True-believer syndrome

True-believer syndrome is a term coined by M. Lamar Keene in his 1976 book The Psychic Mafia. Keene used the term to refer to people who continued to believe in a paranormal event or phenomenon even after it had been proven to have been staged. It has since been applied, more loosely, to refer to any belief without empirical or logical foundations. Keene himself considered it to be a cognitive disorder, and regarded it as being a key factor in the success of many mediums. The term "true believer syndrome" is not used professionally by mainstream psychologists, psychiatrists or medical professionals and it is not recognised as a form of psychopathology or psychological impairment.

Raoul
In his book The Psychic Mafia, Keene tells of a psychic medium named Raoul. Some people still believed that Raoul was genuine even after he openly admitted that he was a fake. Keene wrote "I knew how easy it was to make people believe a lie, but I didn't expect the same people, confronted with the lie, would choose it over the truth. ... No amount of logic can shatter a faith consciously based on a lie."

Carlos
According to the Skeptic's Dictionary, an example of this syndrome is evidenced by an event in 1988, when James Randi, at the request of an Australian news program, coached stage performer José Alvarez to pretend he was channelling a 2000 year old spirit named "Carlos". Even after it was revealed to be a fictional character created by himself and Jose Alvarez people continued to believe that "Carlos" was real. Randi commented: "no amount of evidence, no matter how good it is or how much there is of it, is ever going to convince the true believer to the contrary."

419 scam
Article 419 scams, also known as advance fee fraud involve individuals inveigling others to give them their bank details, supposedly in order to make a large deposit, but actually in order to drain the account. Anti-419 activists refer to those who sometimes continue to believe in the good faith of the fraudsters as "true believers".