Eyewitness memory

Eyewitness memory refers to the episodic memory of specific event, often a crime. Eyewitness memory, which is relied upon in the process of eyewitness identification, is thought to be fragile and easily distorted by information obtained post-event.

Vulnerability to post-event distortion
As with all memories, eyewitness memories can be distorted by what we previously knew (proactive interference) or what we learn in the future (retroactive interference). The distortion of memories by these means has been widely studied in relation to interference theory.

In the case of eyewitness memory, retroactive interference perhaps as a result of police questioning, can lead to difficulty in accurate recall.

A 1974 study by Loftus and Palmer suggests that eyewitness memory is highly vulnerable to post-event distortion. Participants were presented with photographic slides of a multiple-vehicular accident. Experimental group participants were then asked either "About how fast were the cars going when they smashed into each other?" or "About how fast were the cars going when they hit each other?". Participants were questioned a week later as to whether they had seen broken glass in the photographic slides. Although no broken glass was in actuality present in the slides, 32% of participants originally asked if the cars had " smashed into each other" reported they had. This was in comparison to only 14% of those asked if the cars "had hit each other," the conclusion being that the information in the question affected recall of the event.

Verbal overshadowing of visual recall
It has been suggested that verbal reports may interfere with visual recall of an event. This was concluded by Schooler and Engstler-Schooler following their study in 1990. Participants in this study initially viewed a video recording of a crime. Subsequently one group of participants made a detailed verbal report of the physical appearance of the criminal whilst the other group performed an unrelated task. All participants then were asked to visually identify the criminal. The group which made the verbal report performed significantly worse in this final visual identification task. Subsequent research has largely replicated these findings by Schooler et al. although alternative conclusions have been made.