Did you know the word gullible isn't in the dictionary?

We voters are a generally gullible group. But there's something about Barack Obama that makes people willing to believe anything. And there's only so much one can do to dispell the myths: yes, he's a Christian; yes, he's an American citizen; yes, he believes in Israel's right to exist.

Now there's a new one to grapple with: no, Obama is not the Anti-Christ.

Apparently John McCain's attempts to woo the Christian-right has led to some confusion:

"...a not-insignificant number of Americans, after viewing John McCain's Web ad The One, with its Messianic overtones -- come away thinking that Barack Obama has been sent from Hell to Earth to turn its citizens against God. For inspiration, some of these people seem to be drawing from the fictional Left Behind series, which posits a dystopian future where the Anti-Christ comes to Earth as a charismatic politician.

The book's author's, Tim LaHaye and Jerry B. Jenkins, have insisted they don't believe Obama is the Anti-Christ, although they can't resist taking a dig at the candidate in the process...

'I can see by the language he uses why people think he could be the antichrist,' adds LaHaye, 'but from my reading of scripture, he doesn't meet the criteria. There is no indication in the Bible that the antichrist will be an American.'"

How does this happen? Well the media doesn't help. Rather than ignoring the story as unworthy of discussion, CNN's Newsroom broadcast a report on the issue, with the caption "Obama the Anti-Christ?" in bold at the bottom of the screen (to view the video, click the link above the proceeding quote).

But beyond the media, it may be our own brains that are playing tricks on us. According to neurobiologists Sam Wang and Sandra Aamodt, the quirky way we process information causes us to believe some pretty unbelievable things:

Our brains tend to remember facts that accord with our worldview, and discount statements that contradict it. In one Stanford study, 48 students, half of whom said they favored capital punishment and half of whom said they opposed it, were shown two pieces of evidence. One confirmed the claim that capital punishment deters crime, and the other contradicted it. Both groups were more convinced by the evidence that supported their initial position, a phenomenon known as biased assimilation.

This is one reason that propagandists can be effective simply by creating confusion. Unscrupulous campaign strategists know that if their message is initially memorable, its impression will persist long after it is debunked.

The human brain also does not save information permanently, as do computer drives and printed pages. Recent research suggests that every time the brain recalls a piece of information, it is "written" down again and often modified in the process. Along the way, the fact is gradually separated from its original context. For example, most people don't remember how they know that the capital of Massachusetts is Boston.

This phenomenon, known as source amnesia, leads people to forget over time where they heard a statement - and whether it is true. A statement that is initially not believed can gain credibility during the months that it takes to reprocess memories from short-term to longer-term storage. As the source is forgotten, the message and its implications may gain strength. Source amnesia could explain why, during the 2004 presidential campaign, it took some time for the Swift Boat Veterans for Truth campaign against Senator John Kerry to affect his standing in the race.

In another Stanford study, students were exposed repeatedly to the unsubstantiated claim that Coca-Cola is an effective paint thinner. Those who read the statement five times were nearly one-third more likely than those who read it only twice to attribute it to Consumer Reports (rather than the National Enquirer), giving it a gloss of credibility. Thus the classic opening line "I think I read somewhere," or even reference to a specific source, is often used to support falsehoods. Similarly, psychologist Daniel Gilbert and his colleagues have shown that if people are distracted from thinking critically, they default to automatically accepting statements as true.

So the CNN story intended to dispel a ridiculous rumor may have simply propagated it.

Much as we'd like to believe that people stand in voting booths rationally weighing the pros and cons of different candidates, it is simply not the way things work. And worse, this is not a problem that can be solved by people getting "more informed"; that could exacerbate things.

At the risk of sounding pessimistic, we may have to accept this fact of democracy. Voters do not have a great enough incentive to rationally evaluate their political decisions; instead we allow the emotional, reactive part of our brains to take over.

Beyond that, we should encourage Journalism schools to heed Wang and Aamodt's advice for the media:

1. State the facts without reinforcing the falsehood. Repeating a false rumor can inadvertently make it stronger. In covering the controversy over a New Yorker cover caricaturing Barack and Michelle Obama, many journalists repeated the charges against the candidate - often citing polling data on how many Americans believe them - before noting that the beliefs were false. Particularly damaging is the common practice of replaying parts of an ad before debunking its content.

A related mistake is saying that something is newsworthy because "the story is out there." Reporting on coverage by a less credible source such as The Drudge Report, even with disclaimers, will inevitably spread the story. False statements should not be presented neutrally since they are likely to be remembered later as being true.

2. Tell the truth with images. Nearly half of the brain is dedicated to processing visual information. When images do not match words, viewers tend to remember what they see, not what they hear. Karl Rove has said that campaigns should be run as if the television's sound is turned down.

Television journalists should avoid presenting images that contradict the story. One recent CNN report on autism was accompanied by images of concerned mothers, vaccines, doctor’s offices, and autistic children - even though the voiceover reported a scientific finding that debunked a link between vaccines and autism. Another recent story featured a threatening swarthy face subtitled "Obama the Antichrist?" - a statement that CNN would presumably not claim to be true.

3. Provide a compelling storyline or mental framework for the truth. Effective debunking requires replacing the falsehood with positive content. A good response to the McCain rumor, for example, would tell about his adoption of his adopted Bangladeshi daughter Bridget, thereby accounting for photographs of him with a dark-skinned child.

4. Discredit the source. Ideas have special staying power if they evoke a feeling of disgust. Indeed, brain pathways dedicated to processing disgust can be activated by descriptions of morally repellent behavior. The motives of the purveyors of falsehoods can provide a powerful story hook. A recent example is the press coverage pointing out Obama Nation author Jerome Corsi's motivations and past of racist Web commentary and allegations of Bush Administration complicity in the 9/11 attacks.

To avoid contributing to the formation of false beliefs, journalists may need to re-examine their practices. In 1919, Supreme Court Justice Oliver Wendell Holmes wrote that "the best test of truth is the power of the thought to get itself accepted in the competition of the market." Our brains do not naturally obey this admirable dictum. But by better understanding the mechanisms of memory, perhaps journalists can move their modern audience closer to Holmes's ideal.