Nature
A tiny reef fish passed the classic mirror self-recognition test
In 2019, bluestreak cleaner wrasse became the first fish shown to pass the mark test: after time with a mirror, fish marked with a spot only visible in reflection scraped at their own throats to remove it, then checked the mirror again afterward. The result reignited debate over whether mirror self-recognition, long reserved for apes, dolphins, and magpies, truly measures self-awareness.