Let’s say you learn that Asmara is the capital of Eritrea. A week ago, you didn’t even know there was an African country named Eritrea. Now every Uber driver you meet happens to be from … you guessed it, Eritrea. This is a strange phenomenon related to memory—and it’s called the Frequency illusion.

Now that you know about X, is X starting to show up everywhere or was X always there and you’ve just become attuned to noticing it? That is the million-dollar question, as it turns out.

Selective attention reinforces a newly learned concept

Assistant Professor Carly Leonard, PhD, who teaches in the Psychology Department’s Behavioral/Cognitive Neuroscience division, specializes in human attention and memory. Her research explores how different people attend to environmental stimuli. And even though Leonard is more attuned to issues of perception, even she experiences the Frequency Illusion. 

“I was just talking about this with someone right before you contacted me,” she said. Leonard had bought a purple jacket. “I didn’t think I was buying something on trend, and all of a sudden, I started seeing people wearing a jacket of this color everywhere.” Is purple in season for jackets this year? Leonard can’t be sure. What she knows from her research is that “it’s possible you notice purple jackets more—even if there is no true increase in frequency.”

The Frequency Illusion affects everyone as some point in time. For most people, it doesn’t necessarily have important consequences. It’s simply a curious phenomenon, like déjà vu. “This effect occurs because things that are recently important to you receive more attentional processing and are therefore more likely to be consciously perceived,” explains Leonard. In other words, purple jackets became noticeable because you yourself bought a purple jacket.

Frequency Illusion, Recency Illusion, or Baader-Meinhof Phenomenon

Now that the phenomenon itself has been brought to your attention, let’s delve into its various names. It is called the Frequency Illusion (because you’re noticing something frequently), as well as the Recency Illusion (because you’re noticing something you recently learned about). It is also called the Badder-Meinhof Phenomenon—because one person at one point in time learned about a West German militant group called the Badder-Meinhof Gang and then suddenly found mention of Badder-Meinhof everywhere. 

Despite its collection of somewhat amusing names, the Frequency Illusion can have serious consequences. For example, in the fields of criminology and medicine. If a detective trying to solve a crime becomes aware, through the Frequency Illusion, of a certain suspect, then the detective’s mind is prepared to pay attention to that suspect when new information comes up that’s relevant. The Frequency Illusion could help the detective solve the crime—or it could do the opposite. If the detective’s attention is focused solely on the suspect who keeps coming up via the Frequency Illusion, the detective could miss other key information.

Can the Frequency Illusion have life-or-death consequences?

The phenomenon also has life-or-death ramifications. Doctors who learn about a certain diagnosis may consequently make that diagnosis more often. An article in Academic Radiology from June 2019 discusses one medical student’s experience diagnosing “bovine aortic arch,” an embryologic condition that could contribute to thoracic aortic disease. Once he learned about this condition from a radiologist, he spotted it three times in the next 24 hours. “This phenomenon can be thought of as an excellent learning tool,” the article concludes. 

On the other hand, the Frequency illusion could hypothetically blind doctors to other potential diagnoses. 

For people with certain psychological disorders, the Frequency Illusion could aggravate their conditions. Leonard studies attention in people with schizophrenia. In terms of confirmation bias, people with schizophrenia may “confirm their own suspicions” if they start paying attention to aspects of their experience that are consistent with a delusion they currently hold. “It could potentially spiral out of control if you convince yourself of something that isn’t true,” she said.

For most people, the Frequency illusion will not result in unsolved crimes or misdiagnosed patients. Hence, it is simply an interesting phenomenon. It does teach us something important about attentional processing: at any given moment, our brains are ignoring a lot of sensory input.

Leonard puts it this way: “We constantly take in much more information than we are aware of at any moment. Strangely enough, we aren’t usually aware of why we notice what we do. The frequency effect really makes us aware of how much attention shapes our experience of the world!”