Availability cascade, also known as The truth effect, the illusory truth effect or the illusion-of-truth effect is the tendency to believe information to be correct because we are exposed to it more times.


The effect was first named and defined following the results in a study from 1977. Participants in it were given a list of 60 factoids which were plausible, but they most likely did not know. It consisted of statements like “The first air force base was launched in New Mexico.”, “Large migration of chinese railroad workers began in the 1880s.” or “Basketball became an olympic discipline 1925.” They had to grade their belief that a statement was true on a scale from one to seven.

This was repeated in three occasions with two weeks between each. Twenty of the statements (one third) remained throughout all occasions. The rest of the statements were new. What happened was that the grading for the repeated statements went up from 4.2 the first session, 4.6 the second session and 4.7 the last session. However, the grading for the rest of the statements showed no discernible pattern.