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Two experiments demonstrate that post-event information, when delivered by another person, can affect people's memory reports. In the first experiment participants were shown several cars, and later, in pairs, given an 'old'/'new' recognition test on these cars plus several lures. There was a small but reliable effect of memory conformity. When the person was given misinformation this lowered accuracy, while presenting accurate information increased accuracy. In the second experiment participants, in pairs, viewed an identical crime except that half saw an accomplice with the thief and half did not. Initial memories were very accurate, but after discussing the crime with the other person in the pair (who saw a slightly different sequence), most pairs conformed. Confidence ratings strongly predicted which person in the pair persuaded the other. Parallels with eyewitness testimony in the Oklahoma bombing case and implications for police interviewing more generally are discussed.
Eyewitness errors are the most common cause of innocent people being falsely convicted (Huff, Rattner, & Sagarin, 1996). Almost all of the people exonerated by DNA evidence were originally convicted due primarily to errant eyewitness testimony (Connors, Lundregan, Miller, & McEwen, 1996; Wells et al., 1998). Errors are common. In a survey of identification parades (i.e. line-ups) in London, Wright and McDaid (1996) found that approximately 20 % of the time the witness chose someone other than the suspect. Levi (1998) used those data to estimate that 25 % of the time when a suspect is identified, they are innocent. Given that jurors weight eyewitness testimony highly in their decision making these errors will lead to many people being falsely convicted (Loftus, 1979; Loftus & Ketcham, 1991). Clearly it is of vital importance to understand why eyewitness errors occur. One of the most researched topics in the eyewitness testimony literature is the effect of post-event information.
After viewing a crime, eyewitnesses may encounter post-event information (PEI) in three basic forms (Wright & Davies, 1999). It may arise from biasing questions about the event. Loftus and Palmer (1974), and many subsequent studies, have demonstrated that the way in which a question is asked can alter a person's memory. This has become a great concern, particularly with children, as several convictions appear to have resulted due in part to children being...