The year was 1968. American biologist John Calhoun (1917–1995) started his 25th take on an experiment – at the National Institute of Mental Health in Maryland – that consisted of a colony known as the Mortality-Inhibiting Environment for Mice. Or, unofficially, “mouse heaven”.
This rodent utopia consisted of a large pen, replete with all that a mouse could wish for: unlimited food and water, a perfect climate, lots of paper for nest-building, and 256 separate apartments. Calhoun even took care to screen the mice to avoid disease. In theory, having been freed of predators and other worries, mice could reach old age in tranquillity.
But this being the 25th time he performed the experiment, Calhoun knew the outcome from the outset: mouse heaven could degenerate into mouse hell.
Who was John Calhoun?
After earning his PhD in Zoology, in 1946 Calhoun joined the Rodent Ecology Project in Baltimore. The project’s aim was to rid cities of rodent pests. Its biggest shortcoming, however, was that little was known about the behaviour and lifestyle of rats. Calhoun decided to start observing Norway rats with the aim of understanding how rodent populations grow and decline.
In time, Calhoun’s fascination with rodent behaviour deviated from its initial objective, and he decided to create more elaborate and carefully controlled environments, sort of rodent cities. He thought that urbanisation could be studied in rodents first to be then extrapolated to human beings.
“Universe 25”
His most famous utopia – called “Universe 25” (because it was the 25th take on the experiment) – begun in July 1968. It started off with eight albino mice, to which, after three-and-a-half months, the first pups were born. From then onward, the population doubled every 55 days. This rhythm somewhat subsided, but the population continued to grow, peaking at 2,200 mice during Month 19.
This is when problems started to surface. In the wild, predators, disease, and the weather limit population growth. But in the mouse utopia, juveniles rarely died. The abnormal number of youngsters gave rise to a host of problems.
Violence
Rodent societies are organised hierarchically. Dominant alpha males control harems of females and establish dominance through fighting. The less dominant – those who lose – usually leave the community, to start over somewhere else. But in this mouse heaven – most probably the “best in the world” where mice lived “the best of times” – the losing mice could not run away. So they stayed on, and Calhoun called them “dropouts.” As only few juveniles died, huge numbers of dropouts would gather in the centre of the pen. Bearing scars and other marks of past fighting, and it was not infrequent that they would engage in senseless violence.
The dominant males too had to face a lot of violence. At first, they defended the apartments where they kept their harems. But since many mice survived and became restless and violent, the alpha males gave up defending their apartments altogether, out of exhaustion. Consequently, rogue males routinely invaded apartments where females nursed the young ones. The mothers too succumbed to the stress, kicking out the pups from the nest before the pups were ready to face the adult world. Some mothers even attacked their own offspring during the fights, or else left them behind to die of neglect when they fled to other apartments.
Author Esther Inglis-Arkell summarised the observations thus:
“At the peak population, most mice spent every living second in the company of hundreds of other mice. They gathered in the main squares, waiting to be fed and occasionally attacking each other. Few females carried pregnancies to term, and the ones that did seemed to simply forget about their babies. They’d move half their litter away from danger and forget the rest. Sometimes they’d drop and abandon a baby while they were carrying it.”
The “beautiful ones”
Then something else happened. To borrow Inglis-Arkell’s words:
“The few secluded spaces housed a population Calhoun called, ‘the beautiful ones.’ Generally guarded by one male, the females—and few males—inside the space didn’t breed or fight or do anything but eat and groom and sleep. When the population started declining the beautiful ones were spared from violence and death, but had completely lost touch with social behaviors, including having sex or caring for their young.”
While obsessing over their appearance, the “beautiful” males had absolutely no interest in courting females.
The lack of sex and the inability to raise pups properly triggered a population decline. From Month 21 onward, newborn pups rarely lived more than a few days. And then, new births ceased completely. Older mice, living like hermits or grooming all day, little by little died out.
Less than five years into the experiment – in spring 1973 – the population went extinct.
Lack of space
Whereas the mice in this experiment had all they wanted – food, water, bedding, no predators, no disease – they lacked space. Overcrowding and a higher frequency of unwanted social contact ensued. These, in turn, led to elevated levels of stress and aggression. In a small, overcrowded space the choice between fight and flight became non-existent. Not having anywhere to flee to, mice had to fight.
Violence led to cannibalism and infanticide, and males became hypersexual, pansexual, and homosexual. At the end of the experiment, the mice that managed to survive had paid a hefty psychological price: they became asexual and utterly withdrawn, almost “socially autistic”. Edmund Ramsden, a science historian at Queen Mary University of London, concluded that the mice had effectively became “trapped in an infantile state of early development”.
Metaphor for human society?
In the late 1960s and early 1970s, pessimism about human population growth and overcrowding was rife, and Calhoun’s experiment seemed to resonate with the public mood.
In 1968, the year of Calhoun’s 25th take on the experiment, Paul Ehrlich published The Population Bomb, an alarmist book predicting imminent starvation and population crashes due to world-wide overpopulation. The theme was quickly taken up by pop culture: movies like Soylent Green (starring Charlton Heston, 1973), comics like 2000AD, and even one Star Trek episode (“The Mark of Gideon”, 1969) relayed the message to the masses. Calhoun himself actively encouraged parallelisms between his rodent experiments and human (urban) societies: “I shall largely speak of mice, but my thoughts are on man.”
Lately, academics have noticed similarities to the Industrial Revolution and the spread of modern urbanisation. Urban populations exploded in the nineteenth and twentieth century, mostly due to less infant mortality, just like the mice experienced. But in the recent past, human birth rates in developed countries have dropped sharply and it would seem that young people have lost interest in sex. The parallels with the mouse utopia seem too obvious to dismiss.
Others see other parallels: women are choosing not to have children; effete males and hyper-aggressive females are becoming more commonplace.
Others still see the experiment as a refutation of socialist welfare systems – providing populations with too much security limits “personal growth” and leads to widespread decline.
Others see Calhoun’s experiment as a clear warning: “the city [is] a perversion of natural energies.” Some modern sociologists claim that this “obsession” with the city is a contemporary phenomenon – I argue that it is not. The Englishman William Cobbett believed in those very words – and he lived between 1763 and 1835. (The Idea of the City in Nineteenth-Century Britain, edited by B.I. Coleman, 1973, provides a very good background to this subject).
There are many, disparate interpretations one could give to Calhoun’s experiment, and political leanings and personal views obviously colour most if not all of them.
However, academics have over time understood that Calhoun’s work was not simply about population density but about degrees of social interaction. By improving how individuals share space, crowding stress can be avoided. People need privacy, and need to feel they can control a situation and their social role. They also need to see poverty tackled and inequality reduced. In 1979, Calhoun wrote that “no single area of intellectual effort can exert a greater influence on human welfare than that contributing to better design of the built environment.”
Calhoun called the degeneration, or decay, observed in the mouse universe as “behavioural sink” – overcrowding would cause ordered behaviour gradually to disintegrate and social order to break down.
I cannot help but asking myself if there is one interpretation for the entire world (a one-size-fits-all), or whether different countries, with different situations, might each merit their own interpretation.
Does Calhoun’s experiment perhaps apply to Malta rather than to other countries?
Malta is arguably a sui-generis case. It’s extremely small and an island-state. Is there the possibility of fight or flight on this island, or is there no option for “flight”?
Though most of the population can somehow communicate in two languages, in reality the vast majority masters only one and, to compound matters, the island is not integrated in any English-speaking administrative system. Whereas a Greek who lives on an island can move to the mainland and still inhabit the same system (but without the insular constraints), the Maltese has no mainland to move to. Everywhere else is another system for the Maltese.
This is significant because critics of Calhoun’s work have argued that population density among humans – a statistical measure – doesn’t necessarily correlate with crowding – a feeling of psychological stress. Whereas this could apply to bigger countries, perhaps in Malta population density does correlate with overcrowding.
Calhoun argued that too much contact with other members of the community triggers a disorganisation of genetic predispositions. He argued that different brain sizes meant that disorganisation in mice happened to a higher degree than in humans. But it still happens.
Is Malta a self-contained pen? And do the Maltese (and the foreign workers sharing our space) behave like the mice in Calhoun’s experiment?
One last thought
For the Italians, somebody cunning is vecchia volpe and for the French vieux renard (both mean “old fox”). For the English it’s wily old fox.
But for us it’s ġurdien xiħ (“old mouse”).
I don’t know if I’m being ingenious or ingenuous, but perhaps there’s something to be said about our ancestors’ choice of animal to convey this psychological attribute.