In the standard mark test, an animal is marked where it cannot see the mark directly and then given a mirror. Touching or trying to remove the mark is scored as evidence that the animal recognises the reflection as itself. It had been passed by great apes, elephants, magpies and dolphins before a 2019 study reported cleaner wrasse doing the same.
The wrasse first attacked the reflection, then performed unusual movements in front of it, then began scraping its throat on the substrate when a coloured mark was present and visible only in the mirror. Independent replication reproduced the behaviour, so the observation itself is not in dispute.
The interpretation is. Critics argue that a cleaner wrasse is a specialist at inspecting marks on bodies for a living, so a brown mark resembling a parasite may trigger scraping without any self-concept, and that mark-directed behaviour may test something narrower than the phrase self-awareness suggests. The findings have prompted a broader argument about whether the mirror test measures what it is assumed to measure.