The logo of the Baader-Meinhof group.
The term was coined by Terry Mullen in a letter to the newspaper St. Paul Pioneer Press. He described how, when he learned of the Baader-Meinhof gang, a German terrorist group, he shortly afterwards heard about it from a different source.
A scientific explanation for this phenomenon is the concept of the recency effect. The mind is biased towards things it has recently learned – if we learn something new, we are more likely to pay attention to it when we encounter it again shortly after learning.
A similar, related theory says that we are generally biased against information we do not know. After we have learned that piece of information, we more easily become aware of it when we see it.
Either way – it is not like the entire world starts to talk about something when we first learn about it. Rather, the impression arises because of mental bias.
- The Baader-Meinhof effect on Wikipedia.