Visual Processing in Fingerprint Experts and Novices

1. Visual Processing in Fingerprint Experts and Novices Expertise with fingerprint examiners was tested in behavioral and EEG studies. Experts show greater tolerance for noise, are unaffected by longer memory delays, and show evidence of configural processing. This last finding was confirmed in an EEG study where experts show a reliable delay of the N170 component when fingerprints were inverted, while novices did not. Configural processing may be one element that underlies perceptual expertise. Tom Busey Indiana University, Bloomington John Vanderkolk Indiana State Police, Fort Wayne www.indiana.edu/~busey/

2. How Do Experts Make Identifications? Easy Match Hard Match

3. The Madrid Bombing Fingerprints: How Do Experts Make Misidentifications?

4. Testing Fingerprint Expertise:X-AB Sequential Matching Task example stimulus pairs:

5. Image Degradations at Test

6. Partial Masking original inverse Summation Recovers Original Fingerprint Semi-Transparent Masks Fingerprint Partially Masked Fingerprints

7. Behavioral Data Full Images Partial Images Full Images in Noise Partial Images in Noise Experts: No effect of delay, interaction between noise and partial masking.

8. Evidence for Configural Processing Full Image (Both Halves) Partial Image (One Half) info from first half? yes (db) no (1-db) info from second half? info from first half? yes (db) yes (do) no (1-do) no (1-db) info from guessing? info from guessing? yes (g) yes (g) no (1-g) no (1-g) Correct Decision Wrong Decision Correct Decision Wrong Decision Question: What is the relation between db and do? if db = do : One half doesn't influence information acquired from other half if db < do : Get less information from one half when second is present if db > do : Get more information from one half when second is present (consistent with configural or gestalt processing)

9. Multinomial Modeling Conclusions To test for configural processing, fit a reduced model with db = do. If we can reject this model, then we know that the two are not the same. Fit the full model to see the relation between db and do. Experts: No noise: we reject reduced model, so db and do are significantly different Full model: db = .841, do = .944 wrong direction for configural processing In noise: we reject reduced model, so db and do are significantly different Full model: db = .50, do = .30 Consistent with configural processing Novices: No noise: we reject reduced model, so db and do are significantly different Full model: db = .40, do = .54 wrong direction for configural processing In noise: we can't reject reduced model, so db and do are not significantly different Full model: db = .19, do = .13 No evidence for configural processing

10. Configural Processing in Faces: The ‘Thatcher Illusion’ Features are perceived individually, image looks ok. Features are perceived in context, image looks grotesque. (Thomson, 1980)

11. EEG and Configural Processing Faces produce a strong component over the right hemisphere at about 170 ms after stimulus onset, which is called the N170. Inverted faces cause a delay of 10-20 ms in the N170. Trained objects (Greebles) show a delay in the N170 component with inversion, but only in the left hemisphere (channel T5). Data from Rossion, Gauthier, Tarr, Despland, Bruyer, Linotte & Crommelinck (2000) Coupled with behavioral data suggesting configural processing with faces, an advanced N170 to an upright stimulus suggests that the N170 latency differences indicate configural processing. Data from Rossion, Gauthier, Goffaux, Tarr & Crommelinck (2002)

12. An Obvious Experiment: Show upright and inverted fingerprints to Fingerprint examiners and novices. If experts process fingerprints configurally, we should see a delayed N170 to inverted fingerprints. Also test faces to replicate the face inversion effect in our subjects. Test both identification and categorization tasks.

13. Upright Fingerprint Inverted Fingerprint Upright Face Inverted Face Expert Data- Identification Task Electrode T6 Delayed Amplitude (µV) Time (ms) Experts: delayed N170 with inverted fingerprints and inverted faces. Delayed

14. Upright Fingerprint Inverted Fingerprint Upright Face Inverted Face Novice Data- Identification Task Electrode T6 No Delay Amplitude (µV) Time (ms) Novices: no delayed N170 with inverted fingerprints, but see with faces. Delayed

15. Upright Fingerprint Inverted Fingerprint Upright Face Inverted Face Expert Data- Categorization Task Electrode T6 Delayed Amplitude (µV) Time (ms) Experts: delayed N170 with inverted fingerprints and inverted faces. Delayed

16. Upright Fingerprint Inverted Fingerprint Upright Face Inverted Face Novice Data- Categorization Task Electrode T6 No Delay Amplitude (µV) Time (ms) Novices: no delayed N170 with inverted fingerprints, but see with faces. Delayed

17. Summary and Conclusions Fingerprint experts demonstrate strong performance in an X-AB matching task, robustness to noise and evidence for configural processing when stimuli are presented in noise. This latter finding was confirmed using upright and inverted fingerprints in an EEG experiment. Experts showed a delayed N170 component for inverted fingerprints in the same channel that they show a delayed N170 for inverted faces. Thus they appear to be processing upright fingerprints in part using configural or holistic processing, which stresses relational information and implies dependencies between individual features. In the case of fingerprints, this may come from idiosyncratic feature elements instead of well-defined features such as eyes and mouths. www.indiana.edu/~busey/