We all know that certain diseases are contagious, but sometimes behaviour is contagious as well. We take a look at some historical examples—such as the Tanganyika laughter epidemic of 1962, and the 1518 case of uncontrollable dancing—and we consider what might drive copycat crimes. There's also the possibility of suicide contagion. Trigger warning: this episode touches on the subject of suicide, please take care while listening.