Cleaner fish show intelligence typical of mammals

Researchers at Osaka Metropolitan University in Japan have discovered a previously undiscovered behavior in cleaner wrasse (Labroides dimidiatus). When presented with a mirror, the tiny fish not only recognized themselves, but experimented with the mirror themselves, interacting with it using a scrap of food. The results, published in Scientific Reports, suggest that these social fish can perform a higher level of intelligence known as "contingency testing," typically seen in intelligent marine mammals like dolphins.