Effectively, says Ramsden, they became “trapped in an infantile state of early development,” even when removed from Universe 25 and introduced to “normal” mice. Instead of interacting with their peers, males compulsively groomed themselves females stopped getting pregnant. Mice born into the chaos couldn’t form normal social bonds or engage in complex social behaviors such as courtship, mating, and pup-rearing. This iteration, dubbed Universe 25, was the first crowding experiment he ran to completion.Įventually Universe 25 took another disturbing turn. The only scarce resource in this microcosm was physical space, and Calhoun suspected that it was only a matter of time before this caused trouble in paradise.Ĭalhoun had been running similar experiments with rodents for decades but had always had to end them prematurely, ironically because of laboratory space constraints, says Edmund Ramsden, a science historian at Queen Mary University of London. In 1968, Calhoun had started the experiment by introducing four mouse couples into a specially designed pen-a veritable rodent Garden of Eden-with numerous “apartments,” abundant nesting supplies, and unlimited food and water.

The results, laid bare at his feet, had taken years to play out. Calhoun wasn’t the survivor of a natural disaster or nuclear meltdown rather, he was a researcher at the National Institute of Mental Health conducting an experiment into the effects of overcrowding on mouse behavior.

Mouse utopia experiment reddit.pdf