John B. Calhoun (May 11, 1917 – September 7, 1995) was an American ethologist and behavioral researcher noted for his studies of population density and its effects on behavior. During his studies, Calhoun coined the term “behavioral sink” to describe aberrant behaviors in overcrowded population density situations and “beautiful ones” to describe passive individuals who withdrew from all social interaction. His work gained world recognition. He spoke at conferences around the world and his opinion was sought by groups as diverse as NASA and the District of Columbia’s Panel on overcrowding in local jails. Calhoun’s rat studies were used as a basis in the development of Edward T. Hall’s 1966 proxemics theories.


  • Early Years
  • 1943-1949
  • 1949-1951
  • 1951-1962
  • 1962-1963
  • 1963-1983
  • Conclusion
  • Calhoun and “The Secret of NIMH”

Early years

John Bumpass Calhoun was born May 11, 1917 in Elkton, Tennessee, the third child of James Calhoun and Fern Madole Calhoun. Their first child died in infancy. Calhoun had three siblings: an older sister, Polly, and two younger brothers, Billy and Dan. His father was a high school principal who rose to a position in administration in the Tennessee Department of Education. His mother was an artist.

His family moved from Elkton to Brownsville, Tennessee, and finally to Nashville, when Calhoun was in junior high school.

At this time, he began attending meetings of the Tennessee Ornithological Society. A Mrs. Laskey, distinguished for her work in bird banding and in the study of the chimney swift, was a pivotal influence on his developing interest in birds and bird habits. Calhoun spent his junior high and high school years banding birds and recording the habits of birds. His first published article was in The Migrant, the journal of the Tennessee Ornithological Society, when he was 15 years old.

Despite his father’s refusal to help him attend an out-of-state university, Calhoun made his way to the University of Virginia where he earned his bachelor’s degree in 1939. During the summers, he worked for Alexander Wetmore, who was assistant secretary of the Smithsonian Institution in Washington DC, doing ornithology work.

He then earned his M.S. and Ph.D. from Northwestern University in 1942 and 1943. The subject of his thesis was the 24-hour rhythms of the Norway rat.

It was at Northwestern that he met his future wife, Edith Gressley, who was a biology major and a student in one of his classes.


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. Interestingly, 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, similar to the Dunbar number. 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.


He continued studying the Norway rat while posted at Jackson Lab in Bar Harbor, Maine. While in Bar Harbor, his first daughter, Catherine (Cat) Calhoun, was born. The family lived in the guesthouse on the Luquer estate.


Calhoun and family moved to Silver Spring, Maryland, in 1951 wher  he worked for Walter Reed Army Medical Center in the division of neuropsychiatry.  A year or two later he and his wife Edith purchased their first home in Kensington, Maryland.  In 1954 he gained his position at the National Institutes of Health 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, Maryland. 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. Two-foot high partitions divided each room into quarters. (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.


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.

In July 1968 four pairs of mice were introduced into the Utopian universe. The universe 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.

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.

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. 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. His study has been cited by writers such as Bill Perkins as a warning of the dangers of the living in an “increasingly crowded and impersonal world.”


Dr. Calhoun believed that his research provided clues to the future of mankind as well as ways to avoid a looming disaster. During the 1960s, he and Dr. Leaonard Duhl formed an informal group, the Space Cadets, which met to discuss the social uses of space. The members of this group came from as diverse professions as architecture, city planning, physics, and psychiatry. In Calhoun’s own words: “Our success in being human has so far derived from our honoring deviance more than tradition. Template changing always has gained a slight, though often tenuous, lead over template obeying. Now we must search diligently for those creative deviants from which, alone, will come the conceptualization of an evolutionary designing process. This can assure us an open-ended future toward whose realization we can participate.”

Calhoun’s book, Environment and Population: Problems of Adaptation: An Experimental Book Integrating Statements by 162 Contributors, was published in 1983.

Calhoun died on 7 September 1995 at the age of 78. His papers were donated to the National Library of Medicine by Edith Calhoun and the American Heritage Center.

A 2008 paper published by London School of Economics examined the “cultural influence” of Calhoun’s experiments. A documentary on the topic was published in 2012.

Calhoun and “The Secret of NIMH”

The Secret of NIMH, an animated film, was based on the children’s novel Mrs. Frisby and the Rats of NIMH, by Robert C. O’Brien, published in 1971. Although there is no corroborative proof that O’Brien was using Dr. Calhoun’s research as a basis for his book there is substantial circumstantial evidence:

  1. The book describes accurately the unusual type of “gathering cage” used by NIMH
  2. The book incorporates features of the rat habitats, such as the spiral staircases
  3. A scientist in the book extends the lifespan of the rats, something Dr. Calhoun tried, unsuccessfully to do
  4. Nicodemus and the dominant rat in one of Calhoun’s early projects were both blinded in one eye
  5. Dr. Calhoun and his associates regularly played Frisbee on their lunch hour


12 thoughts on “Bio

  1. Having been a Senior Lecturer in Science Education and in charge of the Australian Science Education Project’s Text Book “How many people?”, I used to direct my students to a page on the web that featured a huddle of mice (or was it rats) every one of them having multiple bites taken out of them — especially their tails. Sadly, the last time I went to the web site to access this picture, it had been removed.
    Is there any way that you could provide me a copy of that photo please?
    Raymond F. Smith, see


    1. I apologize for the delay in responding. The site is being created in my spare time and at the moment is on pause. Off hand I do not recall the photo. That being said, I still have dozens of papers to scan and have barely touched the photos. If I come across the photo you mention I will add it to the site.


  2. Thank you for your work,Is this experiment replicable?I’m very happy that this experimental result can verify my theory.


    1. I see no reason why the mouse universe experiment could not be replicated, assuming you have the space and the funding to do so.


      1. First of all, thank you for your reply. I can’t repeat the experiment. When I saw this experiment, I was very interested, but when I investigated this experiment, I found that there were almost no similar experimental data reports, so some questions, do not know whether this phenomenon is accidental or every time? I also wanted to ask where to find the latest results of this experiment. There is no theoretical explanation, no text, and I want to try to make some assumptions. First of all, thank you for your reply. I can’t repeat the experiment. When I saw this experiment, I was very interested, but when I investigated this experiment, I found that there were almost no similar experimental data reports, so some confusion, do not know whether this phenomenon is accidental or every time? I also wanted to ask where to find the latest results of this experiment. There is no theoretical explanation. If not, I would like to try to make some assumptions.


      2. I am sorry for my mistake, time matter I did not carefully look at the content of the site.


  3. Alyson Krasinski Mendes December 30, 2020 — 2:30 am

    I’m really greatful for your father experiments, he was brillant. I’m brazilian, it´s not easy to understand everything about his researschs, but it brings me a light and thanks your father i started to study psychology in order to understand human´s behavior. Is there a site i can find his researschs detailed? Thanks in a advance!


    1. I am glad his work was inspired you. I am not sure what exactly you are looking for. This site has a selection of his papers, written over the course of his career. There is also a section called “Additional Reading/Viewing” which has links to films made about his work during his career and papers written about him more recently.


  4. Hi! Could you cite your sources? This biography is almost identical to

    If you wrote this biography, you deserve to be credited as the author on Wikipedia. However, if you copied it from Wikipedia, you should honor its license:


    1. Excellent catch! I did indeed write 99.9% of the entry in wikipedia. Someone else had entered a paragraph, not entirely accurate, so I wrote a more complete, more accurate, much longer version. I also added photos from my personal collection. Periodically I look in to see what changes people have made, some are correct, some not so much. My goal has been to make his work more accessible.


  5. Hi, this Dr. Lee Dugatkin, an animal behaviorist and a historian of science ( I have long been fascinated with your father’s work. Thank you for creating this very helpful site. I would love to chat with you more about your father and his work. If you’d be willing to do that, the best email to reach me is


  6. Thank you for creating this website! Amazing work.


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