We have, in our minds, a very specific, biological notion of what contagiousness means. But if there can be epidemics of crime or epidemics of fashion, there must be all kinds of things just as contagious as viruses. Have you ever thought about yawning, for instance? Yawning is a surprisingly powerful act. Just because you read the word “yawning” in the previous two sentences—and the two additional “yawns” in this sentence—a good number of you will probably yawn within the next few minutes. Even as I’m writing this, I’ve yawned twice.
