The Baader-Meinhof complex is happening to you right now. It happened to you yesterday; it’ll happen to you tomorrow; and it'll happen the day after that. If you’re starting to see a pattern here, that’s because you’re experiencing the Baader-Meinhof phenomenon (AKA the "frequency illusion"), the prickly sensation that after you see something once, it's everywhere.
All mind trickery aside, the world is made up of patterns. Some people see certain types of patterns, while others may see different types. It really has to do with how a person is educated. After all, someone with a PhD in Applied Mathematics is going to see how numbers fit into the world far better than a person schooled in literature. The patterns you see reinforce your preconceptions and therefore your reality... but what if you see only what you want to see? What if a certain reality only exists because it's the world you want? What if you shut out everything that might challenge that view because you just aren't looking for different patterns?
Like its sister phenomenon the Mandela Effect, in which whole groups of people misremember the same thing, the Baader-Meinhof complex is an example of your mind playing a trick on you in a really effective way. But, given how terrible human memory actually is, you might want to consider reading on to see if you're in the midst of the Baader-Meinhof right now, this very minute. Otherwise, you might just get trapped inside your own mental patterns.
Let’s say you learn a new word. It could be any word. But you notice that, once it enters your brain, you start seeing it everywhere. It could be in magazines, websites, or even books you're reading, but you will start to notice it more and more. Why is everyone using this word all of a sudden? Is it a trendy, millenial slang term? Probably not. In reality, that feeling right there, the one that makes it seem like a new thing you learned is suddenly really popular and all around you, is what it’s like to experience the Baader-Meinhof phenomenon.
There are many psychological processes going on when you learn something new. One of them is selective attention, which has to do with what you focus on. Everyday, your senses are bombarded with stimulation, but, for the most part, you manage to tune it out. Instead, you pay attention to what’s important to you. When you learn something new, it’s on your mind right after you hear it; your attention gets focused on it. Afterward, while it's still pretty fresh, your selective attention takes over, flashing like a light bulb every time the new thing you learned comes up. Here's the thing, though, it was there all along. Your selective attention just wasn't honing in on it.
Have you ever noticed that something you strongly believe always seems to be supported by facts or examples you find? (See party politics if you're feeling doubtful.) Most of the time, that’s because you’re subconsciously picking and choosing examples that support your views. It’s called cognitive bias, and it tends to turn your attention to things that support what you want to see rather than all that is really there. It may even affect how you perceive memories. So, in essence, you have a way of looking for the things you want to see, which includes new things that you've just learned about or encountered. That’s why you tend to find examples of what you just learned in the Baader-Meinhof phenomenon.
Because of their selective attention and cognitive bias, humans start seeing what they learned everywhere. In fact, your brain may even go so far as to create patterns where none existed before because of the new information that it has received. For example, if you somehow get it into your head that two types of cards always show up together in your poker games… you’ll see them show up all the time. They might not actually be together in the game very often, but because you always notice the pairing, it seems to happen frequently. This feeling, which is attached to the Baader-Meinhof phenomenon, pretty much keeps the casino industry afloat.