What Is… the Frequency Illusion (Baader-Meinhof Phenomenon)

Insights into psychology: The frequency illusion, aka Baader-Meinhof phenomenon

In this series, I dig a little deeper into the meaning of psychology-related terms. This week’s term is the frequency illusion, also known as the Baader-Meinhof phenomenon.

Do you ever find that once you start to notice something, all of a sudden, it’s happening a lot? There’s a name for that; it’s a type of cognitive bias called the frequency illusion, which was described by linguist Arnold Zwicky in 2005. He first wrote about it in the context of linguists’ perceptions about how common certain patterns of speech were.

The frequency illusion refers to the same concept that was previously described as the Baader-Meinhof phenomenon. This name came about after “Gigetto on Lincoln” wrote on the Pioneer Press Bulletin Board about this phenomenon he had named. He came up with it after speaking to a friend about the Baader-Meinhof gang (a West German extremist group), and the friend pointed out an article in that day’s newspaper that mentioned the group. Other readers shared that they’d had the same sorts of experiences.

The frequency illusion is the product of selective attention and confirmation bias, often with a dash of recency illusion. Let’s look at what those things are.

Selective attention

You’re probably awake for about 16 hours a day. Think of the amount of input that you’re constantly bombarded with during that time. Selective attention is the way that our brain selects what’s relevant and ignores irrelevant stimuli. There’s only so much attention to go around, and it’s just not possible for everything to register. Imagine how overwhelming it would be if our brains couldn’t filter out information.

Treisman’s attenuation model, shown below, shows how we filter sensory input. These filters are based on what we’re intentionally paying attention to, physical properties like loudness, and then analysis of meaning. Our names, for example, are very meaningful to us, so we’re likely to selectively attend to input that includes our name. Things only make it into working memory if they’ve passed through those filters.

Treisman's attenuation model of how sensory inputs are filtered

That means that things that don’t make it through the selective attention filters aren’t encoded in memory. You don’t remember things as they actually happened; you only remember the bits that caught your attention. That means that there’s a shit ton of stuff that happens each day that you can’t possibly remember because it was never stored in your memory in the first place.

Confirmation bias

Confirmation bias means that we tend to seek out and believe things that are consistent with what we already believe and ignore evidence that’s inconsistent with our beliefs.

Once something has grabbed your attention, you’re likely to notice almost every instance of it that you come across. This skews your perception of the frequency, leading you to think that the frequency has changed. Each time you come across that thing, that confirms your perception that the frequency has increased, and you’re even more sure that you’re now seeing it all the time.

Meanwhile, you could’ve seen the same thing 20 times last week and not remember because it didn’t make it through your attention filters any of those times. The fact that you don’t remember can be interpreted as confirmation that it wasn’t happening, but it’s not possible to fish things out of your memory that weren’t encoded there in the first place.

The recency illusion

The recency illusion makes us think that things that we’ve just noticed or learned about are recent phenomena. Zwicky gives the example of an article on a dictionary website about people misusing “you and I” where they should have used “you and me”. The author of this article thought that this misuse was a hypercorrection that had arisen in the last 20 years or so because of schools emphasizing the “you and I” construction. I certainly remember being corrected for saying “me and Jane played soccer at recess.” However, Zwicky (2005) pointed out that sources show this has been going on for a good 400 years, and “it’s not just Kids These Days.”

The recency illusion often accompanies the frequency illusion. It supports the idea that the thing we think we’re coming across all the time now wasn’t happening at all before. It’s new in our attention, so we think it’s new in general.

Besides having a lot of sensory input each day, we also have a lot of thoughts. Many of them are pretty fleeting, and they may come and go without us remembering them. A study conducted at Queen’s University found that we have about 6200 thought worms a day. These are trains of thought with transitions between them; the thoughts themselves can’t be detected, but the researchers believed they were able to see transitions. We’re not remembering all of those thoughts, which skews our ability to remember how we think about things.

Another possible explanation for a perceived increase in frequency is our inability to wrap our heads around the notion of randomness. We naturally seek patterns, and we’ll find them even when they don’t exist (this is called apophenia).

Examples of the frequency illusion

During pre-COVID times, think about how many people you would see during an average day. You go out and about in your neighbourhood, you go to the grocery store, you commute to work, etc., and there’s a big sea of people you mostly don’t pay any attention to. Let’s say that one day at the grocery store, you trip, and someone catches you and prevents you from falling. Over the next few weeks, all of a sudden you’re seeing this person everywhere, and you don’t remember ever seeing them before. But if they were part of the great big sea, there would have been no reason for you to notice them before. After they helped you, though, you’re likely to notice them every time you come across them, and each time you see them, it reinforces the idea that you’re seeing them everywhere.

If you’re in the market to buy a new car, and you’re considering a particular kind of car, all of a sudden that make of car will jump out at your from the great big sea of cars that you usually pay no attention to.

One article that I came across mentioned that the frequency illusion may be treated as evidence that delusions are true for people experiencing psychosis. If you think that light switches are a way of people spying on you, you’ll suddenly start to notice the loads of light switches that you completely ignore most of the time.

Perception isn’t all that reliable

Zwicky (2005) points out that while sometimes your perception of a change in frequency can be correct, it’s important to confirm that with facts rather than just assuming that your perception is reliable when it’s really “seat-of-the-pants guesses.”

The frequency illusion is very common. Zwicky noted that linguists are particularly like to be affected by the frequency illusion regarding written or spoken language. It’s not a matter of not knowing better; our perception just isn’t as reliable as we might like to think it is.

Is this cognitive bias something that you’ve noticed in your own experience?


The Psychology Corner: Insights into psychology and psychological tests

The Psychology Corner has an overview of terms covered in the What Is… series, along with a collection of scientifically validated psychological tests.

Ashley L. Peterson headshot

Ashley L. Peterson


Ashley is a former mental health nurse and pharmacist and the author of four books.

37 thoughts on “What Is… the Frequency Illusion (Baader-Meinhof Phenomenon)”

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