From the grainy, black-and-white footage of President Kennedy's assassination to President Clinton's videotaped grilling about his affair with Monica Lewinsky, the power of the visual image has often brought reality home to Americans.
Now, the government has released a tape of Usama bin Laden that Bush administration officials say helps fill out a disturbing portrait of the man they believe instigated the Sept. 11 attacks.
The tape showed bin Laden, gathered with companions for a meal, taking satisfaction at the extent of the death and destruction wrought by the terrorists.
It was a frightening glimpse into bin Laden's persona, said Sen. Ron Wyden, D-Ore., who saw it before its release Thursday.
"This video will open a lot of eyes," he said. "The world will see that you are dealing with the level of pathology ... that is very, very twisted and sick."
Visual images often have had a profound impact on the public.
"There's something about the combination of sight and sound that makes the information seem more real," said Robert Lichter, president of the nonpartisan Center for Media and Public Affairs.
When the video of Clinton's four hours of testimony to a federal grand jury in 1998 was made public, after the release of the transcript, it gave Americans a firsthand look at the way he had parried with prosecutors and dodged questions with legalisms.
"I think it was his crucifixion, because you saw what he was doing," said Dr. Stuart Fischoff, a Los Angeles psychologist and expert on media psychology. "It's one thing to hear about Slick Willie; it's quite another to see him in operation."
When Rodney King's beating by Los Angeles police was captured on video in 1991, the jolting images turned what might have been just another report of brutality into a cause celebre.
Racism and police brutality were captured on a $300 video camera, Milton Grimes, one of King's attorneys, later said. "We've spent millions of dollars trying to prove it exists, and here we've captured it on tape."
Yet even that footage was open to interpretation. When four officers were acquitted at trial, Los Angeles erupted in riots. Two of the officers were later found guilty in federal court of violating King's civil rights.
In many cases, the way someone interprets what they see "becomes an ink blot," said Fischoff. "People will interpret things in ways that are consistent with what they want to believe."
When O.J. Simpson made his oft-televised flight from the law in his white Bronco in 1994, many people concluded "he was clearly eluding justice and he must have something to hide," Fischoff said. And yet others on his escape route stood and cheered sympathetically, unswayed from their belief in his innocence.
In the tape shown Thursday, bin Laden discussed some of the planning that led to the attacks on the World Trade Center and recalled hearing the results on radio broadcasts.
"We calculated in advance the number of casualties who would be killed based on the position of the tower," he said, but the destruction exceeded even his "optimistic" expectations.
Experts said in advance that the power of the tape could be diminished by the fact it is in Arabic and needed translation. As it turned out, it was difficult to match the translated words with the images then on the screen.
"If you could simply listen and understand it directly, it would be far more emotional," Fischoff said. Still, he said, "Visual images tap into the far more primitive part of the brain, and have a far more primitive reaction."