A Tiny Reef Fish Can Recognize Itself in a Mirror

It’s something most of us do every morning without a second thought. We wake up, stumble to the bathroom and glance at ourselves in the mirror as we wipe the sleep from our eyes. It may not seem like much, but the simple act of looking at that mirror—and understanding that the eye-rubbing person staring back is really one’s own reflection—demonstrates a remarkably sophisticated level of understanding.

Only a handful of the world’s other brainiest species have proved capable of this: chimpanzees, bonobos, gorillas, orangutans, bottlenose dolphins, killer whales, magpies and at least one Asian elephant. But now a group of researchers based in Japan and Germany has discovered the bluestreak cleaner wrasse(Labroides dimidiatus) a coral reef fish found throughout the Indo-Pacific, may have the same ability. What remains to be seen is what this says about the “mirror self-recognition” test, a longtime scientific standby for assessing self-awareness.

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Emory University primatologist Frans de Waal, who was not involved in the wrasse study, is not quite convinced these fish passed the test as originally devised, however. “When I read the paper,” he says, “I became a bit doubtful about the behavior that they report, and the fact that they cannot do a purely visual mark.” In the classic test, a mark is simply painted onto the animal. But the injection necessary for fish pairs a tactile stimulation—the physical irritation of the jab—with the visual cue. Jordan notes this makes it harder to directly compare the wrasses’ responses with those of superficially marked apes, elephants and other animals.

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