Some of the French volunteers who spent 40 days in a cave for science want to go back - team leader May 05, 2021, 04:59 PM facebook Fred Scheiber/AFP via Getty Images 15 French volunteers emerged from a cave last month after spending 40 days with no external contact. The aim was to see how people behaved with no cues letting them know the time. Some of the volunteers loved it so much they would want to go back, the team's leader told Insider. Some of the volunteers who lived in a cave for 40 days for science were disappointed when the experiment was over and would love to go back, the team's leader told Insider.