If a fish can pass the mark test, what are the implications for consciousness and self-awareness testing in animals?
PLoS Biology February 1, 2019 M. Kohda, Takashi Hotta, Tomohiro Takeyama et al.
A fish, the cleaner wrasse, shows behaviors that may be interpreted as passing the mark test for mirror self-recognition, a cognitive ability previously known only in mammals and birds. When given a colored tag, the fish scrapes their body in front of a mirror to remove it but does not respond to transparent marks or to colored marks without a mirror. The finding challenges whether these behaviors indicate self-awareness in fish or reflect a different cognitive process, raising questions about the mark test's validity across species.