A small fish has demonstrated an astonishing level of intelligence, passing a test once considered exclusive to great apes. In a groundbreaking study, researchers observed a cleaner wrasse, a tiny marine fish, engaging in a mirror test that reveals its remarkable self-awareness. But here's where it gets controversial: while the fish initially failed the test, further experiments suggest it might have passed after all, challenging our understanding of intelligence and self-recognition in animals.
Mirror tests are a standard scientific experiment used to gauge self-recognition in animals. The idea is simple: if an animal can recognize itself in a mirror, it's a sign of advanced intelligence. Chimpanzees, elephants, and dolphins have all passed this test, leading many to believe they possess intelligence comparable to our own. However, the cleaner wrasse, a fish just a few inches long, has now joined this elite group.
The cleaner wrasse, known for its cleaning habits, was first reported to pass the mirror test in 2018. The fish's natural behavior of cleaning parasites from larger fish led researchers to speculate that it might mistake marks on its body for parasites and use the mirror to 'clean' itself. But evolutionary psychologist Gordon Gallup, the founder of the mirror test, believed the fish were simply reacting to marks on their bodies, not recognizing themselves.
Now, a team from Osaka Metropolitan University in Japan and the University of Neuchâtel in Switzerland has refined the experiment to test the wrasse's self-awareness more thoroughly. They marked the fish first, then introduced the mirror, allowing the fish to identify the 'parasite' on its body before seeing its reflection. The results were surprising: the fish tried to rub off the 'parasite' within an average of 82 minutes, suggesting self-awareness before the mirror was even involved.
But the controversy doesn't stop there. After several days of getting used to the mirror, some fish began an unusual behavior. They would pick up a piece of shrimp, carry it to the mirror, and drop it. As the shrimp fell in sync with the real thing, the fish followed the reflection closely, touching the mirror surface with their mouths. This behavior suggests the fish were exploring the mirror's properties, using an object separate from themselves to understand how the reflected images worked.
This kind of 'contingency testing' and mirror tool use has been observed in other species that failed the mark-based mirror test, including pigs, rhesus monkeys, manta rays, and corvids. The findings from this research will likely influence not only academic issues, such as revising evolutionary theory and constructing concepts of self, but also directly impact matters relevant to our lives, including animal welfare, medical research, and even AI studies.
Biologist Masanori Kohda, who was involved in both this new study and the original paper on cleaner wrasse self-recognition, says, 'Our results suggest that self-awareness evolved at a minimum with the bony fishes (450 million years ago) and is likely widespread across vertebrates.' This suggests that self-awareness, once thought to be unique to great apes, is actually a skill that may have arisen in a much wider range of animals, including fish. The research was published in Scientific Reports.
