The Bluestreak cleaner wrasse was already considered unique. It is the only fish on the exclusive list of animals that have passed the "mirror test," which includes humans over 18 months old, other primates, dolphins and whales, elephants, and ants. The mirror test is a classic test of self-recognition and possibly even self-awareness. In a new study, the tiny fish has been found to check itself out in a mirror before deciding whether to attack another fish.
First, Taiga Kobayashi at Osaka Metropolitan University in Japan and his colleagues tested the fish's willingness to go on the attack. Against the glass wall of the fish tank, they held up an image of another wrasse that was either 10 per cent larger or smaller than the real fish. Regardless of the size of the model fish in the photograph, the territorial wrasses picked a fight.
Then, they repeated the test but added a mirror, and the fish checked out their reflection. But when the researchers held up a photo of a larger or smaller cleaner wrasse to the glass pane, the fish chose to fight only smaller rivals.
It appears that it can construct a mental image of itself to compare with its opponent, something not even all humans can do.
Previously: Baby cow looks into a mirror for the first time and makes a handsome new friend (video)
