The Mirror Test Is Broken
Alex Jordan had just surfaced from a dive off the coast of Corsica when he called me back last summer. “We’ve put mirrors in the wild,” he said. “It’s always a bit of a nightmare.” With the help of his students, he’d set them in the sinuous green seagrass of an underwater meadow, where a diverse community of fishes live and breed. Shier species, he told me, tend to avoid their own reflections, but more aggressive ones lunge toward what they take to be a rival in the mirror. At times, their headbutts crack the glass.
Jordan’s mirrors were meant specifically for wrasses, one of the largest families of marine fish. His favorite Mediterranean species, the rainbow wrasse, certainly would have reason to admire its own ribbon-candy body with green and orange stripes. But when Jordan and his students started the experiment, a small and drab species called the black-tailed wrasse exhibited the most curious behavior. These fish relaxed their fins and spun repeatedly around their central axis before the mirror. “It looks like they’re doing a backflip, which is the most bizarre thing for them to do,” he said.
Jordan, an evolutionary biologist at the Max Planck Institute of Animal Behavior, has done extensive underwater fieldwork in Central Africa’s Lake Tanganyika and the Great Barrier Reef. Still, never once in his decade-long career had he observed a wild fish moving like the black-tailed wrasses. From the first time one of his students had shown him a video of the behavior, in 2019, Jordan had suspected that the fish were checking whether the movements of the mirror image matched their own activity. Perhaps they even recognized themselves.
Jordan would need to collect data for many months before drawing any firm conclusions. If indeed the black-tailed wrasses were showing signs of self-recognition—and not just in
