We altered or fabricated five events: Sen. Joe Lieberman voting to convict President Clinton at his impeachment trial (Lieberman actually voted for acquittal); Vice President Cheney rebuking Sen. John Edwards in their debate for mentioning Cheney’s lesbian daughter (in fact, Cheney thanked him); President Bush relaxing at his ranch with Roger Clemens during Hurricane Katrina (Bush was at the White House that day, and Clemens didn’t visit the ranch); Hillary Clinton using Jeremiah Wright in a 2008 TV ad (she never did); and President Obama shaking hands with Iranian President Mahmoud Ahmadinejad (it never happened).

We mixed these fake incidents with three real ones: the 2000 Florida recount, Colin Powell’s prewar assessment of Iraq’s weapons of mass destruction, and the 2005 congressional vote to intervene in the Terri Schiavo case. Each reader who participated in the experiment was shown the three true incidents and one randomly selected fake incident. He was told that all four incidents were true and was asked, picture by picture, whether he remembered each one. At the end, he was informed that one of the four incidents was fake and was instructed to guess which one. (All subjects were eventually shown the truth about the fake photos. To see the original photos and how we doctored them, click here.)

So, how did our subjects do?