[link|http://www.washingtonpost.com/wp-dyn/content/article/2007/09/03/AR2007090300933_pf.html|Washington Post]:

Tuesday, September 4, 2007; A03

The federal Centers for Disease Control and Prevention recently issued a flier to combat myths about the flu vaccine. It recited various commonly held views and labeled them either "true" or "false." Among those identified as false were statements such as "The side effects are worse than the flu" and "Only older people need flu vaccine."

When University of Michigan social psychologist Norbert Schwarz had volunteers read the CDC flier, however, he found that within 30 minutes, older people misremembered 28 percent of the false statements as true. Three days later, they remembered 40 percent of the myths as factual.

Younger people did better at first, but three days later they made as many errors as older people did after 30 minutes. Most troubling was that people of all ages now felt that the source of their false beliefs was the respected CDC.

The psychological insights yielded by the research, which has been confirmed in a number of peer-reviewed laboratory experiments, have broad implications for public policy. The conventional response to myths and urban legends is to counter bad information with accurate information. But the new psychological studies show that denials and clarifications, for all their intuitive appeal, can paradoxically contribute to the resiliency of popular myths.

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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.

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I'm sure a lot of politicians and media pundits have known these things for a long time. Let's hope the body politic notices as well.

Cheers,
Scott.