Frequency Illusion

Once something enters conscious awareness for the first time, it seems to suddenly appear far more often afterward — not because its real-world frequency has changed, but because selective attention now notices it, and confirmation bias then preferentially remembers each new sighting while ignoring the (unchanged) base rate of everything else. Phill Agnew illustrates it with his own experience: after rewatching Home Alone in 2019 and newly noticing its theme tune, he began hearing it — or thought he did — in supermarkets, ads, and even an aircraft cabin chime.

Origin of the name. The phenomenon is popularly known as the "Baader-Meinhof phenomenon," not because the German left-wing terrorist group was ever studied, but because a 1990s online newspaper discussion thread began when someone described hearing the group's name twice in quick succession shortly after first learning of it; other commenters recognized the same pattern from their own lives, and the informal name stuck. Stanford linguist Arnold Zwicky's blog gave the effect its more formal name, "frequency illusion," noting the same pattern with language: once someone notices a specific usage (e.g. "literally" used for emphasis), they suddenly seem to hear it constantly, though the word's actual usage rate hasn't changed.

Empirical confirmation. Martin van der Meulen's 2020/2022 study in the journal Languages tested whether Dutch-language style guides' claims about "common" word usage were actually true, by checking a large newspaper/magazine database. A 1925 guide by author Mortgat claimed the poetic Dutch word for darkness, "duistering," was more frequently used than the plain word "duisternis" — the opposite was true: "duisternis" appeared 909 times in contemporary texts versus just 8 for "duistering." Van der Meulen concludes Mortgat had fallen for the frequency illusion himself: having newly noticed the rarer word, he began seeing it everywhere and wrongly inferred it was common (see Van der Meulen Dutch Frequency-Illusion Study).

Real-world consequences. Doctors who have recently seen one case of a rare disease are more likely to misdiagnose subsequent unrelated patients with that same disease. Media coverage repeatedly describing individual instances of a specific crime can convince audiences a "crime wave" is underway even with no actual change in crime-rate data.

Discussed in

• Episode 280 — 280-when-you-can-t-stop-seeing-the-thing-you-ve-just-discovered

Related

• Van der Meulen Dutch Frequency-Illusion Study
• Tom Bowden-Green
• Luan Wise
• Marketing and Psychology