The Frequency Illusion has two names, and the story behind the more colorful one is pretty good.

In 1994, a man named Terry Mullen wrote a letter to the St. Paul Pioneer Press describing how, after hearing about the Baader-Meinhof Gang for the first time, they were a German terrorist group from the 1970s, he encountered references to it two more times within 24 hours. The newspaper published his letter. The name stuck. And for years, the Baader-Meinhof phenomenon spread across the internet as informal shorthand for this type of experience.

It wasn’t until 2005 that Stanford linguistics professor Arnold Zwicky gave it the more descriptive label that we tend to use today: the Frequency Illusion. Zwicky was writing about language patterns, but the observation applied to everything. The Oxford English Dictionary later recognized the term, defining the Frequency Illusion as “a quirk of perception whereby a phenomenon to which one is newly alert suddenly seems ubiquitous.”

Read that definition a second time. Newly alert. Not newly present.

So why does it happen?

Zwicky attributed the illusion to two psychological processes working together: selective attention and confirmation bias. The first one lights the fire while the second one keeps it burning.

Selective attention is the brain’s triage system. It can’t process everything, so it decides what matters and flags it for closer monitoring. Once something earns that flag, your brain keeps scanning for it without you consciously deciding to. The new UI pattern you just learned about is now on your brain’s radar. So every app you open starts registering it.

Then confirmation bias kicks in. Once you’ve started noticing a specific stimulus, you notice it more — and that noticing feels like confirmation that it’s everywhere, even though the actual frequency hasn’t changed.

One more thing worth knowing: the Frequency Illusion often travels alongside what Zwicky called the Recency Illusion. The recency illusion is the belief that something you’ve only recently noticed must also be recent. It’s a close cousin that compounds the problem. Not only do we think a thing is everywhere, we also assume it just started showing up.

When we put these two effects together, it can make a brand-new idea feel like an emerging trend, a single customer complaint feel like a widespread pattern, and a recently discussed feature feel like the most pressing item on the roadmap.

The Frequency Illusion isn’t a failure of intelligence; it’s more of a quirk of attention. Our brains are wired to prioritize novelty and look for patterns — mostly useful, until a new piece of information hijacks our filter and warps our sense of how common, important, or urgent something actually is.

The Frequency Illusion sounds harmless enough when it’s about Inter or a UI pattern you just discovered. But the same mechanism runs quietly in the background of how product teams read their environment, and it can distort judgment in ways that are hard to spot because they feel exactly like insight.

The most direct place it shows up is in design critique. A designer learns a new term, say, “affordance” or “progressive disclosure,” and suddenly they’re seeing violations of it everywhere. In their own product. In competitor apps they’ve been auditing for months. In designs they reviewed and approved months ago. The designs didn’t change; we just got a new word for something that was always there.

The same thing happens after conferences. Someone comes back with a specific pattern or principle they encountered for the first time, and suddenly it’s visible everywhere: in products they use daily, in the team’s own design system, in research findings they’ve been sitting on for weeks. The pattern was always present. It just didn’t have a name until now.

The tricky part is that this can feel exactly like professional growth. Learning to see things you couldn’t see before is genuinely valuable. Just be careful not to mistake newly-named for newly-present, and treat a pattern you just learned to recognize as more widespread, more urgent, or more significant than the evidence actually supports.

Building the habit of asking “was this always here, or did we just get the right filter?” creates enough friction between noticing and concluding to keep the team honest.