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Vol. LX, No. 15
July 25, 2008

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Plumbing the ‘Behavioral Sink’
Medical Historian Examines NIMH Experiments in Crowding

On the front page...

What happens to people who have to live in cramped quarters? From the mid-1950s to the late 1980s, a noted NIH ecologist and experimental psychologist developed a theory on crowding. To prove it, he built a community of rodents. But could his animal studies tell us anything about human populations? A recent NLM History of Medicine lecture, “Finding Humanity in Rat City: John B. Calhoun’s Experiments at NIMH,” explored concepts—and controversies—raised by his research.

Space, the Final Frontier

Calhoun wasn’t the first scientist to wonder about the effects of overcrowding, said Dr. Edmund Ramsden of the University of Exeter and the London School of Economics. As early as the 1920s—when the number of people in American cities first outpaced population in rural areas—scientists began examining “density-dependent mechanisms.” By 1930, sociologist Louis Wirth had described urban life as one of continuous aggression, frustration, interference and conflict as a consequence of an overload of social interaction leading to depleted social relations, personal grief and personality disorders.


  Dr. Edmund Ramsden  
  Dr. Edmund Ramsden  

But were there identifiable factors that prevented species from overpopulating their space? Concerned with the effects of the physical environment on human behavior, health and well-being, Calhoun turned to the lab “to gain a better understanding of the processes that govern population dynamics,” Ramsden said.

Paradise for Mice

Working at NIMH in 1954, Calhoun launched several experiments with rats and mice. In his first series of tests, he placed 32 to 56 rodents in a 10- by 14-foot case in a barn on a Montgomery County farm. Using electrified partitions, he divided the space into four rooms. Each was designed to support 12 adult brown Norway rats. Rats could move between the rooms only via the ramps he built. Because Calhoun provided unlimited water and food as well as protection from predators, disease and weather, the critters were said to be in “rat utopia” or “mouse paradise,” Ramsden explained.

“The one thing they did not have was space...He allowed the population to grow to 80 in the first instance.”

As the scientist observed, a social hierarchy developed: One despot male and 9 females claimed the two defensible pens with only one ramp provided; 60 others crowded into the other 2 pens with two ramps. Calhoun found that “rodent utopia” rapidly became “hell.”

He described the onset of several pathologies: violence and aggression, with rats in the crowded pen “going berserk, attacking females, juveniles and less-active males.” There was also “sexual deviance.” Rats became hypersexual, pursuing females relentlessly even when not in heat.

The mortality rate among females was extremely high. A large proportion of the population became bisexual, then increasingly homosexual, and finally asexual. There was a breakdown in maternal behavior. Mothers stopped caring for their young, stopped building a nest for them and even began to attack them, resulting in a 96 percent mortality rate in the two crowded pens. Calhoun coined a term—“behavioral sink”—to describe the decay.
Calhoun’s “rat utopia” experiments
Calhoun’s “rat utopia” experiments were conducted at a Montgomery County farm. In the graphic above (from Ramsden’s lecture slides), rodents are shown in four pens separated by electrified partitions. As the population grew past capacity, Calhoun observed a developing social hierarchy with toxic pathologies.

Too Close for Comfort

“He clearly saw these rats and mice as models for man,” Ramsden explained. “Life in an unnatural urban environment of ever-increasing density could result in the complete devastation of humanity.” Calhoun discussed his findings in a widely referenced paper, “Population density and social pathology,” published in 1962 in Scientific American, and would continue his experiments for several more decades. He noted that even when population levels dropped and more space became available, the community never recovered. “Even when healthy rodents are placed in the new environment,” Ramsden said, “they never breed successfully again.”

Partly because of the era, his studies hit home. “Calhoun’s rats seemed to mirror a number of social ills and concerns in a very eventful period in American history,” Ramsden said.

From anthropologists and city planners to landscape architects and lawmakers—all paid close attention. The term “behavioral sink” leaked beyond academia, becoming part of pop culture. Writers on both sides of the Atlantic—from journalists to comic book authors—used the phrase as a synonym for the pitfalls of city life.

Abandoning the Rat Race
Dr. Joan Schwartz, assistant director of the Office of Intramural Research
Medical historian Ramsden explored concepts of overcrowding in a recent NLM History of Medicine lecture, “Finding Humanity in Rat City: John B. Calhoun’s Experiments at NIMH.”

Making the leap from mouse to man, however, was not so simple. “This is where it gets controversial,” Ramsden said, describing how other scientists tried to replicate Calhoun’s results in human populations.

“How do you map Calhoun’s pathologies onto human society? How do you measure sexual deviancy? [Researchers] chose venereal disease, illegitimacy and divorce. That stirred up some controversy. How do you measure breakdown in maternal behavior? They chose public welfare and child assistance rates.”

Others turned to the laboratory. The psychologist Jonathan Freedman 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.”

Crowd Control

Freedman suggested a different conclusion, though. Moral decay resulted “not from density, but from excessive social interaction,” Ramsden explained. “Not all of Calhoun’s rats had gone berserk. Those who managed to control space led relatively normal lives.” Striking the right balance between privacy and community, Freedman argued, would reduce social pathology. It was the unwanted unavoidable social interaction that drove even fairly social creatures mad, he believed. Culture and upbringing also play key roles in adapting to environment, others suggested.

Further studies of space design seemed to prove this. One such study compared students living in two different styles of college dormitory— corridor versus a suite style. Those in the corridor perceived the environment as crowded and exhibited increased stress levels. Those in the suite style, where the dormitory was partitioned into a series of separate communal areas, fared better, even though the level of density was similar, Ramsden said. “By comparing the two, [researchers] were able to provide evidence both of pathology and its amelioration through more effective design.

“Calhoun’s studies remained influential in places,” Ramsden concluded, “but for the social sciences more generally, it seemed that simply associating Calhoun’s rodent universes with pathology instead of its amelioration was an opportunity considered too attractive or perhaps too convenient to miss.” NIHRecord Icon

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