From rodent utopia to urban hell: population, pathology, and the crowded rats of NIMH.

In a series of experiments at the National Institute of Mental Health, the animal ecologist John B. Calhoun offered rats everything they needed, except space. The resulting population explosion was followed by a series of "social pathologies"--violence, sexual deviance, and withdrawal. This essay examines the influence of Calhoun's experiments among psychologists and sociologists concerned with the effects of the built environment on health and behavior. Some saw evidence of the danger of the crowd in Calhoun's "rat cities" and fastened on a method of analysis that could be transferred to the study of urban man. Others, however, cautioned against drawing analogies between rodents and humans. The ensuing dispute saw social scientists involved in a careful negotiation over the structure and meaning of Calhoun's experimental systems and, with it, over the significance of the crowd in the laboratory, institution, and city.