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Ask someone in their sixties where the last ten years went and you’ll often get the same answer: they vanished. The grandchildren were babies a moment ago. The “new” car is somehow a decade old.
The explanation most people reach for is that the memories blur together. Adult life settles into routine, the thinking goes, so there’s less to remember, and a decade with few memorable moments feels short when you look back on it. It’s an appealing idea, and it goes back at least to the psychologist William James in 1890. But when researchers put it to the test, it didn’t hold up the way they expected.
A feeling with a very specific shape
The first study to map this feeling across the whole lifespan was published in 2005 by psychologist Marc Wittmann and his colleague Sandra Lehnhoff. They asked 499 people aged 14 to 94 how fast different stretches of time seemed to pass.
The results were surprisingly narrow. For an hour, a week or a month, age made no real difference. Older people didn’t feel that short periods were racing by any more than younger people did. Only one question showed an age effect: how fast had the last ten years gone? The older people were, the faster that decade seemed, but the effect peaked around age 50 and then held steady into the nineties.
So the feeling is real, but it isn’t simply “time speeds up as you age.” It’s specifically about how the brain looks back over long periods.
Testing the memory theory
If the blurred-memories explanation were right, there should be a link between how many distinct memories people have of the past decade and how fast it felt. A sparse decade should feel short, and a packed one long.
Wittmann and his colleagues tested exactly that in a more recent study, tracking memory and time perception in adults from their twenties to their nineties. The results surprised even them. The number of autobiographical memories people could recall had no link to how fast the decade felt. Older adults didn’t describe their memories as fainter, either. If anything, the memories they kept felt richer and more emotionally meaningful than younger people’s.
That doesn’t mean memory plays no role in how we judge time. Novelty clearly affects how long things feel over shorter periods. But as a full explanation for the vanishing decade, “the memories blur together” falls short.
Two better candidates
The first candidate is stress. In a 2013 study of 868 people, age again affected only the ten-year judgment. The stronger pattern was about pressure. People who said they’d felt heavily time-pressured ten years earlier were the ones who reported the decade had flown by. Interestingly, people also tended to underestimate how pressured they had been in the past.
The second candidate is the aging brain itself. Wittmann has linked the speeding decade to gradual changes in how the brain processes information. Small declines in some cognitive abilities begin around age 30 and become steeper after 50 and 60, roughly matching the period when the decade effect is strongest. It’s a correlation rather than a proven cause, but it points somewhere the memory theory doesn’t.
The brain’s clock runs on experience
To see why the brain might judge a decade so unreliably, it helps to know that it has no built-in clock for long periods. Instead, it seems to stitch time together from what happens to us.
In 2018, researchers at Norway’s Kavli Institute for Systems Neuroscience, led by Albert Tsao and Nobel laureates May-Britt and Edvard Moser, found a network of cells in a region called the lateral entorhinal cortex that appears to do exactly this. The lateral entorhinal cortex sits next to the hippocampus, the brain’s key structure for forming new memories. Recording from rats, the team found that this network timestamps events using the flow of experience itself, rather than ticking along like a clock.
One detail stands out. When the rats ran the same lap of a maze over and over, the time signals for each lap began to overlap and look alike. The brain still tracked time within each lap, but repetition made the laps harder to tell apart. These were rats over hours, not people over decades, so it’s a long way from a complete explanation. But it shows how a brain that measures time through experience could struggle to separate one familiar stretch from the next.
What it means for the next ten years
Put together, the research suggests the vanishing decade comes from a mix of factors rather than one simple cause. Age matters, but only modestly. Stress and pressure seem to matter a lot. And the way the brain builds its sense of time from experience may make long, routine stretches especially hard to judge.
The more hopeful part is that some of this is within reach. Edvard Moser has said that changing what you do, and so the content of your experience, changes the brain’s time signal. Wittmann’s own studies have found that people with a more balanced outlook on past, present and future, and better emotional regulation, tend to feel the last ten years passed more slowly.
None of that can stop the calendar. But it suggests the next decade doesn’t have to disappear quite as fast as the last one did.
