A variety of psychological experiments have shown that political misinformation primarily works by feeding into people's preexisting views. People who did not like Roberts to begin with, then, ought to have been most receptive to the damaging allegation, and this is exactly what Bullock found. Democrats were far more likely than Republicans to disapprove of Roberts after hearing the allegation.
Bullock then showed volunteers a refutation of the ad by abortion-rights supporters. He also told the volunteers that the advocacy group had withdrawn the ad. Although 56 percent of Democrats had originally disapproved of Roberts before hearing the misinformation, 80 percent of Democrats disapproved of the Supreme Court nominee afterward. Upon hearing the refutation, Democratic disapproval of Roberts dropped only to 72 percent.
Republican disapproval of Roberts rose after hearing the misinformation but vanished upon hearing the correct information. The damaging charge, in other words, continued to have an effect even after it was debunked among precisely those people predisposed to buy the bad information in the first place.
Bullock found a similar effect when it came to misinformation about abuses at the U.S. detention facility at Guantanamo Bay, Cuba. Volunteers were shown a Newsweek report that suggested a Koran had been flushed down a toilet, followed by a retraction by the magazine. Where 56 percent of Democrats had disapproved of detainee treatment before they were misinformed about the Koran incident, 78 percent disapproved afterward. Upon hearing the refutation, Democratic disapproval dropped back only to 68 percent -- showing that misinformation continued to affect the attitudes of Democrats even after they knew the information was false.
Bullock and others have also shown that some refutations can strengthen misinformation, especially among conservatives.
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.