Perceptions of time

I have long been interested in how we perceive time. There are many markers of time’s passage, daily and seasonal changes and biological changes being just some of them. Albert Einstein revolutionized our understanding of time by saying that physical time of an event is what is given by clocks placed at the location of the event, and then showed that the interval in clock readings between any two events depended on the state of motion of the clocks.

But there is also the psychological perception of time, the sense of how much time has elapsed when one has no external means such as a clock or diurnal rhythms to keep track of it. In an experiment, 15 volunteers were kept in a deep cave for 40 days without any means of knowing the passage of time other than their sense of it.

The group lived in and explored the cave as part of a project called Deep Time. There was no natural light, the temperature was 10C and the relative humidity 100%. They had no contact with the outside world, no updates on the pandemic nor any communications with friends or family.

In partnership with laboratories in France and Switzerland, scientists monitored the 15 team members’ sleep patterns, social interactions and behavioural reactions via sensors. One sensor was a tiny thermometer inside a capsule that participants swallowed like a pill. It measured body temperature and transmitted data to a computer until it was 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.

When they came out yesterday, their estimated time was around 30 days, with one person thinking it was as little as 23 days. As far as I am aware, no one thought it was longer than 40 days.

While interesting, I am not sure why they had to go into a deep cave to do this. Surely it would have been much easier to place them inside a sealed, climate controlled building? Was exploring the cave an important part of the experiment?


  1. Jörg says

    Surely it would have been much easier to place them inside a sealed, climate controlled building?

    Such buildings, without recurring noises from the outside that reveal time, are probably hard to come by.

  2. says

    Similar tests have been done by individuals, most notably Maurizio Montalbini.

    The people in the French study did it voluntarily had distractions to relieve stress and tedium. And as a group, they had normal, healthy social interaction to deal with the time.

    I have to wonder what happens to prisoners and their perception of time because they suffer sensory deprivation (e.g. unchanged lighting 24/7), isolation (solitary confinement), and abuse (e.g. random violence, interrogations while sleep deprived). Though any data collected on this and used would be on par with that of Nazi experiments.

  3. anthrosciguy says

    I’ve always thought it was odd that you could have two individuals traveling together, doing everything exactly the same, and they could have extremely different perceptions of how fast or slow the time had gone.

  4. Sam N says

    It has already been known for a long time that our circadian rhythm requires day night cycles for calibration, and it otherwise is roughly, but rarely exactly 24 hours long. So based on what you have described about the study, it is another data point to an already very well known phenomenon.

    I find the perception of time over shorter periods to be a more interesting phenomenon. The sort of thing Intransitive seems to be linking to.

  5. Pierce R. Butler says

    Not that long ago, I was thinking about such experiments and decided we’d never see another such, because who could find a set of volunteers willing to lose their internet for so long?

    I’m glad to have been disproven (why is that not officially a word?), but suggest the researchers writing up this study will have to add a caveat about all the test subjects being a-/anti-social weirdos.

  6. Pierce R. Butler says

    Acolyte of Sagan @ # 7: You are kidding about ‘disproven’, right?

    Alas, most dictionaries and spell-checking software -- including those of the computer and browser I’m presently using -- disallow, dismiss, and disrespect “disproven” (while accepting “disproved”, the dismaying and disgusting barbarians!).

Leave a Reply

Your email address will not be published. Required fields are marked *