Explained by a Certified Public Psychologist: The Truth Behind the "Illusory Truth Effect" from 5 Perspectives

Have you ever seen a news story or a social media post recently and thought, "Wait, I've seen something like this before"?

There are surely many of you who have experienced feeling that something might be true before even considering whether the content itself is accurate.

Actually, that is not because you lack attention. It is simply because a common mechanism inherent in the human brain is at work.

Today, I will explain that mechanism as clearly as possible from the perspective of a certified public psychologist.

Why we tend to believe things the more we hear them

In the world of psychology, there is a phenomenon called the "illusory truth effect".

Regardless of whether the information itself is correct or whether the source is reliable, people feel that information is "likely true" simply because they have seen or heard it many times.

Even if you were skeptical at first, thinking "that's ridiculous," as you see it repeatedly, the sense of discomfort gradually fades before you know it. And before you realize it, it changes into a feeling that "it might be true somehow." This is the true nature of the illusory truth effect.

I do not believe this should be dismissed as a mere problem of lack of knowledge or inattention. Rather, I think it is closer to reality to view it as a side effect of the evolutionary wisdom that our brains have devised to use energy efficiently.

3 reasons why the brain is deceived

Why does this illusion occur? I believe it can be organized from three major perspectives.

The first is the sense of "cognitive fluency". The brain is an organ that tries to process information with as little load as possible. When you are repeatedly exposed to the same story, the brain becomes increasingly accustomed to processing it, allowing it to process it smoothly and comfortably. The brain mistakenly reads this "ease of processing" as a sign of "accuracy" or "truthfulness." This is despite the fact that ease of processing and the correctness of content should be completely different things.

The second is the story of the dual structure of thought, as shown by Nobel laureate in economics Daniel Kahneman. It is said that humans have two modes of thinking: "System 1," which is intuitive and fast, and "System 2," which verifies things carefully. Because repeated information is processed instantly and comfortably by System 1, the opportunity for System 2—which would ask, "Where did this information come from?" or "Does this make logical sense?"—never even arises.

The third is the familiar psychological phenomenon called the "mere exposure effect" that works on people and things. You somehow develop a fondness for someone you meet many times. If you understand that this phenomenon works not only on people and things but also on information and discourse itself, it might make a bit more sense.

SNS as an amplifier of illusion

This individual brain mechanism, when combined with the modern social media environment, has a greater influence than you might think.

Many platforms are designed with the goal of extending our time spent on them as much as possible. Therefore, "filter bubbles" where only information that matches your preferences is displayed, and "echo chambers" where people with similar opinions gather, are formed quite naturally.

Within that closed space, you will be exposed to the same information repeatedly. Then, the "availability heuristic," where information that is easier to recall is mistaken for being "common" or "important," is also stimulated, and the feeling that "it must be true because everyone is saying it" is reinforced at the system level.

What is even more troublesome is that this mechanism is sometimes used intentionally, not just by chance. By using programs that automatically spread information, it is possible to artificially create the very feeling of "having heard it before" by repeatedly flooding timelines with large amounts of information.

The reason why simple lies beat complex truths

Here, I would like to share a perspective that I feel is particularly important. It is that scientific facts and baseless misinformation have fundamentally different levels of "ease of access to the brain."

Scientific truths are usually conditional, complex, and sometimes boring. Understanding them requires a certain amount of effort, specifically careful verification by System 2.

On the other hand, misinformation and conspiracy theories have no constraints of reality. That is precisely why they can be freely designed as "sticky stories" that are assertive, simple, and strongly stir up emotions like anger and fear.

As Sander van der Linden, author of "Foolproof: Why Misinformation Infects Our Minds and How to Build Immunity," points out, fake news is inherently structured to hack this illusion effect more easily than the truth.The saying "If you tell a lie big enough and keep repeating it, people will eventually come to believe it," attributed to Nazi Propaganda Minister Joseph Goebbels, can be said to be a classic staple of propaganda that utilizes this illusion effect.

The reality that "correcting it doesn't fix it"

There is one more thing I would like you to know. It is the fact that once misinformation has spread, it is difficult to return to the original state just by making subsequent corrections.

It is said that even if you issue corrective information three times as frequently after a piece of misinformation has spread, it is difficult to return the impact of the misinformation completely to zero. This is called the "asymmetry of the illusory truth effect".

Furthermore, ironically, the very act of denying it by saying, "A rumor is circulating that such-and-such is true, but that is a lie," can result in increasing the number of times people are exposed to the original information of "such-and-such." As time passes, the memory of the context that "it was supposed to have been denied" fades, and only the familiar content remains in memory. This is called "source amnesia." The "backfire effect," where corrections can be counterproductive, and the "continued influence effect," where misinformation remains in the mind, are born from these mechanisms.

So, how should we face this? Three prescriptions

After reading this far, some of you may have become a little anxious. But please rest assured. Just knowing about this mechanism changes how we face it significantly. I would like you to value the following three things.

The first is the habit of doubting "comfort". When you encounter some information, especially when you feel that you can "understand it easily" or "feel like I've heard this somewhere before," try asking yourself, "This might be an illusion." Taking that one breath to stop your intuition and think, "Where is the source?" or "Is there any evidence?" makes a big difference.

The second is a prior "mental vaccination". If corrections are difficult, it is effective to know in advance the tactics often used by fake news spreaders and the mechanism of this illusion itself. This is called "prebunking." It is the image of having immunity in the form of knowledge in your mind beforehand.

The third is to objectively re-examine your own information environment. You might be in a closed space created by algorithms, bathing in only the same kind of information. Being aware of that, try to intentionally expose yourself to media with different stances or primary sources. This is called "lateral reading," and the very act of consciously broadening your perspective becomes the power to distance yourself from illusions.

Conclusion

Let me summarize the points I have shared today once more.

First, the illusory truth effect is a phenomenon that can happen to anyone's brain, where you feel something is "true" just by being exposed to it repeatedly.

Second, in the background, three mechanisms are involved: cognitive fluency, the workings of System 1, and the mere-exposure effect.

Third, the environment of social media makes it easy to amplify that illusion, and it has a structure where simple lies are more likely to spread.

Fourth, misinformation that has spread once is difficult to return to its original state through corrections alone.

And fifth, by having the three perspectives of "doubting comfort," "prebunking," and "lateral reading," we can protect ourselves from this illusion.

You might think, 'I'm intelligent, I'm confident in my logical thinking, so I'll be fine.' Even if you think that, no one can escape this illusion. However, this is by no means a weakness; it is a mechanism common to the human brain. That is precisely why, just by knowing about it, we can change.

Information is not just something to be received; it is the foundation that shapes your own way of thinking. I would be happy if you could keep in the back of your mind from now on that 'familiarity' and 'truth' are two different things.

Thank you very much for staying with me until the end. I hope today's article will serve as a catalyst for you to think about your next steps starting tomorrow.

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