Time & The Human Sense of Duration

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Perhaps the most mysterious aspect of the human experience of time is duration. Duration, by definition, is a time span. 

We have to ask ourselves: how can we perceive an arc of time, operate within a span of time, when the only thing that exists is the now moment?

In other words how do we hold onto a consistent sense of ourselves -- where we have been and where we are going -- in the now moment where everything must reside to exist?

Just as time could not exist without the now moment (see my earlier blogs), we could not function or survive without a sense of duration. We could not start a task and finish it without a sense of duration, for example. 

These popular drawings from the 19th century depicted 

the duration of a lifetime. (commons.wikimedia.org)

As usual the answer lies in the human brain. I believe the brain has a number of areas that hold time in suspension. Parts of our brains are "waiting for the other shoe to drop." 

We all know about short term memory. A waiter must remember each person's order, bring the right food to the right person with the right drinks but then once the customers have finished and left the restaurant, forget that particular order and sequence -- virtually erasing it from memory.

Without short term memory we could not operate. We could not even drive down the road. We must remember that the speed limit has changed, the school children get out in a few minutes, that a car suddenly appeared out of nowhere and is driving just behind us in the left lane.

A lifetime duration for a man -- at the bottom of the picture is Chronos, the Greek God 

of sequential time who rules over our lives. (commons.wikimedia.org)

There are a wide variety of durations as we experience them: from very short term to very long term. As I quoted in an earlier blog: "Humans can perceive relatively short periods of time, in the order of milliseconds, and also durations that are a significant fraction of a lifetime. Human perception of duration is subjective and variable."
http://en.wikipedia.org/wiki/Time_perception

One long term duration we all know is our life story: our parents, where we are from, schools, education, jobs, relationships, marriage, children -- a story which continues as we live.

Photos of me from age 8 to 58 

-- the duration of a lifetime. (Rick Doble)

A shorter term duration might be a job you held for a year or two. In your memory you might recall the early days of the job, the later routine, the final days when you knew you were leaving.

And still shorter term is what you did earlier in the week and plan to do by the end  of the week. Or what you have done today and plan to do by the end of the day. In another month if I asked you about the specifics of either of these -- that occurred a month before -- you might be hard pressed to remember. But today, you know in detail. And more, today you have a mental checklist of what is done or completed and what remains to be done.

I believe the human brain has a number of levels of memory which are related to the sense of duration. 

• Very short term: Minute to minute
• Short term: Hours or days
• Medium Term: Weeks or a month 
• Long term: A year 
• Very long term: Decades or lifelong

It is our brains that stitch time together and give us a sense of duration.

(commons.wikimedia.org)

Over time the shorter term memories tend to get erased, as they are in a sense working memories that must be cleaned out in order to make room for the next task at hand. Yet certain events in the short term, even events that might normally have been erased, can become part of long term memory -- due to their importance. 

For example, you might not realize that when you said hello one morning to a new person at the office, that you would be married to them in a year. That moment of meeting would normally have been forgotten, but now is clearly remembered for the rest of your life.

And while I believe this article has shed some light on how we humans handle a length of time, it also raises a number of questions.

There is, for example, what might be called 'vigilant duration'.

A task, for example, requires that a kind of mental flashing red light keeps blinking until we have finished all aspects of the job. For many of us, we cannot shut off that interior red light until we have done the job to our satisfaction. Then and only then can we check the job as completed. And only then can we begin to erase that job from our memory.

A joyous leap into the air before the senior prom 

-- celebrating the end of a duration, high school. (commons.wikimedia.org)

So the question is this: How does this mental flashing light operate in our brains? How does it continue to flash until the job is done? And how does it shut off when we are done?

And then there is 'remembered duration' -- in which the brain stitches together a number of events over time that are related to each other and creates a coherent memory..

So like most aspects of time, there are a number of ways we sense, understand and operate when it comes to duration. I will save a discussion of this for another blog.