No matter what age we've attained, we can think back to childhood and feel just how agonizingly long it then took for Christmas to come, for the school day to end, for a tray of cookies to come out of the oven. Mysterious as this apparent change in the speed of time may at first seem, it actually makes a kind of intuitive sense: one day represents, at the age of fifty, a tenth of the proportion of the time we've experienced so far than it does at the age of five. As our timeline lengthens, our perception of certain fixed units on that timeline — a minute, a year, a decade — shortens.
But there are other factors in play as well. "Individual perceptions of time are strongly influenced by our level of focus, physical state and mood," write The Independent's Muireann Irish and Claire O'Callaghan. "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." This might well contribute to the childhood perception of slow time, since kids have to spend so many of their days in the classroom, an environment that strikes most of them as expressly designed to induce boredom.
In addition, according to Scientific American, "our brain encodes new experiences, but not familiar ones, into memory, and our retrospective judgment of time is based on how many new memories we create over a certain period. In other words, the more new memories we build on a weekend getaway, the longer that trip will seem in hindsight." The relatively high frequency of distinctive memories created earlier in life and low frequency of distinctive memories created later in life means that "our early years tend to be relatively overrepresented in our autobiographical memory and, on reflection, seem to have lasted longer."
You can see some of the ideas and theories behind this almost universally agreed-on sense that time speeds up as we grow older in the video from the National Geographic Channel show Brain Games above. It also introduces a few new ones into the mix, connecting them all with how much energy the brain uses to record which kinds of experiences, suggesting that even a sense as fundamental as the one we use to mark time has a great deal more complexity to it than we understand. Ultimately, though, it all comes back to the words of no less a thinker on relativity than Albert Einstein: "Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute."
Based in Seoul, Colin Marshall writes and broadcasts on cities and culture. He’s at work on a book about Los Angeles, A Los Angeles Primer, the video series The City in Cinema, the crowdfunded journalism project Where Is the City of the Future?, and the Los Angeles Review of Books’ Korea Blog. Follow him on Twitter at @colinmarshall or on Facebook.