Small tropical reef fish were able to recognize themselves in a mirror, scientists said Thursday, in a finding that raises provocative questions about assessing self-awareness and cognitive abilities in animals.
The study involved experiments in which the bluestreak cleaner wrasse was subject to a mirror self-recognition test, a technique developed in 1970 for gauging animal self-awareness.
In aquarium experiments at Osaka City University, researchers applied a brown-colored mark on the body of the fish in places that could be seen only in a mirror's reflection.