Researchers believe the yawning robot may have triggered some biological mechanism in the chimps that they associated with sleep. Image: Popular Science composite, Getty Images/ RMJM, Aline ...
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Why is yawning contagious?
Seeing or hearing someone yawn can make you yawn. This phenomenon is not limited to humans; some animals experience contagious yawning, too. But why is yawning contagious? Brain cells called mirror ...
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