Graphic by Jieru Ye ‘23.
By Lily Benn ’24
Staff Writer
A recent study by animal sociology and biology researchers concluded with the idea that fish may be able to recognize themselves not only in mirrors but in still photographs. This new information may indicate self-awareness in fish, specifically the Bluestreak cleaner wrasse, Science News reported.
This study is a continuation of research done with the same species of fish in 2019 when researchers first discovered that the Bluestreak cleaner wrasse could recognize itself in the mirror. The corresponding 2019 Science Daily article explains that this was tested by a widely recognized ‘mark’ test that has been studied in many species of animals in the past. The article goes on to explain that this test requires that the subject, when presented with a mirror, be able to notice a mark put on its own body as itself, and not another member of its species. In both 2019 and 2022 mirror studies, researchers injected ink into their scales that resemble what the fish normally recognize as a parasite, Science News reported. Science Daily notes that the test is a challenge for animals such as fish, who do not have limbs that can indicate touch, or have the mobility required to show that they know the mark is on their own body. Instead of pointing to themselves, Science News explained, these wrasse fish indicated they knew it was their own reflection by exhibiting a body scraping behavior.
However, both Science News and Science Daily report that this new information does not necessarily indicate self-awareness in these fish, or in many other animal species tested with the mirror ‘mark’ test. Science News cites Frans de Waal, a primatologist from Emory University of Atlanta who approves of the study, yet explains how the mirror test is not a universally accepted and reliable method of testing animal self-awareness. Science News writes that species known to have strong cognitive abilities such as monkeys and ravens have not passed the mirror test. The article goes on to explain that other species rely less on sight, such as dogs who are stronger in recognition of scent.
The 2023 study takes this information further, by testing this same species of Bluestreak cleaner wrasse fish’s ability to self-recognize with the ‘mark’ test, this time with photographs of the fish. The paper, titled “Cleaner fish recognize self in a mirror via self-face recognition like humans,” published online by the Proceedings of the National Academy of Sciences of the United States of America, is available to be read by the general public. The article reports that this type of study in self-recognition from images was observed in chimpanzees, and this “mental image of the self-face” is a behavior easily observed in humans. The Bluestreak cleaner wrasses were observed exhibiting the same scraping behavior first observed in the original 2019 study after being shown photographs of themselves with the placebo parasite marking. Science News explains that in this same study, the fish readily attacked pictures of other fish in their same species, but stayed calm when presented with pictures of themselves.
The research paper concludes with the discussion that their results may be controversial and that there needs to be more research towards self-recognition in different species and taxa of animals. As of now, there are many discrepancies between different animals’ abilities to complete the mirror test, as it was originally designed for primates. Their final conclusion is that there is a strong cognitive ability in fishes, and self-awareness is suspected by the authors to be more common in the animal kingdom than once thought.