Who is John Calhoun from The Hidden Dimension and what is their importance?

Ethologist John Calhoun conducted a 14-year research study on the effects of overcrowding on rat populations in captivity. Having deliberately overcrowded a series of pens of mice and providing ample food and water, Calhoun noted significant behavioral changes, including increased aggression, reproductive and child-rearing disruptions, and breakdown of social hierarchical structures. From his study came the term "behavioral sink," to describe the gross distortions of behavior he observed.