Home / Concept of the Week / The illusory truth effect
Concept of the Week · Episode 8
The finding that a statement you have heard before feels truer than one you have not, whether or not it is true. Repetition makes a claim easier for the brain to process, and that ease gets misread as evidence.
Where it comes from
Lynn Hasher, David Goldstein and Thomas Toppino, 1977, who had people rate the same trivia statements on three occasions and found that repeated statements were rated truer each time, regardless of whether they were actually true.
How Peter explained it on the show
The illusory truth effect. Something you have heard before is easier for your brain to process than something new, and that ease gets misread as truth. So a claim does not have to be argued well, or evidenced at all. It only has to be repeated. It works on people who know better, it works on claims you have already been told are false, and it is the reason a politician who has been corrected in public will go out the next day and say exactly the same thing again. Peter's point is that this is not a flaw in the gullible. It is how the machinery works in all of us, which is why noticing it is the only defence.
Why it mattered that week
It is the Concept of the Week for episode eight, and Peter puts it more bluntly than the literature does: if you repeat a lie often enough, it becomes encoded in the brain as a truth. His description of the method is the useful part. State something untrue. When people tell you it is untrue, brush the correction off and say it again, and again, until it has been heard so many times that it is absorbed as fact. Backed by money, media presence and a bit of confidence, that is enough. He is careful to say this is not a right wing tool in particular, only that it is being used that way at the moment, and that the left has had its own turn at it. The three headlines in the episode are then three demonstrations: an election won on nostalgia, a health service argument fought with simple slogans, and a chatbot that invents history and then apologises for it.
Hear it in context
The AfD landslide, violence in A&E, and AI's invented facts
Repeat a lie often enough, Peter says, and it stops being something you have heard and becomes something you know. The news then supplies three demonstrations.
Questions people ask
Yes, which is the uncomfortable part. The effect turns up in people who have the correct information available to them, and on claims they have already been told are false. Knowing a thing is untrue does not stop the repetition making it feel familiar, and familiarity is what the brain is reading.
Peter argues that it does, and that this is where it bites hardest. A repeated simple explanation, that it is all the fault of one group, or that the economy will be fixed by stimulating it, works the same way as a repeated false fact. It appeals precisely because it saves you the complicated analysis, and the more often you hear it the less complicated it seems to need to be.
The episode's own answer is the Triple T that follows it: go and look for the evidence. Not to stop using the sources, but to ask where a claim comes from, every time, and to notice how rarely anyone asks.
Other concepts from the series
Mirror neurons · Authenticity · Confirmation bias · Attribution theory · INUS conditions · Variable ratio reinforcement · Role exit
About the series
Concept of the Week is a regular feature of Experience, the weekly podcast in which clinical psychologist Professor Peter Kinderman and communications expert Hilary Jeffs take the news apart to see what is driving it. Peter picks a psychological idea most of us have half-remembered wrong and explains what it actually shows. New episodes every Tuesday. Where to listen.