ABSTRACT
Collective behavior refers to emergent and extra-institutional behavior rather than to institutionalized, routine, day-to-day behavior. Social definitions need not correspond to reality in any "objective" sense, but they do frame the way people perceive the real world and their reactions to it. Social definitions are analogous to a blueprint. For example, a common belief may be that people are poor because they refuse to work hard or because God wills their poverty. When a disease appears suddenly and its cause is unknown, it falls outside the usual interpretation of disease and the norms that guide how people normally react to those who are sick. Records of epidemics in antiquity and the medieval period indicate that reactions to epidemics frequently fit the model amazingly well. The plague bacillus that causes bubonic plague is transmitted to humans by fleas. Epidemics had wracked society for centuries, of course, and a variety of religious and other nonscientific interpretations existed to explain them.
