What Is… the Illusory Truth Effect

Illusory truth effect - truth sandwich: truth/note false information/back to the truth

In this series, I dig a little deeper into the meaning of psychology-related terms. This week’s term is the illusory truth effect.

The illusory truth effect is a type of cognitive bias that makes us more likely to believe false information to be correct the more often we’re exposed to it. It was first described in 1977.

When we evaluate whether or not something is true, we consider it in the context of what we already know and whether it’s familiar. However, the illusory truth effect shows that familiarity can override rationality. Familiarity also speeds up processing time in the brain, which is mistakenly interpreted as an indicator of truth.

The problem with hitting back with truth

Political campaigns often exploit this effect. With the massive number of false statements being made all around, fact-checking seems like a very reasonable thing to do. The problem is, though, that increases the familiarity of the original false information and thereby reinforces it. Also, we don’t process negations as effectively, so if the misinformation is that Jane is a thief, and the corrective information is that Jane is not a thief, the “not” can start to get kind of fuzzy in our minds.

U.C. Berkeley Professor Emeritus George Lakoff suggests dealing with this by using a truth sandwich. While this tweet specifically mentions Donald Trump, it applies just as well to false statements coming from politicians who might not be quite as prolific in their lying.

Believability isn’t required

A study that looked at fake news headlines that appeared on Facebook during the 2016 U.S. presidential campaign found that only a single exposure was enough to trigger the illusory truth effect. This occurred even when the headlines themselves had low believability, were flagged by fact-checkers, and were inconsistent with the viewer’s political beliefs. However, blatantly absurd headlines did not trigger the illusory truth effect. The researchers said the results “suggest that social media platforms help to incubate belief in blatantly false news stories.”

The mental illness-gun violence non-connection

I decided to write this post after reading about this effect in the context of public views on mental illness and gun violence. The issue is far more nuanced than it’s commonly made out to be, but without fail, every time there’s a mass shooting, politicians, law enforcement, the National Rifle Association, and various other bandwagoneers start their spiel about how gun violence is because of crazy people, and guns don’t kill people, crazy people do.

It’s inaccurate, but because it’s so familiar, the illusory truth effect kicks in, and people start to be a lot more afraid of their neighbour on one side who has a mental illness than their neighbour on the other side who’s an angry white dude with a semi-automatic rifle that takes high-capacity magazines, who’s a patriot because he refuses to wear a face mask.

The scary thing is that the illusory truth effect isn’t just a stupid/ignorant people cognitive bias. It’s a mental shortcut that we’re all prone to taking.

Someone needs to come up with a good truth sandwich for the gun violence and mental illness issue. I don’t think I’m qualified because I’d use too many expletives.


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.

26 thoughts on “What Is… the Illusory Truth Effect”

  1. Thank you for writing this post.
    It gave me a better understanding of why people believe the misinformation that spews from politicians.
    Also, thank you for discussing the “mental illness-gun violence non-connection”. Every time there is a mass shooting, the first thing you hear on the news is that the shooter is bi-polar. I just see red when that is said. Bi-polar people on the whole are quite quiet.

  2. You can see this YUGELY on social media and from a certain orange politician. As Joseph Goebbels (nazi) said, “If you tell a lie big enough and keep repeating it, people will eventually come to believe it.”

  3. I’ll be writing a post which will include your excellent discussion of this term here shortly. I’ve solved the problem of that effect to an extent by simply turning off the TV. I have satellite radio too, and am thus spared the rhetoric and lies and pure crap that are spewed every time there’s an election coming. It causes me far too much anxiety to listen to even the teeniest bit. That whole gun versus crazy person is one I’ve sadly heard myself. It seems that the people telling about the gun event (whether it’s a school shooting, a public mass shooting or whatever) will spin things so the gun-person involved is a lunatic of some kind. Every single time. I hadn’t put it together until you wrote this today. That really annoys me. I’m sure some of the gun persons doing those things are sane, as defined by what society thinks of as ‘sane’. But best to blame it on the crazy people. How ugly that is.

  4. Interesting! No wonder so many people believe fake news and conspiracy theories!! I like the truth sandwich. 🙂

    I wonder if it could also be applied to abuse or gaslighting? E.g. if you’re repeatedly told bad or inaccurate information about yourself, you can start to believe it, even if you didn’t believe it in the first place?

  5. I find it’s not just headlines. People take videos at face value without knowing the full context. There was a recent video of a guy accused of knocking a child off her bike when really she pushed through him and came off herself. But that’s not what was shown and people sent him death threats. It’s very sad.

  6. Lol, too many expletives. Interesting post and brought to mind something on Twitter yesterday. One of our MP’s who happens to be black, videoed herself being stopped by the police in her car and told the officers they were racially profiling, stopping the car because she was black.

    There was a real reason why the car was stopped and it wasn’t because she was black. The driver of the car was white! but she didn’t show him in the film and omitted this in her Tweet. Given recent events both in the US and UK, all she’s doing is inciting more hatred and whipping up a storm based on the illusory truth effect.

    1. It’s kind of like when Jussie Smollett made a false claim about being attacked. It does such a huge disservice to the real issue, and what gets stuck in people’s minds is the faking. You’d think they’d have been smart enough to have thought that through ahead of time.

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