Co-Witnesses and the effects of discussion on eyewitness memory

Abstract

The research presented in this thesis was designed to investigate the effects of co-witness information on the accuracy and completeness of eyewitness memory. Co-witness information is defined as information that one eyewitness conveys to another about an event that they both observed. Very little research has focused on co-witness discussion, so the first two studies surveyed real eyewitnesses and police officers to determine how often witnesses discuss the event with one another. The results from these surveys suggested that co-witnesses commonly talk about the event with each other and this outcome provided a clear justification for studying the effects of co-witness discussion on memory. Previous research on co-witness discussion has reached inconsistent conclusions, and the possibility exists that these discrepancies are due to methodological differences. Therefore, this research aimed to determine whether co-witness discussion helps or hinders individual recall, and to investigate this within a closely defined methodological set. In a series of five experiments, participants were shown a crime video and then asked to discuss the video in groups (some of which received experimentally induced misinformation from a cowitness). Following the discussion, participants were asked to give their individual accounts of what happened. These experiments showed that exposure to postevent information from a co-witness can cause people to incorporate this information into their individual testimonies, regardless of the accuracy of the information. This phenomenon has become known as 'memory conformity'. Relevant theories were tested in order to contribute to knowledge regarding the causes of memory conformity. Furthermore, the experiments also aimed to establish whether it is possible to mediate any negative effects of co-witness discussion by employing our theoretical understanding of the causes of memory conformity. Five approaches were utilized in an attempt to reduce the negative effects of co-witness discussion: warnings about possible misinformation, source monitoring, free recall, confidence ratings, and 'remember/know judgments' (Tulving, 1985). Some evidence was found to suggest that when using 'remember/know judgments' it may be possible to distinguish 'real' memories from information obtained from a co-witness. These results are discussed in terms of theoretical and practical implications.