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The ethologist John B. Calhoun coined the term "behavioral sink" to describe the collapse in behavior which resulted from overcrowding. Over a number of years, Calhoun conducted over-population experiments on rats[1] which culminated in 1962 with the publication of an article in the Scientific American of a study of behavior under conditions of overcrowding.[2] In it, Calhoun coined the term "behavioral sink". Calhoun's work became used, rightly or wrongly, as an animal model of societal collapse, and his study has become a touchstone of urban sociology and psychology in general.[3]

In it, Calhoun described the behavior as follows:

Many [female rats] were unable to carry pregnancy to full term or to survive delivery of their litters if they did. An even greater number, after successfully giving birth, fell short in their maternal functions. Among the males the behavior disturbances ranged from sexual deviation to cannibalism and from frenetic overactivity to a pathological withdrawal from which individuals would emerge to eat, drink and move about only when other members of the community were asleep. The social organization of the animals showed equal disruption. [...]

The common source of these disturbances became most dramatically apparent in the populations of our first series of three experiments, in which we observed the development of what we called a behavioral sink. The animals would crowd together in greatest number in one of the four interconnecting pens in which the colony was maintained. As many as 60 of the 80 rats in each experimental population would assemble in one pen during periods of feeding. Individual rats would rarely eat except in the company of other rats. As a result extreme population densities developed in the pen adopted for eating, leaving the others with sparse populations.

[...] In the experiments in which the behavioral sink developed, infant mortality ran as high as 96 percent among the most disoriented groups in the population.[4]

Calhoun would continue his experiments for many years, but the publication of the 1962 article put the concept in the public domain, where it took root in popular culture as an analogy for human behavior.

Calhoun retired from NIMH in 1984, but continued to work on his research results until his death on September 7, 1995. [5]

The experiments

Calhoun's early experiments with rats were carried out on farmland at Rockville, Maryland, starting in 1947.[6]

While Calhoun was working at NIMH in 1954, he began numerous experiments with rats and mice. During his first tests, he placed around 32 to 56 rodents in a 10 x 14-foot case in a barn in Montgomery County. He separated the space into four rooms. Every room was specifically created to support a dozen matured brown Norwegian rats. Rats could maneuver between the rooms by using the ramps. Since Calhoun provided unlimited resources, such as water, food, and also protection from predators as well as disease and weather, the rats were said to be in “rat utopia” or “mouse paradise,” another psychologist explained.[7]

Following his earlier experiments with rats, in 1972 Calhoun would later create his "Mortality-Inhibiting Environment for Mice": a 101-inch square cage for mice with food and water replenished to support any increase in population,[8] which took his experimental approach to its limits. In his most famous experiment in the series, "Universe 25", population peaked at 2,200 mice and thereafter exhibited a variety of abnormal, often destructive behaviors. By the 600th day, the population was on its way to extinction.[6]

Influence of the concept

Template:Expand section The 1968 Scientific American article came at a time at which overpopulation had become a subject of great public interest, and had a considerable cultural influence.[9] The study was directly referenced in some works of fiction,[9] and may have been an influence on many more.

Calhoun had phrased much of his work in anthropomorphic terms, in a way that made his ideas highly accessible to a lay audience.[6] Tom Wolfe wrote about the concept in his article "Oh Rotten Gotham! Sliding Down into the Behavioral Sink", later to be made into the last chapter of The Pump House Gang.[9] Lewis Mumford also referenced Calhoun's work in his The City in History,[10] stating that

No small part of this ugly barbarization has been due to sheer physical congestion: a diagnosis now partly confirmed with scientific experiments with rats – for when they are placed in equally congested quarters, they exhibit the same symptoms of stress, alienation, hostility, sexual perversion, parental incompetence, and rabid violence that we now find in the Megalopolis.[11]

Calhoun's work has been referenced in comic books, including Batman and 2000 AD.[9]

Calhoun himself saw the fate of the population of mice as a metaphor for the potential fate of man. He characterized the social breakdown as a “spiritual death”,[8] with reference to bodily death as the “second death” mentioned in the Biblical book of Revelation 2:11


"Calhoun's work with rats inspired the 1971 children's book, Mrs. Frisby and the Rats of NIMH, by Robert C. O'Brien, which was adapted into a 1982 animated film, The Secret of NIMH." [5]

Mouse to man comparison

Making the leap from mouse to man, however, was not so simple. “This is where it gets controversial,” Dr. Edmund Ramsden of the University of Exeter and the London School of Economics said, describing how other scientists tried to replicate Calhoun’s results in human populations. He cited psychologist Jonathan Freedman's experiment, where he recruited high school and university students to carry out a series of experiments that measured the effects of density on behavior. He measured their stress, discomfort, aggression, competitiveness, and general unpleasantness. When he declared to have found no appreciative negative effects in 1975, the tide began to turn on Calhoun’s utopia. Freedman’s work, Ramsden noted, suggested that density was no longer a primary explanatory variable for society’s ruin. A distinction was drawn between animals and humans. “Rats may suffer from crowding; human beings can cope...Calhoun’s research was seen not only as questionable, but also as dangerous.”[12]


  1. Hall, Edward, T. (1966). The Hidden Dimension: An Anthropologist Examines Humans' Use of Space in Public and in Private, Anchor Books. ASIN B0006BNQW2.
  2. Calhoun, John B. (1962). Population density and social pathology. Scientific American 206 (3): 139–148.
  3. Hock, Roger R. (2004). Forty Studies that Changed Psychology : Explorations into the History of Psychological Research (5th Edition), Prentice Hall.
  4. PMID 18730425 (PMID 18730425)
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  5. 5.0 5.1 NLM Announces the Public Release of the Papers of John B. Calhoun, U.S. National Library of Medicine, 2013-10-13.
  6. 6.0 6.1 6.2 The Behavioral Sink. Cabinet Magazine. URL accessed on 2012-08-24.
  7. Medical Historian Examines NIMH Experiments in Crowding, nih record, 2013-10-13.
  8. 8.0 8.1 8.2 PMID 4734760 (PMID 4734760)
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  9. 9.0 9.1 9.2 9.3 Ramsden, Edmund (2009). Escaping the Laboratory: the rodent experiments of John B. Calhoun & their cultural influence. Journal of Social History 42 (3).
  10. Moore, Adam (2010). Privacy rights moral and legal foundations, University Park, Pa: Pennsylvania State University Press.
  11. Lewis Mumford, The City in History, 1961, p 210. cited in Theodore D. Fuller, et al. "Chronic Stress and Psychological Well-being: Evidence from Thailand on Household Crowding," Social Science Medicine, 42 (1996): 267
  12. Garnett, Carla. (2008). Plumbing the ‘Behavioral Sink’, Medical Historian Examines NIMH Experiments in Crowding. NIH Record. Retrieved 2013-07-07.