Neuronarrative

Musings on the complicated business of thinking

I Must Be Guilty – the Video Says So

Memory is far more fallible than we realize.

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A minor landslide of research from the past few years points to a dismaying fact about memory: it can be manipulated, far more often and extensively than previously thought. One implication of this realization is that eyewitness testimony, a stanchion of our criminal justice system, is no longer beyond reproach. Another is that in a world dominated by endlessly pliable electronic media, we can never be 100% sure that what we're seeing is what really happened. Two studies from the journal Applied Cognitive Psychology illustrate that last point nicely.


Forget What You Thought, Believe What You See

In the first study, researchers wanted to know if they could convince people that they'd committed an act they had not. To accomplish this, they created a computerized multiple choice gambling task for participants to complete, which entailed increasing the winnings from a sum of money as much as possible by answering questions. The money was withdrawn from an online bank based on cues given to participants by the computer program--when they answered questions correctly, they were told to withdraw money from the bank; when they answered incorrectly, they were instructed to deposit money back into the bank. Subjects were videotaped while they completed the task.

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Afterwards, participants were asked to sit and discuss the task with a researcher. During the discussion, the researcher said he'd identified "a problem" during the task, and then accused the participant of stealing money from the bank. Some of the participants were told that video evidence showed them taking the money (but they weren't actually shown the video), while others were shown video "proving" that they took the money. What the participants didn't know, of course, is that the video had been edited to make it appear as if they did something they had not. Participants were then asked to sign a confession stating that they did in fact take money from the bank when they should have deposited it back.

Participants were given two chances to sign the confession, and by the end of the day all of them did. 87% signed on the first request, and the remaining 13% signed on the second. Interestingly, even participants just told, and not shown, that the video showed them taking the money eventually complied with the confession.

I Didn't See It, But I Must Have Seen It

The next study used the same principle, but this time to see if people would accuse someone else of doing something they had not. Again a gambling task was used, but instead of one person completing it, two people placed side-by-side completed it -- sitting not even a foot apart, with monitors in full view of each other. Subjects were videotaped as before, and the video was doctored as before to show one of the two participants taking money.

Afterwards, the "innocent" participant was asked to discuss the task with a researcher, and told that video proof had been obtained showing that the other participant stole money. In order to pursue action against that person, the researcher said, the innocent participant would have to sign a witness statement corroborating the video evidence. Some of the participants were, as before, only told that the video existed, while others were shown the edited video (and there was also a control group neither told about nor shown video).

The results: When first asked to sign the witness statement against the other person, nearly 40% of the participants who watched the video complied. Another 10% signed when asked a second time. Only 10% of those who were only told about the video agreed to sign, and about 5% of the control group signed the statement.

These results point to the alarming power of video to shape and distort memory, not only about others, but also about ourselves. In the first study it wasn't only watching a video that made a difference; merely being told that a video existed made nearly as big an impact. And it's worth noting that in the second study some of the people who signed the witness statement became so convinced that the other person was guilty that they went on to insert even more details of suspicious behavior, as if they knew the other person was doing something wrong all along.

On the upside, the majority of the participants in the second study refused to sign the witness statement under any circumstances. And clearly there are plenty of examples of bad outcomes prevented, and actual wrongdoers caught, via video evidence. But if fabricated images lead even a small percentage of people to throw someone under the proverbial bus, concern (though not paranoia) is still plenty warranted.

Copyright 2010 David DiSalvo

David DiSalvo is a science and technology writer working at the intersection of cognition and culture.

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