BY BRIAN KALLUS
The relationship between eyewitness confidence and accuracy has proven virtually nonexistent when examined in experimental conditions. This has proven difficult for the legal system as eyewitness testimony is given great weight in decisions, especially when that testimony is given with a great deal of confidence. Previous work on the subject of post-event factors affecting confidence and accuracy has shown that post-event factors, such as questioning, may influence either confidence or accuracy independently.
In the current study, Shaw explores this line of research in an attempt to discern whether a post-event questioning can increase eyewitness confidence without increasing eyewitness accuracy. Subjects were presented with slides of a simulated crime scene and asked to make forced choice responses about them as well as rate the confidence of their answers. Subjects were then subjected to post-event questioning about their responses by either reflective thought, or merely thinking of the scene, or by direct questioning, or being asked specifically about objects in the scene. Finally, the subjects again rated their response confidence and repeated the forced choice response test. The results of the experiments show that post-event questioning does increase eyewitness confidence, but does not affect eyewitness accuracy.
Subjects reported increased confidence for both correct and incorrect responses following questioning. These results suggest a retrieval fluency hypothesis. This hypothesis states that the confidence an eyewitness has in their testimony is directly related to the ease at which those memories are retrieved from the mind. When the subjects were forced to retrieve information about the simulated crime scene during post-event questioning, they increased the ease at which the information could be retrieved in the future and likewise increased the confidence in their responses.
Research of the retrieval fluency hypothesis has vast implications for the legal world. Post-event questioning, a common investigation technique used in virtually every aspect of law, has shown to influence the eyewitnesses confidence in their testimony, while leaving the accuracy unaltered. This could lead to mistaken testimony gathering further weight in an eyewitness' mind following repeated questioning and likewise gathering further weight in the minds of individuals, such as juries, who are not given instructions warning them of the possible problems with confident eyewitness testimony. Further work in this area of research will not only shed more light on the working of the human mind in reference to memory recall, but enable medium such as the legal system to function more accurately and effectively.
REFERENCE
Shaw, John S. III, Increases in Eyewitness Confidence Resulting From Post-event Questioning (1996), Journal of Experimental Psychology: Applied, 2(2),126-146.