John B. Calhoun

After graduating from Northwestern, he taught at Emory University and Ohio State University. In 1946, he and his wife, Edith, moved to Towson, Maryland, a suburb of Baltimore. Calhoun worked on the Rodent Ecology Project at Johns Hopkins University. In March 1947, he began a 28-month study of a colony of Norway rats in a 10,000-square-foot (930 m²) outdoor pen. Even though five females over this time-span could theoretically produce 5,000 healthy progeny for this size pen, Calhoun found that the population never exceeded 200 individuals, and stabilized at 150. Moreover, the rats were not randomly scattered throughout the pen area, but had organized themselves into twelve or thirteen local colonies of a dozen rats each. He noted that twelve rats is the maximum number that can live harmoniously in a natural group, beyond which stress and psychological effects function as group break-up forces.

While posted at Jackson Lab in Bar Harbor, Maine, he continued studying the Norway rat colony until 1951. While in Bar Harbor, his first daughter, Cat Calhoun, was born. The family lived in the guesthouse on the Luquer estate.

Calhoun and family moved back to Silver Spring, Maryland, in 1951. He worked for Walter Reed Army Medical Center in the division of neuropsychiatry before gaining his position at the National Institutes of Health in 1954 where he worked for the next 33 years. 1954 was also the year his second daughter, Cheshire Calhoun, was born.

Calhoun pursued his experiments in behavior, using domesticated Norway rats, at his lab on the second floor of a huge barn on the Casey farm in the country outside Rockville, MD. The area is now a suburban center but the barn still stands, renovated for suburban usage. In the days of Calhoun's occupancy there was a small, cluttered office area at the top of the stairs. The rodent odor was overpowering, and it took some time before one could breathe normally.

The research area was divided into three parts. In the center section a box-like room was built. There was a hallway all the way around this box and stairs that led to the top of it. This box was divided into 4 rooms, or habitats, 10 feet x 14 feet x 9 feet (3.0 m x 4.3 m x 2.7 m). Each room had a door for a researcher or caretaker to enter by, and in the ceiling of each room was a glass window. The activity in each room could be observed through these windows. Each room was divided into quarters by 2-foot-high (0.61 m) partitions. "V" shaped ramps connected pens I and II, II and III, and III and IV. Pens I and IV were not connected. Mounted on the wall in the corner of each quarter was an artificial burrow, which could be accessed via a spiral staircase. In two of the quarters the "burrows" were 3 feet (0.91 m) from the floor, and in the other two the "burrows" were 6 feet (1.8 m) from the floor. Each quarter also contained a drinking station and a feeding station. These variations in environment led to differences in behavior patterns and ultimately to the concept of "behavioral sinks."

The research carried on in the lab on Casey's farm began in 1958 and lasted until 1962, when Calhoun was invited to spend a year at The Center for Advanced Study in the Behavioral Sciences in Stanford, California.

John Calhoun with mice experiment

In the early 1960s, the National Institute of Mental Health (NIMH) acquired property in a rural area outside Poolesville, Maryland. The facility that was built on this property housed several research projects, including those headed by Calhoun. It was here that his most famous experiment, the mouse universe, was created.[1] In July 1968, four pairs of mice were introduced into the habitat. The habitat was a 9-foot (2.7 m) square metal pen with 4.5-foot-high (1.4 m) sides. Each side had four groups of four vertical, wire mesh "tunnels." The "tunnels" gave access to nesting boxes, food hoppers, and water dispensers. There was no shortage of food or water or nesting material. There were no predators. The only adversity was the limit on space.

John Calhoun meeting Pope Paul VI on 27 September 1973

Initially, the population grew rapidly, doubling every 55 days. The population reached 620 by day 315, after which the population growth dropped markedly, doubling only every 145 days. The last surviving birth was on day 600, bringing the total population to a mere 2200 mice, even though the experiment setup allowed for as many as 3840 mice in terms of nesting space. This period between day 315 and day 600 saw a breakdown in social structure and in normal social behavior. Among the aberrations in behavior were the following: expulsion of young before weaning was complete, wounding of young, increase in homosexual behavior, inability of dominant males to maintain the defense of their territory and females, aggressive behavior of females, passivity of non-dominant males with increased attacks on each other which were not defended against.[2][3]

After day 600, the social breakdown continued and the population declined toward extinction. During this period females ceased to reproduce. Their male counterparts withdrew completely, never engaging in courtship or fighting and only engaging in tasks that were essential to their health. They ate, drank, slept, and groomed themselves – all solitary pursuits. Sleek, healthy coats and an absence of scars characterized these males. They were dubbed "the beautiful ones." Breeding never resumed and behavior patterns were permanently changed.

The conclusions drawn from this experiment were that when all available space is taken and all social roles filled, competition and the stresses experienced by the individuals will result in a total breakdown in complex social behaviors, ultimately resulting in the demise of the population.

Calhoun saw the fate of the population of mice as a metaphor for the potential fate of man. He characterized the social breakdown as a "second death," with reference to the "second death" mentioned in the Biblical book of Revelation 2:11.[1] His study has been cited by writers such as Bill Perkins as a warning of the dangers of living in an "increasingly crowded and impersonal world."[4]