The positive feeling that is experienced when we hear information that we know is true is similar to the feeling that occurs when we hear information we have heard before. As a result, repetition is often conflated with validity. This explains why certain beliefs such as “Humans only use 10% of their brains” are still widely considered to be true today, despite the large amount of evidence proving the statement to be false. The illusory truth effect was introduced in 1977 in a research paper describing a study by Lynn Hasher, David Goldstein, and Thomas Toppino. It now plays a significant role in various fields. For example, in politics, if information about a candidate is repeated often enough, many voters will believe it is true. This type of manipulation of information can be used in essentially any industry in which public opinion is important.
the first study on the subject in 1977, participants were asked to judge the validity of plausible statements (some of them true, other false) over a couple of weeks. Some of the statements were repeated week after week and participants’ confidence in those statements increased over time, while confidence in non-repeated statements remained steady.