When a parent who refused to vaccinate due to the autism link, who spoke out publicly on the topic and even criticized his friends for following the schedule, is faced with overwhelming evidence that there is no link at all, he may determine that "evidence" to be the product of a far-reaching medical, governmental and corporate conspiracy to maintain high pharmaceutical-industry profits.
Creating a conspiracy is one of the easiest ways to reject evidence. Conspiracies by nature are irrefutable. It's all happening in secret. Anybody can be in on it. The data is faked. The photos are re-touched. The corporate-funded media will say anything.
It's not the only way, though, to validate a threatened belief. The collection of techniques that enable what has come to be called denialism is a varied bag of tricks.
In the case of Festinger's cult, the technique was "reinterpreting the evidence." This involves analyzing any new facts in such a way as to support the original belief. Before Dec. 21, the truth of their faith would be proved by the flood; after Dec. 21, the truth of their faith was proved by the absence of the flood. Similarly, when Andrew Wakefield's seminal study linking vaccination to autism was published in 1998, its presence in the prestigious British Medical Journal was proof of its legitimacy. In 2011, its retraction by that journal was proof of its legitimacy -- obviously, the pharmaceutical industry was frightened enough by the truth of the study to start throwing its weight around [source: CNN]. (Conspiracy can work in tandem with most other denial techniques.)
One can create standards of proof that science can't possibly meet, such as, "I'll believe that climate change is a result of human actions when I see proof that Earth has never undergone a temperature increase before."
One can seek out "experts" who support the irrational belief through pseudoscience, misinterpretations, misrepresentations and logical fallacies, as in "If smoking really caused lung cancer, everyone who smokes cigarettes would get lung cancer."
Pretty effective on their own, these (and all) belief-perseverance techniques have received a tremendous boost with the advent of the Internet. Those looking to maintain an irrational viewpoint need only perform a simple search to locate fellow believers, entire communities of them, and the "experts" who back it all up with appropriate jargon.
In the end, it's not about science at all. It's about avoiding the stress of unlearning, the possibility of regret or the shame of having been wrong. And so, in the interest of cognitive harmony, otherwise reasonable individuals believe vaccines can cause autism, human actions have nothing to do with climate change, smoking doesn't cause cancer, and the test, obviously, was wrong.
For more information on belief perseverance, denialism, and other theories of modern psychology, check out the links on the next page.