The Frequency Illusion

This week I had a good opportunity to discuss an interesting cognitive bias with one of my 4th year medical student while we were on renal rounds. The issue came up when I was examining the belly of one of my young patients, who screamed out, “your hands are cold”. One of our nurses was quick to respond, “Cold hands, warm heart”. My student looked at me then remarked that she had only recently ever heard that expression, and since then has been hearing it over and over again. This, of course, lead to a natural discussion of the cognitive bias called the Frequency Illusion, which also is known as “The Baader-Meinhof Phenomenon”. I admit we had to look up the name, as neither of us could remember what it was called. As physicians and scientists, critical thinking and rational thought are vital, and one way I teach this to my students is by discussing cognitive bias and logical fallacies. These emphasize where limitations of the human mind lie, and how to avoid common pitfalls in thinking that we are all prone towards.

The frequency illusion is one we have probably all experienced from time to time. The example above, is a not unusual. My student may have heard that phrase before, but never really registered it, or perhaps really never did hear it before recently. In any case, the true frequency of the phrase is unlikely to have suddenly increased, but only my students perception of the phrase has lead her to believe that only now is she hearing, “cold hands, warm heart” all over the place. Cognitive scientists propose that when the human mind has been given new information, it creates a bias towards that information so that we are more likely to become aware of seeing or hearing that same information again the next time it is presented. This is known as a “Recency Effect”. In reality the information has always been present at the same frequency but until recently it was part of the background noise and not in the forefront of thought.

Another example of the Frequency Illusion is one that I noticed in myself this week.  This occurred after a friend of mine posted on Facebook that he and his wife were visiting the Florida Keys for vacation. Since then I have noticed several commercials on TV advertising the Florida Keys for tourism. I had never noticed those commercials before. Now, it is possible that those commercials have only just begun to be broadcast, my friend was influenced by the commercial and decided to go to the Florida Keys, and I only started noticing the commercials because they were never on TV before this week. A more likely explanation is that I have fallen victim to the Frequency Illusion.

And yes, my hands really are cold all the time, and my heart is around 98.6 degrees Fahrenheit – so pretty warm. I guess my nurse was right after all!

Reference articles:
1. “The Baader-Meinhof pheonomonen”, How stuff works.

2. Structure of a logical argument. The Skeptics Guide to the Universe page.

3. “The Clumping Effect” Darwin’s Kidneys blogpost.

4. List of Logical Fallacies.  Wikipedia.


4 thoughts on “The Frequency Illusion

  1. Very interesting how our minds need to separate background from signal.

    I wonder if it’s Important to be cognizant of cognitive biases like the frequency illusion.

    Sometimes I feel my subconscious mind is often better at ignoring useless data when it is useless, and prioritizing the useful stuff.


    • I agree. The frequency illusion is simply fun to know about since we likely have all experienced the effect. There are other cognitive biases that are probably more important to be aware of in yourself and others, but sometimes introducing the topic by giving an example we can all relate to can open the door to learning about these other examples. For example, confirmation bias effects us all, and can lead to very poor decisions and beliefs about the world, but it is less likely that people will be receptive to hearing about their own confirmation biases. This is just a good opportunity to open the door to awareness of these cognitive flaws. Also, your last paragraf, “Sometimes I feel my subconscious mind is often better at ignoring useless data when it is useless, and prioritizing the useful stuff.” How sure are you that you ignore the useless data and prioritize the useful stuff? It might be worth considering.


      • I see whay you mean. It’s a big assumption to suspect everything your brain doesn’t pick up on is meaningless.

        Cognitive biases, mental shortcuts, stuff like that I feel are responsible for persistence of nasty things like racism, sexism, etc…. So maybe we should be acutely aware of our these cognitive tricks.

        But maybe these cognitive biases aren’t “flaws” but actually adaptive responses? Could there be a downside to analyzinng your thoughts too much?


      • They probably are adaptive responses, in the sense that they may have served some purpose in helping us to make quick “gut” decisions about a whole range of possible events. That doesn’t exclude them from being flaws, however. Our world is too complex to only rely on our gut feelings and heuristics. Statistical thinking does not come easy to us, and rationality takes time. “Could there be a downside to analyzing your thoughts too much?” I’m sure there is if you do it to the point of “analysis paralysis”. But that is not what rational thinking is about. It is about making the best decisions possible, given the limited time and data available.


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