Universe 25: The Terrifying Mouse Utopia Experiment What happens when a society is given everything it needs to survive , but runs out of space to exist? John B. Calhoun's Universe 25 was designed as a rodent utopia, but quickly became an overcrowded dystopia. In 1968, American ethologist John B. Calhoun initiated an experiment that would echo through the halls of psychology, sociology, and urban planning for decades. He constructed a seemingly perfect world for mice—a veritable Eden dubbed “Universe 25” . For a deep dive into the historical origins of this test, you can read this detailed retrospective by The Scientist . The Hard Data: What Was the Experiment? Calhoun placed four pairs of healthy mice in a specially constructed, enclosed habitat. The physical dim...