How did it get so late so soon?
It’s night before it’s afternoon.
December is here before it’s June.
My goodness how the time has flewn.
How did it get so late so soon?

Dr Seuss

The passage of time is a puzzling thing. While few will dispute that a minute comprises 60 seconds, the perception of time can vary dramatically from person to person and from one situation to the next. Time can race, or it can drag interminably. On rare occasions, it feels as if it’s standing still.

The difference between “real” time, measured by clocks and calendars, and our own individual sense of time can sometimes seem enormous. This is because, in many ways, we are the architects of our sense of time.

Measuring time

Humans have created reliable instruments to measure time by using predictable repeating events that occur naturally, such as day turning to night or winter becoming spring. We think of these events in terms of days, weeks and years, and we use clocks and calendars to mark their passage.

But we also appear to possess an internal timepiece, which regulates our circadian (day/night) rhythms and allows us to register the duration of particular events. We use this “pacemaker” to compare the length of each new event with representations stored in memory. Effectively, we build up a knowledge bank of what a minute, an hour or a day feels like.

What typically begins as our brain’s ability to register short durations – from minutes to seconds – is transformed into an understanding of the flow of time across the lifespan. But, unfortunately, our internal pacemaker doesn’t always keep time as accurately as our external gadgets.

Individual perceptions of time are strongly influenced by our level of focus, physical state and mood. Just as “a watched pot never boils”, when we are concentrating on an event, time occasionally appears to pass more slowly than usual. This is also the case when we’re bored; time can seem to drag endlessly.

In other circumstances, time can appear to speed up. When our attention is divided, for instance, and we’re busy with several things at once, time seems to pass by much more swiftly. This may be because we pay less attention to the flow of time when we are multi-tasking.

The emotional quality of an event also influences our perception of time. Negative emotional states, such as feeling sad or depressed, have the effect of making time feel as if it’s passing more slowly. Fear has a particularly powerful effect on time, slowing down our internal clock so that the fearful event is perceived as lasting longer. In contrast, fun and happy times seem to be over in the blink of an eye.

Just as time may slow or quicken depending on our current emotional state, our perception of time may also become distorted as we age. People over the age of 60 often report time becoming more variable. Christmas seems to come around sooner each year, and yet the days feel long and drawn out.

Key factors

Anomalies in time perception as we age may relate to a number of necessary cognitive processes, including how much attention we can devote to a particular task and how effectively we can divide our attention between several ongoing tasks at once. Our efficiency in these domains gradually dampens as we age and may influence the subjective perception of time.

Perhaps more importantly, our frame of reference for the duration of events also changes as we age. Memories we have stored throughout our lives allow us to create a personal timeline. There’s a suggestion that our perception of time may be in proportion to the length of our lifespan. Known as the “proportional theory”, this idea posits that as we age, our sense of “present” time begins to feel relatively short in comparison to our entire lifespan.

Proportional theory makes intuitive sense if we consider how a year in the lifespan of someone who is 75 years old may feel much quicker, for instance, in comparison to a year in the life of a ten-year-old. But it cannot fully explain our experience of present time as we can move from hour to hour and day to day independently of the past.

Memory may hold the key to time perception, as the clarity of our memories is believed to mould our experience of time. We mentally reflect on our past and use historic events to achieve a sense of our self existing across time.

As the most vividly remembered experiences tend to occur in our formative years, that is, between the ages of 15 and 25, this decade is associated with an increase in self-defining memories, known as the “reminiscence bump”. This memory cluster may help explain why time speeds up with age, as older people move further away from this critical period in their lives.

Accuracy of time perception is also disrupted in various clinical conditions. Developmental disorders, such as autism and attention-deficit hyperactivity disorder, for instance, are often associated with difficulties in accurately estimating time intervals. At the other end of the life spectrum, conditions such as Alzheimer’s or Parkinson’s disease are also associated with inaccuracy in timing short intervals, as well as with difficulty in travelling back in subjective time to remember the past.

Can we slow down the ever-quickening pace of life? Perhaps. Improving cognitive abilities, especially attention and memory, can help us fine-tune our internal pacemakers. And meditation and mindfulness may help anchor our awareness in the here and now. Indeed, they may gradually help us to bring the fast river of time to a slow meander.

This article originally appeared on The Conversation.