Improving Witnesses’ Predictive Confidence Judgments by Enhancing Test Domain Familiarity

Recent research on witnesses’ pre-identification confidence (“predictive confidence”) has suggested that these judgments are moderately related to identification accuracy when witnesses experience encoding variability and appropriate statistical techniques are used. However, other research has shown that under ecologically valid conditions involving a single identification, the relationship between predictive confidence and accuracy deteriorates. One potential explanation for this lack of confidence-accuracy relationship is witnesses’ unfamiliarity with the lineup task, which leads them to underestimate its difficulty.

Identification difficulty is partly determined by the similarity of lineup fillers to the suspect; this similarity cannot be accounted for in a predictive confidence judgment. The current study tested whether witnesses’ predictive confidence could be improved by exposing them to “sample fillers” that matched (or did not match) the similarity of fillers in the actual lineup prior to reporting their predictive confidence. The current study also explored whether self-reported memory strength would predict identification accuracy. Finally, the present experiment evaluated the utility of witnesses’ dichotomous belief that they could make an accurate identification decision in predicting subsequent identification accuracy.

Witnesses viewed a mock crime under one of eight encoding conditions. One week later, they were shown “good”, “poor”, or no sample fillers prior to reporting their predictive confidence, memory strength, and dichotomous lineup prediction, and attempting a lineup identification. Results indicated that exposure to either type of sample filler increased witnesses’ overconfidence (thereby harming calibration). Witnesses’ self- reported memory strength and dichotomous prediction also failed to successfully predict accuracy. Results suggest using predictive confidence to decide whether to present a witness with a lineup would be inappropriate, and that there are important implications of retention interval on the utility of predictive memory judgments.

Major Professor: Dr. Stephen Charman