Every year Christmas seems to come sooner. Does not it? When we were young, the summer holidays seemed to stretch on forever. Now summer is gone in the blink of an eye.
We use clocks and calendars to mark the passage of time in a reliable way. We also have an internal timepiece that provides us with our perception of the passing of time. Our inner perception, however, seldom looks to accord with our external time-counters.
Most of us first notice that time seems to be speeding up when we have become settled in life, ie have fallen into a routine dictated by work, marriage, and family … going to work every day, coming home, eating dinner, going to the gym, cinema or on nights out on regular days of the week.
After a few years we get the sense that the time these routines take seems to be decreasing, as if we are on a thread-mill that is slowly but inexporably picking up speed.
At the same time we develop a tendency to think that past events happened more recently than they actually did, a phenomenon known as forward telescoping .
Personally, I am always way out when thinking of when something happened. If I think it was two years ago, it usually turns out to be five years past.
So, what causes time to speed up in our perception?
There are several theories …
The proportional theory
This theory states that, as you get older, each time period (year, month, week) results in a smaller and smaller fraction of your life as a whole.
For example, for a child of five, a year is 1 / 5th of his life as a whole, while for a man of fifty, a year is 1 / 50th of his life.
So, as you get older, a year becomes a less significant period of time and so seems to pass more quickly.
This theory offers an explanation as to why the perceived speed of time seems to increase gradually. The problem is that it explains present time purely in terms of past time.
But usually we live in terms of small periods of time, such as from hour to hour, dealing with each time period as it comes without reference to the past.
While it is an interesting idea, there does not seem to be any way scientists could prove this theory to be right or wrong.
The metabolism theory
In this theory, the perception that time is speeding up is linked to the fact that our metabolism slows down as we grow older. Children breathe more quickly, their hearts beat faster and their blood flows sooner than older people, suggesting that their internal clocks experience more time in the space of a day than those of adults.
Thus the internal clocks of children run faster than normal external time, while the internal clocks of the older run slower than the norm.
The metabolism theory is an interesting explanation and seems intuitively correct. The only problem is that, like the proportional theory, there is no way of proving it.
The body temperature theory
Experiments during the 1930s showed that body temperature had an effect on our perception of time … that raising a person's body temperature can slow down his or her sense of how quickly time is passing by up to 20 percent.
This makes sense … children have higher body temperatures on average than adults which suggests that time is 'expanded' for them (eg, a time period of one hour seems longer for them).
As we grow older, our body temperature drops gradually. This offers an explanation as to why we feel that time is passing quick and quick as we get older.
This theory too makes intuitive sense. But again there is no way it can be proved.
The perceptual theory
According to this theory, the speeding up of time is related to our perception of the world around us and our experiences, and how this perception changes as we grow older.
Our perception of the speed of time looks to depend on how much information our minds absorb and process … the more information, the slower time goes by.
In experiments in the 1960s, subjects listened to tapes of simple clicking sounds (among other experiments relating perception). The tapes were turned off after a certain period of time. The subjects were then asked to estimate how long they had been listening to the sounds. The number of clicks on the tapes was increased and subjects were tested again.
The researchers discovered that the more information there was on the tapes (ie, the more clicking sounds there were), the longer was the time period as estimated by the subjects.
The researchers also found that when participants were shown paintings and drawings, those who saw the most complex images estimated the time to be longer.
Thus the quantity and complexity of information extends the perceived length of time.
This suggests that one of the reasons time seems to flow slower for children is that they take in massive amounts of perceptual information from the new world that they are experiencing for the first time. They take in all sorts of details that we adults ignore … tiny insects, patterns of sunlight, cracks in surfaces and so on.
As we grow older we lose this intensity of perception … the world becomes dreary and routine, with few surprises, so we stop paying attention to it. We no longer notice the buildings, streets and other parts of our surroundings that we see every day. In other words, we switch off.
So we take in less information, which means that time passes more quickly.
This theory seems logical and provable.
Decline of new experiences as we age
The longer we live, the more familiar we become with the world. This means that, according to the perceptual theory, the amount of perceptual information we absorb decreases with each passing year, so time seems to speed up.
This happens for two basic reasons:
 For a child and teenager, the world is a new fascinating place to be explored. This newness wears off gradually and by the time we reach 40 or so the world contains, for the vast majority of us, much less unfamiliarity … unless we have a job which involves significant overseas travel and interaction with a variety of cultures and technologies .
As a result we absorb less and less perceptual information and our sense of time speeds up.
Because we have used up nearly all our 'stock' of new experiences by the time we are in our forties, you would expect that the speeding up of time would slow down considerately later in life. But this is not so … times speeds up more quickly as we grow even older.
 Subjective time continues to speed up as we get past middle age because the experiences we've had already become more and more familiar to us … with each passing year they are converted into a sort of automatic routine.
In this way our lives become duller and progressively more unreal as we traverse our middle and later years. So we take in less and less fresh information so time continues to speed up.
How to slow down time
Time seems to slow down when we're exposed to new environments and experiences, as most of us have noticed. This is due to the unfamiliarity of new experiences that allows us to take in much more perceptual information.
So how do we slow down time as we perceive it?
The perceptual theory and its ramifications provide the clue.
Just make an effort to expose yourself to as much newness as possible … new environments through foreign travel, new challenges, new situations, new information and ideas. Try a new career or learn new skills. Seek out multi-cultural environments and get swimming in unfamiliar cultural waters.
Not only will time slow down so that you seem to be living longer, you will feel fresher and look more youthful. And, for once in 20 years, you will really begin to enjoy your life again.