This
psychologist was most
famous for his
experiment with
population density/
crowding using
rats. His study was
published in
Scientific American in the early 1960's.
The basic idea of the experiment was pretty simple. He built a kind of rat utopia. There was an unlimited supply of food and water and no predators. Calhoun wanted to see what would happen when conditions allowed for unlimited population expansion without adding space.
He observed erratic behavior in the rats after the inevitable crowding of the rat utopia. There were increased instances of fighting and random attacks among the rats. Cannibalism was common. Their breeding patterns also changed drastically. While some of the rats shifted into hypersexual mode others stopped breeding or mated with the same gender. The young were often neglected and sometimes eaten after birth or abandoned entirely.
This is all fine and dandy but Calhoun tried to apply these behaviors to urban dwelling humans. He tried to explain the chaos that sometimes erupted in cities as a product of crowding. Since then most scientists are very skeptical of extropolating research data from animal studies to human situations. At the time, many people believed that cities and the things that came with them (immigration, religous diversity, etc] were all evils that urbanization played a fundamental part in popularizing. In other words, fucked up conclusions to prove fucked up ideas.
If Calhoun had looked at other densely populated urban areas in other countries this experiment would have never happened. It becomes pretty obvious that humans that act largely apart from instinct are more influenced by external cultural aspects in how they deal with their environment.
All cruddy methodology aside, it was an interesting experiment even if it proved nothing useful outside animal populations. I haven't been able to find any pictures of the actual structure he used but I'd love to see what it looked like.