Hypotheses for the Perception of Time

1) Novel experiences are remembered more clearly — and as we age, there are fewer of them

The assumption behind this hypothesis, Friedman and Janssen write, is that "humans gauge the magnitude of past intervals of time ... according to how many events can be recalled from that period." We use significant events as signposts to gauge the passage of time. The fewer events, the faster time seems to go by.

Childhood is full of big, memorable moments like learning to ride a bike or making first friends. By contrast, adult life becomes ordinary and mechanized, and ambles along by.William James, a 19th-century psychologist, phrased the idea in these bleak, beautiful terms:

Each passing year converts some of this experience into automatic routine which we hardly notice at all, the days and weeks smooth themselves out in recollection, and the years grow hollow and collapse.

Each new minute represents a smaller fraction of our lives. One day as a 10 year old represents about .027 percent of the kid's life. A day for a 60 year old? .0045 percent. The kid's life is just... bigger.

Also, our ability to recall events declines with age. If we can't remember a time, it didn't happen.

2) Time flies when we're busy or distracted — and adults are busier than children

Another possibility is that being busy can somehow trick our memory into feeling like time is going by faster. "Tasks that demand considerable attentional resources are perceived as briefer than tasks that are undemanding," Friedman and Janssen explain. As we age, these tasks — career-related tasks, raising children, etc. — increase.

It's also possible that as adults, we feel like we never have enough time to do things — which our brain then interprets as time speeding up. "[F]inding that there is insufficient time to get things done may be reinterpreted as the feeling that time is passing quickly," they write. Deadlines always come sooner than we'd like.

3) Very memorable events are farther than they appear

No doubt you've seen a Facebook post saying something like, "Want to feel old? The baby on the cover of Nirvana's Nevermind is now 80 years old." This sort of thing can fill us with dread, making us think that time has flown by more quickly than it actually has.

Psychologists have long understood the phenomenon called "forward telescoping" — i.e., our tendency to underestimate how long ago very memorable events occurred. "Because we know that memories fade over time, we use the clarity of a memory as a guide to its recency," science writer Claudia Hammond writes in her book Time Warped."So if a memory seems unclear we assumed it happened longer ago." But very clear memories are assumed to be more recent.

If clear memories form our personal timelines, then everything we remember clearly will seem more recent than it actually was. Realizing that it isn't makes us feel like time has passed us by.