## Why going on holiday gives us more memories

Lucky me. I’ve just returned from a family holiday in that most exotic of countries, Japan. So many fresh sights and strange tastes: from flower gardens, temples and communal baths to robots, bullet trains and the Kawaii Monster Café. Although we were there barely more than a week, it’s hard to believe we packed so much in.

While on an adventurous holiday, many people experience that strange sense of time having slowed down in the most pleasurable way, and of conversations that begin, “Was it really only yesterday that we . . . ?”

Ten days in a far-off land produces a richer treasury of detailed memories than 10 weeks back home. But what is behind this phenomenon? And does it teach us something about living a full life?

One answer comes from Claude Shannon, a titan of computer science still under-appreciated outside his field. In 1948, Shannon published one of his two profound contributions, A Mathematical Theory of Communication.

One of the implications of Shannon’s theory is that a message can be compressed to the extent that it is predictable. Anyone who has played the guessing game of Hangman knows that once a few letters are in place, the remainder are usually easy to guess. Similarly: sntnces wth vwls rmvd sty cmprhsbl. Ritualised conversations (“How are you?” “Very well, thank you. How are you?”) can be heavily compressed; poetry, perhaps, less so.

A movie can be compressed because, between cuts, each frame tends to resemble the previous one. A compression algorithm can start with the first frame after the cut and store a series of “diffs” — changes from the previous frame. The faster and more dramatic the movement or transitions, the harder a video is to compress, because the diffs are almost as big as the original frames.

Although the parallel is not exact, much the same thing seems to be going on with our memories of life. The brain is not a video recorder; we recall the gist. Sometimes the gist is very brief. If I get up in the morning at the usual time, eat my customary breakfast and catch my usual train to the office, why should my brain trouble itself to remember this day two weeks after the fact? The diffs are barely worth bothering with. In contrast, fresh experiences defy compression: the diffs are too big.

We could expand this idea to other aspects of life, maximising information content by keeping things unpredictable. Brian Christian, author of The Most Human Human, a book about conversations between humans and computers, speculates that if we’re seeking advice we should ask the person of whose answer we are least certain. If we want to understand a person, we should ask them the question to which we are least sure of their answer.

Perhaps the best newspaper columnist is the one whose columns are the least predictable? That may be going too far: too much novelty is exhausting, and we need an anchor for our expectations. But I well recall a friend saying that her favourite newspaper pandered to her preconceptions so much she didn’t really need to bother reading it; she could just think hard about everything she already held true. We scribblers should hope to do better.

One would not want a life of endless novelty, if only because that would mean a procession of superficial impressions and comparisons. Static, surprisingly, is impossible to compress without losing information, because its randomness makes prediction or interpolation impossible. Yet static is also meaningless. Too many random novelties, too fast, produces a lived experience not unlike static.

One of the virtues of experience is that it can attune us to subtle details and deep connections: “a world in a grain of sand, and a heaven in a wild flower”. (It may also allow us to draw out meaning from a brief allusion to a larger body of work.) But if repeated experience becomes humdrum, and we do not look for the depths, our days will be thin and forgettable.

So if you want a full life, rich with memories, keep searching for new experiences. That is far easier for the young than the old, but it should be possible for anyone. Surprising conversations are always there for the having and, while a holiday on the other side of the world is a costly (if reliable) source of vivid experiences, novelty is affordable for almost anyone in the form of new music, books, even walking an unfamiliar path through your own home town. It is always worth seeking out whatever is excellent — but for vivid memories, the same old excellence is not quite enough. Freshness matters, too.

I suspect that we all know this, yet we fall back on familiar routines. I often eat the same lunch in the same lunch spot, have a favourite library desk, and enjoy particular genres of film and book. In the moment, these habits are convenient and comforting. In the future, they will result in a life more easily compressed in the memory.

In Japan, it was hard to avoid eye-opening sights and attention-grabbing situations. Now I’m resolved to seek out the new and challenging in the UK, just as we did when far from home.

Written for and first published in the Financial Times on 26 April 2019.

My book “Fifty Things That Made the Modern Economy” (UK) / “Fifty Inventions That Shaped The Modern Economy” (US) is out now in paperback – feel free to order online or through your local bookshop.