Human Confinement Experiment in Caves

Leviathan Press:

Imagine if you were deprived of your senses of sight, hearing, touch, etc., how would you perceive time? Even if you have artificial lighting like Silver in the article, and your hearing, touch, etc. are all normal, but you are just in an isolated environment, what changes will happen to your perception of time?

The passage of time is a subjective experience, and concurrent emotions can easily distort it. Specifically, when people are in a negative emotional state, time seems to pass particularly slowly (days seem like years). Current research suggests that dopamine plays an important role in time perception, causing us to overestimate or underestimate the passage of time. In 1962, a French speleologist named Michel Siffre spent two months in a completely isolated underground cave, without a clock, calendar, or sun (to tell him the time). He only ate when he was hungry and slept when he was sleepy. His goal was to find out how the natural rhythms of human life would be affected when living "outside of time."

Over the next decade, Silver organized a dozen more underground time-isolation experiments, finally returning to spend six months in a Texas cave himself in 1972. His work helped create the field of human chronobiology. Joshua Foer interviewed Silver by email.

Siffre arriving at Paris-Orly Airport on September 17, 1962.

Joshua Foer: You were only 23 years old in 1962. What made you decide to live underground in complete isolation for 63 days?

Michel Silver: You have to understand that I am a geologist by training. In 1961, we discovered an underground glacier in the Alps, about 70 kilometers from Nice. Initially, my idea was to prepare a geological expedition and spend about 15 days underground studying the glacier, but after a few months, I said to myself: "Well, 15 days is not enough. I can't see anything." So, I decided to stay for two months. Then I had this idea - it became an idea that has been with me all my life. I decided to live like an animal: without a watch, in darkness, without knowing the time.

Forre: You ended up not studying caves but time.

Silver: Yes, I invented a simple scientific experiment. I posted a team of people at the entrance of the cave. I would contact them every time I got up, when I ate, and before I went to bed. My team had no right to contact me, so I had no way of knowing the time outside. Without knowing it, I founded the field of human chronobiology. As early as 1922, people had discovered that mice have a built-in biological clock. My experiments showed that humans, like lower mammals, have a biological clock.

Silver's experiment, conducted in Texas in 1972, used reading material that was well suited to the cave-dwelling context: Plato.

Fore: When you first went underground, the temperature was below zero and the humidity was 98 percent. How did you pass the time?

Silver: I had very poor equipment and a small campsite with many things crammed together. My feet were always wet and my body temperature dropped to only 34 degrees Celsius (93 degrees Fahrenheit). I spent my leisure time in the cave reading, writing, and doing research. I also spent a lot of time thinking about my future.

In addition, every time I called the ground, I had to do two tests. First, I would take my pulse. Second, there was a mental test. I had to count from 1 to 120 at a rate of one number per second. With this test, we made a significant discovery: it took me five minutes to count to 120. In other words, I mentally experienced the real five minutes as if they were only two minutes.

Foer: Psychologist Elizabeth Loftus did an experiment where she showed people a video of a bank robbery and asked them to estimate how long it would take. The subjects overestimated how long it would take by 500 percent. It seems that our subjective experience of time is highly variable. How do you feel the passage of time without a clock?

Silver: My sense of time was severely disrupted. I went down into the cave on July 16, and planned to finish the experiment on September 14. When my surface team told me that day had finally come, I thought it was only August 20. I felt like I had another month in the cave. My psychological sense of time was tripled.

Foer: What do you think causes this huge disconnect between psychological time and the real clock?

Silver: This is a big question that I've been studying for 40 years. I believe that when you're in the night -- the cave is completely dark, with only one light bulb -- your memory can't capture time. You forget. You can't remember what you did a day or two ago. The only two moments that change are when you wake up and when you go to bed. Other than that, it's completely dark. It's like one very long day.

Silver weighs himself during an experiment in Texas in 1972.

For: These kinds of isolation experiments can also be easily done in a lab. Why do you always prefer to do them underground?

Silver: The lab is a great place to do these experiments, but you have to find people who are motivated enough. It's difficult to ask people to spend months in a chamber. Between 1962 and 1972, a professor in Germany conducted more than 150 isolation experiments in a man-made underground bunker, but they were short-term experiments, lasting only about a month. The people we send underground are originally cave explorers, who are very interested in the caves themselves and are very motivated to stay longer.

Foer: When you're underground, completely cut off from any human-defined measure of time, your body can sleep as long as it wants. You get perfect sleep, so to speak. What does that feel like?

Silver: My sleep is perfect! My body chooses when to sleep and when to eat. That's very important. Our study shows that my sleep/wake cycle is not 24 hours like people on the ground, but slightly longer, about 24 hours and 30 minutes. But the important thing is that we have demonstrated that there is an internal biological clock that is independent of the natural day and night cycle of the Earth.

Interestingly, in subsequent experiments I conducted with other subjects, all of the cavemen showed circadian cycles that were longer than 24 hours. In fact, they were generally able to establish a 48-hour sleep cycle: they would be active for 36 hours, followed by about 12 to 14 hours of sleep. After we made this discovery, the French army gave me a lot of funding. They wanted me to analyze how it might be possible to double the amount of waking activity in soldiers.

Silver (center) in his cave in 1964.

For: What did you find?

Silver: After my own experiments, I had a man in the cave for four months, and then a woman for three months. In 1966, another person was underground for six months, and then we did two more four-month experiments. We analyzed the sleep stages—REM, dreaming, and slow-wave sleep—and made another discovery.

We showed a correlation between how long a person was awake and how long they dreamed the next night. Roughly speaking, for every ten minutes of wakefulness per day, men spent one minute more in REM sleep. We also found that the more you dream, the shorter your reaction time is during the next waking period. After we made this discovery, the French army tried to find drugs that could artificially increase dreaming time, hoping to keep soldiers awake for thirty hours or more.

Foer: Ten years after your first isolation experiment, you went back underground yourself, this time spending 205 days in the Midnight Cave near Del Rio, Texas. Why did you go back?

Silver: Two reasons. First, I was interested in studying the effects of aging on psychological time. My plan was to do an experiment every ten or fifteen years to see if there were any changes in my brain's perception of time. Second, everyone I put in the underground experiment, except me, had established a 48-hour sleep/wake cycle. I decided to stay underground for six months to try to get that 48-hour cycle.

Fore: Why do people adjust to this 48-hour cycle?

Silver: I don't have a theory about it. I don't do theories. The 48-hour cycle is a fact. I observed it, and I'm convinced of it, but nobody knows what causes such a large desynchronization of the sleep-wake cycle. Now that the Cold War is over, it's harder to get funding. Today, only mathematicians and physiologists can get any closer to this problem.

During the 1972 experiment, Silver had electrodes plastered all over his body to monitor his heart, brain, and muscle activity.

Foer: Your first underground quarantine experiment took place in 1962, the same year that the Cuban Missile Crisis made the importance of bomb shelters clear to the world, and the year before that, Yuri Gagarin went into space for the first time. How did these two events change our view of the underground?

Silver: I arrived at the right time. It was the Cold War, and we knew nothing about the sleep cycle of humans in outer space. Not only were the United States and Russia competing for manned space flight, but France had just started its nuclear submarine program. French headquarters had no idea how to best organize the sleep cycle of submarine crews. This is probably why I received so much financial support. NASA interpreted my first experiment in 1962 and invested money in complex mathematical analysis.

Foer: What is it about the underground that both attracts and scares us?

Silver: Darkness. You need a lamp. If your lamp goes out, you die. In the Middle Ages, caves were where demons lived. But at the same time, caves are a place of hope. We go into caves to find minerals and treasures, and it's one of the last places where you can still have adventures and discover new things.

Foer: You celebrated the millennium with foie gras and champagne in Clamouse, 2,970 feet underground, but you were three and a half days late. You also missed your 61st birthday. Why did it take you almost 30 years to decide to go underground again?

Silver: When I walked out of the midnight cave in 1972, I was $100,000 in debt. I had severely underestimated the cost of bringing my experiment from France to Texas, so I had to leave chronobiology. Most of the data I had from that experiment had not yet been mathematically analyzed. In 1999, I decided to go back to a cave in southern France. I spent two months there studying the effects of aging on circadian rhythms. I was following in the footsteps of John Glenn, who returned to space at age 77.

Fore: I understand you're currently working on a "permanent underground site for human confinement and chronobiology experiments." What else are you working on?

Silver: The experiments in the caves are over. You can't do them anymore. When we first did it, I was young, and we took all the risks. Now, there are restrictions on researchers. Now you have ethics committees. Let me give you an example. In 1964, the second man to go underground after me had a microphone attached to his head. One day he slept for 33 hours, and we weren't sure if he was dead. It was the first time we'd ever seen a man sleep that long. I thought, well, I'll go down into the cave and see what's going on. By the 34th hour, he was snoring, and we knew he was still alive. A few minutes later, he called to the surface to let us take his pulse. Today, the doctor would have to wake him up, or the risk would be too great.

Fore: Have you ever successfully established a 48-hour cycle?

Silver: I have. During two periods in the 1972 experiment in Texas, my circadian rhythms were 48 hours long, but they were not regular. I would be awake for 36 hours straight, and then sleep for 12 hours. I could not tell the difference between these long days and the days that lasted only 24 hours. I studied the journal I kept in the cave, cycle by cycle, and there was no evidence that I perceived the days differently. Sometimes I slept for two hours, sometimes for 18 hours, but I could not tell the difference. I think this is an experience that we can all understand. It's a problem of psychological time. It's a human problem. What is time? We don't know.

Text/Joshua Foer, Michel Siffre

Translated by Kushan

Proofreading/Rabbit's Light Footsteps

Original text/www.cabinetmagazine.org/issues/30/foer_siffre.php

This article is based on the Creative Commons License (BY-NC) and is published by Kushan on Leviathan

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