Conformity in Eyewitness Reports

Eyewitness research has repeatedly shown that exposure to postevent information can affect a witness's ability to accurately report details of an originally encoded event. In everyday life, postevent information might be encountered when individuals who have shared the same experience discuss this with one another. Even when each person has witnessed the same event, their memories are likely to differ because of naturally occurring differences in the details attended to at the time, as well as differences in each person's ability to accurately remember those details. Despite initial differences in recollections of an event, when people talk about their memories they can influence each other such that their subsequent individual memory reports become similar. The phenomenon of people's memory reports becoming similar to one another's following a discussion has been referred to as “memory conformity.” This entry discusses the ways in which researchers have investigated conformity in eyewitness reports, typical research findings, and current theoretical explanations for the memory conformity effect.

When memory conformity occurs in the context of a forensic investigation, there can be serious implications. For example, it might be assumed that seemingly corroborative witness statements are a product of independent witnesses with consistent versions of events, when in fact memory conformity might be responsible for the similarities if there has been some form of interaction between cowitnesses. Therefore, it is important that the police take care not to give undue weight to the consistency of statements from witnesses who may have talked when judging the accuracy of an eyewitness account.

A typical paradigm used to investigate memory conformity in eyewitness reports involves pairs of participants being led to believe that they have encoded the same stimuli (often a simulated crime event shown on video or slides), when in reality they are shown stimuli that bear a similarity but differ in critical ways. These critical differences can take the form of added items (where one dyad member sees an item that his or her partner did not and vice versa) or contradicting items (where both dyad members see the same item, but details of this item differ in terms of color or product). This manipulation allows different features of the encoded stimuli to be observed by each participant. Dyad members are then given time to discuss what they have seen. An individual recall test for the originally encoded stimuli is then administered to examine the effects of cowitness discussion on memory. The dependent variable of interest is whether, and how often, witnesses report an item at test that they have encountered from a cowitness as opposed to seeing with their own eyes.

Alternative procedures to investigate memory conformity include using a confederate to act as a cowitness and purposefully introduce items of misleading postevent information into the discussion. Other experiments have presented cowitness information indirectly by incorporating it into a recall questionnaire, or the experimenter reveals responses that have purportedly been given by other witnesses.

A common finding for memory conformity research, regardless of procedure or stimuli used, is that social influences encountered in the form of postevent information from a cowitness can mediate accuracy in joint recall and recognition tasks, with individuals often exhibiting conformity to the suggestions and judgments of others. Significant conformity effects are also evident following a delay in postdiscussion memory tests that are performed alone.

...