Before I forget

Once again, I recognise the face but the name’s not there. Begins with an M… hmmm… hmmm… hmmm… there it is.

The delay between the first letter and the rest of the name suggests my memory for faces is organised around what programmers call a hash table. The face links to an M; another link gets me (eventually) to the whole name.

Delay – or failure – matching a name to a face is an aspect of nominal aphasia, commonly experienced by older people. It’s generally understood to indicate cognitive decline, a one-way trip in which dementia may precede death. But physical decline might not be the whole story.

Our physical brains are finite, so let’s suppose memory is too. And not just total capacity, but the indexes we ‘search’ to locate a memory. In fact, total capacity might not be the issue at all, because it takes time to search an index and real life often requires a prompt result.

We know these days that curating memory is a vital function of sleep. While we stack Zs, our dreaming brain is figuring out where to put stuff. Let’s get personal. Let’s call this process Susan the Database Administrator.

When I was about six or eight years old I got curious about how far back I could remember clearly. So I replayed in my mind everything I had done or experienced since waking up that day. It seemed to me then I could recall every detail. I tried the previous day, with the same result. And the day before, and the day before that. Everything seemed immediately available.

In those days Susan knew nothing about what I needed to remember. Everything was new to me. Susan stored and indexed everything.

Later she got smarter. Up until 1975, I remembered the name of everyone I met. Effortlessly. Then I stopped, quite suddenly, and had to focus and use the usual tricks to remember the names of new people. I wondered why and discovered I’d stopped listening. This was my first encounter with Susan. When introductions and handshakes were happening I could, if I listened carefully, hear Susan muttering sotto voce, “You’ll never see them again.” I have to go through the palaver of devising mnemonics and repeating it to myself before Susan will reluctantly add a name to her indexes.

Decades later, the indexes are immensely longer and Susan has grown old, canny, and ruthless.

Everyone knows about sleepwalking, and many of us have a story or two to tell about it. The doctor who runs the Sleep Disorders clinic at Guy’s Hospital in London has a doozy. One of his patients gets up in the night and rides her motorbike. She wakes up hours later with no memory of her ride.

The story reminds us at what a high level we function without consciousness. Everyone who learned to drive a car went through a learning process in which what began consciously and awkwardly became smooth and automatic. And so it must. Conscious control is not good enough for safe driving: we need most of it to run on automatic. And automatetd actions do not form memories. Experienced car drivers sometimes find they have arrived at a familiar destination with no memory of the journey just made.

Nothing familiar enough to have been automated gets memory resources from Susan.

I’m leaving the house. I’m about to shut the front door – but did I lock the kitchen and garden doors? I have no idea. I’ve lived here over twenty years. I must have shut and locked those doors thousands of times. Now when I do it, I do not automatically form a memory. Susan will not allocate brain space for information she considers of low value. And if I have a different opinion, I have to work hard to get her to allow an exception.

Some writers have championed a practice for returning to work from a long vacation: shred your inbox. (Or these days, delete it.) The theory is that anything that needs your attention will turn up again later.

I think Susan might have invented it. How many times now do I find myself glazing over while a voice recites instructions? All those terms and conditions! My attention is not your plaything. If I have to know this, it will come back. Or I can look it up. Hooray for Susan, who defends every byte of my capacity.

No doubt the old grey matter is deteriorating. No doubt too it’s filling up, and the indexes have got long and harder to maintain in the dreaming downtime. But Susan has got smart now, and her assessments of what I will need to remember later are based on her decades of experience rather than my changeable opinions.

So when I can’t immediately recall what I had for breakfast this morning, or the name of the man who talked to me at a party that time, I silently give thanks, and salute Susan, guardian angel of my memory.