Humans and other social animals suffer from something called contagious itching. It's when you see somebody else scratching and suddenly need to scratch yourself, too. Now, a group of scientists led by Zhou-Feng Chen at the Center for the Study of Itch at Washington University in St. Louis have discovered that mice have the same problem. In the process, the scientists may have identified what causes some contagious behaviors.
Once Chen and his colleagues had established that mice have contagious itching just like other mammals, they wanted to know more. How did such behavior arise in the neurocircuitry of mouse brains? One possibility was that it was a kind of empathetic reaction to mice they knew well or that it was a response to smelling or touching an itchy mouse. But they found that mice could catch itches from strange mice—and even from mice they saw on video (see video above). So clearly all they needed was to see another itchy mouse to get itchy themselves.
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