The term and concept derive from a series of over-population experiments Calhoun conducted on Norway rats between 1958 and 1962.[1] In the experiments, Calhoun and his researchers created a series of "rat utopias" - enclosed spaces in which rats were given unlimited access to food and water, enabling unfettered population growth. Calhoun coined the term "behavioral sink" in his February 1, 1962 report in an article titled "Population Density and Social Pathology" in Scientific American[2] on the rat experiment.[3] He would later perform similar experiments on mice, from 1968 to 1972.