Introduction

It is a commonplace that the findings of laboratory experiments will come to do work outside the laboratory walls. Less often explored is how that process is actually effected – more so in the case of the social and behavioural sciences. In what follows, we will see how facts generated by one particular series of experiments with rodents came to stand as evidence for social scientists, planners, architects, environmentalists and population activists concerned with human problems. How did it happen that these specific claims were received by such a broad audience and became evidence for diverse claims? The laboratory experiments were crowding studies conducted by the animal ecologist and psychologist John B. Calhoun at the National Institute of Mental Health (NIMH) from 1954 until 1986. They explored the detrimental effects of high population density or crowding among various strains of laboratory rats and mice. Calhoun’s first paper documenting his results – “Population Density and Social Pathology,” published in Scientific American in 1962 – rapidly became one of the most widely referenced in psychology and in studies of urban populations. It even became a source of information for the design of buildings, such as hospitals, prisons and college dormitories, by architects, planners and psychologists. Although concern with crowding was not new, as one psychologist recollected: “[I]t was a study by Calhoun with rodents that stimulated social and environmental psychologists into action” (Paulus 1988, p. 1).

However, for the sociologist Amos Hawley, this interest in Calhoun’s work within the human sciences was a “curious phenomenon” (1972, p. 522). Certainly, Calhoun had presented his rats and mice as models for man: He argued that with increased population density, social animals became overloaded by unwanted interactions. This, in turn, resulted in social disorganisation and psychological, even physiological, breakdown. He graphically illustrated a variety of behavioural pathologies that emerged: aggression, withdrawal and sexual deviance, pathologies that surely resonated with concerns surrounding human population growth and urbanisation. Nevertheless, social scientists had long been careful in circumscribing the boundary between human and animal. Indeed, the interest in Calhoun’s findings from “people who have so studiously held their work aloof from any comparison with findings of biological researches,” was, Hawley observed, “rather ironic” (1972, p. 522). In spite of common interest in the ecology of human and animal populations, relations between social and biological scientists were strained and superficial, borrowings metaphorical (Gaziano 1996). Although Gregg Mitman (1992, p. 1) describes ecology as “the borderland between the social and the biological sciences through the study of the interrelationships between and among individual organisms and their environment,” this was a border that was carefully policed. Many in the social sciences felt a great deal of distrust towards biological modes of explanation – fears that were hardly allayed by the claims of biologists such as Raymond Pearl that Malthusian problems were better studied through “lower forms of life in the laboratory, under physically and chemically controlled conditions, than from any manipulation of never quite satisfactory demographic statistics” (Pearl 1925, p. 5).