Michele Siffre’s cave study

• Michel Siffre is an adventurer and scientist interested in the study of caves.

  In 1962, at 23 years old, he decided to live in a cave alone in the French Alps for two months, which was partly due to finding a glacier there sometime before he wanted to study.
• He then had the idea of living without any natural light, with no clue what time it was. So instead of studying the glacier, he ended up studying time. He spent his time in the cave reading, writing, researching, and thinking about the future. He settled into a sleep-wake cycle of around 24 hours and 30 minutes.
• He went into the cave on 16 July 1962 and came out of the cave on 14 September 1962. However, Siffre thought the day he came out of the cave was the 20 of August, showing how his time in the cave had warped his sense of time.
• Afterwards, Siffre also had other people participate in cave experiments but found their sleep-wake cycle was 48 hours. Siffre wanted to see if he could also get his sleep-wake cycle to be 48 hours. In addition, this was when people were starting space exploration, and Siffre thought his cave studies could help us know the experiences astronauts go through, which might be similar to being in a cave.
• So, in 1972, when he was 33 years old, he decided to live alone in a cave again – this time, for six months.
• Siffre (1975) found that the absence of external cues significantly altered his circadian rhythm: When he returned from an underground stay with no clocks or light, he believed the date to be a month earlier than it was.
• This suggests that his 24-hour sleep-wake cycle was increased by the lack of external cues, making him believe one day was longer than it was, and leading to his thinking that fewer days had passed.
• Therefore providing us evidence to support the idea that the sleep wake cycle can be longer than 24 hours and we use external cue’s more than we thought!