Frequency illusion

Frequency illusion, also known as the Baader–Meinhof phenomenon or frequency bias, is a cognitive bias referring to the tendency to notice something more often after noticing it for the first time, leading to the belief that it has an increased frequency of occurrence.[1][2][3] The illusion is a result of increased awareness of a phrase, idea, or object – for example, hearing a song more often or seeing red cars everywhere.[4]

The name "Baader-Meinhof phenomenon" was coined in 1994 by Terry Mullen in a letter to the St. Paul Pioneer Press.[5] The letter describes how, after mentioning the name of the German terrorist group Baader-Meinhof once, he kept noticing it. This led to other readers sharing their own experiences of the phenomenon, leading it to gain recognition. It was not until 2005, when Stanford linguistics professor Arnold Zwicky wrote about this effect on his blog, that the name "frequency illusion" was coined.[2]