Tracking the growth of visual evidence in fingerprint comparison tasks

Fingerprint comparisons are extended in time due to the fine details (minutiae) that necessitate multiple eye fixations throughout the comparison. How is evidence accumulated across these multiple regions? The present work measures decisions at multiple points during a comparison to address how feature diagnosticity and image clarity play a role in evidence accumulation. We find that evidence is accumulated at a constant rate over time, with evidence for identification and exclusion accumulated at similar rates. Manipulations of image diagnosticity and image clarity demonstrate two exceptions to this constant rate: Highly diagnostic evidence followed by weak evidence tends to lose the initial benefits of the strong start, and low image clarity at the start of the comparison can be overcome with high image clarity at the end of the comparison. The results suggest that examiners tend to treat each region fairly independently (as demonstrated by linear evidence accumulation), with only weak evidence for hysteresis effects that tend to fade as additional regions are presented. Data from transition probability matrices support an incremental evidence accumulation account, with very little evidence for rapid "aha" moments even for exclusion decisions. The results are consistent with a model in which each fixated region contributes an independent unit of evidence, and these accumulate to form an eventual decision. Fingerprint comparisons do not seem to depend on which regions are selected first, and thus examiners need not worry about finding the most diagnostic region first, but instead focus on conducting a complete analysis of the latent print.