Time is objective—except between your ears, says neuroscientist Dean Buonomano. Each of us intuitively feels what has been written about since at least 1890, in William James’ ‘The Principles of Psychology’: a warping of our internal clock that is inconsistent with the notion of time as a constant force. Here, Buonomano explains our paradoxical experience of time. In the moment, pleasure is fleeting, while pain and boredom seem to last forever. But that’s just one way our brain interprets time: prospectively. In the opposite view, retrospective timing, the tables are turned, and the good times are rebuilt to hold much more weight in our memory while that six-hour delay at the airport fades into oblivion. How we remember time is vastly different to how we experience it. Dean Buonomano is the author of Your Brain Is a Time Machine: The Neuroscience and Physics of Time.

Dean Buonomano: So I think something almost everybody can relate to is the mismatch that we all experience between objective time and subjective time.

So everybody’s familiar with this notion that “time flies having fun” or “a watched pot never boils”. When you’re tightly engaged in a task, or where you’re doing something that you find enjoyable, time—we say time seems to fly by. Which means that your internal clock is probably going a bit slower than an external clock because you’re surprised that maybe an hour has elapsed in external time, but your internal clock is telling you, “No, maybe only 15 minutes have gone by."

Now in order to understand that, it’s very important for us to distinguish between two types of timing. One we call 'prospective timing' and one we call 'retrospective timing'. So this relates to something called the vacation paradox.

So maybe you’re on vacation, you’re in Athens for the first time. During the day you’re experiencing a bunch of new events and new sights and sounds, and as it’s going by—that is prospectively, it seems to be flying by. In retrospect however, maybe the next day or you’re back from vacation, looking back upon that, it seems to be a long day. So retrospectively it seems that it was an extended period of time. And this is something that was pointed out as far back as William James in his 'Principles of Neuroscience' over a hundred years ago.

And the point is that retrospectively we’re not so much telling time but we’re rebuilding or estimating how much time has elapsed based on the number of experiences we have in memory. So retrospectively you’re more estimating how much time has elapsed, if there was a period full of new memories then you’re left with the impression that it was a long period of time retrospectively. But prospectively as it was taking place you were paying attention to some sort of internal clock in our brain, which you were looking at or querying, that was telling you that not much time has elapsed, because you weren’t paying much attention to time.
So on the other hand when you’re very bored or in an anxious state people experience time as dragging or going slow—again, prospectively. If you’re very anxious, you’re waiting to hear from somebody who you know is at the hospital or you just got an important telephone call and you’re waiting for somebody to call you back, time seems to drag. It seems to be going slowly. Of course prospectively, you’re attending to time. You’re very—you’re at the airport, the airplane is delayed, you’re very bored, you’re waiting for news about whether you’re going to make your trip or not and then you find out it’s going to be in six hours, now you’re just in sort of this on-hold mode in which time seems to be dragging, going very slowly, prospectively.
You look back on that, and that’s merely a blip in time. Because retrospectively there’s not many items in your memory. There’s nothing particularly exciting about visiting the airport bathroom for the first time so that doesn’t stick in your memory. So you’re left with this feeling, retrospectively, that time actually was not very long lasting. So you have this paradox in which retrospectively time seemed to have not occupied much of your conscious experience but prospectively you were aware of it dragging.