Anyone who saw Professor Nathaniel Kleitman and his assistant graduate student Bruce Richardson descending Mamoth Cave on June 4, 1938, would think they were part of a geological expedition or the advance guard of a team of archaeologists searching for ancient deposits. Normal. Wrapped up to the eyebrows, with jackets and hoods and loaded with backpacks, flashlights and books, that peculiar couple looked like a hybrid between Indiana Jones and Carlos Darwin in their good years of exploration.
Which Kleitman y Richardson They searched deep in Cave Mamoth, Kentucky, away from sunlight, traffic noise, and any other stimulus that might remind them of the frenetic pace of civilization, was something else entirely: sleep. His goal was to sleep. Although following certain guidelines, of course.
Everything to know better sleep cycles and answering a question that seemed as simple as it was complex was its background: Is it essential that we abide by 24-hour days? Do we humans have an ingrained 24-hour cycle? Could we adjust our circadian rhythms if we wanted to?
Objective: isolate yourself from the world… and the days
Kleitman was determined to get answers. And he also wanted to do it his way, in the first person, experimenting with his own flesh or, if necessary, with his own nights of sleep. For this purpose, he decided that he and Richardson would undergo an experiment that even today, 85 years later, is often cited in the “TOP 10” most delirious scientific tests in history.
For just over a month —32 days, to be precise— both scientists remained voluntarily cloistered in the Kentucky cave to adapt to a 28 hour day. His intention was relatively simple: instead of “living” following weeks with seven 24-hour days, Professor Kleitman and his assistant tried to adjust to a somewhat different format: six days, only special ones, with four hours more than the conventional ones. .
The experiment was peculiar. The conditions that it required, or that Kleitman considered at least more propitious, too. The researchers wanted to adapt to 28-hour days in “uniform conditions of temperature, lighting” and taking advantage of the “calmness of the cave.”
Hence, they opted for Mammoth, at a depth of more than 42.5 meters, a space without natural light, indicators of whether the moon was waning or shining outside and a constant temperature of 12.2ºC. It might not be the most comfortable lab in the world, but the scientists made up for it with artificial light cast by flashlights, a table, and a bunk that kept them safe from cave rats. As for their routine, they spent ten hours at work, nine at leisure, and the same number sleeping. The time they went to bed also changed throughout the study.
The food was supplied from a hotel they seek to Mammoth Cave after Kleitman gave those responsible very precise guidelines, with deliveries based on “time on the surface” and tailored to their own sleep-wake cycles. The first meal was served from 1 pm to 5 pm or 9 am, depending on the day of the experiment. The staff who delivered the food and a courier in charge of delivering and collecting letters were the only people from the outside world with whom Kleitman and Richardson had contact during those 32 days.
“The idea was to see how sleep could be generated in the absence of normal environmental cues, especially light and temperature,” Jerome Siegel, a sleep researcher at the University of California, explained to The Scientist magazine in 2016. One of his objectives was to study the body’s ability to adapt to a cycle other than the normal one, of 24 hours, for which they needed, among other things, to control how their body temperature cycle evolved.
Interestingly, despite the self-imposed 28-h rhythm, the scientists found an endogenously generated 24-h body temperature cycle. Even without external signals —they verified— the bodies maintain a 24-hour temperature cycle linked to our own sensation of sleepiness.
Not only that. The reaction of one and the other, Professor Kleitman and his assistant Richardson, separated by a considerable age range, was curious. To the first, Kleitman, almost 43 years old, the change seemed like a world. Despite the new hours, he still felt tired around ten at night and awake after eight hours. His colleague Richardmon, two decades his junior, seemed adapt better to the change of pattern after a week in the cave.
His findings did not remain an accumulation of measurements and a curious experience for the anecdotes of the history of science. In 1939 Kleitman expressed his conclusions in a book entitled ‘Sleep and Wakefulness’ and -remember in The New York Times- not long after, during World War II, he used his data to recommend that soldiers and workers follow shifts regular. His goal: for their bodies to adjust to a 24-hour cycle, which in turn would lead to increased efficiency when carrying out their tasks.
The one in the Kentucky cave may be the most curious experiment of all that Kleitman starred in, but he is not the only one who demonstrates his scientific zeal and the extent to which he was willing to take his studies to the extreme. Extreme that he did not hesitate to apply to his flesh, as he well demonstrated in July 1938.
Years after the Cave Mamoth test, in 1948, Kleitman passed two weeks aboard a submarine to study the sleep patterns of sailors, and during the 1950s experimented with sleep deprivation to an almost insane extreme, once staying awake for 180 hours. “It gets to the point where someone would confess to anything just to sleep,” he explained in statements collected by The Guardian.
His words, unfortunately, were not just that and sleep deprivation was used, indeed, as a form of torture to which PIDE agents in Portugal did not hesitate to resort, for example, during the Salazar dictatorship.
Cover image: US Government (Open Parks Network) and Renel Wackett (Unsplash)
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