This article was originally printed in Issue 399 (May/June 2012) of the Australian Mensa magazine, TableAus.

It’s a poor sort of memory that only works backwards.

– Lewis Carroll, Alice Through the Looking Glass

Ask any physicist worth his salt and he will tell you that time travel, for the moment, is confined to the realms of science fiction. Ask a psychologist or a mnemonist, however, and you will get a very different answer. They won’t be able to tell you anything about time as the physicist understands it, but they will both be intimately familiar with the elastic nature of our perception of time, and its links to memory. The way we relate to our memories can expand or shrink the perceived lengths of our lives and let us engage in a form of mental time travel. When our memories fail us, they can leave us stranded at one moment in time.

Stuck in time

E.P., as he is known in the scientific literature, is a man stuck in time. Like Groundhog Day in reverse, time shuffles on around E.P. while he repeats the same moment day after day, unable to form any new memories.

In November 1992, E.P. was struck down by a virus. At first, his symptoms suggested a mild flu, but after a few days he began to have seizures, and his wife quickly summoned an ambulance. The virus, a strain of Herpes Simplex, tore through his hippocampus and surrounding tissue, the part of brain associated with memory. By the time the virus had run its course, E.P. was a man transformed.

E.P. found himself unable to form new memories (a condition known as anterograde amnesia), and, to the horror of his family, had also lost some of his old memories (retrograde amnesia). Joshua Foer, a science journalist and one time US Memory champion who met with E.P., recounts that “when informed of the birth of his grandchildren, EP’s eyes welled up each time – and then he promptly forgot that they existed.” In fact, E.P. doesn’t have any memories after the 1950’s. His memories of his life up till then, his personal narrative, is remarkably intact but in his world the USSR is still a global superpower and internet hasn’t been invented.

Without memories, we would not experience the passage of time. Our memory-less selves would be unable to compare how we feel now to how we were feeling moments before and would be unable to judge the quality or direction of our lives.

Stretching time out

A patient visits his doctor’s office after undergoing a complete physical exam. He enters the consultation room to be greeted by the graven face of his physician.

“I’ve some bad news.” the doctor tells him. “You only have six months left to live.”

“Oh doctor!” the patient replies through trembling teeth. “What am I to do?”

“Stay away from alcohol, gambling and beautiful women.” the doctor tells him.

“Will that help me live longer?” asks the patient.

“No,” says the doctor, “but it will SEEM longer.”

This joke captures an intuition that we all have, that when we are doing something boring, time seems to slow to a crawl and that it flies when we are having fun. Surely, there is some truth to this but if we are to learn anything from the story of E.P., it is that our lives are structured by our memories of significant events.

When asked “when did you get your gallbladder removed?” we can easily imagine someone responding “Well now, let’s see…it was right after my sons first birthday. He is 24 years old now, so it must have been…23 years ago!” We structure our chronological memories in relation to landmark events.

These landmark events are characterized by their affect and their novelty. If we spend our lives doing the same thing day in and day out, one day is bound to blend into the next. We ought to also be guarded against excessive automaticity; we have all had the experience of walking or driving somewhere familiar and of just zoning out; you arrive at your destination but have no memory of how you got there. You were, for that moment, an attention-less zombie, making your way through the world without any conscious inner life. Since this is, as far as we know, the only life we get, learning to be present for it is, in a sense, a matter of life and death. If we want to stretch out time to lengthen our perceived lives, then, we ought to do violence to our daily routines, seek out adventure and try new things and cultivate our capacities for attention.

The masters of transforming the mundane into the memorable are the competitors of the World memory championships. These mental athletes transmute endless pages of binary numbers, among other things, into vivid mental stories. In 1991, Tony Buzan hosted the first ever World Memory Championships. The event attracted the top memorizers of the day, including Creighton Carvello, the man who held the world record for the memorization of Pi, Harry Lorayne, a stage magician who used memory techniques in his acts and Kenneth Wilshire, who used his memory skills to count cards in blackjack. Needless to say, with such a colorful cast of characters, it was a most memorable event.

Traveling back in time

The most familiar way in which our memories allow us to warp our experience of time is, in some ways, also the most dramatic. Recalling memories of the long-since-past allows us to temporarily relive those experiences in a way that is fairly described as a form of mental time travel. In fact, it may be our capacity to do that makes us who we are.

Think of an experience from your childhood. Something you remember so clearly that you can see, hear and maybe even smell it, as if you were really there. After all, you were there, right?

Here is the kicker: You weren’t. In almost every sense, you are different to the person in your memory. You are most likely a different size and shape, cell turnover is rapid (cells in the gut, for example, are completely replaced in 48 hours) and even the atoms that make you up now are completely different to the ones that made you up then. If we are going to go looking for ourselves in our bodies, we are going to be in trouble.

This is known in philosophy as the problem of the ship of Theseus. If you replace the individual components of a boat, one at a time, until it is completely replaced, is it still the same ship? If not, when did it become a different one? Regardless of the answer to this particular version of the puzzle, most philosophers who work in the area of personal identity over time appeal to the causal connectedness of our memories as key our personal identities.

From our own perspectives at least, who we are is defined by the sum total of our life experience, recorded, albeit with modifications, by our stream of memories, the unique fingerprint of our conscious experience. Time, as recorded by our memories, is mysterious and inconstant rather than the precise ticking of an atomic clock. Such is its mystery and appeal.