I am pretty sure but not 100%: obtaining, interpreting and presenting eyewitness confidence statements
Abstract
Eyewitness identification confidence is typically studied using scales (generally
numeric); in practice, eyewitnesses typically provide confidence in their own words.
Verbal and numeric confidence similarly predict accuracy, but verbal confidence is
difficult to interpret reliably (Mansour, 2020). To minimize miscommunication,
eyewitnesses could provide scale ratings after verbal judgements or vice versa, but we
do not know if the order in which such confidence statements are obtained affects the
confidence-accuracy relationship. I tested the utility of requesting both verbal and
numeric confidence and whether order effects exist. Participants (N = 198) viewed a
mock-crime video with two perpetrators. After a delay, they viewed two simultaneous
lineups with one perpetrator each and provided confidence for each perpetrator verbally
(in their own words) and then numerically (0-100%) or numerically and then verbally.
Numeric confidence in identifications was higher when provided first, t(393.82) = 2.40,
p = .02, d = 0.24. Confidence-accuracy characteristic (CAC) curve analysis indicates the
effect is driven by medium-confidence judgements (numeric range). No order effect was
found for verbal confidence (p = .32). However, for low and high numeric confidence,
verbal followed by numeric was better calibrated than numeric followed by verbal.
When the numeric judgement came first, none of the subsequent verbal judgements
could be categorized as high confidence using our coding scheme. These data provide
preliminary evidence that eyewitnesses should provide only a single confidence
judgement.