice with noticeable ink was trying to erase the ink in front of a mirror? The researchers discovered that when rats recognized themselves in the mirror, nerve cells responded in the hippocampus, the brain area responsible for memory and learning. In mice that did not groom themselves in front of a mirror, these neurons did not respond either.
Also, the rats that responded to the mirror were rats that socialized a lot with other rats similar to themselves. Rats that were weaned and raised in isolation or with white rats did not respond to mirrors. The research team’s interpretation was that “social experiences influence how we perceive ourselves through the mirror.” This means that the information needed to recognize oneself is learned through the hippocampus when one socializes with rats that look similar to oneself.
‘Mirror test’ to see if an animal recognizes itself
Researchers at the University of Texas used the ‘mirror test’ proposed by Gordon Gallup, a psychology professor at the State University of New York at Albany, in 1970. This is an experimental method designed to determine whether animals have visual self-recognition abilities. Here, ‘self-awareness’ refers to whether one recognizes oneself as an individual being. This means that we can distinguish between ourselves and other animals beyond the simple sense of being hungry or sick.
Professor Gallup plans an experiment to show mirrors to animals and see whether they recognize their reflections as themselves. Professor Gallup’s target was a wild chimpanzee. When a chimpanzee saw a mirror for the first time, it made threatening gestures. She thought it was a strange chimpanzee invading her territory. After some time, she realizes that the mirror reflects her. She played around picking her nose in the mirror and making strange faces. She even groomed parts of her body that were otherwise invisible to the naked eye, like her butt.
Professor Gallup went one step further. After anesthetizing the chimpanzee, they applied dye over its eyebrows and ears. The chimpanzee that woke up from anesthesia did not try to remove the dye when there was no mirror, but when there was a mirror, it tried to remove the dye by looking at the mirror. The same experiment was performed on two species of monkeys other than chimpanzees, but the monkeys did not realize that the image in the mirror was themselves. Professor Gallup published a paper in the international journal Science summarizing the fact that other than humans, only apes such as chimpanzees have self-recognition.
A robin attacks itself in the mirror
Since Gallup’s research, scientists have tried the mirror test on a variety of animals. In 2001, for the first time, an animal other than an ape passed the mirror test. It was a bottlenose dolphin, known as a smart animal. Since it is a social animal and communicates with other dolphins using ultrasound, it would have been capable of self-recognition. Among mammals, elephants, which tend to herds, also passed the mirror test. At first I couldn’t pass, but it turned out that it was because the mirror was too small compared to the elephant’s body. When we changed the mirror to one large enough to reflect the elephant’s body, it passed the mirror test.
As time passed, unexpected results also emerged. In 2008, the Magpie passed the mirror test. They put a yellow marker around her neck and she struggled to get it off. In 2019, it was discovered that fish are also self-aware. The main character is the green cleaning wrasse, which is well known as an animal that acts in groups and exhibits intelligent behavior. It has also been revealed that he remembers being caught in a net 11 months ago. I also passed the mirror test with ease. I even put a mole in a place that I couldn’t see without a mirror, so I tried to remove the mole by looking at that area in the mirror.
A 2015 study found that monkeys, akin to great apes, initially failed the mirror test but were able to recognize themselves in the mirror after repeated training. On the other hand, robins and Thai willow carp did not recognize the image in the mirror as themselves until the end. They thought they were different animals of the same species, so they courted or attacked them.
On the other hand, there is criticism that the mirror test is only a limited way to check self-awareness. First of all, animals use various senses, such as smell, hearing, and touch, to perceive things around them, but mirror inspection relies only on visual judgment. Also, there may be animals that do not react even if they recognize the image reflected in the mirror as themselves. It seems that the self-recognition ability of animals will need to be discovered in more diverse ways in the future.
2023-12-25 18:01:02
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