A group of 15 volunteers has left a cave in southwestern France where they had stayed for 40 days, in an study called the "Deep Time" project probing the limits of human adaptability to isolation.
The underground isolation experiment saw the subjects, aged between 27 and 50, give up watches, phones and natural light, exchanging modern comforts for a cave system with a constant 12 Celsius (54 Fahrenheit) temperature and 95 percent humidity.
Members had to generate their own electricity with a pedal bike and draw water from a well 45 metres below the earth.
Clot, founder of the Human Adaptation Institute, had said the "Deep Time" experiment would test humans' ability to adapt to the loss of their frame of reference for time and space.
Such questions have gained urgency given the widespread isolation people have experienced during the coronavirus pandemic.
But while some researchers joined the project, other scientists criticised the setup of the experiment.
Data on participants' brain activity and cognitive function were gathered before they entered the cave, for comparison with their levels after they left.
But like other experts, Pierre-Marie Lledo of the CNRS government research centre and the Institut Pasteur noted that there was no "control group" in the experiment.
Comparing an unaffected group with those making changes is usually a vital component in scientific studies.
The volunteers plan to give a press conference later Saturday about their experience.