Illusory truth effect

"Why are so many people convinced that we only use 10% of our brains, or that Eskimos have no words for snow...?" The illusory truth effect (also known as the truth effect, the illusion-of-truth effect, the reiteration effect, the validity effect, and the frequency-validity relationship) is the tendency to believe information to be correct after repeated exposure to the claim in question. This is an illusion that appears due to unconscious cognition.

This phenomenon has been studied extensively, with the term first appearing in psychology literature in a psychology paper from the late 1970s. The illusion is now backed up by several psychology experiments.

The illusion is thought to be partly caused by the concept of by which familiar concepts are more easily processed, tricking the mind into thinking something is true without any real evidence of it being so.