Are You Gullible? Yup. The Illusion of Truth Effect

The more often a statement is repeated, the more likely you are to believe it even if it’s not true.

This is called the ‘illusion of truth effect’ and it is one of the scarier findings in the study of how we humans think and behave.

The Experiment that Discovered the Illusion of Truth Effect

Read the following statements. On a scale of 1-7, grade each statement as to how convinced you are that it is true.

  • Lizzie Borden killed her parents.
  • A clementine is a baby orange.
  • Sydney is the capital of Australia.
  • Scots wear a short, plaid skirt called a sari.

If you were a participant in the scientific version of this little experiment, I would give you 60 statements, not three.

I would invite you back to my lab twice more, leaving two weeks between each visit.

Each time you would receive 60 statements. 20 of the statements would be the same each time; 40 of the statements would be new.

Results of the Original 1977 Experiment

The 20 statements that were repeated three times, two weeks apart, were graded higher each time.

Participants were more convinced these statements were true each time they heard them.

This was not the case with the 40 statements that were new each time.

6 Head-Shaking Variations on the Original Experiment

  1. If one person in a group says the same thing several times, others believe that person’s opinion is representative of the group’s opinion.
  2. When you recall an idea from your memory, it has the same impact as if you’d heard it multiple times.
  3. A dark blue sentence on a white background is easier to read than a yellow sentence on a white background. When a statement is easier to read, we think it’s true.
  4. You are more likely to believe a statement about human behaviour is true if it is done in rhyme.
  5. Repeatedly reading a false statement makes you more likely to believe it, even when you know it is untrue.
  6. If you are an eyewitness to a crime and someone repeatedly makes misleading suggestions when they are questioning you, you are very likely to say that you remember observing the suggested events.

What’s Going On in Your Brain?

I have said it thrice. What I tell you three times is true.

Lewis Carroll

Repeated exposure to a message makes that message more familiar. A concept called cognitive fluency explains that when something is familiar, your brain doesn’t have to work as hard to process the idea. The feeling of ease you unconsciously experience makes you believe that you are reading or hearing the truth.

Are You Doomed to Remain Gullible Forever?

The answer is ‘Yes’, but with some caveats.

Research shows that you have maximum confidence in an idea if you hear it 3-5 times. More frequently than that gets annoying and you may start to disbelieve. Advertisers subtly vary their ads so you don’t get annoyed.

Repetition only works if you’re not paying attention. If you are paying attention and the argument that’s made is weak, your brain will go into reasoning mode and repetition won’t work.

Back to Scary

There are three classic categories of examples for the illusion of truth effect: the opinions of public figures, such as celebrities touting the latest diet; commercials or advertisements, and political campaigns. Enough said.

Finally, just in case you were wondering: a clementine is a cross between a mandarin and an orange; Canberra is the capital of Australia, and the short, plaid skirt worn by Scots is called a kilt. For the answer to the Lizzie Borden question, watch this fascinating short video.

Were you as surprised by the Lizzie Borden video as I was? Let me know in the comments below. 

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  1. Weird, now I don’t know what to trust is the truth. My brain is fooling me if I hear something three times. I will have to make sure to listen to it more than 5 times and get into the reasoning mode.

    As for the Lizzie Borden rhyme; yes, I remember that well however I did see a documentary on tv once that disproved the veracity of it. Poor Lizzie. =( Lost her parents AND got blamed for it (at least at first until she was acquitted.)

    This was extremely interesting Karen…things that make you go hmm. 😉

  2. I’m glad you liked the post, Susan. Thank you. I found it all so fascinating too as I was researching it. But am I the only one who didn’t know that Lizzie Borden was innocent? This was a big news flash for me but, sadly, not for several of the tribe – clearly you included!

  3. Add me to the gullible list, Karen. I did not know that Lizzie was not guilty. And let me get this right: Lizzie was wrongfully accused, acquitted, but then remains wrongfully remembered…Isn’t there an Atwood novel based on Lizzie’s story too?

    1. Yup, you’ve got it exactly right, Gayle. And thanks for joining me in my ignorance of the Lizzie Borden story. By the way, I just looked and Atwood’s novel Alias Grace is apparently “Canada’s answer to Lizzie Borden”. Grace Marks was a 16-year-old chambermaid who was tried, convicted and sentenced to life imprisonment for murdering her employer and his housekeeper/mistress. Unlike poor misunderstood Lizzie, it remains uncertain whether Grace did the evil deed or not. Thanks for writing, Gayle.

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