The past is vividly alive in the Old Town of Würzburg in Germany. Walking the spindly streets, I felt transported to the medieval days: I could practically see the ruddy burghers going about their business in the shadows of aged church facades.

Often when we engage with things of the past, with the material lives of our forebears, we’re in search of a sense of authenticity. Seeing the actual items that people, long dead, dealt with in their day-to-day lives seems in some way to bring them back: what they’ve left behind invigorates our historical imagination of what their lives were like. The things that populated the lives of expired generations gives us a visceral connection to them, and Würzburg amply provides the material for that sense of intimacy with the vanished past.

Or so I thought. The same day I so romantically strolled through the Old Town, I learned that it’s not old at all – younger, in fact, than me. The Allies bombed the place to annihilation, destroying 90 per cent of the city (more than Dresden). After the war, the Würzburgers rebuilt the Old Town exactly as it had been, a project not completed until the 1990s. So while it seems that you’re engaging with the world of yesteryear, in fact it’s a reproduction.

And that shattered the connection to the past. But why? Walter Benjamin called the uniqueness of a work of art its aura. An identical poster of The Scream (1893), even if arranged the same way as the original, will resonate far less if the viewer knows that Edvard Munch’s brush never touched it. Its aura is gone. So, upon learning of its recency, the aura of Würzburg’s Old Town dissolved – and I was left instead with a sense of falsity, nothing but an unsettling replica of authenticity.

Browsing Spotify for music to pull me through the slog of a grey February in New York, I came across the work of Labi Siffre, a 1970s artist I had never heard of. I was immediately taken with his delicate voice and simple, intimate musical arrangements.

Shortly after my precious discovery, Labi Siffre turned up in random places. I heard his crooning in coffee shops, a friend put him on at karaoke, and the singer-songwriter Lucy Dacus mentioned him as an artist who epitomised yearning. Labi Siffre was following me. Or at least that’s how I’d think about it if I didn’t know better. Instead, I thought: Baader-Meinhof.

The Baader-Meinhof phenomenon, also known as the frequency illusion, is a type of cognitive bias where, once you learn about something – such as a word, person or concept – you start to notice it more frequently. Your best friend clues you in on a slang term, and suddenly you see it endlessly in your feed. Your brother recommends a supplement, and you start repeatedly hearing ads for it. It feels eerie, especially if you don’t have a name for what’s happening.

Terry Mullen recalled feeling similarly when, after learning about a 1970s terrorist group called the Baader-Meinhof Gang, he encountered another mention of them the next day. He wrote to a newspaper about it in 1994. About a decade later, a Stanford professor proposed that a mix of selective attention and confirmation bias explains why something you are newly aware of might seem to happen all the time.

I first learned about this phenomenon in a psychology class at university. Today, when I feel it in action, I mutter ‘Baader-Meinhof’ under my breath. It helps me notice what I’m noticing, and the knowledge that my brain is primed for recognition dispels the feeling that I’m being sent some coded, mystical message – musical or otherwise.

As you read, do you scribble around the edges? Over the years, writers have sworn by the practice. Edgar Allan Poe once wrote: ‘In getting my books, I have been always solicitous of an ample margin … for the facility it affords me of pencilling suggested thoughts, agreements and differences of opinion …’

I tend to make notes digitally nowadays. And if I include magazines and newspapers, most of my reading is online, where I probably could annotate with the right software, but can hardly doodle. That’s a shame. Apart from the fact that annotating boosts recall, we’d lose something if freeform margin-writing faded away. One of the meanings of ‘marginalia’ is ‘non-essential’, yet it’s anything but.

For one thing, scribbled-upon books have helped reveal the web of influences between writers and thinkers. Herman Melville’s annotated copy of John Milton’s Paradise Lost shows how it fed into Moby-Dick. And Charles Darwin’s comments in his books – from Charles Lyell’s Principles of Geology to his grandfather Erasmus Darwin’s The Temple of Nature – inform how they shaped his theory.

Marginalia can reveal everyday insights too. Historians occasionally find scrawls in manuscripts that speak of long-dead readers’ lives. A recent exhibition in Dublin features scriptures doodled on by medieval Irish monks. One described feeling ‘ale-killed’ (hungover); another complained about his materials (‘New parchment, bad ink. O I say nothing more’). Turns out nuns did similar. In 2022, researchers found surprisingly modern cartoons of people around the edges of an 8th-century Act of Apostles. A nun etched them, perhaps mischievously.

Reading about these examples made me think I should annotate more – not everything, but the writing I care about. Or perhaps I’ll take a leaf from a wholesome TikTok trend I discovered while writing this: gifting an annotated book. This 21st-century practice suggests digitalisation may not be annotation’s death knell after all. Poe might have approved.