Mice pass the mirror test, a classic indicator of self-recognition

Researchers report December 5 in the journal Neuron that mice display behavior that resembles self-recognition when they see themselves in the mirror. When the researchers marked the foreheads of black-furred mice with a spot of white ink, the mice spent more time grooming their heads in front of the mirror—presumably to try and wash away the ink spot. However, the mice only showed this self-recognition-like behavior if they were already accustomed to mirrors, if they had socialized with other mice who looked like them, and if the ink spot was relatively large.