Altered time perception: Does longevity provide diminishing returns or is it a double gift?

I've heard that life speeds up as we get older. And as I approach my 50th year on this planet, I’ve been waiting with a mixture of fascination and dread for this to happen.

I don't think it has.

I do seem to remember childhood as a sort-of slow-motion experience but, as far as I can tell, the years that followed my adolescence have all moved along at about the same pace. Certainly, some years have been happier. Some have been sadder. Some years were really hard on me. Others came with seemingly endless gifts of joy.

But a second has always felt like a second. And a day a day. And so on.

And sure, I certainly recognize the brevity of human existence. In the grand scheme of the universe, after all, 50 years is nothing. It is the firing of a synapse.

Within that fleeting instant, though, my perception of time doesn't seem to have picked up pace and, if anything, it seems my most recent years might even be slowing down. Lately I've been wondering if there were other people like me, out there.

"My perception of time doesn't seem to have picked up pace and, if anything, it seems my most recent years might even be slowing down."

There are, although not many, it seems.

Say what you will about the scientific shortcomings of social media polls. (You're right, of course.) But Twitter is a rather simple way to put a question to the world. And it's fun. (Yes, scientists can have fun. I have been assured it is permissible in certain circumstances.)

So this is the question I asked of the Twitterverse:

"It's a common, but not universal, observance that life feels like it speeds up as we get older. What has your experience been?"

A week went by, and some 3,000 people participated in the survey.

About 10 percent chose the last option, "Who am I? Where am I?" as their answer; we'll count this group as "decline to answer." As for the rest? 78 percent of the participants said life speeds up and 9 percent said it stays the same.

Just 3 percent said it slows down.

There are lots of good guesses about why so many people feel as though time moves more quickly as we age. Philosophers have pondered this question for as very long time.

One of the first people to write about the passage of life's time was the Roman philosopher Seneca. He wrote:

"It is not that we have a short time to live, but that we waste a lot of it... But when it is wasted in heedless luxury and spent on no good activity, we are forced at last by death’s final constraint to realize that it has passed away before we knew it was passing. So it is: we are not given a short life but we make it short, and we are not ill-supplied but wasteful of it."

Some 2,000 years later, James Broadway and Brittiney Sandoval, both then of the University of California, Santa Barbara, sought to answer the question for 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," they wrote in 2016. "From childhood to early adulthood, we have many fresh experiences and learn countless new skills. As adults, though, our lives become more routine, and we experience fewer unfamiliar moments. As a result, our early years tend to be relatively over-represented in our autobiographical memory and, on reflection, seem to have lasted longer."

Perhaps these ideas do help explain why time seems to speed up for some people. But there doesn't seem to have been a lot of thought about why, for a small number of people, time slows down. And while in some ways that makes sense, given how rare that experience appears to be, it's also a terrible shame.

Because if time does speed up for most people as the years go by—and especially if it goes faster and faster as the years add up—then therapies aimed at slowing aging will have diminishing returns.

"If time does speed up for most people as the years go by... then therapies aimed at slowing aging will have diminishing returns."

If we are going to significantly extend healthy human lives (and, for the record, I believe healthy lifespan extension is all but inevitable) it seems it would behoove us to better understand the circumstances under which our perception of time either remains constant or slows down. This, of course, could provide us a pathway to help more people experience those circumstances, and thus longevity might actually feel like longevity.

Thus, my Twitter poll.

From the small contingent of people who said life seems to have slowed down with age, many opined that mindfulness is the key.

"It sped up," philosopher Chris Kelly wrote of his life. "But once I started meditating, it slowed back down again."

Indeed, added singer and songwriter Shawn Prest, time seemed to move faster and faster "until I started doing mindfulness meditation, then it started to slow down again."

Retired schoolteacher Linda Susan said that once she stopped working, she realized "how rapidly I was living life during those 35 years." Now, she said, "time is slower. There is more effort put into enjoying little things. I am wiser and considerably more deliberate in my thinking and actions."

This is good news. If Chris, Shawn and Linda are correct, there likely are interventions that anyone can access to push against the perceived acceleration of time. Meditation, yoga and mindfulness exercises, like those espoused by Buddhist monk and peace activist Thich Nhat Hanh, could be key to living a longer life that actually feels longer.

Echoing the ideas of Broadway and Sandoval, many other respondents suggested that the perception of time can be slowed by the avoidance of repetitive tasks and actions. Take a new route to work every day. Start a new hobby or venture every few years. Learn a new language. Write a new song. Take a trip. Find a person to love, or rekindle the love you already have.

This makes a lot of sense. It might help explain why my 40s—a period of time in which I was starting new companies, traveling to many new places, and meeting lots of new people—seemed to move a bit slower than my 20s and 30s, when I spent a lot more time hovered over lab benches and computer keyboards. (Please don't get me wrong, though. Those years may have moved more quickly, but they were years very well spent.)

Again, this would be good news. For if new experiences can make life feel slower again, and if new experiences are facilitated by healthy minds and bodies, and if we are able to keep people healthier longer, then it certainly stands to reason that added years don't have to feel like shorter years.

I do wonder, though, if there are factors that aren’t so easily changed.

It seems very possible that there could be a genetic component to time perception — a nexus of “time genes.” Some people may in fact be born to experience time in a different way than others. It would also make sense that the accumulation of epigenetic changes over time could alter the programming of our neurons in such a way as to change the way they control our ever-oscillating circadian clocks.

Might there also be a significant biochemical component to people's differing experiences? The organ that perceives time, after all, is beholden to the ever-changing mixture of chemicals in which it swims. Good chem for your brain is like good fuel in your car. And the faster your mind works, perhaps, the slower time is perceived.

I take several molecules that have been shown in model organisms to be effective at slowing aging. Can these molecules be credited for speeding up my mind? It sure feels like it. I feel as though I am thinking faster and better than ever before. Perhaps the greatest unexpected side-effect of life-extending molecules will be longer perceived lives. In this way, we might get a double gift.

As it goes with many of the questions I find myself asking, these days, I am hopeful that big data and artificial intelligence might help us unlock some of the complexities of this mystery.

I recently visited Henry Markram and his Blue Brain project at the Swiss Federal Institute of Technology in Lausanne. His team has built a working simulation of a mouse brain that takes on emergent properties and may be a precursor to advance AI and even consciousness. We discussed how to simulate brain aging, how the simulated brain perceives time now, and how that might change over time.

Until Henry and I have a working mathematical model of an old brain, a group of 3,000 Twitter users is a fun start. But it wouldn't take much more to begin unlocking this mystery. A single question ("has your perception of time sped up, stayed the same, or slowed down as you've aged?") on a global health survey, or posed to millions of people whose DNA and epigenomes are increasingly known, could be the Rosetta Stone that offers a solution to this puzzle.

In the coming weeks and months, I'll be exploring this idea with more of my colleagues around the world. I am eager to learn more. For I don't think we can afford to take it slow.

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I have lots of weird ideas. Some of them turn into research questions. Others turn into companies. Some simply get tweeted, and that's the end of that. Head over to Twitter — I'm @davidasinclair — to find out what's on my mind.