I had dinner with a friend of the family recently, who described attending the 50th anniversary of her teenage youth group. They used to play ping-pong in the late 1950s in a recreation room beneath the church hall.

When they met again, most of the attendees hadn’t seen each other in the intervening five decades. They were all over 70. My friend looked around, she said, and thought, “Who are all these old people?”

The frisson of that moment will, in all likelihood, be denied to members of subsequent generations. When they hit 70, they will have spent the preceding 60 years watching each other age yearly on Instagram, on Facebook or whatever comes after, updating everyone they ever met on each phase of their lives.

The potent longing that comes from looking back, from not knowing how everything turned out, that imbues so many sequences in novels and films, is being fundamentally altered by technologies that urge us to hang on to everything. To feel nostalgia for nostalgia is a weird paradox, but there you are. Something is lost when nothing is lost.

What’s interesting here is that Facebook and its ilk are aware of what a powerful sentiment nostalgia can be; if it moves people, it can be monetised, and so the social network has in the last year or so been trying to introduce features that capitalise on the powerful but oblique sentiments that come with our need to dwell on the past.

Features such as the Year in Photos and the “On This Day” prompt, which reposts old items on our timelines on the anniversary of the original posting, are, on one level, merely devices to get users to spend more time on the site. But they are also premised on the notion that triggering old memories makes us feel good and provokes us to reconnect with those who feature in them. As initiatives, they push the network into something that feels, to be melodramatic for a moment, akin to the outsourcing of memory. The difficulty with this is that an automated prompt to nostalgia interferes with two of its primary characteristics —happenstance, and distance.

Unintelligible shifts and triggers

Part of what it is to be human hinges on the serendipity of our mental landscapes; what is retained, what is discarded and the hierarchy therein is premised on thousands of unintelligible shifts and triggers. When an outside agency gets involved in rationalising this process, promoting some “memories” over others or contaminating old memories with updates of what the people in them are doing now, it starts to alter the composition of our interior lives.

For a moment, it’s fun to find out what the class nerd looks like now, or who has been three times married. But that information also alters the recollection of when you first knew them. It breaks the seal on the memory, which, like every other scarce resource, is valuable precisely because it is unattainable. If, as a matter of programming, life events are dragged annually into the light, they start to occupy some new, all-encompassing version of the present. Facebook eliminates the very thing its purports to be striving for.

The same goes for all those cultural artefacts that used to be inaccessible and are now instantly available. In the first year of college, when a decade seemed like a century, the staple conversation of first-year students at college was the kids’ TV we’d all watched, and that, with the exquisite sadness of the moody late-teen, we assumed we’d never see again.

Now, obviously, you just call them up on YouTube. And I did; the Flumps , Button Moon and Bagpuss . I noted how posh the narrator in Button Moon sounded, and how shoddy the production values were. But there wasn’t the thrill of the time-capsule discovery, the romance of stumbling on the box buried in the garden — itself now surely an anachronism. Remembering doesn’t mean much when you are never, ever permitted to forget.

— Guardian News & Media Ltd