The mirror test: for decades it has been a method favored by biologists to conduct research into self-recognition and, perhaps, self-awareness in animals. The American psychologist Gordon Gallup devised the test in 1970. Animals are marked on their faces and placed in front of a mirror. If an animal thinks it sees a fellow animal in front of it, it will try to remove the mark from there. That’s for example in giant pandas the case.
Some animals, on the other hand, realize that it is a reflection and therefore grab their own heads. The chimpanzee was the first animal species after humans to be shown to recognize itself in a mirror. Later, dolphins, Asian elephants, magpies and even some fish followed: in 2023, Japanese biologists discovered that the cleaner wrasse Labroides dimidiatus passed the mirror test. Fish that saw the mark try to scrape it off themselves.
But in a current follow-up trial, described in Scientific Reportssomething unexpected happened. The fish deliberately dropped pieces of shrimp in front of the mirror to see how their movement coincided with the reflection – they were, according to the biologists’ interpretations, examining the mirror itself. Similar behavior had previously been observed in rays and dolphins following air bubbles in a mirror.
According to the biologists, the new findings make it plausible that the fish really do have self-awareness and that the previous behavior was not due to chance. By the way, the ‘cleaning’ in the species name refers to what the fish are good at, nipping away at parasites from larger fish.
