Contagious yawning

If someone with whom you identify yawns, chances are you’ll yawn, too. Contagious yawning has been observed in other vertebrates, not just mammals or primates. Even so, it’s hard to say why we yawn when we aren’t sleepy or tired. Professor Jim Bough, however, says he’s figured it out. When we’re sleepy or tired, he says, instinctual behaviors dominate. Yawning might have originated in the Paleozoic with the evolution of fish and amphibians as a means of communication. When another animal yawns we instinctively reply in kind.