Human beings aren’t the only animals to yawn when they see another of their kind doing the same. So do dogs and some primates, including chimpanzees. But in a new study at Yerkes National Primate Research Center in Atlanta, chimps appear to make an intriguing distinction: they were more likely to yawn in response to a member of their immediate group than to strangers. Researchers say “contagious yawning” is a sign of empathy. Parents say covering your yawn is a sign of good manners.