Humanities:Experiment rat population Circa 50's?

Answer 1

Experimental psychologist John B. Calhoun in his paper “Population Density and Social Pathology” (published in Scientific American in 1962)?

This was the famous Malthusian rat experiment: in which Calhoun placed an expanding rat population in a crammed room with sufficient food and water and soon observed that the rats set about killing, sexually assaulting and, eventually, cannibalizing one another.