In February, a team of researchers published a paper showing that the cleaner wrasse, a small fish known for cleaning parasites from bigger fish, had passed the mirror test.
The mirror test — more formally known as the mirror self-recognition test — has long been considered a gauge of whether or not an animal has self-awareness.
Mirror Testing Fish
It usually works like this: Researchers test the animal by exposing it to a mirror long enough to get used to it. Then, while the animal is anesthetized, researchers place a mark on the animal's body in some place it can't see without looking in the mirror — typically the forehead for primates and most other mammals.
