We're only now beginning to understand how our mental state can bend, stretch and compress the perception of time.
We may not yet be hurtling through history in time machines, but, in our own way, each of us has come a little unstuck in time. Every day, we witness time elongating, compressing, and generally wobbling around — not because of sci-fi devices or interfering wizards, but because of our brains.
You may already know about the tiny blind spot in the middle of the retina, where visual information cannot be processed, but is instead inferred from images around the spot and from the other eye. Likewise, our experience of time is full of gaps that our minds fill in so smoothly that we don’t notice a problem. Instead of a gap, we may feel that certain moments last longer than we expect, like when we glance at a clock and the second hand seems to stand still a fraction too long before ticking forward.
It is theorised that when our eyes sweep from a previous object of interest to the clock in a rapid movement, called a saccade, the brain blocks the blur of fast-moving images and replaces them with an extended reel of the clock as it appears when we first see it. You can observe a similar effect by looking in the mirror and focussing on one eye, then the other, and then the first eye again. You won’t see your eyes move, even though they undeniably have.
This discarding of useless, motion-blurred images, called saccadic masking, reconciles our eyes' constant darting from point to point with our experience of the world as largely unmoving. In a 2004 paper, Italian psychologist David Burr wrote that “our world remains perceptually stable and constant, despite the distinctly unstable platform on which our sensors are mounted”. That the brain cuts and pastes tiny periods of time countless times a day might seem manipulative, even dishonest, but it’s all to maintain a perception of the world that matches reality.
The factor with perhaps the strongest pull on our experience of time is how much of it we’ve been around for — that is, our age. As we grow up and move through life, almost everyone laments that the months and years are whipping by too fast. This possibly occurs because absolute intervals, like a year, are continually shrinking relative to the time we’ve been alive. Some observations back up this complaint. In a small study, 19- to 24-year-olds could accurately estimate when three minutes had passed, but 60- to 80-year-olds guessed the three-minute mark after an average of three minutes and 40 seconds.
Other evidence suggests that this swifter passage of time is due not to age, but to the pressure of fulfilling more responsibilities, which naturally can accumulate over a lifetime. It may also result from the drop-off in new experiences as we get older and get used to the routines of living. According to American psychologist David Eagleman, this may be why time seems to speed up as you age: "You develop more compressed representations of events, and the memories to be read out are correspondingly impoverished." On the other hand, says Eagleman, “When you are a child, and everything is novel, the richness of the memory gives the impression of increased time passage".
The varying density of encoded memories also explains how time warps according to our emotions, especially negative emotions. For example, fear pushes the brain — specifically, the amygdyla — into a higher gear and increases the vividness of the memories made in that state. One theory of time perception, the internal-clock model, suggests that this arousal accelerates the internal timekeeper and thus lengthens the subjective experience of time. As a result, terrifying events seem to last longer than they actually do.
Because we are used to remembering a certain amount of detail over a certain amount of time, stronger memories create the impression of longer memories. Thus, people free-falling from a 15-storey tower or watching a video of a bank robbery significantly overestimated the durations of those events — indeed, the length of the robbery was multiplied by a factor of five.
In the free-fall experiment, each participant was fitted with a wristwatch-like device that flashed the image of a number alternating with the negative image of that number. When the two images flash in quick succession, the number is illegible. During free-fall, participants were unable to interpret the rapidly flashing images any better than they could in a steadier state. So the free-fallers did not experience the fall in literal slow motion; instead, the time stretch was seemingly constructed in retrospect.
Social exclusion and depression also seem to dilate time, with depression extending perceived time by a factor of about two. Other disorders that affect the brain also compromise our time perception: schizophrenia and Parkinson's disease may impair our ability to estimate and differentiate short intervals, and attention deficit disorder, like depression, makes periods of time feel much longer than they are.
Short-term alterations of the body mess with our experience of time, as well. Higher body temperature slows time, making short intervals seem longer, as you may have noticed if you’ve ever felt the minutes stretch abnormally while sick with a fever. Conversely, lower body temperature — say, after a scuba dive — makes time proceed faster. Drugs also bend our temporal perceptions: stimulants may hasten time, and depressants have been observed to decelerate time, likely because of their effects on dopamine.
What about dreams? The timeline in your dream realm often seems faster than in the waking world, giving you the opportunity to embark on all sorts of epic, meandering adventures. Some historical thinkers have proposed the same. Nineteenth century French scholar Alfred Maury dreamt a seemingly lengthy dream about the French Revolution, awaking at the moment of his execution when a piece of his bed fell on his neck. He concluded that his entire dream was assembled at the moment of his waking. This kind of dreaming is, to an extent, supported by observations of electroencephalographic activity during sleep, which showed that narratively intricate dreams were often perceived to take much longer than they really did.
More mundane dreams, however, may not outstrip occurrences in the real world; they might, in fact, proceed more slowly. A 2013 experiment using lucid dreamers — those with the ability to become aware they are dreaming and control their in-dream actions — compared the timing of activities like walking and performing a gymnastics routine between the waking and sleeping states. The lucid dreamers signalled the start and end of their actions by moving their eyes in a recognisable pattern. The tasks involving motor activity took significantly longer in dreams than in reality. The participants may have experienced time differently while dreaming; alternatively, they may simply have been less agile in their dreams.
We perceive time more chaotically when disoriented by emotion, disease or sleep, and also when we are temporally separated from the event whose duration we are trying to estimate. Take the simple act of planning. In his 2011 book Thinking, Fast and Slow, psychologist Daniel Kahneman describes how consistently and severely people underestimate the time needed to finish projects. The planning fallacy characterises the tendency to ignore past situations similar to our own and expect unrealistically good results in the situation at hand. Most of us can relate to this short-sighted optimism when it comes to setting deadlines or embarking on a new undertaking.
As for past events, we often misplace those, too, by exaggerating the remoteness of recent events and the recency of remote events; this bias is called the telescoping effect. In our memory, events that took place more than three years ago cluster toward the present. In general, this clustering makes any given kind of incident — for instance, plane crashes — seem more frequent than they really are.
What can we do to counter our unreliable internal timekeeper? Not much; cognitive biases and illusions usually persist even after we have become aware of them. But given what we know, we may be able to fend off at least one of these distortions: the acceleration of time as we age. If predictable living blurs the days into a fast-passing slurry, then seeking out new experiences, or just varying your routine, could slow time back down by giving you more memories to hold on to.
Edited by Andrew Katsis and Ellie Michaelides