Often when one hears about some group of people claiming to experience a highly strange event or similarly acting out in bizarre and irrational manners, it's easy and common to dismiss the episode as a case of "mass hysteria." Phenomena like the audience reaction to Orson Welles' War of the Worlds radio broadcast, "The Dancing Plague of 1518," the "Windshield-Pitting Mystery of 1954," and "The Mad Gasser of Mattoon" are considered by much of the public to be examples of mass hysteria. In the late 1930s and decades after, some sociologists used occurrences like those to help model their theory of "Social Contagion." Like the idea that one or several people claim to experience something unusual, others hear about it and start to see the same thing. Soon it all spirals into an epidemic of vast numbers of people all testifying to the same weirdness with no real, mystical cause. But is the potentially antiquated term of mass hysteria or even its modern descendant "mass psychogenic illnes...