Ben Goldacre, an English Science geek, reports on some interesting
research into human perception: the influence of evidence on decision
making and formation of opinions.
He describes research which show that corrections to news
articles have the effect of reinforcing the proven false allegation,
rather than removing or reducing it. No idea why yet. Test subjects
reading faux news articles which contained corrections to allegations
presented earlier in the text vs. the control group that read the
same first bit but without the corrections determined that if the
first part coincides with the test subject's existing biases then the
correction has the counter-intuitive effect of reinforcing the
information contradicted by the correction.
For more details and a link to the research study see Goldacre's Evidence based smear campaigns