Mice may be one of only a small group of mammals that can recognize themselves in a mirror. A group of laboratory mice were given an assessment of consciousness called the mirror test. The study published December 5 in the journal Neuron suggests that some rodents display a behavior that resembles self-recognition and might be able to differentiate themselves from other mice.
[Related: What video game-playing mice taught neuroscientists about memory-making.]
Previous studies have shown that mammals including humans, great apes, chimpanzees, elephants, and dolphins have demonstrated the signs that they can recognize their reflections. The fish cleaner wrasse and the large-brained bird the Eurasian magpie have also demonstrated this ability in other studies. (However, the mirror test has faced criticism for its ability to measure self-awareness and can produce false negatives in human children.)
In the study, scientists from the University of Texas Southwestern Medical Center in Dallas marked the foreheads of black-furred mice with a spot of white ink, or black ink on white-furred mice. They observed the mice spending more time grooming their heads in front of the mirror—presumably trying to wash away the new ink.
However, the team cautions that this does not mean that the mice are fully “self-aware.” The only mice that showed this potentially self-recognition-like behavior were those either already accustomed to mirrors, mice that socialized with other animals who looked like them, and the mice with a relatively large spot of ink on their heads.
“The mice required significant external sensory cues to pass the mirror test—we have to put a lot of ink on their heads, and then the tactile stimulus coming from the ink somehow enables the animal to detect the ink on their heads via a mirror reflection,” study co-author and psychiatrist Jun Yokose said in a statement. “Chimps and humans don’t need any of that extra…
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