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Scientists find some fish can ‘recognise themselves’ in mirror
by binder

    The cleaner wrasse (Labroides dimidiatus) is about 10cm long with a stripe, and lives in coral reefs. Previous research has revealed these fish have complex social lives, forming allegiances and enemies, making logical inferences about whether they will beat other fish in fights and showing a capacity for deception. The fish live in mutually beneficial partnerships with larger client fish from whom they feed on dead skin and parasites.

    During the mirror test, the researchers placed a mark on the fish in a location that could only be seen in a mirror reflection. Initially, the fish reacted aggressively and repeatedly tried to bite their reflections. But over the next few days, they stopped biting and started “behaving weirdly” in front of the mirror, swimming upside down, for instance, or doing repeated bursts of acceleration past the mirror.

    According to the authors, the fish were “contingency testing” – doing strange things to see whether the reflection did the same as a way of figuring out the function of the mirror. They were also observed attempting to remove the marks by scraping their body on hard surfaces after viewing themselves in the mirror. These activities were not seen when the fish were given marks without a mirror present or when they interacted with marked fish across a clear divider.