The Baader-Meinhof Phenomenon
You learn a new word, and suddenly you see it everywhere. You hear about a band, and within a week it seems like everyone is mentioning them. You buy a car, and now the roads are full of the same model.
The world hasn't changed—your attention has.
This cognitive bias has two names. The folksy one, the Baader-Meinhof phenomenon, originated in 1994 when Terry Mullen wrote a letter to the St. Paul Pioneer Press describing how, after mentioning the name of the German militant group Baader-Meinhof once, he began noticing it constantly. Other readers shared similar experiences, and the term stuck.
The formal name, frequency illusion, was coined in 2005 by Stanford linguist Arnold Zwicky in a blog post on Language Log. Zwicky identified two psychological mechanisms at work: selective attention and confirmation bias. Once your brain tags something as relevant or interesting, it begins filtering for it unconsciously. You don't notice how often you ignore the stimulus before learning about it, so when you start noticing it afterward, the frequency seems to have spiked. In reality, you're just seeing what was always there.
A related effect Zwicky called the recency illusion makes you believe that whatever you've recently noticed must also be new. People encountering an unfamiliar word assume it's a recent coinage, even if it's been in the dictionary for a century. The two illusions compound: you notice something more, and you assume it's suddenly appearing more because it must be new.
The phenomenon is harmless but difficult to shake. Even knowing it's a cognitive bias, you will still feel surprised when the thing you just learned about seems to materialize everywhere. Your brain is very good at finding patterns. It's less good at remembering all the times the pattern wasn't there.