The frequency illusion, also called the Baader-Meinhof phenomenon, is a cognitive bias in which someone learns a novel word or concept—and then “suddenly” encounters it everywhere, whereas in fact it it is just more salient because it has been recently observed.

Psychology Today magazine

When we learn a new word, discover a favorite car, or unearth a previously unknown historical fact, and then come across it multiple times in short succession, the frequency illusion is at work. 

This cognitive bias leverages the brain’s penchant for pattern recognition: We direct selective attention to our novel discovery and scan the world for matches. We choose what to focus on and confirm more sightings of it—involving another cognitive bias, the confirmation bias, as well.

For me personally, I was not overtly aware of this phenomena until I read the Rabbits novel series. After that and ever since, I have seen multiple references to rabbits everywhere without actively searching for them.

We remember what we prime the mind to attend to. If we select a new concept, we’ll identify that concept more often; the minds will actively seek out more stimuli related to that concept to seek confirmation.