Out of the cave: French isolation study ends after 40 days

Ever wondered what it would feel like to unplug from the world and hide in a dark cave for 40 days?

In France, 15 people did that, emerging Saturday from a scientific experiment to say that time seemed to pass more slowly in their cavernous underground abode, where they were deprived of clocks and light.

With big smiles on their pale faces, the 15 left their voluntary isolation in the Lombrives cave to a round of applause and basked in the light of day while wearing special glasses to protect their eyes after so long in the dark.

"It was like pressing pause," said 33-year-old Marina Lancon, one of the seven women in the experiment, adding that she did not feel there was a rush to do anything.

Although she wished she could have stayed in the cave a few days longer, she said she was happy to feel the wind blowing on her face again and hear the birds sing in the green trees of the French Pyrenees.

For 40 days and 40 nights, the group lived in and explored the cave without a sense of time as part of the Deep Time project. There was no sunlight inside, the temperature was 10° Celsius  and the relative humidity stood at 100 per cent.

The cave dwellers had no contact with the outside world, no updates on the pandemic nor any communication with friends or family.

Scientists at the Human Adaptation Institute leading the $1.5 million project said the experiment will help them better understand how people adapt to drastic changes in living conditions and environments, something much of the world can relate to because of the coronavirus pandemic.

As expected, those in the cave lost their sense of time.

“And here we are! We just left after 40 days. For us it was a real surprise," said project director Christian Clot, adding for the majority of the participants, “in our heads, we had walked into the cave 30 days ago.”

At least one team member estimated the time underground at 23 days.

In partnership with labs in France and Switzerland, scientists monitored the 15-member group's sleep patterns, social interactions and behavioural reactions via sensors. One of the sensors was a tiny thermometer inside a capsule that participants swallowed like a pill. The capsules measure body temperature and transmit data to a portable computer until they are expelled naturally.

The team members followed their biological clocks to know when to wake up, go to sleep and eat. They counted their days not in hours but in sleep cycles.

On Friday, scientists monitoring the participants entered the cave to let the research subjects know they would be coming out soon. They said many in the group miscalculated and thought they had another week to 10 days to go.

“It’s really interesting to observe how this group synchronises themselves,” Mr Clot said earlier in a recording from inside the cave.

Working together on projects and organising tasks without being able to set a time to meet was especially challenging, he said.

Although the participants looked visibly tired, two-thirds expressed a desire to remain underground a bit longer in order to finish group projects started during the expedition, Benoit Mauvieux, a chronobiologist involved in the research, told The Associated Press.