Baader–Meinhof Effect

You learn the word "serendipity" on Monday. By Friday you have seen it three times. The word was not suddenly popular. You were suddenly awake to it.

The machinery has two parts. First, the brain is a filter, not a camera — it must ignore almost everything, or you would drown in sensation. Second, anything newly learned gets marked "important," and the filter stops throwing it away. The world did not change. The filter did.

This is why buying a blue car floods the streets with blue cars, and why a new worry fills the newspaper with confirming disasters.

Remember it in both directions. When a pattern appears everywhere all at once, suspect your filter before you suspect a conspiracy. And use the trick on purpose: learn the name of something you want more of — kindness, good design, clear thinking — and you will start finding it in the crowd.