What is the illusory truth effect?

It is the tendency to judge a statement as more likely true simply because you have been exposed to it before, regardless of the statement's actual accuracy or the evidence behind it. It was first demonstrated by Lynn Hasher, David Goldstein, and Thomas Toppino in a 1977 study that found repeated trivia statements received higher truth ratings over time than statements seen for the first time, even when participants had been warned that repetition was not a reliable indicator of truth.

Does the illusory truth effect work even on claims I know are false?

Largely, yes. Lisa Fazio and colleagues' 2015 study "Knowledge Does Not Protect Against Illusory Truth" found that repetition increased perceived truthfulness even for statements that contradicted knowledge participants could correctly state on a separate test. Existing knowledge reduces the effect somewhat but does not eliminate it.

Is the illusory truth effect the same as confirmation bias?

No, though the two often compound each other. Confirmation bias is about favoring information that matches beliefs you already hold. The illusory truth effect operates independently of prior belief — it is driven purely by how many times you have encountered a statement, through the mechanism of processing fluency, not by whether that statement fits what you wanted to believe going in.

Can trying to correct a myth make people believe it more?

Sometimes, yes — a pattern researchers call the familiarity backfire effect. Irene Skurnik and colleagues' 2005 study found that repeating a false claim in order to label it "myth" could, after a delay, increase belief in the myth among some readers, likely because the claim's growing familiarity outlasted memory of the "false" label attached to it. The practical takeaway is to state corrections as standalone facts rather than repeating the myth verbatim.

How does Chapterly help with the illusory truth effect?

Chapterly's AI tutor generates review questions from your actual highlights and can be prompted to test the reasoning and evidence behind a claim, not just whether you remember the claim itself. Because review is spaced and pulls from your full highlight history across a book — and across your library — it surfaces where the same claim keeps recurring, which is exactly the pattern worth double-checking rather than trusting by default.

The Illusory Truth Effect: Why Repeating a Claim Makes It Feel True | Chapterly

The Illusory Truth Effect: Why Repeating a Claim Makes It Feel True Quick Answer: The illusory truth effect is the tendency to rate a statement as more likely true simply because you have encountered it before, independent of whether it is actually accurate or of any evidence supporting it. It was first demonstrated experimentally by Lynn Hasher, David Goldstein, and Thomas Toppino in 1977, and later work found the effect persists even for claims that contradict what a person already knows to be true. The mechanism is processing fluency: repeated statements are easier for your brain to process than novel ones, and that ease gets misread as a signal of accuracy. For readers, this matters most in nonfiction, where the same anecdote, statistic, or "finding" often gets recycled across book after book — not because it has been independently re-verified each time, but because later authors are citing earlier ones. By the fifth book, the claim feels like established fact. It may just be well-traveled. Open three popular nonfiction books on habit formation, productivity, or decision-making, and there is a good chance you will run into at least one shared claim — a study, a statistic, an anecdote — retold...