How Time Flies

This statement, or something close to it, was repeated many times by survivors interviewed by media outlets on the 15th anniversary of the 9/11 terrorist attacks. Indeed, to most people old enough to remember that day, it does seem like yesterday. Except it was not yesterday; it is a full decade-and-a-half later. In that same period of time, 3-year olds grew into full-fledged adults. Clunky Blackberries, carried by a few, evolved into sleek smartphones carried by almost everyone. Facebook, LinkedIn, and Twitter all went from nonexistent to ever-present.Similarly, time seems to speed up as we get older.

When we were 5, Christmas took forever to get here as we anxiously awaited the fulfillment of our wish list. At 50, however, we remark, “It’s Christmas already? Again?” Of course, objectively, we know that a year always takes the same 365 days to pass (except on a leap year, of course), and that each of those days contains the same 24 hours. Yet we all know that this is not at all how it feels.

Why is it that some things that happened years ago seem like yesterday, while other things seem lost in the past? And why is it that time seems to pass faster as we get older? Why does it seem that our brains warp the perception of time based on circumstances and subject matter?

Psychologists have been noticing this feature of the human mind, and have been forming theories about its origins, since psychology began as a discipline. In 1890, William James wrote in his classic text, “Principles of Psychology,” that this phenomenon was essentially the result of life becoming increasingly boring as we age.

In other words, adulthood is marked by fewer and fewer events worth remembering as we grow older.

The younger we are, the more firsts we experience.

As small children, almost every moment is filled with novel experiences. In adolescence and young adulthood, life has become more habitual, but there are still many firsts — first kiss, first car, first apartment.

Looking at older adults, James grows rather glum about the thrill of living: “The days and weeks smooth themselves out and the years grow hollow and collapse.” Because they lack unique significance, our days pass us by in rapid succession, according to the theory.

Another long-standing theory is called the “ratio theory,” first proposed in 1877 by French psychologist Pierre Janet.

According to this premise, days seem to pass more quickly because they equal an increasingly smaller portion of our entire lives.

For example, one year is one-fifth (20 percent) of the entire lifespan of a 5-year-old, so a year to a tot of this age seems an eternity. By contrast, a year is only one-fortieth (2.5 percent) of a 40-year-old’s life.

The ratio theory, although offering a partial explanation of the phenomenon, does not quite fit people’s actual experience, however. In one study conducted at Munich University, participants were asked the question, “How fast did the last 10 years pass for you?” Interestingly, people of all ages reported that a decade felt like much less than 10 years. And as expected, the older they were, the shorter people perceived those 10 years to be. However, the tendency largely dissipated after age 50. People over 50 experienced the 10 years as much shorter than an actual decade, but the estimated passage of perceived time did not decrease by much after that age. In other words, the ratio of time-tolifespan continued to decrease, but the perception of time speeding up did not increase by an equivalent amount, as the ratio theory would suggest it should.

The Munich researchers suggested a reason why 50 was an age at which time slows its perceived acceleration: Time doesn’t just fly “when we’re having fun,” as the old adage says, but whenever we are very busy. A 50-year-old perceives time passing more quickly than a 25-year-old because they have more responsibilities in life and in work. There is never enough time in the day to get everything done.

The perception of time speeding up levels off in middle age because our busyness typically increases up to that point as we advance in our careers and become more involved with the activities of our growing children. Then, after 50, it levels off as we reach the zenith of our career and our children become more independent.

If you want to slow the perceived passage of time, you have to stay in what researchers call “specious time.”

Interestingly, this is similar to what spiritual teachers call “the present moment” or “the now.”

Psychologists, including pioneers like Janet and James, have noted that time slows and ex- perience is deeper when we stay completely focused on what we are doing and what is happening in the present.

Toddlers live almost completely within this mental space, so time has no past or present; it is essentially infinite. Older people, on the other hand, tend to be anywhere but the present, spending much more time worrying about the to-do list for the day ahead and reliving a hurtful comment made two weeks ago by a friend.

But how does this explain the seeming warping of time that occurs with big events like 9/11? Why does that event seem like yesterday, while others from the same time period seem so distant? This effect is probably the result of the way our memories process negative experiences. Any novel event will stand out in the memory, but negative ones, especially those that evoke great fear, will stand out in even greater detail.

Brain researchers believe this is true for a couple of reasons. First, it is a survival adaptation — our ancestors needed to remember where dangers lurked in order to avoid them. Second, our psyche needs to process these events, to make sense of them and to integrate them into our understanding of the world. So, it could be that 9/11 feels like yesterday because our minds are still consciously and unconsciously processing the tragedy, both for our own survival and for our sense of ourselves in the world.

The same holds true individually. Surprising events, including positive ones like receiving a marriage proposal or winning a prize, will likely remain more vivid in memory, and our brains will want to keep the tough moments of life, such as confrontations with bullies, car accidents, and nasty breakups, front and center in the mind, in order to deal with their lingering psychological ramifications.

David Eagleman, director of the Laboratory for Perception and Action at Baylor College of Medicine, has considered this feature of the human brain from the physiological point of view. In an article written for the popular e-zine Edge, he explains that different kinds of sensory information are processed by different structures of the brain.

For that reason, the brain has to reconstruct the parts of each experience to have them make sense as a whole. Even at an early age, we are very good at doing this, unless the details are so nonsensical to us that we can’t make them make sense. The ones we have a difficult time reconstructing become what he calls “temporal illusions” — similar to optical illusions but with time instead of visual information.

When we look at optical illusions, our brains are given contradictory information disrupting their ability to translate all the visual information in a concrete way. In temporal illusions, our brain’s ability to reconstruct time has been disrupted, so we end up with a distorted version of time that never quite matches with reality.

One more thing is known about perception of time by the human brain — humans everywhere have the same tendencies. The results of these time-perception studies have been practically identical among German, Austrian, Dutch,

Japanese, and New Zealander participants. All of them experience the speeding up of time with age and the distortion of time when experiencing surprising events.

This suggests that it is a brain-based phenomenon, not something created by cultural differences. As neuroscientists unravel the many mysteries that remain about the nature of consciousness, and the nature of our brain’s existence within the time-space continuum, many questions will certainly be asked about how and why the brain perceives time as it does.