In case you missed this little gem from the Washington Post:

Long-term memories matter most in public health campaigns or political ones, and they are the most susceptible to the bias of thinking that well-recalled false information is true.

The experiments do not show that denials are completely useless; if that were true, everyone would believe the myths. But the mind’s bias does affect many people, especially those who want to believe the myth for their own reasons, or those who are only peripherally interested and are less likely to invest the time and effort needed to firmly grasp the facts.

The research also highlights the disturbing reality that once an idea has been implanted in people’s minds, it can be difficult to dislodge. Denials inherently require repeating the bad information, which may be one reason they can paradoxically reinforce it.

Indeed, repetition seems to be a key culprit. Things that are repeated often become more accessible in memory, and one of the brain’s subconscious rules of thumb is that easily recalled things are true.

Many easily remembered things, in fact, such as one’s birthday or a pet’s name, are indeed true. But someone trying to manipulate public opinion can take advantage of this aspect of brain functioning. In politics and elsewhere, this means that whoever makes the first assertion about something has a large advantage over everyone who denies it later.

Furthermore, a new experiment by Kimberlee Weaver at Virginia Polytechnic Institute and others shows that hearing the same thing over and over again from one source can have the same effect as hearing that thing from many different people — the brain gets tricked into thinking it has heard a piece of information from multiple, independent sources, even when it has not. Weaver’s study was published this year in the Journal of Personality and Social Psychology.

The experiments by Weaver, Schwarz and others illustrate another basic property of the mind — it is not good at remembering when and where a person first learned something. People are not good at keeping track of which information came from credible sources and which came from less trustworthy ones, or even remembering that some information came from the same untrustworthy source over and over again. Even if a person recognizes which sources are credible and which are not, repeated assertions and denials can have the effect of making the information more accessible in memory and thereby making it feel true, said Schwarz.