Eyewitness testimony is a crucial part of many criminal trials even though research increasingly suggests that it may not be as accurate as we (and many lawyers) would like it to be. For example, if you witness a man in a blue sweater stealing something, then overhear people talking about a gray shirt, how likely are you to remember the real color of the thief's sweater?
Studies have shown that when people are told false information about an event, they become less likely to remember what actually happened - it is easy to mix up the real facts with fake ones. However, there is evidence that when people are forced to recall what they witnessed (shortly after the event), they are more likely to remember details of what really happened.
Psychologists Jason Chan of Iowa State University, Ayanna Thomas from Tufts University and John Bulevich from Rhode Island College wanted to see how providing false information following a recall test would affect volunteers' memories of an event that they witnessed. A group of volunteers watched the first episode of "24" and then either took an immediate recall test about the show or played a game. Next, all of the subjects were told false information about the episode they had seen and then took a final memory test about the show.
The results, reported in the January issue of Psychological Science, were surprising. The researchers found that the volunteers who took the test immediately after watching the show were almost twice as likely to recall false information compared to the volunteers who played the game following the episode.
The results of a follow-up experiment suggest that the first recall test may have improved subjects' ability to learn the false information - that is, the first test enhanced learning of new and erroneous information. These findings show that recently recalled information is prone to distortion. The authors conclude that "this study shows that even psychologists may have underestimated the malleability of eyewitness testimony."
- Chan et al. Recalling a Witnessed Event Increases Eyewitness Suggestibility: The Reversed Testing Effect. Psychological Science, 2009; 20 (1): 66 DOI: 10.1111/j.1467-9280.2008.02245.x
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