New research from Duke University says time flies as we age because of our brains maturing — and degrading.

Image credits Gerd Altmann.

The shift in how we perceive time throughout our lives takes place because our brain’s ability to process images slows down, reports a study penned by Adrian Bejan, the J.A. Jones Professor of Mechanical Engineering at Duke. This is a consequence of the natural development of our brains, as well as wear and tear.

Hardware, oldware

“People are often amazed at how much they remember from days that seemed to last forever in their youth,” said Bejan. “It’s not that their experiences were much deeper or more meaningful, it’s just that they were being processed in rapid fire.”

Bejan says that, as the bundles of nerves and neurons that make up our brains develop both in size and complexity, the electrical signals that encode sensory data have to travel through longer paths. We also grow in size, making the nerves feeding information to the brain physically longer. Nerve fibers are good conductors of electricity — but they’re not perfect; all that extra white matter slows down the transfer of data in our biological computers.

Wear and tear also play a role, he adds. As neural paths age, they also degrade, which further chips away at their ability to transport information.

These two elements combine to slow down our brain’s ability to transport, and thus process, data. One tell-tale sign of processing speeds degrading with age is the fact that infants tend to move their eyes more often than adults, Bejan explains. It’s not that they’re more ‘filled with energy’ or simply have shorter attention spans. Younger brains are quicker to absorb, process, and integrate new information, meaning they need to focus for shorter spans of time on a single object or stimuli to take it all in.

So, how does this impact our perception of time? The study explains that older people basically view fewer new images in a given unit of time than younglings, due to the processes outlined above. This makes it feel like time is passing more quickly for the former.  Objective, “measurable ‘clock time’ is not the same as the time perceived by the human mind,” the paper reads, as our brains tend to keep track of time by how many new bits of information it receives.

“The human mind senses time changing when the perceived images change,” said Bejan. “The present is different from the past because the mental viewing has changed, not because somebody’s clock rings.”

“Days seemed to last longer in your youth because the young mind receives more images during one day than the same mind in old age.”

It’s not the most heartening of results — who likes to hear their brains are getting laggy, right? — but it does help explain why we get that nagging feeling of time moving faster as we age. And, now that we know what’s causing it, we can try to counteract the effects.

That being said, maybe having a slower brain isn’t always that bad of a thing. If you’re stuck out on a boring date, or grinding away inside a cubicle from 9 to 5, at least you feel like you’re getting out quicker. Glass half full and all that, I suppose.

The paper “Why the Days Seem Shorter as We Get Older” has been published in the journal European Review.