Perceptual Expertise in Fingerprint Classification

Abstract

Fingerprint examiners classify crime scene prints as belonging a left or right hand and to a finger-type – thumb index, middle, ring or little – to help narrow their search for known candidate prints. While fingerprint examiners have been found to have impressive perceptual expertise little in known about their perceptual abilities in this aspect of the fingerprint examination process. The present study served as a first test of fingerprint classification expertise, probing experienced (n = 30) and novice (n = 30) examiners in their ability to classify a controlled, fully rolled, set of prints by hand-type and finger-type in a 10-alternative forced-choice task. Using a yoked novice-expert design performance was measured at two levels of specificity: a coarse-grained level accounting for hand-type classifications (i.e. “left” versus “right”), and a fine-grained level accounting for finger-type classifications (i.e., “thumb”, “index’, “middle”, “ring”, “little”). The results revealed experienced fingerprint examiners were indeed sensitive to the type of hand a fingerprint originated from and were significantly better than novices at these classifications. The experts were also able to classify fingerprints by finger-type, performing significantly above chance. Novices, on the other hand, did not differ from chance at classifying fingerprints by finger-type. These expert-novice differences remained large, even when accounting for response times when classifying prints by hand and finger-type. These data suggest that fingerprint experts are able to generalise their highly specific perceptual expertise with fingerprint to coarser grained levels of analysis: moving from identity to hand and finger classification.