The experiments
Calhoun's early experiments with rats were carried out on farmland at Rockville, Maryland, starting in 1947.[7]
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 from disease and weather, the rats were said to be in "rat utopia" or "mouse paradise", another psychologist explained.[8]
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,[9] 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.
https://en.wikipedia.org/wiki/Behavioral_sinkhttps://en.wikipedia.org/wiki/John_B._Calhoun