Tom Brady and the Illusory Truth Effect

Well, it’s happening. Tom Brady is coming back to the NFL! Apparently bored with what he has been doing, he’s returning to what he’s best at (and the best ever at). I, for one, can’t wait.

Okay, I just lied. So far as I know, Brady isn’t coming back. But my lie was for a purpose, which was to illustrate the Illusory Truth Effect. The phenomenon was discovered in 1977 when a group of psychologists asked volunteers in a study how confident they were about the truth of sixty plausible (but not necessarily true) statements.

Sure enough, people were much more likely to believe that statements were true if they were repeated. It seems that if you repeat a statement enough times (for example, “Space aliens landed in Roswell, New Mexico, in the 1940s,” or ““Kids become hyperactive if they have a lot of sugar”), people will start believing it.

Since 1977, the illusory truth effect has been found in numerous independent studies. It has been found with factual statements of very different kinds—involving historical events, geography, science, and politics. It has been found outside the laboratory with members of the general public. It has been found with short rather than long intervals between repetitions.

To be sure, we shouldn’t overstate these findings. You are not likely to believe false statements if you are confident that they are false. If you are repeatedly told that the earth is flat or that the Holocaust never happened, you are not necessarily going to believe either of those statements even if you hear them repeatedly (although some people do). The only point is that repetition can make people think that a proposition is more likely to be true, whether or not it is—so if someone wants to convince you of a falsehood, stating it over and over and over, and then once more, might actually do the trick.

The most likely explanation for the Illusory Truth Effect is that repetition creates a feeling of familiarity. When something sounds familiar, people tend to think that it is true. In a nutshell: People are more likely to believe something if it is easier to process, and statements that are familiar are easier to process. (The neuroscientist Tali Sharot and I discuss the Illusory Truth Effect at some length in our book, LOOK AGAIN.)

Conspiracy theories often spread, and seem credible, because of the Illusory Truth Effect. You can think of your favorite or least favorite examples.

For business and politics, the Illusory Truth Effect creates an excellent opportunity. If you repeat something, a lot of people are going to believe it. For consumers and citizens, the Illusory Truth Effect creates a serious challenge. The law of fraud should be applied with awareness of the fiendish power of repetition. For politics, we can get pretty clear on the problem — but we don’t yet know the solution.