6 min read

Why time speeds up as you get older

Ask anyone over thirty and you get the same answer: the years are getting shorter. It's one of the most consistent subjective reports in psychology. It's also one where the popular explanation is the weakest one on offer.

The explanation everyone has heard

The proportional account goes back to the nineteenth century and it is pleasingly tidy. A year is one fifth of a five-year-old's life and one fiftieth of a fifty-year-old's. If we judge durations relative to how much life we've already lived, each successive year should feel smaller, and the compression should follow a smooth curve.

It's a good story, and it survives mostly because it's easy to repeat. The problem is the mechanism. Nobody experiences a Tuesday by dividing it into their accumulated lifespan; there's no plausible process by which the denominator gets into the judgement. The theory also predicts the sharpest compression in early childhood, when children conspicuously do not report that their years are flying by.

What the measurements actually show

Here's the part that gets left out of the magazine version. When you bring people into a lab and test their timing directly, asking them to judge or produce intervals of a few seconds, the age effects are small, inconsistent, and nothing like the dramatic speed-up people describe. Older adults are somewhat more variable, which is true of most perceptual and motor measures, but they are not living at double speed.

That immediately rules out the simplest physical stories, including the popular claim that the brain's internal clock slows with age so that external time appears to rush. If your interval clock had shifted that much, it would show up on a stopwatch task, and it doesn't.

The better explanation: memory density

The account that fits the evidence starts from the fact that remembered duration tracks remembered events. A stretch of time you can't break into distinguishable episodes collapses when you look back at it.

Now consider how the density of distinguishable episodes changes across a life. Adolescence and early adulthood are a dense sequence of firsts: first job, first move, first relationship, first country, first funeral. Autobiographical memory reflects this directly: people asked to recall their lives produce a marked surplus of memories from roughly fifteen to thirty, a pattern robust enough to have its own name, the reminiscence bump.

Later decades are frequently more stable and more repetitive. Same house, same commute, same shape of week. Not worse, just less differentiated, and the brain encodes repetition cheaply. Ten similar years compress into a much smaller memory footprint than ten varied ones, and small footprint is what “that went quickly” means.

This account explains the things the proportional theory can't:

• Why a year with a house move, a new job, or a new child feels long in retrospect regardless of your age.
• Why time compression isn't smooth. It tracks the eventfulness of particular periods, not the ticking of a proportional clock.
• Why long stretches of enforced routine produce the strange double report of days crawling and months vanishing. The two systems are answering different questions.

The novelty argument, stated carefully

There's a related idea that novel stimuli demand more processing, and that the brain reads heavier processing as more time. It's a real effect at short timescales, where an unexpected item in a stream looks longer than the identical items around it. Extending it to whole decades is a much bigger leap, and honest summaries treat it as a suggestive analogy rather than a demonstrated cause.

What's not in doubt is the practical direction, which both accounts share: novelty lengthens time in retrospect, and routine shortens it.

Whether you can do anything about it

You can, but not by trying to feel time differently. The lever is memory, so the interventions are all the boring, obvious ones, and they work for the reason the theory says they should.

• Break the sameness. A different route, a new place, an unfamiliar skill. Anything that gives a period its own distinguishable texture gives it length in memory.
• Create landmarks. Periods bounded by a distinct event stay separable in recall. Undifferentiated months merge.
• Attend to what you're doing. Events you barely noticed are encoded thinly, and thin encoding is exactly what makes a span vanish afterwards.

Note what's not on the list: getting better at judging intervals. Practising a timing task will sharpen your prospective accuracy at the scale of seconds, and that is a genuinely trainable skill. It will not slow down your decade. These are two different senses of “a sense of time”, and it's worth keeping them apart. Most of the confusion in popular writing on this subject comes from quietly swapping one for the other.