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In a recent post I discussed the strange experience of déjà vu. As far as we know, it is exclusively a human experience. I explored the possible reasons we experience that eerie sense where we feel we have experienced something previously, when in fact the experience is quite new. I mentioned that as we get older, we tend to have less déjà vu events. Why is this? Thiss relevant to another fairly universal human experience.

It’s this: As we get older, time seems to flow by more quickly than it did when we were children. It seems to be a universal effect that just about everyone experiences as they grow older. What might be the possible explanations for this?

Well, firstly, physicists believe that time does not flow uniformly. Scientists have reported an effect where people who are at sea-level experience time more slowly than those who are at altitude. It’s a tiny difference, but the time-differential increases the further you travel from earth’s gravitational field (Rovelli, 2018). Einstein showed almost a century ago that time is not a constant. It is relative not only to your location in space, but also to your velocity. If you travel very quickly, far from the earth, and your identical twin remains on the earth, you’ll age less quickly (Hawking, 1990). But this physical phenomenon does not explain why many of us experience time passing more quickly as we grow older. Most of us have never travelled outside the earth’s gravitational field nor travelled quickly enough for relativity to take effect. Time compression therefore has to be a psychological effect – that is, it has to derive from our perceptions of the passing of time – and this in turn is contingent on our memories.

Psychologists have demonstrated that the human brain is attuned to new experiences, but does not often encode familiar experiences and events (Broadway, 2016).  As with all episodic memories (events, places, occurrences) the more novel the event, the stronger will be our memory. As we get older, most of us tend to fall into routines where novel events become rarer, and this gives us the perception that time is moving faster as we age. If you do the same things every day, time is likely to pass more quickly for you. Alternatively, if you go away on holiday to a new location, or spend time at the weekends doing something novel and new, time will seem to slow down for you.

If the passage of time is more or less constant on earth, time compression effects are illusory, and therefore a largely psychological effect. However, the novel encoding conjecture is a plausible explanation as to why children experience the passage of time more slowly than adults.

References
Broadway, J. M. (2016) Why Does Time Seem To Speed Up With Age? Scientific American, July 1. Available online here.
Hawking, S. (1990) A Brief History Of Time. London: Bantam Press.
Rovelli, C. (2018) The Order Of Time. London: Penguin Science.

#BrainTime 2: Time will tell by Steve Wheeler was written in Plymouth, England and is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.