Coping with Crowding; May 2000; Scientific American Magazine; by de Waal, Aureli, Judge; 6 Page(s)

In 1962 this magazine published a seminal paper by experimental psychologist John B. Calhoun entitled "Population Density and Social Pathology." The article opened dramatically with an observation by the late-18th-century English demographer Thomas Malthus that human population growth is automatically followed by increased vice and misery. Calhoun went on to note that although we know overpopulation causes disease and food shortage, we understand virtually nothing about its behavioral impact.

This reflection had inspired Calhoun to conduct a nightmarish experiment. He placed an expanding rat population in a crammed room and observed that the rats soon set about killing, sexually assaulting and, eventually, cannibalizing one another. Much of this activity happened among the occupants of a central feeding section. Despite the presence of food elsewhere in the room, the rats were irresistibly drawn to the social stimulation-even though many of them could not reach the central food dispensers. This pathological togetherness, as Calhoun described it, as well as the attendant chaos and behavioral deviancy, led him to coin the phrase "behavioral sink."