The influence of item difficulty on the relationship between eyewitness confidence and accuracy

Research indicates that the confidence eyewitnesses express in information heavily influences both the investigative process and the credence which jurors give to eyewitness testimony. However, studies in this area suggest that there is either no relationship or only a small positive relationship between eyewitness confidence and accuracy. Nevertheless, it is argued here that researchers may have paid insufficient attention to the issue of item difficulty, and have used statistical procedures that fail to consider highly accurate responses with low variance. In an attempt to address these issues, two experiments were conducted which measured confidence-accuracy in response to information seen in video films. In each case questions were used that ranged in difficulty. Higher confidence-accuracy correlations than are usually reported were found in both experiments. Furthermore, when participants were 'absolutely certain' that a piece of information was correct, they almost invariably were accurate.