Unsurprisingly, mice kept in environs like those detailed above are “inhibited” in certain ways. They develop abnormal behavioral patterns. In other words, they go crazy. It’s more complex than that as there is even a difference in weight between the brain of an “impoverished” mouse – one with a small, neat cage devoid of toys – and an “enriched” one – a mouse living in a cage with mazes, ladders and other pleasant diversions.

While the prevailing theory of why animals develop such useless, repetitive behavior, known as stereotypic behavior, is based on cage size, research suggests that the animals are repeating an action which may have had a reason in the past (like escape) but has ceased to have meaning and has merely become an end unto itself. In the words of one of the behavioral biologists, “You can say, ‘Oh well, they’re stereotyping because they want to get out,’” Mason says. “But it doesn’t explain why they might do this hour after hour, day after day, month after month. It doesn’t explain why a vole jumps up and down 45,000 times in a night.“

The bottom line has more to do with science than ethics, though. Despite the fact that the entire discourse started because of the ethical concerns of keeping lab mice in small, plain cages with nothing to do for hours on end, it continues because of the ramifications for research. How valid can any research be if performed using mice with severe behavioral problems, much less cognitive and behavioral experiments? How useful is the data when all of the test subjects are obsessive-compulsive?