Political scientists Brendan Nyhan and Jason Reifler provided two groups of volunteers with the Bush administration's prewar claims that Iraq had weapons of mass destruction. One group was given a refutation -- the comprehensive 2004 Duelfer report that concluded that Iraq did not have weapons of mass destruction before the United States invaded in 2003. Thirty-four percent of conservatives told only about the Bush administration's claims thought Iraq had hidden or destroyed its weapons before the U.S. invasion, but 64 percent of conservatives who heard both claim and refutation thought that Iraq really did have the weapons. The refutation, in other words, made the misinformation worse.
A similar "backfire effect" also influenced conservatives told about Bush administration assertions that tax cuts increase federal revenue. One group was offered a refutation by prominent economists that included current and former Bush administration officials. About 35 percent of conservatives told about the Bush claim believed it; 67 percent of those provided with both assertion and refutation believed that tax cuts increase revenue.
In a paper approaching publication, Nyhan, a PhD student at Duke University, and Reifler, at Georgia State University, suggest that Republicans might be especially prone to the backfire effect because conservatives may have more rigid views than liberals: Upon hearing a refutation, conservatives might "argue back" against the refutation in their minds, thereby strengthening their belief in the misinformation. Nyhan and Reifler did not see the same "backfire effect" when liberals were given misinformation and a refutation about the Bush administration's stance on stem cell research...
Reifler questioned attempts to debunk rumors and misinformation on the campaign trail, especially among conservatives: "Sarah Palin says she was against the Bridge to Nowhere," he said, referring to the pork-barrel project Palin once supported before she reversed herself. "Sending those corrections to committed Republicans is not going to be effective, and they in fact may come to believe even more strongly that she was always against the Bridge to Nowhere."
Update 9/15 11:07 AM: My co-author Jason Reifler is discussing the article with readers on washingtonpost.com right now (from 11 AM-12 PM EST).
Update 9/17 11:16 AM: Here's the Duke press release on our research.