The "illusory truth effect" is one of the major reasons why people continue to believe lies as truth, even after the lie has been proven to be false. This effect is where the human mind is more likely to believe familiar statements than unfamiliar ones, even when the familiar statement is a provable lie.
Take the whopper of a lie told by Dr. Andrew Wakefield in 1998 where he falsified data and tried to link certain diseases to the MMR vaccine; since the day this lie was published in the 'The Lancet' it was known to be false, and has since been definitively proven to be an "elaborate fraud", resulting in Wakefield's medical license being revoked. This massive lie has spread globally and resulted in the needless suffering and deaths of thousands of innocent children, all due to the continued belief in this lie by a small percentage of individuals.
The "illusory truth effect", originally studied in 1977, is one of the major factors as to why these easily proved lies still resonant in our society. Educating ourselves and others on how the human mind makes these types of cognitive errors, is one of the best ways to help end the spread of this horrible and deadly lie.
Elitist scientists that sat back and chose not to speak up, as they felt they were "above dealing with such lowly issues" as challenging clear and blatant falsehoods, are to blame for much of the spread of this lie. By allowing the continued and unchallenged spread of this lie, it became familiar and accepted as truth by some percentage of our population.
The "illusory truth effect" is one of the reasons why it is so important that we must adopt a policy of "conversational criticism" and continuously and immediately challenge known lies.