One source of misleading information comes from leading questions. However, misleading information in the real world can come from other sources, for example other witnesses (co-witnesses), when they discuss the details of a crime of accident, following an incident. This is known as post-event discussion.
Gabbert et al. (2003) investigated the effect of post-event discussion on the accuracy of eyewitness testimony. Her sample consisted of 60 students from the University of Aberdeen and 60 older adults recruited from a local community.
Participants watched a video of a girl stealing money from a wallet. The participants were either tested individually (control group) or in pairs (co-witness group). The participants in the co-witness group were told that they had watched the same video, however they had in fact seen different perspectives of the same crime and only one person had actually witnessed the girl stealing. Participants in the co-witness group discussed the crime together. All of the participants then completed a questionnaire, testing their memory of the event.
Gabbert et al. found that 71% of the witnesses in the co-witness group recalled information they had not actually seen and 60% said that the girl was guilty, despite the fact they had not seen her commit a crime. These results highlight the issue of post-even discussion and the powerful effect this can have on the accuracy of eyewitness testimony.
The results of Gabbert et al. also have questionable ecological validity. The participants in the co-witness condition witnessed different perspectives of the same crime, as would typically be the case in real life crimes. However, like Loftus and Palmer, these witnesses knew they were taking part in an experiment and were more likely to have paid close attention to the details of the video clip. Therefore, these results do not reflect everyday examples of crime, where witnesses may be exposed to less information.
Gabbert et al. tested two different populations, university students and older adults and found little difference between these two conditions. Therefore her results provide good population validity and allow us to conclude that post-even discussion affects younger and older adults in a similar way.
Although Gabbert’s results provide an insight into the effect of post-event discussion on the accuracy of eyewitness testimony, we are unable to conclude why the distortion occurs. The distortion could be the result of poor memory, where people assimilate new information into their own accounts of the event and are unable to distinguish between what they have seen and what they have heard. On the other hand, it could be that the distortion occurs due to conformity and the social pressure from the co-witness. Further research is required answer this question.
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