I Must Be Guilty – the Video Says So

videoA 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 plyable electronic media, you can never be 100% sure that what you’re seeing is what really happened. Two recent 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 never did.  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 The money was withdrawn from an online bank based on cues given to participants by the computer program: when they answered questions correctly, they were told to withdraw money from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.

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 merely told 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 about ourselves as well.  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.

Wade, K., Green, S., & Nash, R. (2009). Can fabricated evidence induce false eyewitness testimony? Applied Cognitive Psychology DOI: 10.1002/acp.1607

Nash, R., & Wade, K. (2009). Innocent but proven guilty: Eliciting internalized false confessions using doctored-video evidence Applied Cognitive Psychology, 23 (5), 624-637 DOI: 10.1002/acp.1500



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24 responses to “I Must Be Guilty – the Video Says So

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  3. noamgr

    I see a few holes in this study. The second one especially seems to be more a study on the participants’ moral values than their memory. The question of whether someone is willing to testify against somebody they don’t know over a minor crime, one they’re not even sure they witnessed.

    And in the first one, participants might merely finally “give in”. This is seen to happen even in witnesses who are being interrogated for serious crimes, but it doesn’t mean they necessarily “remember” committing the crime. Many people, out of anxiety, would rather just admit to a crime they didn’t commit than continue to be interrogated by an authority figure.


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  5. Aldebrn

    How large were the sample sizes?

  6. noamgr — I had the same idea about “giving in” and I’m sure that had to be a factor for some percentage of the subjects, though it’s impossible to say how many.

    Aldebrn — 30 for each experiment in the first study, 60 in the second.

  7. Thanks for the excellent post, as usual.

    It’s amazing how psychology and pressure/implication works!

  8. Brian

    The biggest problem with the first study for me is this:

    It involves a process where the “offenders” might believe they accidentally withdrew money when they should have deposited it, and as one commenter already posted, might just give in to the interrogation. HOWEVER, it is highly unlikely that anybody would “remember” shooting somebody in the head, even if “video evidence” “showed them doing it”. I agree with the other commenter, this proves NOTHING about memory, and it certainly does not prove that anybody would believe video evidence showing something they clearly did not do. This video evidence shows something they might have actually done (accidentally).

  9. Brian, actually exactly that does sometimes happen. Somebody is coerced to make a false confession for a serious crime (including homicide) – it may be intimidation, they may be confused from stress and lack of sleep, or they may want to protect somebody else – and then, a few weeks or months later they turn out to really believe their own confession, even though they understood the confession to be false at the time.

    Memory really is very, very malleable. They end up believing that “since I said I did it, I must have.” This goes for many other situations too, where, once you’ve recalled a situation to somebody, you remember what you told them, not the original incident. This is one reason eye witnesses and confessions should be treated very sceptically and should always, always be backed up by solid independent evidence.

  10. I did it!

    ‘aaang on….


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  13. David – this is a very interesting study. I remember something similar at university, and please forgive me for by bad memory (!!) as this was told to me in the early 90s. A french writer told a story of how she remembered fleeing her village in world war II as a very young girl – over head there were German planes as her and her family and the rest of the village fled for their lives. Many years later she watched a film depicting exactly the same scene and this prompted her to ask her mother about the event and what she remembered about it. Her mother told her they had never fled the village and the event had never happened (I think the woman may not have even been born until right at the end of the war so it was impossible that she would have remembered this). She realised that she had seen the same film as a child and had reappropriated the scene into her own memories.

  14. mark

    They do this on “The Closer” pretty frequently (tell the defendant there’s evidence when there really isn’t).

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  16. alexeilebedev

    I think there is a methodological problem with the study. There is potential adverse selection of participants. First, there is the selection of those people who agree to participate in a study. This should be studied for correlation with suggestibility. Perhaps only people unsure of themselves, or those ready to change their minds, agree to participate in studies like this one. The second problem is just “doing your job” as a participant. It is possible that the participants viewed confession signing as part of their job as study subjects. Did the confession have a severe negative on their face or reputation? Did the participants think that by signing the confession they were admitting to everyone that they were a bad, guilty person, or were they simply admitting a mistake made when playing a certain game?

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