Eyewitnesses to a crime or other incident often recall that event dozens of times while waiting for a trial that may take place months or even years later. These recall episodes are often in response to questioning by arresting officers, police detectives, district attorneys, friends, other witnesses, private investigators, and defense attorneys, among others. Even in the absence of direct questioning, witnesses often recall what they have seen on their own, sometimes to prepare themselves for testimony at trial and other times simply because the event was frightening, disturbing, or otherwise vivid. The effects of such repeated recall on eyewitness accuracy and confidence are complex. Although repeated recall can occasionally yield new information, it may also cause memory distortions due to postevent misinformation effects, imagination inflation, increases in witness confidence, and retrieval-induced forgetting.
Generally speaking, repeated recall helps strengthen memory associations and can make the practiced information easier to retrieve in the future. In some circumstances, repeated recall can even lead to hypermnesia, which is the recall of additional information that was not recalled initially. Hypermnesia is most likely to occur when the repeated recall involves multiple retrieval cues. One prominent method of interviewing witnesses—the cognitive interview—is designed to elicit as much information as possible by encouraging witnesses to recall an event from multiple perspectives. If administered properly, the cognitive interview can yield increases in the total amount of information as compared with straightforward questioning.
Given that repeated recall can help strengthen memory associations and may even lead to the production of additional information, one would think that an eyewitness should recall the target event as often as possible. However, recalling information repeatedly is not without potential costs; repeated recall can actually alter a witness’s memory of the target event.
One well-known side effect of repeated recall is the postevent misinformation effect. When a witness is exposed to inconsistent or misleading information that is embedded in questions posed to that witness, the misleading postevent information can impair later memory reports of the original target event. For example, if a witness is asked how fast the car was going when it went through the stop sign (when in fact the car went through a yield sign), that witness is more likely to report later on that there was a stop sign than is a witness who was not exposed to the misleading information. The effects of postevent misinformation are especially strong when the witness is exposed to the misinformation multiple times.
A related phenomenon is imagination inflation. When someone repeatedly recalls an imagined event that did not actually occur, eventually she or he will come to believe that the event really did occur, often with great confidence. As is the case with postevent misinformation, the magnitude of the imagination inflation effect generally increases with multiple imaginings (i.e., with repeated recall).
There are other equally troublesome side effects of repeated recall that can occur even in the absence of misleading information or imagined events. For example, repeated questioning of eyewitnesses can lead to increases in witness confidence without corresponding changes in witness accuracy. This effect occurs independent of the content of the questions; in fact, just asking a witness to think repeatedly about an event can lead to later increases in witness confidence. Such increases in confidence are problematic because trial jurors place a great deal of weight on witness confidence when judging the accuracy of a witness’s testimony.
Repeated recall of portions of an event can lead to retrieval-induced forgetting. Many studies in the cognitive literature, some using eyewitness memory paradigms, have demonstrated that the act of recalling certain information about an event can actually impair a person’s performance on a future memory task for other previously unretrieved items. That is, repeated questioning about some details of an event (e.g., the male robber in a bank heist) may make it more difficult for the witness to recall other details about the robbery later on (e.g., the female robber who was waiting outside). Because interviews of eyewitnesses conducted by the police, investigators, and attorneys often constitute incomplete retrieval tasks, repeated questioning of witnesses can lead to retrieval-induced forgetting that may impair recall later at trial.
Finally, it should be noted that young witnesses, particularly children, are generally more suggestible than adult witnesses, and they are especially susceptible to all the effects of repeated recall discussed here. In addition, some studies have shown that children will change their answers to questions that are asked multiple times, simply because they assume that their original answers must have been wrong.
- MacLeod, M. (2002). Retrieval-induced forgetting in eyewitness memory: Forgetting as a consequence of remembering. Applied Cognitive Psychology, 16, 135-149.
- Shaw, J. S., III, & McClure, K. A. (1996). Repeated postevent questioning can lead to elevated levels of eyewitness confidence. Law and Human Behavior, 20, 629-653.
- Zaragoza, M. S., & Mitchell, K. J. (1996). Repeated exposure to suggestion and the creation of false memories. Psychological Science, 7, 294-300.