Illusions of Truth
The Illusions of Truth bias describes how repeated exposure to a statement or phrase increases its perceived truthfulness, due to cognitive ease and System 1's reliance on familiarity, making it difficult to distinguish familiarity from truth.
THE IDEA
ILLUSIONS OF TRUTH
“New York is a large city in the United States.” “The moon revolves around Earth.” “A chicken has four legs.” In all these cases, you quickly retrieved a great deal of related information, almost all pointing one way or another. You knew soon after reading them that the first two statements are true and the last one is false. Note, however, that the statement “A chicken has three legs” is more obviously false than “A chicken has four legs.” Your associative machinery slows the judgment of the latter sentence by delivering the fact that many animals have four legs, and perhaps also that supermarkets often sell chicken legs in packages of four. System 2 was involved in sifting that information, perhaps raising the issue of whether the question about New York was too easy, or checking the meaning of revolves.
Think of the last time you took a driving test. Is it true that you need a special license to drive a vehicle that weighs more than three tons? Perhaps you studied seriously and can remember the side of the page on which the answer appeared, as well as the logic behind it. This is certainly not how I passed driving tests when I moved to a new state. My practice was to read the booklet of rules quickly once and hope for the best. I knew some of the answers from the experience of driving for a long time. But there were questions where no good answer came to mind, where all I had to go by was cognitive ease. If the answer felt familiar, I assumed that it was probably true. If it looked new (or improbably extreme), I rejected it. The impression of familiarity is produced by System 1, and System 2 relies on that impression for a true/false judgment.
The lesson of figure 5 is that predictable illusions inevitably occur if a judgment is based on an impression of cognitive ease or strain. Anything that makes it easier for the associative machine to run smoothly will also bias beliefs. A reliable way to make people believe in falsehoods is frequent repetition, because familiarity is not easily distinguished from truth. Authoritarian institutions and marketers have always known this fact. But it was psychologists who discovered that you do not have to repeat the entire statement of a fact or idea to make it appear true. People who were repeatedly exposed to the phrase “the body temperature of a chicken” were more likely to accept as true the statement that “the body temperature of a chicken is 144°” (or any other arbitrary number). The familiarity of one phrase in the statement sufficed to make the whole statement feel familiar, and therefore true. When you cannot remember the source of a statement or relate it to other things you know, cognitive ease can feel like evidence. You can also suspend judgment and look for a source before accepting it.
When to use it
Politicians repeating a catchphrase or slogan to make it seem true, even if unsubstantiated.
Advertisers using repeated exposure to brand names or product claims to increase consumer belief.
In court, repetitive questioning can make a false fact seem more credible to jurors.
Online echo chambers and social media algorithms that repeatedly expose users to the same misinformation, reinforcing its perceived truth.
FROM THEORY TO EVERYDAY LIFE
In practice
True vs False Statements about Chickens
The statement 'A chicken has four legs' is less obviously false than 'A chicken has three legs' because associative machinery retrieves related information (many animals have four legs, chicken legs are sold in packs of four), slowing judgment and making it easier to accept as true.
Repeated Phrase Experiment
Psychologists found that people repeatedly exposed to the phrase 'the body temperature of a chicken' were more likely to accept as true the statement 'the body temperature of a chicken is 144°' (or any arbitrary number), even without repetition of the full statement. The familiarity of one phrase made the whole claim feel familiar and therefore true.
A MOMENT TO REFLECT
Put it to work.
When was the last time you accepted a statement as true simply because it felt familiar, even though you had no evidence? Could it have been false?
How can you guard against the illusion of truth when evaluating news, advertisements, or political claims?
Think of a slogan or phrase that is repeated often in media. Does that repetition make it seem more truthful to you? How might you test its actual validity?
CONTINUE THE CONVERSATION
Source texts
- Thinking, Fast and Slow (Daniel Kahneman)