Imagine a fish the size of your finger passing a test once thought to be the exclusive domain of great apes. It sounds like science fiction, but it’s real. A tiny cleaner wrasse, known for its job of picking parasites off larger fish, has not only recognized itself in a mirror but also used a piece of food to investigate how the mirror works. This challenges everything we thought we knew about animal intelligence.
The mirror test, a classic experiment in animal cognition, has long been the gold standard for measuring self-awareness. It’s simple yet profound: if an animal can recognize itself in a mirror—say, by fixing a mark on its body—it’s considered a sign of self-awareness, a trait we’ve historically associated with humans and a few other highly intelligent species like chimpanzees, elephants, and dolphins. But here’s where it gets controversial: Could a fish, with its seemingly simple brain, really join this elite club?
In 2018, the cleaner wrasse made headlines by passing this test. Researchers observed the fish trying to remove a mark on its body after seeing its reflection, suggesting self-recognition. But not everyone was convinced. Evolutionary psychologist Gordon Gallup, who pioneered the mirror test, argued that the fish might have mistaken the mark for a parasite on another fish. And this is the part most people miss: Self-awareness isn’t just about recognizing a mark; it’s about understanding the mirror itself as a tool for reflection.
To address these doubts, a team from Osaka Metropolitan University in Japan and the University of Neuchâtel in Switzerland redesigned the experiment. Instead of introducing the mirror first, they marked the fish and then showed it the mirror. The fish, already aware of something unusual on its body, reacted almost immediately—within 82 minutes on average—by trying to remove the mark. This suggests the fish had a sense of self even before encountering the mirror.
But the real surprise came later. After getting used to the mirror, some fish started picking up small pieces of shrimp, carrying them to the mirror, and dropping them. As the shrimp fell in sync with its reflection, the fish would touch the mirror with its mouth, seemingly testing how the reflection worked. This behavior, known as contingency testing, is a sophisticated way of exploring the mirror’s properties—something we’ve seen in species like pigs, rhesus monkeys, and even manta rays, despite their failure in traditional mark tests.
So, what does this mean for our understanding of intelligence? Biologist Masanori Kohda, involved in the study, believes these findings could reshape evolutionary theory and our concept of self. They also have practical implications for animal welfare, medical research, and even AI. If a tiny fish can exhibit self-awareness, what other hidden capabilities might animals possess?
The team’s conclusion is bold: self-awareness may have evolved as far back as 450 million years ago with bony fishes and could be far more widespread across the animal kingdom than we ever imagined. But here’s the question we’re left with: If intelligence isn’t exclusive to humans or even mammals, how should we redefine our relationship with the animal world? Let’s discuss—do you think this fish’s behavior truly qualifies as self-awareness, or is there more to the story?
