It’s a standing joke among scientists that most headlines about health breakthroughs should be suffixed with the words “in mice”: “Vitamin D regulates cancer immunity”? Sure – in mice. For there’s many a slip ’twixt mouse and man, and not only in medicine but also in psychology and sociology, as Jon Adams and Edmund Ramsden’s fascinating tale attests.
Mice and their more intelligent brethren, rats, have long been used as proxies for humans in the lab. The notorious psychologist BF Skinner invented the “operant conditioning chamber”, or what became known (to his chagrin) as the “Skinner box”: in it, a rat or pigeon pressed a lever to get a pellet of food, or was encouraged to move from one side of the box to the other as the walls were heated up. From Skinner’s accounts of such experiments, we gained the concept of “positive reinforcement” of behaviour.
The hero of Rat City, John B Calhoun, was an American scientist who thought such experiments far too circumscribed to tell us much about reality. Instead, from 1947 to 1982, he built an increasingly complicated series of wooden habitation complexes (which he later came to call “universes”) for rats and mice, containing dozens or even hundreds of animals, and recorded the rise and fall of entire rodent societies. His results became famous, and contributed to mid-century panics about global overpopulation and social decline.
Why rats? There were too many of them in the wrong places, so they were urban “pests”. Poisoning a whole city block of rats didn’t work, because all that did was encourage neighbouring colonies to expand their territory to fill the gap. Many people assumed that the prevalence of rats in impoverished districts proved that poor people were dirty, but as Calhoun and others showed, the people had a rat problem because they had a quality-of-housing problem. Demolishing slums and decanting the poor into concrete high-rises didn’t make their lives better.
Indeed, Calhoun’s work seemed to show why the promise of tower blocks was false. As the population of his rat cities grew, the animals became more stressed. We call this “overcrowding”, but as Calhoun discovered, the reason for the rats’ distress wasn’t the lack of physical space for each animal, but rather the constant unwanted social contact. Individuals could no longer form small groups, but suffered constant adrenaline spikes from being around everyone else all the time.
