People believe what they see, and they're willing to punish each other for it — apparently even when what they're seeing is a fake video that doesn't jibe with real-life experience.

Psychologists have long known that our memories of past events can be influenced by misleading information, but now they've proven that doctored video evidence can convince people to offer false eyewitness testimony. In a study of 60 college students performing a computerized gambling task, nearly half were willing to testify that they saw their partner cheat in real life after watching fabricated video evidence. Of students who were told that video evidence existed but didn't watch the footage themselves, only 10 percent gave false testimony.

"Our participants were willing to sign a statement to say that they witnessed another person cheating in an experiment, when in fact, that person never cheated," psychologist Kimberley Wade of the University of Warwick wrote in an e-mail. "So we now know that digitally altered footage can change people’s perceptions of an event, and have serious consequences for how people behave." Wade and her team published their findings this month in Applied Cognitive Psychology.

Most eyewitness studies have been carried out in a setting where there were no consequences for reporting that a person had cheated, but in this study, participants were told that their partner would be disciplined for cheating if they signed the testimony.

In the study, each student was paired with a member of the research team disguised as another participant. The pair sat side-by-side and played a computerized gambling game, which involved betting fake money based on the likelihood of answering a multiple choice question correctly. Each person was in charge of keeping track of their own wins; when a subject correctly answered a question, they got to take money from a shared "bank," and when they incorrectly answered a question, they had to put money back. Participants were told that at the end of the game, the person who made the most money would win a prize.

After the gambling concluded, the researchers used Final Cut Pro to alter a video recording of the game and make it look like the partner had cheated. Five to seven hours after the first task, students were called back to the lab and told that their absent partner was suspected of cheating. One-third of the students were also told that the researchers had video evidence of the cheating, and another one-third got to watch the doctored video themselves.

Before asking participants to sign an eyewitness testimony, the researchers emphasized that no one should testify unless they were 100 percent sure they had seen their partner cheat, and they emphasized that the cheater would be punished. Students who watched the fake video were far more likely to give false testimony than students who heard about the video or were simply told that their partner was suspected of cheating.

When asked to describe what they had seen, some participants even invented memories. "One subject told us that the other person had acted suspiciously and taken money from the bank when there was clearly a cross on the screen," Wade wrote. "So we are confident that a significant portion of people who saw the fake video genuinely believed—or even falsely remembered—that they had witnessed the cheating."

The scientists offered several possible explanations for why video had such a strong effect on memory. "First, people still view photos and videos as reliable records of the past," psychology graduate student Robert Nash wrote in an e-mail. "Around 75 percent of the people who participate in our research know something about photo or video editing software, yet many of the people in this study were convinced by our edited footage."

In addition, watching a person cheat on video makes the cheating incident feel familiar, and when an event feels familiar, it's often confused for something that was really witnessed. "So our participants may have misremembered seeing our confederate cheat," Nash wrote, "because when they were asked about the cheating incident they may have thought, 'Well, now that you mention it, that sounds kind of familiar to me, so perhaps I did see that happen.'" Upon debriefing, participants in the study expressed complete surprise that the video had been fake and that their memory was false.

"I believe these results, definitely," said memory expert Elizabeth Loftus of the University of California, Irvine, who was not involved in the research. "The whole body of work with doctored photos and videos is kind of scary; it is very visual and it is powerful evidence. And now we know it can contaminate the memory and make someone accuse another person of doing something wrong."

In an era of easily manipulated photo and video evidence, the researchers say their findings have major implications for law enforcement officials and policy-makers, adding yet more evidence that eyewitness testimony cannot always be accepted as fact.

"We need to remember that witnesses' memories should be treated like fingerprints, DNA, and other physical evidence — with a lot of care," wrote Wade. "If we don’t treat them with care, then we run the risk of contamination."

Image 1: Flickr/joegratz. Images 2 and 3: Kimberley Wade and Robert Nash/ University of Warwick.

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